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8.4 TEST MODE
The test mode is initiated by shorting the TEST pins. In this mode of operation, the
enable temperature is ignored and all timers are sped up by a factor of 240. To initi-
ate a manual defrost, short the TEST pins. Remove the short when the system
switches to defrost mode. The defrost will terminate on time (14 minutes) or when
the termination temperature has been achieved. Short TEST pins again to termi-
nate the defrost immediately.
8.5 DEMAND DEFROST OPERATION
It is important that such systems be off for a minimum of 5 minutes before restarting
to allow equalization of pressures. The thermostat should not be moved to cycle
unit without waiting five minutes. To do so may cause the compressor to stop on an
automatic opening overload device or blow a fuse. Poor electrical service can cause
nuisance tripping on overloads or blow fuses. For PSC type operation, the refriger-
ant metering must be done with cap tubes, flow check, or bleed type expansion
valve because of low starting torque.
IMPORTANT: The compressor has an internal overload protector. Under some
conditions, it can take up to 2 hours for this overload to reset. Make sure overload
has had time to reset before condemning the compressor.
8.6 TROUBLE SHOOTING DEMAND DEFROST
Set the indoor thermostat select switch to heat and thermostat lever to a call for
heat.
Jumper the "test pins" to put the unit into defrost. If the unit goes into defrost and
comes back out of defrost, the indication is that the control is working properly.
If the unit did not go into defrost using the test pins, check to ensure that 24V is
being supplied to the control board. If 24V is present then replace the control.
9.0 EVACUATION PROCEDURE
The life and efficiency of the equipment is dependent upon the thoroughness exer-
cised by the technician when evacuating air and moisture from the system.
Air in the system causes high condensing temperatures and pressure, resulting in
increased power input and non-verifiable performance.
Moisture chemically reacts with the refrigerant and oil to form corrosive hydrofluoric
and hydrochloric acids. These attack motor windings and parts, causing breakdown.
After the system has been leak checked and proven sealed, connect the vacuum
pump and evacuate system to 500 microns. The vacuum pump must be connected
to both the high and low sides of the system through adequate connections. Use
the largest size connections available since restrictive service connections may lead
to false readings because of pressure drop through the fittings.
IMPORTANT: Compressors (especially scroll type) should never be used to evacu-
ate the heat pump system because internal electrical arcing may result in a dam-
aged or failed compressor.
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Troubleshooting
