Carrier 38MFC - Auto Mode; Forced Operation Function

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Defrost
Defrost on heat pump units is controlled by the microprocessor and
is initiated if either of the following conditions occur:
1 If for the outdoor temperature, T4>32_F(0_C):
— The outdoor coil temperature (T3) has been lower than
37F(3℃) for about 40 minutes and during that period,
the coil temperature is lower than TCDI for more than 3
minutes.
— The outdoor coil temperature (T3) has been lower than
37F(3℃) for about 80 minutes and during that period,
the coil temperature is lower than (TCDI+2℃)formore
than3minutes.
2 If for the outdoor temperature, T4＜32_F(0_C):
— If the conditions described above are satisfied, then the
program judges if the evaporator coil temperature (T2)
has decreased more than 41F(5℃). When the
evaporator coil temperature has decreased more than
41F(5℃), the defrost mode starts.
3 At any value of outdoor ambient temperature (T4):
— If the machine runs with a condenser coil temperature
lower than 37F(3℃) for more than 120 minutes and the
outdoor coil temperature (T3) has been lower than
(TCDI+4℃) for more than 3 minutes, the machine will
enter into defrost mode.
Where: TCDI = --7_C = 19.4_F
Defrost cycle termination:
If any one of the following conditions is satisfied, the defrost cycle
will end and the system will return to normal operation:
1 The outdoor coil temperature (T3) reaches (TCDE1).
— For 9K--12K: TCDE1 = (64_F) 18_C
— For 17K--22K: TCDE1 = (59_F) 15_C
2 The outdoor coil temperature (T3) is kept at about 46F
(8℃) for at least 80 seconds.
3 The defrost cycle reaches 10 minutes.
The cycles of defrost algorithm are shown below:
For 9K,12K models:
Compressor
on
off
on
on
on
off
off
off
4-way valve
Outdoor fan
Indoor fan
Indoor fan breeze(10s)
xx
10s
30s
10s
Defrost Cycle
(no longer than 10 min.)
xx=60s for 9k & 12k models
A14478
For 17K, 22K models:
XX=60 for 17k model, XX=90 for 22k model
Compressor
on
off
on
on
on
off
off
off
4-way valve
Outdoor fan
Indoor fan
Indoor fan breeze(10s)
xx
Defrost Cycle
(no longer than 10 min.)
30s
10s
10s
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AUTO MODE
In the Auto mode, the temperature can be set to values between
62~86F (17~30℃). In this mode, the machine will choose cool-
ing, heating or fan--only mode according to ΔT.
NOTE: ΔT =T1-- Ts, where T1 represents the indoor room
temperature and Ts represents the set temperature.
ΔT=T1--Ts
Running mode
ΔT＞1℃ Cooling
-- 1 < ΔT≤1℃
Fan--only
ΔT≤-- 1 ℃
Heating
Indoor fan will run at an automatic fan speed for each running mode.
The louverwill also operate depending in relevant mode taking place.
If the machine switches mode between heating and cooling, the
compressor will stop for 15 minutes and then choose a mode ac-
cording to ΔT.
If a new set temperature is commanded, the system will choose a
running mode according to ΔT.
FORCED OPERATION FUNCTION
When the machine is off, pressing the manual button will carry the
machine to forced auto mode. Pressing the button once again,
within 5 seconds, the machine will turn into forced cooling mode.
In forced auto, forced cooling or any other operation mode,
pressing the manual button will turn off the machine.
When in this mode, all general protections and remote control
functions are available.
Forced cooling
mode:
The compressor runs at F2 frequency and indoor fan runs as
breeze.
After running for 30 minutes, the machine will turn to auto mode
with a 75_F(24℃) set temperature.
Forced auto
mode:
The action of forced auto mode is the same as normal auto mode
with a 75_F(24_C) set temperature.