Mr. Heater MHU50NG Le manuel du propriétaire

OPERATING INSTRUCTIONS

AND OWNER’S MANUAL

MODEL#

MHU50

MHU80

MHU125

READ INSTRUCTIONS CAREFULLY: YOUR SAFETY IS IMPORTANT TO YOU AND TO OTHERS.

Read and follow all instructions. Place instructions in a safe place for future reference. Do not allow anyone

who has not read these instructions to assemble, light, adjust or operate the heater.

Installer: Leave this manual with the appliance. Consumer: Retain this manual for future reference.

WARNING: Improper installation, adjustment, alteration, service or maintenance can cause

injury or property damage. Refer to this manual. For assistance or additional information

consult a qualified installer, service agency or the gas supplier.

-WHAT TO DO IF YOU SMELL GAS

ǞDO NOT try to light appliance.

ǞDO NOT touch any electrical switch, do not use any phone in your building

ǞLeave the building immediately

ǞImmediately call your gas supplier from a phone remote from the building. Follow the gas suppliers

instructions

ǞIf you cannot reach your gas supplier, call the Fire Department.

- Installation and service must be performed by a qualified installer, service agency or the gas supplier.

FOR YOUR SAFETY:

Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this or any other appliance.

WARNING: If the information in these instructions are not followed exactly, a fire or explosion may result causing

property damage, personal injury or loss of life.

COMPACT UNIT HEATER

FOR RESIDENTIAL/COMMERCIAL USE

60185 REV C

www.mrheater.com • 800-251-0001

Compact Unit / Utility Heater 2Operating Instructions and Owner’s Manual

WARNING:

YOUR SAFETY IS IMPORTANT TO YOU AND TO OTHERS,

SO PLEASE READ THESE INSTRUCTIONS BEFORE YOU

OPERATE THIS HEATER.

WARNING:

FIRE OR EXPLOSION HAZARD

Failure to follow safety warnings exactly could result

in serious injury, death or property damage. Be sure to

read and understand the installation, operation, and

service in this manual. Improper installation, adjustment,

alteration, service or maintenance can cause serious

injury, death or property damage.

WARNING:

FIRE, BURN, INHALATION, AND EXPLOSION HAZARD.

KEEP SOLID COMBUSTIBLES, SUCH AS BUILDING

MATERIALS, PAPER, OR CARDBOARD, A SAFE DISTANCE

AWAY FROM THE HEATER. AS RECOMMENDED BY

THE INSTRUCTIONS NEVER USE THE HEATER IN SPACES

WHICH DO OR MAY CONTAIN VOLATILE OR AIRBORNE

COMBUSTIBLES, OR PRODUCTS SUCH AS GASOLINE,

SOLVENTS, PAINT THINNER, DUST PARTICLES OR

UNKNOWN CHEMICALS.

LANGUAGES

ENGLISH ..........................................................1 - 24

SPANISH ....................................................... 25 - 48

FRENCH ........................................................ 49 - 72

CONTENTS

PRODUCT SPECIFICATIONS ........................................... 3

MOUNTING DIMENSIONS ............................................. 4

SHIPPING ...................................................................... 5

REQUIREMENTS ............................................................ 5

UNIT HEATER INSTALLATION ........................................ 6

COMBUSTION & VENTILATION AIR .............................. 6

VENTING ...................................................................... 6

ELECTRICAL CONNECTIONS ........................................ 10

GAS CONNECTIONS ................................................... 11

LEAK CHECK ............................................................... 11

START-UP OPERATION ................................................ 11

HEATING SEQUENCE OF OPERATION ......................... 12

IGNITION CONTROL LED ............................................. 12

SERVICE ...................................................................... 13

WIRING DIAGRAM ..................................................... 14

FUEL CONVERSION ..................................................... 15

PARTS LIST ................................................................. 20

WARRANTY ................................................................ 24

GENERAL INFORMATION

RETAIN THIS MANUAL FOR FUTURE REFERENCE.

FOR QUESTIONS, PROBLEMS, MISSING PARTS BEFORE

RETURNING TO RETAILER PLEASE CALL WITH MODEL NUMBER

AND SERIAL NUMBER OF HEATER:

1-800-251-0001

MONDAY-FRIDAY 8-5 EASTERN TIME

OR E-MAIL USING THE MR. HEATER WEBSITE:

WWW.MRHEATER.COM

In order to provide the best service possible Mr. Heater is now

giving you more ways to get in touch with us:

FACEBOOK: Find us on Facebook

TWITTER: Find us on twitter

YouTube: There are now informational videos on Youtube.

WARNING:THIS PRODUCT CAN EXPOSE

YOU TO CHEMICALS INCLUDING LEAD AND LEAD

COMPOUNDS, WHICH ARE KNOWN TO THE STATE

OF CALIFORNIA TO CAUSE CANCER AND BIRTH

DEFECTS OR OTHER REPRODUCTIVE HARM. FOR MORE

INFORMATION VISIT WWW.P65WARNINGS.CA.GOV

WARNING: Fuels used in liquefied propane

gas appliances, and the products of combustion of such

fuel, can expose you to chemicals including benzene, which

is known to the state of California to cause cancer and

cause birth defects or other reproductive harm, for more

information go to www.P65Warnings.ca.gov

Compact Unit / Utility Heater 3Operating Instructions and Owner’s Manual

MHU125 MHU80 MHU50

V/A/H/Phase 120v / 3a / 60hZ / 1Ø 120v / 2.3a / 60hZ / 1Ø 120v / 2.3a / 60hZ / 1Ø

BTU Input 125,000 BTU 80,000 BTU 50,000 BTU

BTU Output 100,000 BTU 64,000 BTU 40,000 BTU

Efficiency % 80% 80% 80%

PRODUCT SPECIFICATIONS

GENERAL PERFORMANCE DATA

Rear View

Width

Height

Length

Width

Dimensional Data

Top View

BTU input BTU output Size

[BTU/HR] [BTU/HR] WIDTH LENGTH HEIGHT

MHU50 50,000 40,000 25.5” 24” 13”

MHU80 80,000 64,000 25.5” 24” 18”

MHU125 125,000 100,000 27” 26.5” 25.5”

Compact Unit / Utility Heater 4Operating Instructions and Owner’s Manual

MOUNTING DIMENSIONS

FLUE OUTLET DIMENSION

MHU50 MHU80 MHU125

C 4.25” 6.75” 9.43”

ELECTRICAL INLETS

FLUE OUTLET

REAR VIEW

6” GAS INLET

C

START-UP AND PERFORMANCE CHECK LIST

Job Name: ___________________________ Job No.: _____________________________ Date: ___________________________

Job Location: _________________________ City: ________________________________ State/Province: ___________________

Installer: _____________________________ City: ________________________________ State/Province: ___________________

Unit Model No.: _______________________ Serial No.: ____________________________ Service Technician: ________________

Electrical Connections Tight? _____________________________ Flue Connections Tight? _________________________________

Supply Voltage ________________________________________ Fan Timer Operation Checked? ___________________________

Gas Piping Connections Tight & Leak-Tested? _______________ THERMOSTAT Calibrated? _______________________________

Motor Amps __________________________________________ Heat Anticipator Properly Set? ____________________________

Furnace BTU input _____________________________________ Level? _______________________________________________

Line Pressure _________________________________________

Manifold Pressure W.C. _________________________________

MHU50/MHU80 Bracket Dimensions MHU125 Bracket Dimensions

520mm (20.47")

320mm (12.6")

160mm

(6.3")

500mm (19.69")

310mm (12.2")

150mm

(5.9")

160mm

(6.3")

160mm

(6.3")

520mm (20.47")

320mm (12.6")

160mm

(6.3")

TOP VIEW TOP VIEW

AIR FLOW

Rear Bracket Identical

to Front Bracket

Compact Unit / Utility Heater 5Operating Instructions and Owner’s Manual

SHIPPING

The heater is completely assembled. Installation instructions, two

mounting brackets (shipped loose), and a flue transition are included.

