Hot gas bypass

[Kirky]

Hi all hope everyone is well. Just after a bit of advise about a hot gas solenoid valve making a noisey hammering sort of sound. I was called out to a airedale chiller working as part of a close control system . I was called out because chiller wasnt working. Found that the system had lost its gas due to a crack on the hotgas bypass pipework. I cutout the solenoid valve and repaired the leak. I then replaced the solenoid valve. The system now works fine except that the solenoid valve makes a loud hammering sound when the coil energises. I thought it may be the valve which was faulty so I replaced it again but it still makes the same sound. I then thought the solenoid valve was installed the wrong way round but direction wise the flow goes from the discharge to the suction which as far as i know is right. What am I missing is there any other factors governing the installation of the valve

[michaele]

Did you replace it with an OEM solenoid? Is the pressure rating correct?

[NoNickName]

Solenoid valves are not suitable for hot gas bypass(80-90°C). They are only suitable for low temperature liquid refrigerant (40-50°C).
Additionally, the membrane is subject to pulsation from the compressor, and that's the reason why the pipe broke in first instance.
It's just a matter of time before it breaks again. It's an inherently design fault from airedale.

[lana]

Hi there,

I have seen few systems with HGB with solenoid valve. They work OK but when SV opens then you hear gas flow and thus a noise. The same thing happens with HGB valve which regulates the hot gas flow. If you hear "fssssss" then it's gas flow.
Important thing about HGB is the thermal stress which breaks the joints. The "T" section where the HG is introduced into the suction is the weakest part. A special "T" joint must be used. Danfoss has it.
In one system I build the "T" joint by two pipes going into each other. Have a look at Danfoss HGB valve cat. the T joint is shown there.

Cheers