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Loss of communication can be attributed to a grounded
transformer with a secondary voltage of 21 vac supplying
the PSIO, DSIO-LV, or 4 IN/4 OUT; the 12.5-vac trans-
former supplying the DSIO-EXV module, or the 24-vac trans-
former supplying PS1 for the transformers.These transformers
should not be grounded, or serious damage to controls can
result. Check to be sure the transformers are not grounded.
Code 36 Low refrigerant pressure, Circuit A (alert)
Code 37 Low refrigerant pressure, Circuit B (alert)
If suction pressure transducer senses a pressure below set
point for more than 5 minutes at start-up or more than
2 minutes during normal operation, affected circuit shuts down
without going through the pumpout process. Reset is auto-
matic when pressure reaches 10 psig above set point if there
have been no previous occurrences of this fault on the same
day. If this is a repeat occurrence on same day, then reset is
manual, with LOCAL/ENABLE-STOP-CCN switch. Fac-
tory configured set point is 27 psig for standard chillers and
12 psig for brine chillers.
Possible causes of fault are low refrigerant charge, faulty
EXV, plugged filter drier, or faulty transducer.
Code 38 Failure to pump out, Circuit A (alert)
Code 39 Failure to pump out, Circuit B (alert)
The pumpout process is terminated when saturated suc-
tion temperature is 10° F (5.6° C) below temperature at be-
ginning of pumpout, or 10° F (5.6° C) below leaving water
temperature or reaches a saturated suction temperature of
–15 F (–26 C). If appropriate saturated suction temperature
is not met within 3 minutes (on 2 consecutive tries), circuit
shuts down without pumpout. Reset is manual with LOCAL/
ENABLE-STOP-CCN switch, and start-up follows normal
sequence.
Possible causes for this alarm are a bad thermistor or trans-
ducer or a faulty expansion valve.
Code 40 Low oil pressure, Circuit A (alert)
Code 41 Low oil pressure, Circuit B (alert)
LEGEND
CB — Circuit Breaker
CGF — Ground Fault Module
COMM — Communications Bus
CR — Compressor Contactor Relay
DSIO — Relay Module (Low Voltage)
HPS — High-Pressure Switch
LV — Low Voltage
PL — Plug
SNB — Snubber
TB — Terminal Block
TRAN — Transformer
U—Unloader
*And associated modular units.
Fig. 11C — 24-V Safety Circuit Wiring (130-210 and Associated Modular Units)
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