Check the unit for shipping damage. The receiving party should

contact the last carrier immediately if any shipping damage is found.

REQUIREMENTS

REQUIREMENTS – CSA IN THE USA

Installation of gas unit heaters must conform with local building codes

or, in the absence of local codes, with the current National Fuel Gas

Code ANSI Z223.1.

Installation in aircraft hangers must be in accordance with the current

Standard for Aircraft Hangers ANSI/NFPA No. 409.

Installation in parking structures must be in accordance with the

current Standard for Parking Structures ANSI/NFPA No. 88A.

Installation in repair garages must be in accordance with the current

Standard for Repair Garages ANSI/NFPA No. 88B.

These units are approved for residential applications. For installation in

a residential garage these units must be installed so that the bottom

of the heater is located no less than 8 feet (2.438m) above floor.

Heater must be located or protected to avoid physical damage by

vehicles. Refer to the National Fuel Gas Code, ANSI Z223.1, current

edition.

Authorities having jurisdiction should be consulted before NFPA

installation. Air for combustion and ventilation must conform to the

methods outlined in ANSI Z223.1, section 5.3, Air for Combustion

and Ventilation, or applicable provisions of local building codes. The

National Fuel Gas Code is available from:

American National Standard Institute Inc.

11 West 42nd Street

New York, NY 10036

These units are CSA International design certified. These unit heaters

are certified for installation to combustible material as listed in table

1 and on unit rating plate. Accessibility and service clearances must be

observed in addition to fire protection clearances.

All electrical wiring and ground for unit must be in accordance with

the regulations of the current National Electric Code ANSI/No. 70.

The National Electric Code is available from:

National Fire Protection Association

1 Batterymarch Park

PO Box 9101

Quincy, MA 02269-9101

TABLE 1

UNIT CLEARANCES

Top Sides Access Panel

in mm in mm in mm

1 25 1 25 18 457

Bottom Rear

in mm in mm

0 0 18 456

REQUIREMENTS – CSA IN CANADA

The instructions are intended only as a general guide and do not

supersede local codes in any way. Authorities having jurisdiction

should be consulted before installation. The installation must conform

with local building codes or in the absence of local codes, with the

current CSA B149.1, Natural Gas and Propane Installation Code. All

electrical wiring and grounding for the unit must also comply with the

Canadian Electrical Code CSA C22.1, current edition.

These heaters are CSA International certified for the clearances to

combustible material listed on the rating plate and table1. Provide

adequate clearance around air openings into the combustion

chamber, clearances from combustible material, and provisions for

accessibility and for combustion and ventilation air supply. Provision

shall be made for service accessibility to the heater. Note that fire

protection clearances may be exceeded to provide additional space for

service and accessibility.

GARAGE INSTALLATIONS

Installation in parking structures must be in accordance with the

current Standard for Parking Structures ANSI/NFPA No. 88A.

Installation in repair garages must be in accordance with the current

Standard for Repair Garages ANSI/NFPA No. 88B.

1. In a storage area, clearance from heaters to combustible materials

must be such that the material shall not attain a temperature above

160°F by continuous operation of the unit.

2. Eight foot minimum clearance from the floor to the bottom of the

heater must be maintained. Refer to the CSA B149.1, Natural Gas

and Propane Installation Code.

AIRCRAFT HANGER INSTALLATIONS

Installation of gas unit heaters must conform with local building codes

or, in the absence of local codes, with the current National Fuel Gas

Code ANSI Z223.1.

1. In an area where aircraft are housed or serviced, 10’ minimum

clearance from highest surface of aircraft to bottom of the heater

must be maintained.

2. In other areas, 8’ minimum clearance from the floor to bottom of

heater must be maintained.

3. Heaters should be located so as to be protected from damage from

aircraft or other appliances needed for servicing of aircraft. Refer to

requirements of the enforcing authorities.

Compact Unit / Utility Heater 6Operating Instructions and Owner’s Manual

These units are certified for residential applications. For installation in

a residential garage, these units must be installed so that burners and

ignition source are located no less than 18” (457mm) above floor.

Heater must be located or protected to avoid physical damage by

vehicles. Refer to CSA B149.1, Natural Gas and Propane Installation

Code current edition.

IN CANADA: In a confined area, the heater must be installed in

accordance with the CSA B149.1, Natural Gas and Propane Installation

Code. Be sure to check with local codes and ordinances for additional

requirements.

UNIT HEATER INSTALLATION

Unit is shipped ready for installation. Unit may be installed as shown in

figure 1 or inverted 180o depending on desired location as governed

by clearances, vent connection, air direction, gas supply, electrical

supply and service accessibility.

1. If installing unit in an inverted position: Remove and retain screws

securing door and rotate door 180o. Secure with retained screws.

Rotate louvers directing airflow as desired.

2. Choose location for mounting brackets.

3. Remove and retain three screws along top edge (bottom edge

when inverted) of front of unit.

4. Align screw holes on mounting bracket with holes along top edge

(either upright or inverted) of unit. Secure one mounting bracket to

front of unit with retained screws. Secure other mounting bracket

to back of unit with screws retained on the back of unit.

5. To support unit, secure mounting bracket to ceiling joist or truss.

Unit may also hang on rods as shown in figure 1.

INSTALL UNIT / UTILITY HEATER

FIGURE 1

MOUNTING

BRACKETS (2)

SUPPORT

RODS

COMBUSTION & VENTILATION AIR

Adequate facilities for supplying air for combustion and ventilation

must be provided in accordance with the latest edition of section 5.3,

Air for Combustion and Ventilation, of the National Fuel Gas Code,

ANSI Z223.1, in the U.S.A., CSA B149.1 Natural Gas and Propane

Installation Code, or applicable provisions of local building codes.

All gas fired appliances require air to be used for the combustion

process. In many buildings today, there is a negative indoor air

pressure caused by exhaust fans, etc. If sufficient quantities of

combustion air are not available, the heater or another appliance will

operate in an inefficient manner, resulting in incomplete combustion

which can result in the production of excessive carbon monoxide.

CAUTION:Insufficient combustion air can cause headaches,

nausea, dizziness, asphyxiation or death.

If indoor air is to be used for combustion, it must be free of the

following substances or the life of the heat exchanger will be

adversely affected: chlorine, carbon tetrachloride, cleaning solvent,

halogen refrigerants, acids, cements and glues, printing inks, fluorides,

paint removers, varnishes, or any other corrosives.

VENTING

A – GENERAL RECOMMENDATIONS AND REQUIREMENTS

NOTE: The vent is a passageway, vertical or nearly so, used to convey

flue gases from an appliance, or its vent connector, to the outside

atmosphere. The vent connector is the pipe or duct that connects a

fuel-gas burning appliance to a vent or chimney.

Unit heaters must be vented in compliance with all local codes

or requirements of the local utility, the current standards of the

(American) National Fuel Gas Code, ANSI Z223.1 or (Canada) CSA

B149.1 Natural Gas and Propane Installation Code, and the following

instructions.

Do not intermix different vent system parts from different

manufacturers in the same venting system.

