BMC Heat Pump GTA3600UD1AA ユーザーズマニュアル

Manual 2100-537

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1.  Caution owner to maintain clean air filters at all times.  

Also, not to needlessly close off supply and return air 

registers.  This reduces airflow through the system, 

which shortens equipment service life as well as 

increasing operating costs.

2.  Check all power fuses or circuit breakers to be sure that 

they are the correct rating.

If the refrigerant charge is removed from a scroll equipped 

unit by bleeding the high side only, it is sometimes possible 

for the scrolls to seal, preventing pressure equalization 

through the compressor.  This may leave low side shell and 

suction line tubing pressurized.  If the brazing torch is then 

applied to the low side while the low side shell and suction 

line contains pressure, the pressurized refrigerant and 

oil mixture could ignite when it escapes and contacts the 

brazing flame.  To prevent this occurrence, it is important 

to check both the high and low side with manifold gauges 

before unbrazing.

This unit is equipped with an ECM motor.  It is important 

that the blower motor plugs are not plugged in or unplugged 

while the power is on.  Failure to remove power prior to 

unplugging or plugging in the motor could result in motor 

failure.

Both the high and low side of the scroll compressor 

must be checked with manifold gauges before 

unbrazing system components.  Failure to do so 

could cause pressurized refrigerant and oil mixture 

to ignite if it escapes and contacts the brazing flame

causing property damage, bodily harm or death.

A nominal 24-volt direct current coil activates the internal 

compressor solenoid.  The input control circuit voltage must 

be 18 to 28 volts ac.  The coil power requirement is 20 VA.  

The external electrical connection is made with a molded 

plug assembly.  This plug contains a full wave rectifier to 

supply direct current to the unloader coil.

If it is suspected 

that the unloader is not working, the following methods may 

be used to verify operation.
 1.  Operate the system and measure compressor amperage.  

Cycle the compressor solenoid on and off at 10-second 

intervals.  The compressor amperage should go up or 

down at least 25 percent.

 2.  If step one does not give the expected results, shut unit 

off.  Apply 18 to 28 volts ac to the solenoid molded 

plug leads and listen for a click as the solenoid pulls 

in.  Remove power and listen for another click as the 

solenoid returns to its original position.

 3. If clicks can’t be heard, shut off power and remove the 

control circuit molded plug from the compressor and 

measure the solenoid coil resistance.  The resistance 

should be 32 to 60 ohms depending on compressor 

temperature.

 4. Next, check the molded plug.

: Apply control voltage to the plug wires 

(18 to 28 volts ac).  The measured dc voltage at the female 

connectors in the plug should be around 15 to 27 vdc.

: Measure the resistance from the end of 

one molded plug lead to either of the two female connectors 

in the plug.  One of the connectors should read close to zero 

ohms, while the other should read infinity.  Repeat with 

other wire.  The same female connector as before should 

read zero, while the other connector again reads infinity.  

Reverse polarity on the ohmmeter leads and repeat.  The 

female connector that read infinity previously should now 

read close to zero ohms. 
Replace plug if either of these test methods does not show 

the desired results.

Do not plug in or unplug blower motor 

connectors while the power is on.  Failure  

to do so may result in motor failure.