Carrier High Wall Duct Free Split System 38MVC Service Manual page 23

Auto Fan
When the fan speed is set to Auto, the fan will run at either the
medium or low speed based on the difference between the room
temperature and the set point temperature as shown below:
Room temp. down
Med. Speed
0
T = Room Temperature
Ts = Set Point Temperature
Fig. 28 – Auto Fan - - Heating Mode
Manual Indoor Fan
The indoor fan will run continuously in heating at the set fan speed
(even if the compressor cycles off) unless the indoor coil
temperature begins to drop. When the coil temperature drops to
the TE3 limit, the 18k and 24k unit indoor fan switches to low
speed. On the 9k and 12k unit the indoor fan switches to ultra low
speed. When the coil temperature drops to the TE4 limit, the
indoor fan on all systems shuts off to prevent cold blow as shown
below. The cold blow algorithm also applies to the auto fan
setting.
Low Speed /
Ultra Low Speed
T temp. down
Fan off
TE4 TE1
Fig. 29 – Manual Indoor Fan - - Heating Mode
Indoor Coil Temperature ˚F (˚C)
Parameter
40MVQ 40MVQ
009--- 1 012--- 1
TE1 88 (31) 88 (31)
TE2 93 (34) 91 (33)
TE3
86 (30) 81 (27)
TE4 72 (22) 68 (20)
Sleep Mode
When in heating mode additional energy savings can be realized
by selecting the Sleep setting. When the Sleep setting is selected,
the temperature set point is adjusted automatically as shown below:
Set Point
1.8ºF
1.8ºF
1 2
Fig. 30 – Sleep Mode - - Heating
The unit will shut off 7 hours after the Sleep mode is selected.
Low. Speed
Room temp. up
T-Ts
3.6°F
A08112
Set fan speed
T temp. up
(Coil temp.)
TE3 TE2 T
A08111
40MVQ 40MVQ
018--- 3 024--- 3
77 (25) 82 (28)
90 (32) 93 (34)
86 (30) 90 (32)
68 (20) 75 (24)
Time (hour)
A08110
Defrost
Defrost on heat pump units is controlled by the microprocessor and
is initiated if either of the following conditions occur:
1. The outdoor coil temperature is lower than 32_F (0_C) for
more than 40 minutes and during that period, the coil
temperature is continuously lower than 26.6_F (- -3_C) for 3
minutes.
2. If the first condition does not occur within 90 minutes of
termination of the last defrost cycle.
The defrost cycle will terminate 10 minutes after initiation or when
the coil temperature reaches 68_F (20_C). At the end of the
Defrost cycle the timer resets automatically.
The cycles of defrost algorithm are shown below:
On
Compressor
Off
4-way valve
Outdoor fan
Indoor fan
10s
Fig. 31 – Defrost Cycle
Auto Mode
When the Auto setting is selected, the microprocessor looks at the
difference between the room temperature (T) and the set point
(TS). The algorithm determines which mode the unit will run in as
shown below:
Heating (fan only in cooling)
-1.8
Fig. 32 – Auto Mode
When the unit shifts modes, it will remain in that mode for at least
15 minutes while the algorithm ignores the difference between T
and TS. This ensures that the unit cannot change modes too
frequently.
23
Defrost 10 or 6 minutes
25s
5s
2s
A08114
Fan only Cooling
F 3.6 F
° ° T-TS
A08115