Vent connectors serving Category I and Category II Appliances shall

not be connected into any portion of mechanical draft systems

operating under positive pressure.

A metal stamped/extruded transition is supplied with this certified

unit. It must not be modified or altered and must be installed on the

outlet of the induced draft blower assembly prior to the installation

of the vent or vent connector. Failure to comply with this requirement

will void the certification of the unit by the approval agencies. All

joints shall be secured with at least two corrosion resistant screws. All

joints must be checked for gas tightness after installation.

The heater and the venting system shall be inspected once a year by a

qualified service agency.

B – VERTICAL VENTS USING METAL VENT PIPE

– COMMERCIAL AND RESIDENTIAL INSTALLATIONS

MHU compact unit heaters are listed as Category I appliances for

vertical vent installations.

1. US: MHU unit heaters are to be used with NFPA- or ANSI-approved

chimneys, U.L. listed type B-1 gas vents, single wall metal pipe,

or listed chimney lining system for gas venting where applicable,

as well as the modifications and limitations listed in figure 2. Seal

single wall vent material according to the section A - General

Recommendations and Requirements.

Canada: Listed Category I Unit Heaters are to be used with Type

B gas vent. Minimum clearances of gas vent from combustible

material: 1 inch (25 mm)

2. The vent connector shall be 4”(102 mm) diameter on 50 & 80

& 125k units. In all cases, a flue transition piece (supplied) is

required to fit over the outlet of the induced draft assembly on the

appliance.

3. Keep the vent connector runs as short as possible with a minimum

number of elbows. Refer to the (American) National Fuel Gas Code

ANSI Z223.1 or (Canada) CSA B149.1 Natural Gas and Propane

Compact Unit / Utility Heater 7Operating Instructions and Owner’s Manual

Installation Code for maximum vent and vent connector lengths.

Horizontal run of the vent connector from the induced draft blower

to the chimney/vent cannot exceed the values in table 2.

4. When the length of a single wall vent, including elbows, exceeds

5 feet (1.5m), the vent shall be insulated along its entire length

with a minimum of 1/2” thick foil faced fiberglass 1-1/2# density

insulation. If a single wall vent is used in an unheated area it shall

be insulated. Failure to do so will result in condensation of flue

gases.

5. The unit may be vented vertically as a single appliance or as a

common vent with other gas-fired appliances. In common venting

situations, vent connectors for other appliances must maintain a 4”

(100mm) vertical separation between the vent connectors. Refer to

common venting tables in the (American) National Fuel Gas Code

ANSI Z223.1 or (Canada) CSA B149.1 Natural Gas and Propane

Installation Code for proper vent size.

6. Clearance to combustible material is 6” (152mm) for single wall

vent material except where a listed clearance thimble is used.

Clearance to combustible material for type B-1 vent or factory-built

chimney is per manufacturer’s instructions.

7. The vent connector shall be supported without any dips or sags.

Vertical vents shall be supported in accordance with their listing and

manufacturers’ instructions. All horizontal vent connector runs shall

have a slope up to the vertical vent of at least 1/4” per foot (1mm

per 50mm).

8. All vertical type B-1 vents, single wall vents, or listed chimney lining

system must be terminated with a listed vent cap or listed roof

assembly.

9. The vent must extend at least 3’ (1m) above the highest point

where it passes through a roof of a building and at least 2’ (0.6m)

higher than any part of a building within a horizontal distance

of 10’ (3.05m) unless otherwise specified by the (American)

National Fuel Gas Code, ANSI Z223.1 or (Canada) CAN/CGA-B149

Installation Code. The vent must extend at least 5’ (1.6m) above the

highest connected equipment flue collar.

TABLE 2

MAXIMUM HORIZONTAL VENT LENGTHS

No. of Elbows Feet m

1 25 7.6

2 20 6.1

3 15 4.6

4 10 3.0

5 5 1.5

Maximum length of vent connector not to exceed 30 ft. (9.1m).

VENT TERMINATION ON SINGLE WALL VENT

ROOF FLASHING

ROOF PITCHED FROM

0° TO 45°

SHALL NOT BE A

CONCEALED SPACE

2” CLEARANCE

THIMBLE

ROOF FLASHING

ROOF PITCHED FROM

0° TO 45°

SEAL JOINT BETWEEN SINGLE WALL VENT

AND “B” VENT AND THE ANNULAR SPACE

OF THE “B” VENT

12” MAX

CLEARANCE TO BE AS

SPECIFIED ON TYPE “B”

VENT PIPE

FIGURE 2

C – HORIZONTAL VENTING – GENERAL

Due to changes to Z83-8 2009 CSA2.6-2009, the use of single wall

B-Vent is no longer permitted as an acceptable material when venting

horizontally, this change covers both residential and commercial

installations. All horizontally vented units manufactured after July

of 2011 must be vented as a Caterory III Unit/Utility Heater in

compliance with UL 1738 & ULS636. Common venting is not allowed

when horizontally venting the unit heater.

The minimum horizontal vent length is 3 feet (914mm).

1. If possible, do not terminate the horizontal vent through a wall

that is exposed to prevailing wind. Exposure to excessive winds can

affect unit performance.

2. Vent termination must be free from obstructions and at least 12”

(306mm) above grade level and maximum snow height.

3. Do not terminate vent directly below roof eaves or above a walk-

way, or any other area where condensate dripping may be trouble-

some and may cause some staining. Avoid windows where steam

may cause fogging or ice buildup.

4. When horizontally vented, minimum clearance for termination from

any door, window, gravity air inlet, gas or electric meter, regulators,

and relief equipment is 4 ft. (1.2m) for U.S. installations. Refer to

NFPA 54/ANSI Z223.1 in the U.S.A. and CSA B149.1 Natural Gas

and Propane Installation Code and .2 in Canada or with authorities

having local jurisdiction. In Canada, vent termination must have a

minimum 6 ft. (1.8 m) horizontal clearance from gas and electric

meters and relief devices as specified in the Canadian B149.1, Natu-

ral Gas Installation Code.

5. Vent termination must be a minimum of 4’ (1.2m) below or 4’

(1.2m) horizontally from any soffit vent or under-eave vent.

6. Vent must be a minimum of 6’ from an inside corner formed by two

exterior walls. If possible, leave a 10’ clearance.

SINGLE WALL TERMINATION

DOUBLE WALL (TYPE B-1) TERMINATION

Compact Unit / Utility Heater 8Operating Instructions and Owner’s Manual

7. Vent termination must be a minimum of 10’ (3m) from any forced

air inlet (includes fresh air inlet for other appliances, such as a

dryer).

8. When termination is routed through an exterior combustible wall

the vent must be supported using a listed clearance thimble. Seal

the connection between the single wall and double wall pipes and

the annular space of the double wall pipe as shown in figure 2.

Inside edge of vent termination tee must be at least 12 inches from

outside wall as shown in figure 3.

9. For horizontal venting, the vent pipe shall be supported with

hangers no more than 3ft. (1m) apart to prevent movement after

installation.

D – HORIZONTAL VENTING – COMMERCIAL

1. Horizontal commercial installations are for buildings which are not

attached to living spaces. The vent may be stainless steel sealed

single walled cat III vent material and must be installed according to

the sections

• A - General Recommendations and Requirements, and

• C - Horizontal Venting General, and

• D - Horizontal Venting - Commercial.

Refer to figure 3.

2. The vent pipe diameter for horizontal commercial installations shall

be 4” (76mm). a transition piece has been supplied and is already

attached to your heater. Refer to figure 4

3. Select a wall termination point that will maintain 1/4” rise per foot

slope of horizontal run of vent pipe.

