Carrier 38MGRBQ18B-3 - Heating Mode; Defrosting Control

38MGRBQ: Service Manual
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
22
Heating Mode
Fig. 28 — Heating Mode
Table 20 — Heating Mode
Table 21 — Heating Mode
NOTE: The final result is an integer.
Modify the result according to a T2 average (correction).
NOTE: Average value of T2; sum of T2 value of all indoor units)/
(indoor units number).
Fig. 29 — T2 Average
Use Table 22 and the final capacity request to confirm the operating
frequency.
Table 22 — T2 Average
The maximum running frequency is adjusted according to the outdoor
ambient temperature.
Fig. 30 — T2 Average
Defrosting Control
Defrosting Conditions
After the compressor starts and enters a normal operation, mark the
minimum value of T3 from the 10th to the 15th minute as T30.
If any one of the following conditions is satisfied, the unit enters the
Defrosting mode:
1. If the compressor’s cumulative running time reaches 29 minutes and
T3<TCDI1 and T3+T30SUBT3ONE ≦T30.
2. If the compressor cumulative running time reaches 35 minutes and
T3< TCDI2 and T3+ T30SUBT3TWO≦T30.
3. If the compressor cumulative running time reaches 40 minutes and
T3<
24°C for 3 minutes.
4. If the compressor cumulative running time reaches 120 minutes and
T3<15°C.
Defrost Stop Conditions
If any of the following conditions is satisfied, defrosting ends and the unit
returns to the normal heating mode:
....T3 rises above than TCDE1°C
....T3 remains at TCDE2°C or above for 80 seconds
....Unit runs for ten consecutive minutes in DEFROSTING mode
Defrosting Actions
Fig. 31 — Defrosting Action
Capacity Area abcde f
Norm code (N) 3 2 1.5 1 0.5 0
Model 9K 12K 18K 24K
HP 1.0 1.2 1.5 2.5
Frequency
(Hz)
0 HEAT_F1 HEAT_F2
...
...
HEAT_F24 HEAT_F25
Amendatory
Capacity
Demand
01 2
...
...
24 25
T1 Ts
4
0
a
3
1
ï1
3
1
2
0
b
c
d
e
f
2
Decrease frequency
Keep frequency
Increase frequenc
y
°C T2 average
47
40
no īo
Cool-F9
10S 30S
TimeA
10S
compressor
Indoor fan
Outdoor fan
EXV open
frequency
Max 10 minutes
frequency
Compressor stops
oī
oī
s042 rof P084 P084