Heating (hot water heat only)
When the thermostat calls for heat, the circuit between R and W is completed, activating the hot water circulating pump. If a field
installed circulating pump is being used the control board can still be wired to the pump directly or to an isolation valve supplying hot
water to the Air Handler using the control board’s 24V relay switch. A similar 24 V dry switching relay labeled TT can be used to
activate a boiler or water heater valve. After the circuit between R & W are completed
1. Units with Factory Installed Aquastats- The water temperature inside the hot water coil must
reach 130 deg. F before the circuit between R and G are complete activating the indoor blower
motor. To deactivate a factory installed aquastat simply move the selector pin on the multi-
function control board (See drawing above) from the on position to the off position.
2. Units without Factory Installed Aquastats or Deactivated Aquastats- A time delay of 60 seconds
follows before the circuit between R and G are complete activating the indoor blower motor.
The Air Handler fan will turn off 30 seconds after the Thermostat stops calling for heating.
Heating (heat pump with hot water heat)
When the thermostat calls for heat, the circuits between R and Y and R and G are completed. Circuit R-Y energizes the contactor
starting the outdoor fan motor and the compressor. Circuit R and G energizes the blower relay starting the indoor blower motor.
Circuit R and O or R and B energizes the reversing valve, switching it to the cooling position (depends on outdoor unit).
If the room
temperature should continue to fall, the second stage heat room thermostat completes the circuit between R and W. If a field
installed circulating pump is being used the control board can still be wired to the pump directly or to an isolation valve supplying hot
water to the Air Handler using the control board’s 24V relay switch. A similar 24 V dry switching relay labeled TT can be used to
activate a boiler or water heater valve. After the circuit between R & W are completed
1. Units with Factory Installed Aquastats- The water temperature inside the hot water coil must
reach 130 deg. F before the circuit between R and G are complete activating the indoor blower
motor. To deactivate a factory installed aquastat simply move the selector pin on the multi-
function control board (See drawing above) from the on position to the off position.
2. Units without Factory Installed Aquastats or Deactivated Aquastats- A time delay of 60 seconds
follows before the circuit between R and G are complete activating the indoor blower motor.
The Air Handler fan will turn off 45 seconds after the Thermostat stops calling for heating.
Freeze Protection (hot water heat)
If the temperature of the water within the hot water coil were to drop below 40
°
F the circuit between R and W is completed, activating
the hot water circulating pump, external circulating pump or isolation valve. Once the water temperature rises above 70
°
F the circuit
between R and W is opened and hot water will stop circulating within the hot water coil.
Pump Timer (hot water heat)
The State of Massachusetts requires the use of a pump timer on domestic water applications to periodically circulate water during the
off cycle. This pump timer requirement is a standard factory installed feature on all MX Series Air Handlers with hot water heat. The
Pump timer activates the circulating pump or isolation valve for one minute every six hours by completing the circuit between R and
W. The Pump timer is skipped while the outdoor compressor is operating.
MX Series Air Handler Maintenance
At the beginning of each heating season the unit should be serviced by a qualified installer or servicing agency.
Assistance or Service
If you need further assistance, you may contact us at the address below or e-mail us with any questions or concerns. Please
include a daytime phone number in your correspondence.
Advanced Distributor Products
1995 Air Industrial Park Road
Grenada, MS 38901
18