4. For upward sloped vent a condensate tee and drain must be

installed within the first 5’ (1.5m) from the unit heater to protect

the appliance. If a flexible condensate drain line is used, the drain

line must include a loop entering the structure. If the unit is shut

down for an extended period of time and will be exposed to sub-

freezing temperatures, the condensate may freeze.

E – HORIZONTAL VENTING – RESIDENTIAL

1. For horizontal residential installations these units are certified as

Category III appliances. Venting A - General Recommendations and

Requirements and C - Horizontal Venting General and E - Horizontal

Venting - Residential. Refer to figure 5.

2. The vent pipe diameter for horizontal residential installations shall

be 4” on all units. A transition piece has been supplied and is

already attached to your heater. Refer to figure 4

3. The maximum vent length is 25’ (7.6m) plus one 90-degree elbow.

The minimum length is 5’(1.5m).

4. The vent must maintain a ¼1/4” rise per foot of slope (1mm per

50mm). upwards toward the termination.

Flue Transition (attached) FIGURE 4

CONDENSATE DRAIN THROUGH TEE PIPE AND DRAIN LOOP

UPWARD SLOPE ON HORIZONTAL VENT-COMMERCIAL INSTALLATION

CATEGORY III VENT ACCORDING TO THESE INSTALLATION INSTRUCTIONS.

SLOPE: +¼ INCH FOR 1 FOOT RUN MINIMUM (1mm per 50mm)

12 INCHES MIN

(30.5 CM)

EXHAUST VENT

TERMINATION TEE

12 INCHES MIN (30.5 CM)

MINIMUM ABOVE ALL

HIGHEST SNOWFALL

LISTED THIMBLE

THROUGH

COMBUSTIBLE WALL

DRAIN LOOP WITH WATER

TRAP (TO CONDENSATE DRAIN)

FLUE TRANSITION

(PROVIDED)

NOTE - MINIMUM HORIZONTAL LENGTH 3 FT. (1.5M)

NOT INCLUDING CAP FOR TERMINATION.

MAXIMUM HORIZONTAL LENGTH AND NUMBER OF ELBOWS

REFER TO TABLE 2.

FIGURE 3

COMMON VENTING NOT ALLOWED WHEN HORIZONTALLY VENTING THE UNIT / UTILITY HEATER

Compact Unit / Utility Heater 9Operating Instructions and Owner’s Manual

HORIZONTAL VENTING - RESIDENTIAL INSTALLATION

UPWARD SLOPE

CATEGORY III VENT ACCORDING TO THESE INSTALLATION INSTRUCTIONS.

SLOPE: +¼ INCH FOR 1 FOOT RUN MINIMUM (1mm per 50mm)

12 INCHES MIN

(30.5 CM)

VENT TERMINATION CAP

INDUCED DRAFT BLOWER

FLUE TRANSITION

(PROVIDED)

LISTED THIMBLE THROUGH

COMBUSTION WALL

NOTE - MINIMUM HORIZONTAL LENGTH 3FT. (1.5M)

NOT INCLUDING CAP FOR TERMINATION

MAXIMUM HORIZONTAL LENGTH AND NUMBER OF ELBOWS REFER TO TABLE 2

COMMON VENTING NOT ALLOWED WHEN HORIZONTALLY VENTING THE UNIT / UTILITY HEATER

FIGURE 5

F – VENTING USING A MASONRY CHIMNEY

The following additional requirements apply when a lined masonry

chimney is being used to vent the compact unit / utility heater.

1. Masonry chimneys used to vent Category I units heaters must

be either tile-lined or lined with a listed metal lining system or

dedicated gas vent. Unlined masonry chimneys are prohibited. A

category I appliance must never be connected to a chimney that is

servicing a solid fuel appliance. If a fireplace chimney flue is used

to vent this appliance, the fireplace opening must be permanently

sealed.

2. A fan assisted unit heater may be commonly vented into an existing

lined masonry chimney provided:

• The chimney is currently serving at least one draft-hood equipped

appliance.

• The vent connector and chimney are sized in accordance with

venting tables in the (American) National Fuel Gas Code ANSI

Z223.1 or (Canada) CSA B149.1 Natural Gas and Propane

Installation Code.

IMPORTANT Single appliance venting of a fan assisted unit

heater into a tile lined masonry chimney (interior or outside wall) is

prohibited. The chimney must first be lined with either type B-1 vent or

an insulated single wall flexible vent lining system, sized in accordance

with venting tables in the (American) National Fuel Gas Code ANSI

Z223.1 or (Canada) CSA B149.1 Natural Gas and Propane Installation

Code.

3. A type B-1 vent or masonry chimney liner shall terminate above

the roof surface with a listed cap or a listed roof assembly in

accordance with the terms of their respective listings and the vent

manufacturer’s instructions.

4. Do not install a manual damper, barometric draft regulator, or flue

restrictor between the unit heater and the chimney.

5. If type B-1 double-wall vent is used inside a chimney, no other

appliance can be vented into the chimney. Outer wall of type B-1

vent pipe must not be exposed to flue products.

6. Insulation for the flexible vent pipe must be an encapsulated

fiberglass sleeve recommended by the flexible vent pipe

manufacturer.

7. The space between liner and chimney wall should NOT be insulated

with puffed mica or any other loose granular insulating material.

8. If type B-1 vent or an insulated flexible vent pipe cannot be used

as liners, the chimney must be rebuilt to accommodate one of

these methods or some alternate approved method must be found

to vent the appliance. When inspection reveals that an existing

chimney is not safe for the intended purpose, it shall be rebuilt to

conform to nationally recognized standards, lined or relined with

suitable materials or replaced with a gas vent or chimney suitable

for venting unit heaters. The chimney passageway must be checked

periodically to ensure that it is clear and free of obstructions.

G –REMOVAL OF UNIT FROM COMMON VENT

In the event that an existing unit heater is removed from a venting

system commonly run with separate gas appliances, the venting

system is likely to be too large to properly vent the remaining

attached appliances. The following test should be conducted while

each appliance is in operation and the other appliances are not in

operation, yet remain connected to the common venting system. If

the venting system has been installed improperly, the system must be

corrected.

1. Seal any unused openings in the common venting system.

2. Visually inspect the venting system for proper size and horizontal

pitch. Determine there is no blockage or restriction, leakage,

corrosion, or other deficiencies which could cause an unsafe

condition.

3. If practical close all building doors and windows and all doors

between the space in which the appliances remaining connected

to the common venting system are located and other spaces of the

building. Turn on clothes dryers and any appliances not connected

to the common venting system. Turn on any exhaust fans, such

as range hoods and bathroom exhausts, so they will operate at

maximum speed. Do not operate a summer exhaust fan. Close

fireplace dampers.

4. Follow the lighting instructions. Place the appliance being

inspected in operation. Adjust thermostat so appliance will operate

continuously.

Compact Unit / Utility Heater 10 Operating Instructions and Owner’s Manual

5. Test for spillage at the draft hood relief opening after five minutes

of main burner operation. Use the flame of a match or candle, or

smoke from a cigarette, cigar, or pipe.

6. After it has been determined that each appliance remaining

connected to the common venting system properly vents when

tested as outlined above, return doors, windows, exhaust fans,

fireplace dampers and any other gas-burning appliance to their

previous condition of use.

