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Marvair Wall Mount H/P MAA1020H-1048H/MGA1072H I&O Manual
02/2021 Rev.2
Start-Up
Important: If your heat pump unit has a crankcase heater be sure that the crankcase heater has been
energized for at least 24 hours prior to start-up of the unit. Double check all electrical connections before
applying power. Various thermostats can be used to control the heat pump. The thermostat may have a
fan switch with an Automatic and On positions, a system switch with Heat, Cool, and Off positions, and
an emergency heat position with lights. The spec sheets have detailed description of the various Marvair
®
thermostats. Since other thermostats or remote control systems may be used, the following procedures
should be viewed as guidelines for standard thermostats with system and fan switches.
3.1 Check-out of Cooling Cycle
Procedure:
1. Set the fan switch to "Auto" and the system switch to "Off".
2. Move the cooling set point temperature on the wall thermostat to a point higher than the room
temperature. Move the heating set point temperature to a temperature that is lower than the room
temperature.
3. Set the thermostats system switch to "Cool" or "Auto" position. Nothing should operate at this time.
4. Set the time delay in the control box to three minutes. Note that time delay is an option on some
Marvair units and may not be on your heat pump.
5. Remove the cover plate from the thermostat. Slowly lower the thermostat cooling set point temperature.
Once the indoor fan turns on, allow approximately three minutes for the compressor and outdoor fan
to start.
For units equipped with the low ambient control, note that the outdoor fan may not come on immediately,
because it is cycled by refrigerant pressures. Some units have a time delay module which prevents the
compressor from restarting immediately after interruption of power. See section 1.5 for details on the
operation of the low ambient control and the time delay.
If the unit fails to operate, refer to the troubleshooting information in Chapter 4.
Heat Pump unit with Economizer
1. Set the fan switch to "Auto" and the system switch to "Off".
2. Set the cooling set point temperature on the wall thermostat to a point higher than the room temperature.
Set the heating set point temperature to a temperature that is lower than room temperature.
3. Set the thermostat system switch in the "Auto" or "Cool" position. Nothing should operate at this
time.
4. Set the time delay in the
Heat Pump with Economizer
control box to 3 minutes. Check the enthalpy
changeover setting of the H205A or dry bulb sensor, and reset it if needed. See section 1.7.
5. Slowly lower the thermostat’s cooling set point temperature. The indoor fan should operate.
Once the indoor fan comes on, allow approximately three minutes for the compressor to start. Note that
the outdoor fan may not come on immediately because it is cycled by refrigerant pressures
Note: To check the system operation under different ambient conditions, the air temperature and enthalpy
