5188235-YIM-E-0518
Johnson Controls Ducted Systems
57
contactor is pulled in. Check for loose wiring between the
contactor and the supply air blower motor.
4.
If M2 is pulled in and voltage is supplied to M2, lightly touch
the supply air blower motor housing. If it is hot, the motor
may be off on internal protection. Cancel any thermostat
calls and set the fan switch to AUTO. Wait for the internal
overload to reset. Test again when cool.
5.
If M2 is not pulled in, check for 24 volts at the M2 coil. If 24
volts are present at M2 but M2 is not pulled in, replace the
contactor.
6.
Failing the above, if there is line voltage supplied at M2, M2
is pulled in, and the supply air blower motor still does not
operate, replace the motor.
7.
If 24 volts is not present at M2, check that 24 volts is
present at the UCB supply air blower motor terminal,
“FAN”. If 24 volts is present at the FAN, check for loose
wiring between the UCB and M2.
8.
If 24 volts is not present at the “FAN” terminal, check for 24
volts from the room thermostat. If 24 volts are not present
from the room thermostat, check for the following:
a. Proper operation of the room thermostat (contact
between R and G with the fan switch in the ON position
and in the AUTO position during operation calls).
b. Proper wiring between the room thermostat and the
UCB.
c. Loose wiring from the room thermostat to the UCB.
9.
If 24 volts is present at the room thermostat but not at the
UCB, check for proper wiring between the thermostat and
the UCB, i.e. that the thermostat G terminal is connected to
the G terminal of the UCB, and for loose wiring.
10. If the thermostat and UCB are properly wired, replace the
UCB.
On a call for cooling, the supply air blower motor is operating
but the compressor is not (the room thermostat fan switch is in
the “AUTO” position).
1.
If installed, check the position of the economizer blades. If
the blades are open, the economizer is providing free
cooling and the compressors will not immediately operate.
If both stages of cooling are requested simultaneously and
the economizer provides free cooling, following a short
delay the compressor will be energized unless it is locked
out, unless this option has been disabled through computer
communications.
2.
If no economizer is installed or the economizer is not
opening to provide free cooling and the compressor does
not energize on a call for cooling, check for line voltage at
the compressor contactor, M1, and that the contactor is
pulled in. Check for loose wiring between the contactor and
the compressor.
3.
If M1 is pulled in and voltage is supplied at M1, lightly touch
the compressor housing. If it is hot, the compressor may be
off on inherent protection. Cancel any calls for cooling and
wait for the internal overload to reset. Test again when
cool.
4.
If M1 is not pulled in, check for 24 volts at the M1 coil. If 24
volts are present and M1 is not pulled in, replace the
contactor.
5.
Failing the above, if voltage is supplied at M1, M1 is pulled
in, and the compressor still does not operate, replace the
compressor.
6.
If 24 volts is not present at M1, check for 24 volts at the
UCB terminal, C1. If 24 volts is present, check for loose
wiring between C1 and the compressor contactor.
7.
If 24 volts is not present at the C1 terminal, check for 24
volts from the room thermostat at the UCB Y1 terminal. If
24 volts is not present from the room thermostat, check for
the following:
a. 24 volts at the thermostat Y1 terminal
b. Proper wiring between the room thermostat and the
UCB, i.e. Y1 to Y1, Y2 to Y2
c. Loose wiring from the room thermostat to the UCB.
8.
If 24 volts is present at the UCB Y1 terminal, the
compressor may be out due to an open high-pressure
switch, low-pressure switch, or freezestat. Check for 24
volts at the HPS1, LPS1, and FS1 terminals of the UCB. If
a switch has opened, there should be a voltage potential
between the UCB terminals, e.g. if LPS1 has opened, there
will be a 24-volt potential between the LPS1 terminals.
9.
If 24 volts is present at the UCB Y1 terminal and none of
the protection switches have opened, the UCB may have
locked out the compressor for repeat trips. The UCB
should be flashing an alarm code. If not, press and release
the ALARMS button on the UCB. The UCB will flash the
last five alarms on the LED. If the compressor is locked
out, cancel any call for cooling. This will reset any
compressor lock outs.
NOTE:
While the above step will reset any lockouts, the
compressor may be held off for the ASCD. See the next
step.
10. If 24 volts is present at the UCB Y1 terminal and none of
the switches are open and the compressor is not locked
out, the UCB may have the compressor in an ASCD.
Check the LED for an indication of an ASCD cycle. The
ASCD should time out within 5 minutes. Press and release
the TEST button to reset all ASCDs.
11. If 24 volts is present at the UCB Y1 terminal and the
compressor is not out due to a protective switch trip, repeat
trip lock out, or ASCD, the economizer terminals of the
UCB may be improperly wired. Check for 24 volts at the Y1
“OUT” terminal of the UCB. If 24 volts is present, trace the
wiring from Y1 “OUT” for incorrect wiring. If 24 volts is not
present at the Y1 “OUT” terminal, the UCB must be
replaced.
12.
For units without economizers
: If 24 volts is present at the
Y1 OUT terminal, check for 24 volts at the Y1 “ECON”
terminal. If 24 volts is not present, check for loose wiring
from the Y1 “OUT” terminal to the Mate-N-Lock plug, the
jumper in the Mate-N-Lock plug, and in the wiring from the
Mate-N-Lock plug to the Y1 “ECON” terminal.
