MAU Installation Manual
Page
20
START UP PROCEDURE and TROUBLE SHOOTING
1. Apply power to the MAU.
a. Verify with a voltmeter on the line side of the contactor lugs that the proper voltage is present
and phases correctly.
2. If the lockout circuit is being used close the auxiliary devices or jumper across L-L to test the unit.
3. Close R1 and R2 with the activation switch being used or jumper across R1 & R2 to test the unit.
4. Increase the thermostat set point above the ambient air temperature and make sure the duct sensor is
connected, otherwise no heat will be produced.
5. The Fan and heating circuit should engage.
6. Check that the Fan is operating, and the green LED lights are blinking on the SSR controller, this will
indicate the SSR relays are modulating the heating elements. Tempered air should be discharging out of
the MAU.
a. If not check the load side of the contactor to verify voltage is present.
b. Check the terminal strip points marked 24V HOT/24V COM for 24VAC, this is the control power
for the internal control circuit, the contactor coil, the relay coil, and the ECM motor. They
require 24VAC coming from CPT-1 and will not operate if no voltage is present.
c. If 24VAC is not present in the control circuit, check to see if the high temp limit is tripped. It is
an electrically held limit and is reset by opening the R1-R2 switch or turning off power to unit
for a few minutes and then turning the power back on. The limit can also be tested by jumping
around the switch see if it is defective. Do not operate unit without a working limit switch, it
can create a dangerous overheating situation.
d. If the High limit is working, check the element high temperature limits that are wired in series,
one per element, check for continuity across the string and then individually, these are
normally closed devices, if an open limit is found, replace it.
7. Check that the 24VAC power is present across D 24V - D com, this is the damper circuit. The control
relay energizes a separate control power transformer to run the damper motor. It requires a spring
return damper. This circuit is activated in both the modulating heating mode (R1-R2) and the Fan only
mode (G-R1)
8. Check that the 24VAC power is present across EF 24V - EF com, this is the exhaust fan circuit. The
control relay energizes a separate control power transformer (CPT-2) to close an exhaust fan relay or
other auxiliary 24VAC devices.
9. Note: Maximum limit of 40VA for the sum of these two circuits, D-D and EF-EF.
10. Remove the R1-R2 switch or jumper to test the Fan only circuit by closing G-R1. The fan should operate
without the heating circuit activated. The power contactor will not close, only the control relay will
close to supply 24VAC to the damper and exhaust fan circuit.
a. If the fan does not operate check L1, L2 and L3 to verify line voltage is present. The motor takes
the operating power from the line side of the contactor. The motor is switched on and off using
the 24VAC control power from CPT-1.
b. Make sure the brown fan only wire is connected from the motor terminal block (1-5) to the G
terminal as noted in the wiring schematic.
c. Check that there is 24VAC at the motor terminal block.
11. In fan only mode, check that there is 24VAC at the damper (D-D) terminals and 24VAC at the exhaust
fan (EF-EF) terminals.
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