AAON ASM01891 User Manual

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Zone
Two Condenser Head Pressure II Module Technical Guide
13
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Zone
TROUBLESHOOTING
Head Pressure Module Valve / Fan Position Troubleshooting
Head Pressure Module Valve/Fan
Position Troubleshooting
If congured for Water valve:
Aout Signal is 2 to 10 volts.
2 volts = 0% valve position or fully closed
10 volts = 100% valve position or fully open
PWM signal is not used for water valve but does modulate.
At Startup for cooling, valve will open to 75% or 8 volts for 3
minutes then will modulate to try to maintain head pressure
setpoint.
For heating, valve will open and stay at 100%.
If congured for Air Condenser Fan:
Aout Signal is 0 to 10 volts.
Minimum fan speed is 1 volt. (10%)
Maximum fan speed is 10 volts. (100%)
Anything less than 1.5 volts the fan will be o.
PWM signal is 0 to 100%
PWM+ (to ground) will always read 24 vdc.
PWM- (to ground) can be measured for volts dc and this
formula will tell you the percentage signal: (24 – measured
value)/24 (measured value = PWM- to ground)
PWM-
0 volts = 100% fan speed
6 volts = 75% fan speed
12 volts = 50% fan speed
18 volts = 25% fan speed
20.4 volts = 15% fan speed
Above 20.4 volts = 0% fan speed
At Startup for cooling, fan will start at 100% for 3 minutes
and then will modulate to try to maintain head pressure
setpoint.
For heating, fan will run and stay at 100%.
Safeties:
If the head pressure signal is above 500 PSIG, fan will go to
100% (high pressure safety).
If the head pressure signal is below 1 PSIG, fan will go to
100% (assuming bad sensor).
If the head pressure rises 50 PSI above setpoint, the condenser
signal will go to 100%.

AAON ASM01891 Specifications

General

Brand	AAON
Model	ASM01891
Category	Control Unit
Language	English