7. If improper venting is observed during any of the above tests,

the common venting system must be corrected. The common

venting system should be re-sized to approach the minimum size as

determined by using the appropriate tables

ELECTRICAL CONNECTIONS

NOTE: The MHU series unit/utility heaters use a direct spark ignition

system. There is no pilot necessary as the spark lights the main burner

as the gas valve is turned on. The direct spark ignition control board

emits radio noise during burner ignition. The level of energy may

be enough to disturb a logic circuit in a microprocessor controlled

thermostat. It is recommended that an isolation relay be used when

connecting the unit heater to a microprocessor controlled thermostat.

Select circuit protection and wire size according to the unit rating

plate. Install a separate disconnect switch (protected by either fuse

or circuit breaker) near the unit so that power can be turned off for

servicing. Remove electrical junction box cover and connect wiring

through knockout on the junction box located on the side of the

heater. Refer to heater wiring diagram for connection information.

Use 18 gauge wire or larger for line power connections. Make sure to

connect line power to wires located in the external electrical junction

box behind junction box cover. DO NOT CONNECT LINE POWER TO

THERMOSTAT TERMINAL STRIP ON OUTSIDE OF HEATER.

Electrically ground the unit in accordance with local codes or in the ab-

sence of local codes, in accordance with the current National Electrical

Code (ANSI/NFPA No. 70) in the USA, and in Canada with the current

Canadian Electrical Code, Part 1 CSA C22.1

NOTE: Un-insulated ground wire must be wrapped in electrical tape to

avoid damage to the electrical system.

Make line voltage connections as shown in figure 6. Connect field

wiring as shown on wiring diagram on unit. Also, refer to typical

diagram in this manual.

To use the blower for air circulation only, your thermostat must have

a “fan only” or fan selection setting. In case your thermostat has this

option. an additional wire should be run to the “G” terminal on the

thermostat connection block. See wiring schematic on page 13.

UNIT

LINE VOLTAGE FIELD WIRING

L1

N

BLACK

WHITE

EQUIPMENT

GROUND

BLACK WIRE WITH WHITE TAPE

OR WHITE WIRE WITHOUT TAPE FIGURE 6

DRIP LEG

GROUNDED

JOINT UNION

MANUAL

MAIN SHUT-OFF VALVE

(FURNISHED BY INSTALLER)

GAS FLOW

GAS SUPPLY CONNECTION

FIGURE 7

UNIT HEATER

CAP

ISOLATE GAS

VALVE

MANUAL MAIN SHUT-OFF

VALVE WILL NOT HOLD

NORMAL TEST PRESSURE

GAS SUPPLY TO UNIT HEATER

FIGURE 8

Compact Unit / Utility Heater 11 Operating Instructions and Owner’s Manual

WARNING

Electric shock hazard. Can cause injury or death.

Do not use this heater if any part has been

under water. Immediately call a qualified service

technician to inspect the furnace and to replace

any part of the control system and any gas

control which has been under water.

WARNING

Electric shock hazard. Can cause injury or death.

Before attempting to perform any service or

maintenance, turn the electrical power to unit

OFF at disconnect switch(es). Unit may have mul-

tiple power supplies.

WARNING

Danger of explosion. Can cause injury or product

or property damage. If over-heating occurs or if

gas supply fails to shut off, shut off the manual

gas valve to the appliance before shutting off

electrical supply.

WARNING

Danger of explosion and fire. Can cause injury or

product or property damage. You must follow

these instructions exactly.

GAS CONNECTIONS

When connecting gas supply lines, the length of the piping run from

the meter to the heater must be considered in determining the pipe

size to avoid excessive pressure drop. A line pressure of 7” WC

(178mm WC) for natural gas should be maintained when sizing the

piping.

A line pressure of 13” WC (330mm WC) should be maintained for

propane (LP) gas. NOTE: Compounds used on threaded joints or gas

piping must be resistant to the actions of Liquefied petroleum gasses.

WARNING: TO PREVENT HEATER DAMAGE. WHEN USING A

PROPANE TANK TO SUPPLY HEATER, A MINIMUM 11”W.C.

LOW PRESSURE REGULATOR TO A MAXIMUM 14”W.C. LOW

PRESSURE REGULATOR IS REQUIRED. THIS REGULATOR

MUST BE INSTALLED BETWEEN THE TANK AND THE HEATER.

Regulator not supplied with heater.

For correct sizing of piping, refer to the (American) National Fuel Gas

Code ANSI Z223.1, or (Canada) CSA B149.1, National Gas and Pro-

pane Installation Code or consult the utility having jurisdiction.

A drip leg should be installed in the vertical pipe run to the unit. In

some localities, codes may require that a manual main shutoff valve

and union (furnished by installer) be installed external to the unit.

Union must be of the ground joint type. A drip leg should be readily

accessible to permit cleaning and empting. See figure 7.

NOTE: Leave a min of 4’’ clearance to the electrical connections box

on the back of the heater to allow for access.

A 1/8” NPT plugged tap shall be installed immediately upstream of the

gas supply connection to the heater. The purpose of this is to be able

to check for proper gas pressure entering the heater.

LEAK CHECK

CAUTION DO NOT use matches, candles, flame or other sources of

ignition to check for gas leaks.

After gas piping is completed, carefully check all piping connections,

(field and factory), for gas leaks. Use a soap solution or other pre-

ferred means.

Due to the natural heating cycles and vibration of this unit it is recom-

mended, as part of its annual maintenance, to check these connec-

tions for proper tightness and leak-check with a soap solution or other

preferred means prior to putting into service.

IMPORTANT The heater and its individual shut off valve must be

disconnected from the gas supply piping system during any pressure

testing of that system at test pressures in excess of 1/2 psig (3.45kPa).

The appliance must be isolated from the gas supply piping system by

closing its individual manual gas shutoff valve during any pressure

testing of the gas supply system at test pressures equal to or less than

1/2 psig (3.45kPa). See figure 8.

NOTE In case emergency shutdown is required, shut down main gas

valve and disconnect main power to unit. These devices should be

properly labeled by the installer.

START-UP OPERATION

UNIT START–UP

FOR YOUR SAFETY READ BEFORE LIGHTING

BEFORE LIGHTING smell all around the appliance area for gas. Be

sure to smell next to the floor because some gas is heavier than air

and will settle on the floor.

Use only your hand to move the gas control knob to the on position.

Never use tools. Do not use excessive force to switch valve from off to

on position. Force or attempted repair may result in a fire or explosion.

MHU 50/80/125 unit heaters are equipped with an automatic spark

ignition system. There is no pilot. In case of a safety shutdown, move

thermostat switch to OFF, then return the thermostat switch to HEAT

position.

Should overheating occur, or the gas supply fail to shut off, shut off

the manual gas valve to the appliance before shutting off the electrical

supply.

GAS VALVE OPERATION FOR HONEYWELL

VR8205M SERIES VALVE

MANIFOLD PRESSURE ADJUSTMENT

SCREW

(UNDER CAP)

GAS VALVE ROTARY SWITCH KNOB

MANIFOLD

PRESSURE

TAP

GAS

SUPPLY

INLET PRESSURE TAP

FIGURE 9

Compact Unit / Utility Heater 12 Operating Instructions and Owner’s Manual

1. STOP! Make sure you have read and understand all of the safety

information regarding the operation of this gas appliance. Any and

all service should be performed by a licensed installer

2. Set the thermostat to lowest setting.

3. Turn off all electrical power to appliance.

4. This appliance is equipped with an ignition device which

automatically lights burner. DO NOT attempt to light the burners

manually.

