Unitary Products Group
29
246681-YTG-B-0607
b.
Verify 24 volts to A130 circuit board terminals
XFORMER "+" and "-". The terminals must be pow-
ered to allow blower contactors to operate.
c.
Verify 24 volts to A130 circuit board terminals TB 37
numbers "1" and "3". Terminal "1" is the hot and "3"
is the common side of the power source from activa-
tion power source (a/c unit, energy management
control, etc.). Typically, "1" would be from the blower
contactor on an a/c unit.
2.
Verify high voltage power to UERV.
a.
Check for correct voltage for UERV to L1 and L2 on
1-phase units.
b.
Check for correct voltage for UERV to L1, L2, and
L3 on 3-phase units.
c.
Verify the F29 fuses are good. Replace any bad
fuses.
d.
Verify that the T27 transformer has the UERV volt-
age correctly applied to the correct transformer ter-
minals.
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 terminals Exhaust "A" (hot)
and "B" (common) are outputting 24 volts to K163 con-
tactor terminal "A" and "B" and that the contacts are
closed.
3.
Verify power to B28 wheel motor.
4.
Verify B28 wheel motor C23 capacitor is good. Replace
the capacitor if it is bad. (Except VR074 to VR122)
5.
If the optional Stop, Start, Jog (SSJ) feature is installed,
verify that the timer 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.
Check that the blower belt is in place and tight on belt
drive models. If it is loose, tighten it. If it is broken replace
it.
2.
Verify the A130 circuit board terminals Exhaust "A" (hot)
and "B" (common) are outputting 24 volts to K163 con-
tactor terminal "A" and "B", and that the contacts are
closed.
3.
Verify power to B26 exhaust blower motor.
4.
On direct drive models, verify B26 wheel motor C25
capacitor is good. Replace if necessary.
5.
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.
Check that the blower belt is in place and tight on belt
drive models. Tighten it if it is loose. Replace it if it is bro-
ken.
2.
Verify the A130 circuit board terminals Fresh "A" (hot)
and "B" (common) are outputting 24 volts to K164 con-
tactor terminal "A" and "B", and that the contacts are
closed.
3.
Verify power to B27 fresh air blower motor though J/
P148 plug assembly.
4.
On direct drive models, verify B27 wheel motor C26
capacitor is good. Replace if necessary.
5.
On units equipped with the optional low ambient control,
verify that the circuit on the A130 circuit board terminal
"5" and "6" is closed. The low ambient control will stop
the fresh air motor operation and close the optional out-
side air damper if it senses frost on the UERV wheel.
Terminal "5" and "6" can be jumped together to verify if
the low ambient control has the fresh air blower stopped.
6.
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 the A130 circuit board terminals
XFORMER "+" and "-".
2.
Verify 24 volts to A130 circuit board terminals TB 37
numbers "1" and "3". Terminal "1" is the hot and "3" is the
common side of the power source from activation power
source (a/c unit, energy management control, etc.). Typi-
cally, "1" would be from the blower contactor on an a/c
unit.
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 PIVOTING WHEEL
(USED WITH 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.
