High ambient AC Start

[CamLoch]

I have a client with a system shutdown on high head pressure when trying to start his AC system at 130 DegF ambient at the condenser and the evaporator. If the pressure switch is jumpered out, the system will run and drop to normal operation pressures after 20-30 seconds. Any recommendations for this start-up condition? Will a crankcase regulating valve prevent the suction pressure from causing high head pressure on discharge side?

 

[imok2]

The primary job of the CRO is to protect the compressor
motor against overloading due to high suction pressure, it is important to arrive at the correct pressure setting to offer this protection. The best way to see if the motor is overloaded is to check the current draw at start-up or after a defrost cycle. If an overloaded condition is evident, a suction gauge should be put on the compressor because the CRO setting may be too high and may have to be adjusted. For more information go here:

http://www.sporlanonline.com/SD-036.pdf

 

[dcasto]

use a time delay relay. Your experience says the unit can stand the short time.

 

[SAK9]

How about installing an unloader solinoid vale that sits on a 1/4" bypass line between suction and discharge line.This can be opened for 30 seconds(using a timer)during start up and will help relieve the pressure

 

[gxmplx]

First check the pressure reached at startup and the pressure switch setting.

If the high pressure is not normal but the switch is ok you may have a faulty/dirty expansion device.

Only if this fails I agree with the other suggestions.

 

[hollandhvac]

Maybe the refrigerant system has not been vacuumt properly and there is still air in the system. But this is just my 2 cents. I have simular experiance with high temperature and high pressure cut outs and we had to re-vacuum the system.

 

[gscrivener]

If everything else is working correctly and the system was installed correctly, a poperly sized CPR will fix your problem. This is precisely what a kind of situation a CPR is designed for. That being said, if the compressor is not "over-amping" than it is not in as much danger of being damaged and simply adjusting the pressure control or installing a bypass time delay around the control would be a less expensive alternative. (Note that bypassing the safety or increasing it past design pressure or relief pressure could cause other problems and code violations in some areas)