5. There is a black rotary switch knob that can be moved between the

on and off position. Rotate the switch knob to the off position. (See

Figure 9)

6. Wait five minutes to clear out any gas. If you then smell gas, STOP!

Immediately call your gas supplier from a neighbor’s phone. Follow

the gas supplier’s instructions. If you do not smell gas go to next

step.

7. Rotate the black switch knob to ON.

8. Turn on electrical power to unit.

9. Set the thermostat to desired setting.

10. The combustion air blower will start. The burners will light within

30 seconds.

11. If unit does not light first time (gas line not fully purged) it will

attempt up to two more ignitions before locking out.

12. If lockout occurs, repeat steps 1 through 9.

13. If appliance still will not operate, follow the instructions “TO TURN

OFF GAS TO UNIT” and call your service technician or gas supplier.

TO TURN OFF GAS TO UNIT

1. Set thermostat to lowest level.

2. Turn off all electrical power to unit if service is to be performed.

3. Rotate black knob to OFF position.

HEATING SEQUENCE OF OPERATION

1. When the thermostat calls for heat, the combustion air blower

starts immediately.

2. Combustion air pressure switch proves blower operation before

allowing power to the ignition controller. This switch is factory set

and no adjustment is necessary.

3. After pre-purge of approximately 30 seconds, the spark ignition is

energized and the solenoid valve opens in the gas valve.

4. The spark then ignites the gas, the ignition sensor proves the flame

and the combustion process continues.

5. In the event that the flame is not detected after the first 10-second

trial for ignition, the controller will repeat steps 3 and 4 an

additional two times before locking out the gas valve. Refer

to ignition control board table 3. Ignition control will then

automatically repeat steps 3, 4, and 5 after 60 minutes.

To interrupt the 60-minute lockout period, move thermostat from

“HEAT” to “OFF” then back to “HEAT.” Heating sequence then

restarts at step 1.

6. The burners shall light without noticeable crossover delay. There

shall be no flame lifting from the burner heads, flashback or

burning within the burner. The flames shall be predominantly blue

in color and shall be approximately centered in the tubes with no

apparent impingement taking place. If your burner characteristics

do not match those described above. Refer to the trouble shooting

sections.

7. The ignition control will energize the fan approximately 45 seconds

after ignition is established.

8. After the thermostat demand is satisfied the gas valve is closed; 5

seconds after the demand is satisfied the combustion air blower is

shut off.

9. The control center shall shut off the system fan approximately 150

seconds after the gas valve is de-energized.

IGNITION CONTROL LED

The ignition control board contains a green LED which indicates the

following: TABLE 3 IGNITION CONTROL LED

LED UNIT OPERATION

Slow Flash Normal Operation - No call for heat.

Fast Flash Normal Operation - Call for heat

Current signal at FLAME terminal 0.6 to 1.0 microamps

2 Flashes System lockout - failed to detect or sustain flame

Current signal at FLAME terminal <0.6 microamps

3 Flashes Pressure switch failed closed before CAB is energized or failed

open after CAB is energized

4 Flashes High limit or rollout switch open

5 Flashes Flame sensed and gas valve not energized

Steady Off Loss of power/Check 3AMP Fuse on circuit board

Steady On Ignition control failure

*When thermostat is placed in continuous fan mode LED will slowly

flash

LIMIT CONTROL

The limit control switch is factory set and not field adjustable.

LOUVER VANE ADJUSTMENTS

Rotate louver vanes to direct airflow upward, downward, straight,

or any combination of these directions. When unit is installed in an

inverted position, louvers may be positioned in the same manner.

COMBUSTION AIR PRESSURE SWITCH

This pressure switch checks for proper combustion air blower

operation before allowing an ignition trial. The switch is factory set

and no field adjustment is necessary. If a 3 flash LED occurs Please

make sure your venting is not blocked up. Next, remove the end of

the pressure switch tubing from the EXHAUST FAN hose barb. There

might be an obstruction in the hose barb opening clear out the

opening with a thin object that will fit inside the hose barb. Push that

through the length of the hose barb PLUS at least another 1/2 inch,

into the exhaust fan housing. This will clear out anything stopping the

vacuum from engaging the pressure switch.

FLAME ROLLOUT SWITCH

The flame rollout switch(es) are located on the burner box top, behind

the ignition control board. This normally closed switch opens on a

temperature rise. Check for adequate combustion air before manually

resetting switch.

Compact Unit / Utility Heater 13 Operating Instructions and Owner’s Manual

HIGH ALTITUDE

Units may be fired at full input up to 2000 ft. (610m) above sea level.

Above 2000 ft. (610m), manifold pressure must be adjusted on some

units. Adjust pressure regulator to pressure shown in table 4 for

natural gas and table 5 for LP/propane gas.

Table 4

NATURAL GAS MANIFOLD PRESSURES - IN. W.C.. (KPA)

MHU 50/80/125 ALTITUDE FT. (M)

0-2000 (0-610) 2000-4500 (610-1370)

MHU 50/80/125 4.0”WC (0.99 KPA)* 3.6”WC (0.89 KPA)

*NO ADJUSTMENT REQUIRED

Table 5

LP/PROPANE GAS MANIFOLD PRESSURES - IN.W.C.. (KPA)

MHU 50/80/125 ALTITUDE FT. (M)

0-2000 (0-610) 2000-4500 (610-1370)

MHU 50/80/125 10”WC (2.62 KPA)* 8.5”WC (2.12KPA)

*NO ADJUSTMENT REQUIRED

GAS FLOW

To check for proper gas flow to the combustion chamber, determine

the Btu input from the appliance rating plate. Divide this input rating

by the Btu per cubic feet of available gas. Result is the required

number of cubic feet per hour. Determine the flow of gas through the

gas meter for two minutes and multiply by 30 to get the hourly flow

of gas.

GAS PRESSURE

1. Check gas line pressure with unit firing at maximum rate. A

minimum of 5.0” w.c. for natural gas or 10.9” w.c. for LP/propane

gas should be maintained for proper unit operation.

2. After line pressure has been checked and adjusted, check manifold

pressure. Correct manifold pressure is shown on the unit rating

plate. See figure 9 for gas pressure adjustment screw location. A

natural gas to LP/propane gas changeover kit is required to convert

unit. Refer to installation instructions provided with changeover kit

for conversion procedure.

SERVICE

CAUTION Turn off gas and electrical power to unit before performing

any maintenance or service operations on this unit. Remember to

follow lighting instructions when putting unit back into operation after

service or maintenance.

If any of the original wire as supplied with the appliance must

be replaced, it must be replaced with wiring material having a

temperature rating of at least 105°C. Do not use this appliance if

any part has been under water. Immediately call a qualified service

technician to inspect the appliance and replace any gas control which

has been under water.

BURNERS

1. Periodically examine burner flames for proper appearance during

the heating season.

2. Before each heating season examine the burners for any deposits or

blockage that may have occurred.

3. Clean burners as follows:

• Turn off both electrical and gas supplies to unit.

• Disconnect gas supply piping, high tension and sensor leads.

Remove gas manifold. Remove burner tray.

• Clean burners as necessary. Make sure that burner heads line up

properly to ensure flame crossover. Check spark gap on electrode

and adjust if required. The gap should be between 0.110 inch and

0.140 inch (2.79mm to 3.56mm). The gap may be checked with

appropriately sized twist drills or feeler gauges.

• Reinstall burner tray, gas manifold, high tension and sensor leads.

Reconnect gas supply piping.

• Restore electrical power and gas supply. Follow lighting instructions

to light unit. Check burner flame.

