TK 56321-18-IM-EN
37
Suction Pressure Regulator (SPR) Adjustment
Procedures - MAX 20
IImmppoorrttaanntt:: Using the absence of bubbles in the sight glass as an indicator of correct refrigerant charge can be
misleading, YYOOUU MMUUSSTT refrigerate the box to 0-5ºC to get a more precise indication from the sight glass.
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IImmppoorrttaanntt:: All new unit installations require these adjustment procedures. Failure to do so may not allow the unit to
operate at its maximum capacity.
NNoottee:: 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.
MMAAXX 2200 units are equipped with a SPR valve located in the evaporator (See illustration below). The valve is used to
limit the load on the standby compressor. This also affects the current draw of the electric motor. Monitor the current
drawn of the electric motor when making this adjustment to ensure it is below the motor overload relay setting.
MMAAXX units are equipped with a SPR valve located in the evaporator (See illustration below). The valve is used to limit
the load on the compressor. This also affects the current draw of the electric motor.
1. Install gauge manifold set onto the suction service port at the standby compressor (See illustration below).
2. Install gauge manifold set onto the suction service port at the compressor (See illustration below).
3. Attach an additional compound gauge on suction service port located on copper suction tube in evaporator to
monitor suction pressure going to the SPR valve (See illustration below).
4. Connect clamp on amp meter to T1 (Black) 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.
5. Connect standby power receptacle to an appropriate electric power source.
6. Place jumper wire between the 12 and CHB wires at the defrost termination switch to verify the unit will run in
defrost.
7. 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).
8. Start unit and run in defrost on the electric compressor until the pressure on the additional compound gauge
attached to the suction service port stabilizes at a pressure above 45 psig (310 kPa).
9. 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
10. Check the suction pressure on the gauge attached to the service port at the electric compressor. It should be not
higher than 40 +-2psig ( 275kPa +-14kPa).
NNoottee:: If the customer is expecting to use the heating function of the unit, the optimal setting would be 26+-2psig
(180kPa+-14kPa).
11. If the pressure is not within range, or the current is above the specific values, remove the protective cap and adjust
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