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15. MQ frequently asked questions
1. What causes the MQ to start?
Answer: The MQ is equipped with both an
internal ow switch and pressure switch. Each of
these can turn the MQ on, depending on water
consumption. The pump will start when: The ow
rate is greater than 0.3 gpm
OR
the pressure is below 29 psi.
2. What causes the MQ to stop?
Answer: Other than the manual on/off button,
only the ow switch is authorized to automatically
stop the MQ during normal operation when ow
drops below 0.3 gpm. The pump will shut off in
12-15 seconds after ow stops.
Additionally, the MQ will be turned off in the event
of a dry-run or overtemperature alarm.
3. What is the maximum height of a tap above
the MQ?
Answer: If a tap or faucet is installed at heights
greater than 50 ft above the MQ, there is the
potential risk that the MQ will never start.
In cases where the MQ starts due to low pressure
(low ow rates), the pressure has to fall below
the pressure switch activation point (28-30 psi
factory setting). To allow for the pressure of 50 ft
of water, tolerances and a safety margin, we
recommend a maximum height of 50 ft between
the MQ and any tap.
4. What is the purpose of the built-in pressure
tank?
Answer: The built-in pressure tank comes from
the factory, pressurized at approximately 23 psi
(with the pump pressure at zero) and holds a
volume of 14 ounces of water. It is designed to
minimize motor startup due to small leaks.
5. How is the dry-run condition determined?
Answer: The dry-run alarm is declared when the
motor is running AND the ow rate is less than
1.6 gpm AND when pressure is less than the
pressure switch setting. When this condition lasts
for 12 seconds, the alarm will be declared after
1 minute, and the motor is stopped. The MQ
attempts to automatically restart every
30 minutes for a maximum of 24 hours. If more
than 24 hours pass without water, the pump must
be restarted manually.
6. What is the maximum inlet pressure allowed
in the MQ?
Answer: For MQ 3-45, the maximum internal
pressure allowed is 109 psi. The maximum inlet
pressure when added to the MQ pressure must not
exceed 109 psi. Remember that inlet pressure adds
to the MQ pressure, so with a 40 psi inlet pressure
supplied to the MQ 3-45, internal pressures can
reach approximately 103 psi (63 + 40 psi).
Additionally, if inlet pressures exceed the built-in
pressure switch activation point (28-30 psi factory
setting), the pressure switch will be unable to
activate, and the ability to turn the MQ on at low
ow rates will be lost. In this situation, only the ow
switch will be able to turn the MQ on at ow rates
above its activation point of 0.3 gpm.
7. What is the priming capacity of the MQ?
Answer: Approx. 1.2 gallons.
8. How is overload temperature/overtemperature
of the MQ detected?
Answer: The motor has a thermal switch
incorporated in the motor windings.
The switch will cut out the motor and start again.
See the table below.
Cut-out
Thermal protection
[V] [°F] [°C]
115 302 150
230 275 135
Cut-in Both 151 65-67
9. Where can a pressure gauge be easily
installed to measure the discharge pressure?
Answer: In the discharge piping or in 3/8” GAS
straight thread opening used to add priming
water to the pump.
16. Disposal
This product or parts of it must be disposed of in an
environmentally sound way:
1. Use the public or private waste collection service.
2. If this is not possible, contact the nearest Watts
company or service workshop.
Subject to alterations.
WARNING: This product contains chemicals known to the
State of California to cause cancer and birth defects or
other reproductive harm.
For more information: Watts.com/prop65
English (US)