FLUE PASSAGEWAY AND FLUE BOX

The flue passages and flue box should be inspected and cleaned prior

to each heating season. The sequence of operation should be as

follows:

1. Turn off both electrical and gas supply to unit.

2. Disconnect combustion air blower wiring.

3. Remove screws securing flue box to unit. Remove flue box. If

necessary, remove blower assembly from flue box. Clean flue box

with wire brush.

4. Remove turbulator retention bracket and turbulators. Clean

turbulators with wire brush.

5. Remove burners as described in section “BURNERS” section.

6. Clean tubes with a wire brush.

7. Reassemble unit. The combustion air and flue box gaskets should

also be replaced during reassembly.

8. Restore electrical power and gas supply. Follow lighting instructions

to light unit. Check operation of unit.

COMBUSTION AIR BLOWER

Under normal operating conditions, the combustion air blower should

be checked and cleaned prior to the heating season with the power

supply disconnected. Use a small brush to clean blower wheel.

ELECTRICAL

1. Check all wiring for loose connections.

2. Check for correct voltage at unit (unit operating).

3. Check amperage draw.

FLUE AND CHIMNEY

Check all vent and vent connector joints for tightness. Ensure that

connections are sealed and that there are no blockages.

FAILURE TO OPERATE

If unit fails to operate check the following:

1. Is thermostat calling for heat?

2. Is main disconnect closed?

3. Is there a breaker tripped or a fuse blown?

4. Is gas turned on at meter?

5. Is manual shutoff valve open?

6. Is unit ignition system in lock out? If unit locks out again, call service

technician to inspect unit.

7. Is pressure switch closed? Obstructed flue will cause unit to shut off

at pressure switch. Check flue passage and outlet.

Compact Unit / Utility Heater 14 Operating Instructions and Owner’s Manual

L1

ACB COOL

ACB HEAT

ACC LOW

ACC

HTG ACC

CWB BLWR

THERMOSTAT

24 VAC (HOT)

FLAME SENSOR

PSW RTN

PSW OUT

HIL RTN

HIL OUT

SPK ELE

VLV RTN

VLV OUT

GND

24 V POWER (R)

MAN BLOWER (G)

HEAT 1 (W1)

GND PRO THER

24 V (COMM) (C)

24V

120 V

Transformer

BlackWhite

Combustion Blower

BlackFan

White

Black

White

L1

(HOT)

N

(NEUTRAL)

EQUIPMENT

GROUND

Flame

Sensor

Flame Rollout

Switch

Air Switch

Red

Flame Rollout

Switch

Igniter

Gas Valve

Equipment Ground

Blue

Yellow

White

Blue

Black

Orange

Blue

LADDER DIAGRAM

1

2

1

5

2

1

6

3

4

R

G

W

C

R

G

W

C

R

G

W

C

2

Red

White

OPTIONAL THERMOSTAT INSTALLATION

IT IS RECOMMENDED TO USE 18AWG WIRE WHEN INSTALLING THE

THERMOSTAT. CONNECT ANALOG THERMOSTAT WIRING TO TERMINALS

‘R’ AND ‘W’ AS ILLUSTRATED ON THE SCHEMATIC DIAGRAM OR

CONNECT A DIGITAL/WiFi THERMOSTAT TO ‘R’ ‘W’ ‘C’ AS ILLUSTRATED.

NOTE: THERMOSTAT TERMINAL CONNECTIONS ARE MOUNTED ON THE

BACK PANEL OF THE HEATER.

EXTERNAL THERMOSTAT TERMINAL STRIP WANING: DO NOT CONNECT

LINE POWER TO THE THERMOSTAT TERMINAL STRIP.

24 Vac POWER

OPTIONAL FAN CONTROL

HEAT 1

COMMON

THERMOSTAT WIRING CONNECTOR ON HEATER

NOTE -

IF ANY WIRE IN THIS APPLIANCE IS REPLACED,

IT MUST BE REPLACED WITH WIRE OF LIKE SIZE,

RATING AND INSULATION THICKNESS.

WARNING -

ELECTRIC SHOCK HAZARD CAN CAUSE INJURY

OR DEATH. UNIT MUST BE GROUNDED IN

ACCORDANCE WITH NATIONAL AND LOCAL

CODES.

DISCONNECT ALL POWER BEFORE SERVICING!

MAXIMUM LOAD NOT TO EXCEED

20VA AT 24V, CLASS 2

(2) S47 USED IN

75, 80 AND 125 ONLY

DESCRIPTION

KEY COMPONENT

A3 CONTROL BOARD (PCB)

B3 MOTOR CIRCULATION

B6 MOTOR-COMBUSTION AIR INDUCER

C4 CAPACITOR-BLOWER MOTOR 1

C5 CAPACITOR-INDUCED DRAFT MOTOR

DL36 RELAY-RELAY (N/A TO THESE MODELS)

GV1 VALVE-GAS

S10 SWITCH-PRIMARY GAS

S18 SWITCH-COMB AIR BLOWER

S47 SWITCH-FLAME ROLLOUT

T1 TRANSFORMER-CONTROL

BLACK

WHITE

CHASSIS GROUND

CONNECT CHASSIS

GROUND TO

EARTH GROUND

L1 CMB

BLWR ACC ACC

BLACK

WHITE

CAPACITOR USED IN 125 ONLY

C5

C4

BLACK

WHITE (COM)

GREEN

B3

B6

A3 LINE VOLTAGE FIELD INSTALLED

ANALOG THERMOSTAT WIRING

A3

GND

BLUE

YELLOW

GV1

SPARK

ELECTRODE

FLAME

SENSOR

BLUE

BROWN

(1)S47 (2)S47 ORANGE

24VAC

HOT

FLAME

1 TO 6

P1 ON BOARD

PRES. SW.

RETURN

PRES. SW.

OUT

HIGH LIMIT

SW. RETURN

HIGH LIMIT

SWITCH

OUT

GAS VLV

RETURN

GAS VLV

OUT

CAPACITOR USED IN

75, 80 AND 125 ONLY

S18

BROWN

RED

S10

WIRING DIAGRAM

120V

BLACK

BLUE

WHITE

GREEN / YELLOW 24V

Blue/Black

ANALOG

DIGITAL / WiFi

DIGITAL / WiFi THERMOSTAT WIRING

Compact Unit / Utility Heater 15 Operating Instructions and Owner’s Manual

FUEL CONVERSION

FUEL CONVERSION INSTRUCTIONS

FUEL CONVERSION Section 1: FUEL CONVERSION KITS

Fuel Conversion Part Numbers

Model # BTU/HR

Natural - To - LP

F260163

MHU 50 50,000

MHU 80 80,000

MHU 125 125,000

HONEYWELL KIT #393691

Orifice

(See P/N Table Below)

Gas Conversion Labels

For Converting from Natural Gas to L.P. Gas

Part Number Description 50 80 125

13575 Gas conversion label 111

60232 Converted Rating tag 1

60233 Converted Rating tag 1

60234 Converted Rating tag 1

11727 Spring - gas valve (label inc.) 111

60156 L.P. Orifice 358

13576 Control Conversion Label 111

Control Conversion Labels

Fuel Conversion Part Numbers

Model # BTU/HR

LP - To - Natural

F260164

MHU 50 50,000

MHU 80 80,000

MHU 125 125,000

HONEYWELL KIT #393691

Orifice

(See P/N Table Below)

Gas Conversion Labels

For Converting from L.P. Gas to Natural Gas

Part Number Description 50 80 125

13575 Gas conversion label 111

60235 Converted Rating tag 1

60236 Converted Rating tag 1

60237 Converted Rating tag 1

11727 Spring - gas valve (label inc.) 111

60049 L.P. Orifice 358

13576 Control Conversion Label 111

Control Conversion Labels

Compact Unit / Utility Heater 16 Operating Instructions and Owner’s Manual

4 screws

FUEL CONVERSION Section 2: FUEL CONVERSION INSTRUCTIONS

R

o

t

a

t

e

V

a

l

v

e

/

M

a

n

i

f

o

l

d

R

o

t

a

t

e

V

a

l

v

e

/

M

a

n

i

f

o

l

d

A

s

A

s

e

m

s

e

m

b

l

y

b

l

y

FIGURE 10 FIGURE 11

WARNING: Electrical Shock Hazard

Unplug the electrical cord from the outlet before

performing any service maintenance.

