York SUNLINE 2000 Installation Manual page 33

66396-YIM-C-1004
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-pres-
sure 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 ter-
minals, 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.
While the above step will reset any lockouts,
NOTE:
compressors #1 and #2 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 compres-
sor 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 econ-
omizer 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-
Unitary Products Group
Lock plug, and in the wiring from the Mate-N-Lock
plug to the Y1 "ECON" terminal.
13. For units with 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, a poor connection between the
UCB and economizer Mate-N-Lock plugs, loose
wiring from the Mate-N-Lock plug to the econo-
mizer, back to the Mate-N-Lock plug, and from the
Mate-N-Lock plug to the Y1 "ECON" terminal. If
nothing is found, the economizer control may have
faulted and is failing to return the 24-volt "call" to
the Y1 "ECON" terminal even though the econo-
mizer is not providing free cooling. To test, discon-
nect the Mate-N-Locks and jumper between the
WHITE and YELLOW wires of the UCB's Mate-N-
Lock plug. If compressors #1 and #2 energize,
there is a fault in the economizer wiring or the
economizer control.
14. The UCB can be programmed to lock out compres-
sor operation during free cooling and in low ambi-
ent conditions. These options are not enabled by
default. Local distributors can test the UCB for this
programming.
15. If none of the above corrected the error, test the
integrity of the UCB. Disconnect the C1 terminal
wire and jumper it to the Y1 terminal. DO NOT
jump the Y1 to C1 terminals. If the compressor
engages, the UCB has faulted.
16. If none of the above correct the error, replace the
UCB.
On calls for the second stage of cooling, the supply air
blower motor and compressors #1 and #2 are operat-
ing but compressors #3 and #4 are not (the room ther-
mostat 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. If the second stage of
cooling is requested, following a short delay,
compressors #1 and #2 will be energized unless
they are locked out. Typically, compressors #3 and
#4 are energized only during free cooling if the call
for the second stage of cooling persists for 20
minutes.
2. Compressors #3 and #4 will not energize simulta-
neously with compressors #1 and #2 if a call for
both stages of cooling is received. The UCB delays
compressors #3 and #4 by 30 seconds to prevent a
power surge. If after the delay compressors #3 and
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