High Condenser Coil Temperature Protection; Outdoor Unit Anti-Freezing Protection; Oil Return; Low Outdoor Ambient Temperature Protection - Carrier 38MGR Series Service Manual

High Condenser Coil Temperature Protection

T3
Fig. 30 — High Condenser Coil Temperature
Protection

Outdoor Unit Anti-Freezing Protection

When T2<39°F (4°C) for 250 seconds or T2< 32°F (0°C), the indoor
unit capacity demand is zero and resumes the normal operation when
T2>46.4°F (8°C) and the protection time is no less than three minutes.

Oil Return

Rules for Operation:
1. If the compressor frequency remains lower than the frequency set
for the setting time, the unit raises the frequency to the frequency
set for the setting time and then resumes the former frequency.
2. The EXV continues at 300p while the indoor units maintain their
operation. If the outdoor ambient temperature is higher than the set
frequency during the oil return, the unit stops the oil return process.

Low Outdoor Ambient Temperature Protection

When the compressor is off and T4 is lower than -31°F (-35°C) for ten
seconds, the unit stops and displays "LP."
When the compressor is on and T4 remains lower than -40°F (-40°C)
for ten seconds, the unit stops and displays "LP."
When T4 is no lower than -25.6°F(-32°C) for ten seconds, the unit
exits protection.

Controls and Functions

Capacity Request Calculation
Cooling Mode
T1 Ts
3
2
1
0
1
Fig. 31 — Cooling Mode
38MGR-04SM
Off
Decrease
Hold
Resume
a
4
3
b
2
c
1
d
e
0
f
Specifications subject to change without notice.
Table 25 — Cooling Mode
CAPACITY AREA a
NORM CODE (N) 3
Table 26 — Cooling Mode
MODEL 9K
HP 1.0
NOTE: The final result is an integer.
Use Table 27 and the final capacity request to confirm the operating
frequency.
Table 27 — Cooling Mode
Frequency
0 COOL_F1 COOL_F2
(Hz)
Amendatory
Capacity 0 1
Demand
The maximum running frequency is adjusted according to the outdoor
ambient temperature.
Fig. 32 — Maximum Running Frequency
b c d e
2 1.5 1 0.5
12K 18K 24K
1.2 1.5 2.5
...
COOL_F24 COOL_F25
...
...
2 24 25
...
T4FREMAXC0
27
f
0