Iced up TEV

[kfjoe]

Have got an issue with a number of TEVs being very badly iced up and unit going out on LP. At first thought it maybe moisture as warming up TEV and removing ice build up put the system back to normal running. But after system vac , gas, drier and oil change the problem returns. I am thinking it may be charge migration as these are mop valves.
My question is why and how to stop it? This only seems to happen on a few units of many.

Any advice would be greatly appreciated

Thanks

[monkey spanners]

Seems like charge migration is a problem that mop valves can suffer from,

http://www.danfoss.com/NR/rdonlyres/CA5E4257-4F6B-4F41-A268-8CB4FE6874DD/0/PFA00A102.pdf

Are the systems running with low head pressure and cool liquid lines? Would think the relatively warm liquid entering the valve would be the main way that the valve is warmer than the bulb to prevent charge migration.

Don't use mop valve so not got any practical advice...

[Rob White]

.

Are the valve bodies actually freezing over?

If the bulb is encased in ice this can effect the workings
so it is a good idea to insulate the bulb onto the suction.

Rob

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[chemi-cool]

If they are fed from one liquid line, check the drier, could be parcialy blocked.

[kfjoe]

Thxs for the replies guys

Yes the valve body and power head are encased in ice
The bulb is insulated

[mikeref]

Pull the orifice and check for debris or discolouration.