Hot gas bypass on Airedale

[Kirky]

Hi all hope everyone is well

Got a problem with a Airedale chiller working as part of a close control system for a lab. The problem is with the hot gas bypass solenoid valve. Got called out to the unit yesterday. System had no charge. Found that the solenoid valve on the hot gas bypass had ruptured. What's funny is that the valve was a simple liquid line solenoid valve installed on a hot gas bypass. I always thought that a standard liquid line solenoid valve was no good for HGP. Anyway contacted Airedale who specified a replacement which I've got and fitted. Recharged the unit and system ran however the solenoid valve is very noisey almost like a hammer sort of sound. I've had to extend the bypass pipe as the new valve was too heavy to suspend on 1/4 inch pipe so extending to base of the unit. The hammer sound would make me think that the coil isn't powerful enough for the job. Although I have worked with solenoid valves in the past and know how they operate haven't studied HGP in any great detail. Can anyone explain why this hammer noise is happening as I've spoken to Airedale who assure me I've got the right valve

[NoNickName]

It's because the pressure changes as the valve opens, and when it opens, the pressure rises, and the valve closes. So basicly it just opens and closes on its own feedback, and ultimately this could have been the cause of the failure.
I would put the blame on the pressure switch that controls the HGB valve and would try to enlarge the differential or lower the setpoint. I'm with you that the coil seems to be insufficient for the job, as there should be no need for a HGB in a constant-load application.

[Kirky]

Makes sense I will try and lower the setpoint also trying to trace a more powerful coil the existing coil was a 14watt the new one is a 11.5 so definitely think it's not up to the job cheers

[simon@parker]

just seen this how exactly did the valve rupture ? is the hot gas being used to maintain suction pressure ? as in to stop evap freezing or keep compressor loaded ? if your using standard sol valve with diaphram they not very good on dischage as it wears them very quickly and then they dont seal had that alot steel diaphram valves are much better got any pics so can have a look lol

[NoNickName]

Makes sense I will try and lower the setpoint also trying to trace a more powerful coil the existing coil was a 14watt the new one is a 11.5 so definitely think it's not up to the job cheers

Actually I was thinking about the evaporating coil, not the solenoid coil.

[Kirky]

Hi guys

The customer tells me the unit has ran fine for a number of years with no changes to heat loads so dont think the evap is undersized. The hot gas is used to keep the comp loaded and the valve had ruptured on the stem of the valve splitting it almost right round the middle, defo not up to the job and sorry no pics. I have replaced the valve with that specified by the manufacturer (Airedale) and the unit is running fine. The only problem I do have is that the new valve makes a load buzzer sound when the coil energises. I have come accross this once before and ended up changing the coil for a more powerful one which sorted the problem out. However at the mo im struggling to source a more powerful coil for this valve. I have worked with solenoid valves before many times changing them out when the fail and replacing burnt out coils etc. As a rule I have always replaced like for like. My question is if the power supply is the same and it fits and secures onto the valve stem can any coil be used you dont have to stick with the one supplied with the valve ????