Carrier 69NT40-561-300, Руководство по эксплуатации и обслуживанию

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4–13 T-365
6. Delta T Logic: If the difference between return and supply air temperature (Delta T) becomes too great indi-
cating possible reduced airflow over the evaporator coil caused by ice buildup requiring a defrost.
a. In Perishable Pull Down - Delta T increases to greater than 12°C, and 90 minutes of compressor run time
have been recorded.
b. In Perishable Steady State – A baseline Delta T is recorded following the first defrost cycle after steady
state conditions are reached, (the unit is cooling, and the evaporator fans and heaters must remain in a
stable state for a period of five minutes). Defrost will be initiated if Delta T increases to greater than 4°C
above the baseline, and 90 minutes of compressor run time have been recorded.
c. In Frozen Mode - Defrost will be initiated if Delta T increases to greater than 16°C and 90 minutes of
compressor run time have been recorded.
NOTICE
When defrost is initiated, the controller closes the EEV, opens contacts TC, TN and TE (or TV)
to de-energize the compressor, condenser fan and evaporator fans.
NOTICE
The controller then closes contacts TH to supply power to the heaters. The orange DEFROST
light and heat light are illuminated and the COOL light is also de-energized.
Figure 4.10 Defrost
The EEV and DUV are independently operated by the microprocessor. Complete schematics and legends are
located in
Section 8 .
Defrost will terminate when the DTS reading rises above one of two model number configurable options selection,
either an upper setting of 25.6°C (78°F) which is default or lower setting of 18°C (64°F).
When the DTS reading rises to the configured setting, the de-icing operation is terminated.
4.3.22 Defrost Related Parameters
DTS Failure
When the return air temperature falls to 7°C (45°F), the controller ensures that the defrost temperature sensor
(DTS) reading has dropped to 10°C or below. If it has not, it indicates a failed DTS. A DTS failure alarm is triggered
and the defrost mode is operated by the return temperature sensor (RTS). Defrost will terminate after 1 hour. If the
DTS fails to reach is termination setting, the defrost terminate after 2 hours of operation.
ENERGIZED
DE-ENERGIZED
24 VOLT POWER
TG
ST
F
HPS
CH
IP-CM
TC
CF
TE
IP-EM1
EF
IP-EM2
HTT
TH
HR
ESV
TS
TV EF ES
TN
FS
LC
TG CF FS
LC