How to pump down a R404a coldroom system

[cool runner]

hi there, i have only experience in air con systems, splits,v.r.v. /v.r.f, etc, is pumping down a R404a coldroom system into the liquid reciever a different proceedure, could you please give me a step by step please?

[Brian_UK]

Hi Cool Runner and welcome to the forum.

It depends on how far you need to pump down the system.

Have your guages fitted to the compressor suction and discharge and the system running.

1. To pump down just the evaporator section - remove power from the liquid line solenoid valve.

Override the low pressure switch and monitor the suction pressure.

When the pressure falls to 0bar/psi close the compressor suction valve and turn the compressor off.

Be aware that the pressure in the pumped down section may rise either due to a leaking liquid line valve of residual refrigerant in the evaporator. You may need to bump the compressor to drop the pressure again.

2. To pump down from the receiver - proceed as before but close the receiver outlet valve instead of de-powering the liquid line valve.

When you have completed whatever works are needed - replace any driers, pressure test, evacuate and prepare to restart the system. Open the receiver outlet valve, open the compressor suction valve, remove any links in the low pressure switch and restart. The solenoid should open, the pressure will rise in the evaporator and the LP switch will make enabling the compressor.

3. Just thought - if you have to work on the compressor then after getting down to 0bar/psi and shutting off then close the compressor discharge valve as well.

Hope this helps.