246681-YTG-B-0607
28
Unitary Products Group
UERV TROUBLESHOOTING GUIDE
UERV BELOW 600 CFM WITH STATIONARY WHEEL
(NO ECONOMIZER)
UERV will not operate.
1.
Quick check items.
a.
Verify S51 door switch is closed. The switch must be
in the closed position to power the A130 circuit
board.
b.
Verify the A130 circuit board switch SW1 Power is in
the “on” position.
c.
Verify 24 volts to A130 circuit board terminals TB1
“G” and “C” if in the cooling mode, or “W” and “C” if
in the heating mode. The terminals must be pow-
ered to allow any blower relays / contactors to oper-
ate.
2.
Verify high voltage power to UERV.
a.
Verify 110 volts for UERV to L1 and L2 on TB2 on
the A130 board.
b.
Verify the F1 fuse is good. Replace any bad fuses.
c.
Verify that the T28 step down transformer on 208,
230, and 460 volt units have the voltage correctly
applied to the correct transformer terminals.
UERV has power, but the enthalpy wheel does not spin.
1.
Check wheel belt is in place and tight.
2.
Verify the A130 circuit board switch SW1 Power is in the
"on" position.
3.
Verify the A130 circuit board terminals Wheel "1" and "2"
are outputting 110 volts to B28 wheel motor through J/
P150 plug assembly.
4.
Verify B28 wheel motor C23 capacitor is good. Replace
the capacitor if it is bad.
5.
If the optional Stop, Start, Jog (SSJ) feature is installed,
verify that the temperature setpoint on the SSJ does not
have the wheel stopped.
6.
If all of the above are operational, the wheel motor is
bad. Replace it with new motor.
UERV has power, but the exhaust blower does not
operate.
1.
Verify the A130 circuit board switch SW1 Power is in the
"on" position.
2.
Verify the A130 circuit board terminals Exhaust "1” and
"3” if in high speed operation, or "1” and "2" if in low
speed operation are outputting 110 volts to B26 exhaust
blower motor though J/P151 plug assembly.
3.
Verify B26 wheel motor C25 capacitor is good. Replace
the capacitor if it is bad.
4.
If all of the above are operational, the exhaust motor is
bad. Replace it with new motor.
UERV has power, but the fresh air blower does not
operate.
1.
Verify the A130 circuit board switch SW1 Power is in the
"on" position.
2.
Verify the A130 circuit board terminals Fresh "1” and "3"
if in high speed operation, or "1” and "2" if in low speed
operation are outputting 110 volts to B27 fresh air blower
motor though J/P148 plug assembly.
3.
On units equipped with the optional low ambient control,
verify that the A130 circuit board TB3 terminals marked
"low ambient" are closed. The low ambient control will
stop the fresh air motor operation and close the optional
outside air damper if it senses conditions for frost on the
UERV wheel. The "low ambient" terminals can be
jumped together to verify if the low ambient control has
the fresh air blower stopped.
4.
Verify B27 wheel motor C26 capacitor is good. Replace
the capacitor if it is bad.
5.
If all of the above are operational, the fresh air motor is
bad. Replace it with new motor.
UERV has power, but the optional motorized fresh air
damper does not open.
1.
Verify 24 volts to A130 circuit board terminals TB1 "G"
and "C" if in the cooling mode, or "W" and "C" if in the
heating mode.
2.
Verify the A130 circuit board switch SW1 Power is in the
"on" position.
3.
Verify 24 volts to B30 motorized outdoor air motor
through J/P160 plug assembly.
4.
If all of the above are operational, replace the outdoor air
damper motor.
UERV ABOVE 600 CFM WITH STATIONARY WHEEL
(NO ECONOMIZER)
UERV will not operate.
1.
Quick check items.
a.
Verify S51 door switch is closed. The switch must be
in the closed position to power the A130 circuit
board.
