York SUNLINE MAGNUM WJ240 Installation Manual page 69

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 economizer, 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 fail-
ing to return the 24-volt "call" to the Y1 "ECON" ter-
minal even though the economizer is not providing
free cooling. To test, disconnect the Mate-N-Locks
and jumper between the WHITE and YELLOW
wires of the UCB's Mate-N-Lock plug. If compressor
#1 energizes, there is a fault in the economizer wir-
ing 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.
For units with factory installed economizers, the
UCB is programmed to lock out compressor opera-
tion when the LAS set point is reached.
For units without factory installed or with field
installed economizers, the UCB allows compressor
operation all the time. This programming can be
checked or changed by the local distributor.
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 compressor #1 are operating but
compressor #2 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. If the second stage of
cooling is requested, following a short delay,
compressor #1 will be energized unless it is locked
out. Typically, compressor #2 is energized only
Johnson Controls Unitary Products
during free cooling if the call for the second stage
of cooling persists for 20 minutes.
2. Compressor #2 will not energize simultaneously
with compressor #1 if a call for both stages of cool-
ing is received. The UCB delays compressor #2 by
30 seconds to prevent a power surge. If after the
delay compressor #2 does not energize on a sec-
ond stage call for cooling, check for line voltage at
the compressor contactor, M2, and that the contac-
tor is pulled in. Check for loose wiring between the
contactor and the compressor.
3. If M2 is pulled in and voltage is supplied at M2,
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 inter-
nal overload to reset. Test again when cool.
4. If M2 is not pulled in, check for 24 volts at the M2
coil. If 24 volts is present and M2 is not pulled in,
replace the contactor.
5. Failing the above, if voltage is supplied at M2, M2
is pulled in, and the compressor still does not oper-
ate, replace the compressor.
6. If 24 volts is not present at M2, check for 24 volts at
the UCB terminal, C2. If 24 volts are present,
check for loose wiring between C2 and the com-
pressor contactor.
7. If 24 volts is not present at the C2 terminal, check
for 24 volts from the room thermostat at the UCB
Y2 terminal. If 24 volts is not present from the room
thermostat, check for the following: a) 24 volts at
the thermostat Y2 terminal, b) proper wiring
between the room thermostat and the UCB, i.e. Y1
to Y1, Y2 to Y2, and c) loose wiring from the room
thermostat to the UCB.
8. If 24 volts is present at the UCB Y2 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 HPS2, LPS2, and FS2
terminals of the UCB. If a switch has opened, there
should be a voltage potential between the UCB ter-
minals, e.g. if LPS2 has opened, there will be 24
volts of potential between the LPS2 terminals.
9. If 24 volts is present at the UCB Y2 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 a code. If
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