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Compressor Pressure Regulator (CPR) Adjustment
Procedures - MAX 30
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 3 3 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). It is used to limit the suction pressure during heat.
1. Install a gauge manifold set on the suction service port located on the upper suction tube in the evaporator to
monitor suction pressure going to the CPR valve (See illustration below).
2. Attach an additional compound gauge to the accumulator suction service port to monitor suction pressure after the
CPR valve (See illustration below).
3. Place a jumper wire between the 12 and CHB wires at the defrost termination switch to verify the unit will run in
defrost.
4. Start the unit and run it in defrost on the roadside compressor until the pressure on the gauge manifold set attached
to the suction service port in the evaporator stabilizes at a pressure above 45 psig (310 kPa).
5. Check the suction pressure on the compound gauge at the accumulator suction service port. It should be 24 ± 2 psig
(165 ± 14 kPa). If the setting is incorrect, remove the protective cap and adjust the compressor pressure regulator
valve to the correct setting.
6. Remove the gauge manifold set and the additional compound gauge when finished with the test.
TK 56321-18-IM-EN
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