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Compressor Pressure Regulator (CPR) Adjustment
Procedures - MAX 50
I I m m p p o o r r t t a a n n t t : : All new unit installations require these adjustment procedures. Failure to do so may not allow the unit to
operate at its maximum capacity.
N N o o t t e e : : The following procedures are for initial settings. Sometimes conditions such as high or low ambient
temperatures may require that the settings be fine-tuned for optimum performance.
M M A A X X 5 5 0 0 units are equipped with a compressor pressure regulator (CPR) valve located in the accumulator module
mounted on the back of the evaporator (See illustration below). The valve is used to limit the load on the standby
compressor and limit suction pressure during heat mode. This also affects the current draw of the electric motor.
Monitor the current drawn of the electric motor when making this adjustment to verify it is below the overload relay
setting.
1. Install gauge manifold set to the suction service port at the electric standby compressor (See illustration below).
2. Attach additional compound gauge on suction service port located on copper suction tube in evaporator to monitor
suction pressure going to the CPR valve (See illustration below).
3. Connect clamp on amp meter to T1 motor wire on a 115V/230V 1 PH unit, or to the leg of the highest voltage motor
wire of a 230V 3 PH unit.
4. Connect standby power receptacle to an appropriate electric power source.
5. Place jumper wire between the 12 and CHB wires at the defrost termination switch to verify the unit will run in
defrost.
6. Start unit and run in defrost on the electric standby compressor until the pressure on the additional compound
gauge attached to the suction service port stabilizes at a pressure above 45 psig (310 kPa).
7. Check the suction pressure on the gauge attached to the suction service port at the standby compressor. It should
be 24 ± 2 psig (165 ± 14 kPa) without exceeding the following electric motor current draws:
VOLTAGE
OVERLOAD RELAY SETTING
115/1/60
14 Amps
208/1/60
9.5 Amps
230/1/60
9 Amps
208/3/60
7.2 Amps
230/3/60
7 Amps
8. If the pressure is not within range, or the current is above the specific values, remove the protective cap and adjust
the CPR valve to the correct setting.
9. Remove gauge manifold set, the additional compound gauge, and the jumper wire when finished with the
procedure.
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TK 56321-18-IM-EN
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