15
Balance point adjustment
The balance point is the lowest outdoor temperature at which
the heat pump can heat the space without the use of the
supplementary electric heaters.
The balance point depends on the following:
1) Design outdoor temperature.
2) Building's heat loss.
3) Pump's capacity.
The balance point is usually predetermined by the instal-
lation's project, but if it has not been predetermined the
factory's adjustment at 6°C can be kept.
Logic module
The control module responds to the thermostat's demand
signal, it examines the values given by the sensors outdoor,
discharge and liquid and determines if the heat pump and/or
the supplementary electric heater must operate.
Discharge sensor
It is a thermistor located in the discharge line of the
compressor, connected in series with a high pressure cutout.
It protects the compressor against high discharge tempe-
ratures (and pressures).
It stops the compressor when the discharge temperature
exceeds the set point or the pressure is greater than
28 kg/cm
2
.
It protects the compressor when there is a refrigerant leak or
a flow reduction through outdoor or indoor coils.
It allows the reset of the compressor circuit after a lockout
condition, by removing the power supply to the control
module, or pressing the reset button.
Outdoor sensor
This is a thermistor located in the air intake of the outdoor coil,
that registers the air temperature.
It controls the heat pump operation, stopping it when the
outdoor temperature nears -15 °C. This prevents the
compressor from operating at a high compression ratio that
could damage it.
Allows the connection of the duct electric heater (optional)
controlled by the 2nd stage of the room thermostat if the
outdoor temperature is less than -15 °C.
It allows by means of the balance point for the adjustment of
the temperature at which the supplementary electric heater
should come into operation.
Utilization limits
Liquid sensor
It is connected in the liquid line of the outdoor coil.
This sensor starts the defrost cycle after 30, 60 or 90 minutes
from start or last defrost cycle depending on selection, if the
temperature it senses is -5 °C or less.
Indicates the end of the defrost cycle when the liquid
temperature reaches 13 °C or stays at a minimum of 7 °C
during 1 minutes.
Prevents the cycle from starting in mild climates since
sufficiently low liquid temperatures are not detected.
The initial time reading for defrosting of 30, 60 or 90 minutes
is nominal. These times assume an exterior temperature of
2°C, a highly unfavourable level causing much frost
formation.
At lower temperatures the total humidity content of the ambi-
ent air is lower, permitting prolongation of the defrost cycles,
saving energy. For example: at -10°C exterior temperature
the initial time readings for defrost will be 60, 90 and 120
minutes.
Balance point
Prevents the operation of the supplementary heating system
when the outdoor temperature is above the balance point as
adjusted on the plaque.
This way the electric heater is not used as long ads the heat
pump is capable of meeting the space heating demand.
The balance point can be adjusted between 14 °C and -4 °C.
This way an additional outdoor thermostat is not needed.
Timer
Delays start during 5 or 2 minutes to avoid repeated starting
cycles. This way operating pressures are equalized before
the compressor is started. If the thermostat or manipulation
cause false contacts the heat pump is not affected.
It delays the start after a power supply cut, thus allowing the
line voltage to regain its normal level.
Stoppage of interior fan during defrost
This module allows the option of stopping the interior fan
during the defrost cycles. This option is only for when it is not
possible to instal an auxiliary electric heater.
- With the JP-19 bridge in position (factory standard) the
interior fan continues to function during defrosting.
- With the JP-19 bridge open (modified at jobsite) the interior
fan is deactivated.
Minimum
Maximum
Minimum
Maximum
Cool
Heat
Cool
Heat
Cool WB
Heat DB
Cool WB
Heat DB
198
254
342
436
19
-20
(1)
46
24
15
10
(2)
23
27
Indoor coil inlet air
temperature
Voltage limits
Outdoor coil inlet air
temperature DB
Operating cycle
Operating cycle
Nom. 400 V
Nom. 230 V
Minimum °C
Maximum °C
Maximum °C
Minimum °C
Notes: WB - Wet bulb. DB - Dry bulb.
(1) At an outdoor temperature of -20 °C only the emergency electric heater (optional) continues to operate.
(2) The equipment can work for a short period at a temperature of less than 10°C in order to raise the air temperature in the conditioned space to
10 °C.
