Heatcraft H-IM-QRC, Installation And Operation Manual, Page: 6 / 40

6
Box Temperature Control Settings
•
There is an on board room thermostat on the Heatcraft
Quick Response Controller board which can be adjusted
to the desired room temperature. The temperature
differential is 2°F.
Temperature Differential
When a system is in the cooling mode and the box
setpoint is 35°F, the system will continue to cool until
the box temperature gets to 34°F. At this point, the
compressor will pumpdown and shut off. The system
will restart cooling when the box temperature has risen
to 36°F.
It is important to note that Heatcraft Quick Response
Controller has a minimum 2 minute “
ON ” time and a
minimum 4 minute “ OFF ” time. This means that the
system will run in the cooling mode a minimum of 2
minutes even if the setpoint temperature is met. In
applications where the system is grossly oversized,
the box temperature could go below the differential
temperature before the system cycles off.
In the “OFF” cycle the system will be off for a minimum
of 4 minutes even if the box temperature goes above the
differential temperature, before cooling will be restarted.
• The on board room thermostat is factory set at 35°F
for Air Defrost systems and -10°F for electric defrost
system.
Box Temp Control Settings
Leak Testing
After all lines are connected, the entire system must be leak
tested. The complete system should be pressurized to not more
than 150 psig with refrigerant and dry nitrogen. The use of an
electronic type leak detector is highly recommended because
of its greater sensitivity to small leaks. As a further check, it is
recommended that this pressure be held for a minimum of 12
hours and then rechecked. For a satisfactory installation, the
system must be leak tight.
Recommended Low Pressure Control Settings for Outdoor Air Cooled Condensing Units
*Minimum Temp.
˚F
R-404A/R-407A/R-448A R-407C
Cut-In PSI Cut-Out PSI Cut-In PSI Cut-Out PSI
50 90 35 70 40
40 70 35 55 25
30 55 35 40 20
10 45 25 30 10
0 25 7 15 0
-10 20 2 15 0
-20 12 1 10 0
-30 8 0 6 0
* Minimum ambient or box temperature anticipated
* The standard preset low pressure switch used for pumpdown is set for 15 PSI cut in / 4 PSI cut out and is a good setting for most pumpdown systems