Failure to follow these instructions will result in death,

injury or property damage.

WARNING: Explosion Hazard

Turn off the gas supply to the heater before perform-

ing any service or maintenance.

Failure to follow these instructions will result in death,

injury or property damage.

The electrode and sensor are not adjustable. DO

NOT change location or position as part of this

conversion kit.

Step 1

CAUTION THE UNIT MUST NOT BE CONNECTED TO EITHER

THE GAS SUPPLY OR THE ELECTRICAL POWER SUPPLY, BEFORE

PROCEEDING WITH CONVERSION.

Step 2

Remove and retain the four screws holding the manifold on to the

burner box (Figure 10). Rotate the valve/ manifold assembly, away

from the burners (Figure 11). The valve/manifold assembly holds

the orifices (3 orifices on unit MHU50, 5 orifices on unit MHU80, 8

orifices on unit MHU125). This will allow access to the orifices on the

manifold, and also the adjustment spring in the valve/regulator.

Step 3

Remove and discard the adjustment spring cap from gas valve/

regulator with a flat blade screw driver by turning the screw counter-

clockwise. Remove and discard the regulator adjustment screw found

under the cap. Remove and discard the spring that is located under

the adjustment screw. Take the spring kit from the conversion kit,

and compare the part number of the kit to the parts list on page 14. If

it does not match, immediately contact Mr. Heater, Inc. for the correct

kit. After confirming the spring kit is correct for the heater model you

are converting, install the new spring and adjustment screw. Turn

spring adjustment screw clockwise (in) until the screw stops, then turn

it counter-clockwise (back) 1 ½ turns. Place conversion label supplied

with the spring kit on the valve near the adjustment screw cover

opening.

Step 4

Remove and discard the orifices (3 orifices on unit MHU50, 5 orifices

on unit MHU80, 8 orifices on unit MHU125) from the manifold with

using a ½ “ open end wrench. Turn them counter-clockwise to

remove. Take the new orifices from the conversion kit and before

installing, confirm that the number stamped on the side of the

orifice matches the number for the kit being installed. If it does not,

immediately contact Mr. Heater, Inc. for the correct kit. If they are

the correct orifices, install them in the manifold using caution not to

cross thread.

WARNING

This conversion kit shall be installed by a qualified service

agency in accordance with the manufacturer’s instructions

and all applicable codes and requirements of the authority

having jurisdiction. If the information in these instructions is

not followed exactly, a fire, explosion or production of carbon

monoxide may result causing property damage, personal injury

or loss of life. The qualified service agency performing this work

assumes responsibility for the proper conversion of this appliance

with this kit.

Compact Unit / Utility Heater 17 Operating Instructions and Owner’s Manual

6

5

4

3

2

1

0

1

2

3

4

5

6

5

4

3

2

1

0

1

2

3

4

5

6

4” 10”

N.G. L.P.

FIGURE 12

Step 5

Rotate the valve/ manifold assembly back up into the burner box,

making sure that all the orifices are indexed into the burners and are

not caught on the locating ring on the back of each burner. Secure

the manifold to the burner box with the four screws removed in step 2.

Step 6

Following the instructions in the unit heaters operations manual

mount the heater and connect the gas supply (making sure to leak

check all connections with soapy water).

Step 7

Remove valve pressure test plug and retain for later use. Connect a

water-filled U-tube manometer to the test port. See Figure 12. Use a

manometer because test gauges are not reliable and may give a false

reading.

Step 8

Connect main electrical power supply, and turn main gas supply on.

Step 9

Turn up the thermostat to call for heat, thereby starting the ignition

sequence for the heater.

Step 10

When the burners light, set the manifold gas pressure by turning the

adjustment screw to the regulator spring that was replaced in step 6.

Once the pressure has been adjusted, replace the adjustment screw

cover with a new one from the conversion kit.

Decrease Pressure

Counter-Clockwise

Increase Pressure

Clockwise

Refer to Table 6 for inlet pressure requirements, and set manifold

pressures according to gas type and altitude(See Table 4 and Table 5).

The manometer illustration (See Figure 12) shows each of the pressure

readings.

Step 11

Turn down the thermostat and allow the heater to complete a cool

down cycle. Then disconnect main electrical power, and turn the

main gas supply off to appliance.

Step 12

Disconnect the manometer from appliance and replace the test plug

on valve removed in step 6.

Compact Unit / Utility Heater 18 Operating Instructions and Owner’s Manual

FUEL CONVERSION Section 3: RATE TAG CONVERSION INSTRUCTIONS

FIGURE 13

Step 13

Connect main electrical power, and turn main gas supply back on.

Turn up thermostat to call for heat. When the main burners light

using soapy water check all connections thoroughly for gas leaks.

Remembering to also check the pressure test plug replaced in step

12. Allow the heater to operate for at least 5 minutes, then observe

the main burner flame. A hard blue flame extending into the tube is

normal. Slight yellow tipping is acceptable. There is no air adjustment

to the burner.

Step 14

See figure 13. Remove the data tag for their respective gases. Remove

label and place over the existing portion of the tag. This tag is

preprinted with all the correct information for the converted heater.

Step 15

Remove the converted information tag from the kit and fill in the

information. Then place this tag below the updated rating tag on the

unit.

Step 16

Replace any panels and operate heater following all warnings/cautions

and instructions in the operator’s manual and labels.

Table 4

NATURAL GAS MANIFOLD PRESSURES - IN. W.C.. (KPA)

MHU 50/80/125 ALTITUDE FT. (M)

0-2000 (0-610) 2000-4500 (610-1370)

MHU 50/80/125 4.0”WC (0.99 KPA)* 3.6”WC (0.89 KPA)

*NO ADJUSTMENT REQUIRED

Table 5

LP/PROPANE GAS MANIFOLD PRESSURES - IN.W.C.. (KPA)

MHU 50/80/125 ALTITUDE FT. (M)

0-2000 (0-610) 2000-4500 (610-1370)

MHU 50/80/125 10”WC (2.49 KPA)* 8.5”WC (2.12KPA)

*NO ADJUSTMENT REQUIRED

Table 6

INLET PRESSURES:

Natural Gas

MAX - 14” WC (3.49 kPa)

MIN - 5”WC (1.25 kPa)

Propane

MAX - 14” WC (3.49 kPa)

MIN - 11”WC (2.74 kPa)

Compact Unit / Utility Heater 19 Operating Instructions and Owner’s Manual

THIS PAGE INTENTIONALLY LEFT BLANK

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CETTE PAGE A ÉTÉ INTENTIONNELLEMENT LAISSÉE VIERGE

Compact Unit / Utility Heater 20 Operating Instructions and Owner’s Manual

REPAIR PARTS

When ordering parts include the complete unit model number listed on the unit rating plate.

Mr. Heater • Compact / Utility Heater • Model # MHU50 / MHU80

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