Sequence Of Operation - Carrier High Wall Duct Free Split System 38MVC Service Manual

Indoor Coil Freeze Protection
The indoor coil can freeze due to any of the following:
S Low system charge
S Reduced indoor airflow
S Restricted refrigerant flow
S Low ambient temperature (outdoor)
S Low load (indoor)
In cooling mode, the thermistor located on a return bend of the
indoor coil monitors the coil temperature continuously. Any time
the coil temperature drops below the TE5 limit for five consecutive
minutes, the compressor and outdoor fan will be switched off until
the coil temperature rises above the TE6 as shown below:
EVAP temp. down
Compressor and outdoor
fan off (after 5 mins)
TE5
Fig. 20 – Indoor Coil Freeze Protection
Coil Temperature ˚F (˚C)
Parameter
40MVC(Q) 40MVC(Q)
009--- 1 012--- 1
TE5 39 (4) 41 (5)
TE6 50 (10) 54 (12)
Condenser High Temperature Protection
Condenser high temperature can occur due to any of the following
conditions:
S High outdoor ambient
S Outdoor fan blocked
S Outdoor coil blocked
The outdoor coil thermistor on a heat pump unit continuously
monitors the temperature of the outdoor coil. Anytime the coil
temperature exceeds the TE10 limit, the compressor is switched off
and the outdoor fan continues running to reduce the coil
temperature. When the coil temperature drops below the TE11
limit, the compressor is switched back on as shown below:
COND temp. down
Compressor on
Outdoor fan on
TE11
Fig. 21 – Condenser High Temp Protection
Parameter
38MVQ018--- 3
TE10 149 (63)
TE11
131 (55)
Compressor and
outdorr fan on
EVAP temp. up
T
TE6
(Evap Temp.)
A08118
40MVC(Q) 40MVC(Q)
018--- 3 024--- 3
36 (2) 36 (2)
54 (12) 54 (12)
Compressor off
Outdoor fan on
COND temp. up
TE10 T
A08119
Condenser Temp.
˚F (˚C)
38MVQ024--- 3
158 (70)
149 (65)
Indoor High Temperature Protection
High indoor coil temperature (in heating mode) can occur due to
any of the following:
S High outdoor ambient temperature
S Indoor fan blocked
S Indoor coil blocked (including dirty filters)
The indoor coil thermistor on a heat pump unit continuously
monitors the temperature of the indoor coil during heating
operation. Anytime the coil temperate exceeds the TE8 limit, the
outdoor fan is switched off. If the coil temperature continues to
climb and exceeds the TE7 limit, the compressor is switched off.
When the coil temperature drops below the TE9 limit, the
compressor and outdoor fan are switched back on as shown
below:
Compressor on
T temp. down
Compressor on
Fan on
TE9 TE8
Fig. 22 – Indoor High Temperature Protection
Condenser Coil Temp.
Parameter
40MVQ 40MVQ
009--- 1
TE7 140 (60) 140 (60)
TE8 129 (54) 129 (54)
TE9
118 (48) 118 (48)

SEQUENCE OF OPERATION

Interface
A wireless remote control, supplied with the unit, is the interface
between the fan coil and the user. The wireless remote control has
the following characteristics:
S Capable of displaying _C and _F with _C being the default
setting. To change the default setting, refer to the Owner's
Manual or push the recessed F/C button once using a paper
clip or similar object*.
S The remote control setpoint range is from 62_F (17_C) to
88_F (30_C) in increments of 2_F (1_C).
S There is a dedicated cooling only and heat pump remote
control.
S The wireless remote control has an operating range of 25 ft.
(7.62 m).
S The same remote control can be used to control more than one
unit.
S If the remote control is lost, damaged, or the batteries are
exhausted, the system can be operated by using the manual
button (forced Auto) located under the front panel.
Fig. 23 – Manual Button Location on Unit
* On units produced during week 12 (2008) and later. Units
produced before week 12 have dedicated _C or _F controls.
21
Compressor off
Fan off
Fan off
T temp. up
TE7 T
A08120
˚F (˚C)
40MVQ 40MVQ
012--- 1 018--- 3 024--- 3
145 (63) 145 (63)
129 (54) 129 (54)
122 (50) 122 (50)
Manual button
A07364