HVAC- compressor pressure drop problem

[nesamani_27]

Dear all, We are operating Packaged HVAC system of 60 Tons.
We are facing the problem of compressor suction falling suddenly & compressor trips due to low suction pressure. We suspect that the NRV in the outlet of Air cooled condenser is the cause.

Refer the attached SLD. If we start the compressor A, then condenser-A will start automatically. the NRV (Red) in the outlet of the condensor-B passes the gas sometimes, so the R-22 gas enter the standby condensor-B, causing the Pr. drop in the system.

Kindly help us to get rid off this problem.

[install monkey]

as a temporary measure can u not shorten the delay for starting system 2 so the pressures equalise and keeps operation, ideally you dont want both systems starting at the same time as the startup current may cause problems, ideally a 10 second delay or if its controlled via a stat then trim the differential so it starts sooner. gives u time to source a new nrv

[monkey spanners]

Does it run ok with system B running only?

If the NRV is letting by then it wants replacing or rebuilding anyway.

Driers want replacing too while you have the system apart.

[install monkey]

good idea john , swap the sequence over to start system b first then system a as the 2nd stage!- can give u any points as i need to share them!!

[chemi-cool]

I don't think its the NRV, the condenser can not hold the charge for 60 tons, I would suspect the TXV, might lost charge and closed, a burnt coil on SV?

[install monkey]

to prove the nrv is passing have you had a gauge on circuit b whilst circuit a starts to prove the pressure is rising

[D.D.KORANNE]

It is the low side system problem ; check if the suction service valve on the compressor is partially closed......... The time lag to shut down is too short hence this guess