246681-YTG-B-0607
30
Unitary Products Group
b.
Verify 24 volts to A130 circuit board terminals
XFORMER "+" and "-". The terminals must be pow-
ered to allow any blower relays / contactors to oper-
ate.
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 correct voltage for UERV to L1 and, L2 on 1-
phase units.
b.
Check for correct voltage 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 1 "A"
(hot) and "B" (common) are outputting 24 volts to K163
contactor terminal "A" and "B" and that the contacts are
closed.
3.
Verify power to B28 wheel motor through J/P150 plug
assembly.
a.
If there is no power on the T1 leg of the motor (pivot-
ing models only) verify that the S110 switch located
inside the B29 damper motor is in the closed posi-
tion.
4.
Verify B28 wheel motor C23 capacitor is good. Replace
the capacitor if it is bad.
5.
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. If it is
loose, tighten it. If it is broken replace it.
2.
Verify the A130 circuit board terminals Exhaust 1 "A"
(hot) and "B" (common) are outputting 24 volts to K163
contactor terminal "A" and "B", and that the contacts are
closed.
3.
Verify power to B26 exhaust blower motor though J/P151
plug assembly.
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.
Energy Recovery Mode of operation.
a.
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 broken.
b.
Verify the A130 circuit board terminals Fresh "A"
(hot) and "B" (common) are outputting 24 volts to
K164 contactor terminal "A" and "B", and that the
contacts are closed.
c.
Verify power to B27 fresh air blower motor though J/
P148 plug assembly.
d.
On units equipped with the optional low ambient
control, verify that the circuit on the A130 circuit
board terminal "5" and "6" is made. The low ambient
control will stop the fresh air motor operation and
close the optional outside air damper if it senses
frost on the UERV wheel. Terminal "5" and "6" can
be jumped together to verify if the low ambient con-
trol has the fresh air blower stopped.
e.
On direct drive models, verify B27 wheel motor C26
capacitor is good. Replace if necessary.
f.
If all of the above are operational, the fresh air motor
is bad. Replace it with new motor.
2.
Economizer Mode of operation.
a.
The fresh air blower is not operational in the econo-
mizer mode.
UERV has power, but the wheel does not rotate out of
airstream during economizer operation.
1.
Check the linkage from the B29 damper motor to the
UERV wheel.
2.
Verify shipping retainers are removed.
3.
Verify the S122 economizer end switch is closed. The
switch is located on the damper and closes when the
damper moves from minimum position to the economizer
position (field adjustable).
4.
Verify the B29 damper motor has 24 volts to terminals
"B" and "T1" through J/P160 plug assembly
5.
If all of the above are operational, replace the damper
motor.
