21
Indoor Coil Freeze Protection
The indoor coil can freeze due to any of the following:
SLow system charge
SReduced indoor airflow
SRestricted refrigerant flow
SLow ambient temperature (outdoor)
SLow 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:
Compressor and outdoor
fan off (after 5 mins)
Compressor and
outdorr fan on
EVAP temp. down EVAP temp. up
TE5 TE6 T
(Evap Temp.)
A08118
Fig. 20 – Indoor Coil Freeze Protection
Parameter
Coil Temperature ˚F(˚C)
40MVC(Q)
009 --- 1
40MVC(Q)
012 --- 1
40MVC(Q)
018 --- 3
40MVC(Q)
024 --- 3
TE5 39 (4) 41 (5) 36 (2) 36 (2)
TE6 50 (10) 54 (12) 54 (12) 54 (12)
Condenser High Temperature Protection
Condenser high temperature can occur due to any of the following
conditions:
SHigh outdoor ambient
SOutdoor fan blocked
SOutdoor 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:
Compressor on
Outdoor fan on
COND temp. down
TE11 TE10 T
COND temp. up
Compressor off
Outdoor fan on
A08119
Fig. 21 – Condenser High Temp Protection
Parameter
Condenser Temp.
˚F(˚C)
38MVQ018 --- 3 38MVQ024 --- 3
TE10 149 (63) 158 (70)
TE11 131 (55) 149 (65)
Indoor High Temperature Protection
High indoor coil temperature (in heating mode) can occur due to
any of the following:
SHigh outdoor ambient temperature
SIndoor fan blocked
SIndoor 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:
TE9 TE8 TE7 T
T temp. up
Compressor on
Fan on
T temp. down
Compressor off
Fan off
Compressor on
Fan off
A08120
Fig. 22 – Indoor High Temperature Protection
Parameter
Condenser Coil Temp.
˚F(˚C)
40MVQ
009 --- 1
40MVQ
012 --- 1
40MVQ
018 --- 3
40MVQ
024 --- 3
TE7 140 (60) 140 (60) 145 (63) 145 (63)
TE8 129 (54) 129 (54) 129 (54) 129 (54)
TE9 118 (48) 118 (48) 122 (50) 122 (50)
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:
SCapable of displaying _Cand_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*.
SThe remote control setpoint range is from 62_F(17_C) to
88_F(30_C) in increments of 2_F(1_C).
SThere is a dedicated cooling only and heat pump remote
control.
SThe wireless remote control has an operating range of 25 ft.
(7.62 m).
SThe same remote control can be used to control more than one
unit.
SIf 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.
Manual button
A07364
Fig. 23 – Manual Button Location on Unit
* On units produced during week 12 (2008) and later. Units
produced before week 12 have dedicated _Cor_F controls.
38/40MVC, MVQ