T.E.V Ball of ice.

[N.Lewis]

Hi guy's, doing routine service on a computer room A/C unit, opened door to compressor compartment and found the expansion valve covered in a ball of ice,:eek: does this just indicate a blockage or some other disaster, system is R22.

Thanks.:D

[powell]

Hi guy's, doing routine service on a computer room A/C unit, opened door to compressor compartment and found the expansion valve covered in a ball of ice,:eek: does this just indicate a blockage or some other disaster, system is R22.

Thanks.:D
Sounds like a restriction in the TEV. Knowing the systems pressures would help. Keep in mind the restriction could be ice buildup internally due to moisture being present in the system indicating a leak on the low side.

[N.Lewis]

Cheers powell, just going back to unit to investigate further, if a blockage would you recomend heating valve to clear??.

[N.Lewis]

Just incase anyones interested, guages were showing 32psi low side-175psi high side, heated t.e.v, pressures rose to 50-225psi, a better reading, but removed filters to check evap and found all capillary lines from t.e.v to evap are heavaly iced also:(.....
Any ideas welcome:o

[The MG Pony]

let them defrost, let it run for an hour then do a superheat reading.

If it seems off and it freezes, could be low on charge, double check by sub-cooling as well.

If both are good yet it freezes up again check your filter delta, if it clears then even though the filter may not be blocked you indeed may have moisture in the system, or plugged TXV inlet screen.

If thats the case you need to pull the charge so might as well ensure the TXV is free, replace the F/D and pull a 500 micron vac.

A fast way to check for TXV opperation is take the phile off and hold it and see if the TXV floods the evap, if it does then we can be assured it is opening and closing.

[nike123]

Be sure that you have clean evaporator and air quantity is OK!

[Daikin=Overated]

Hey N.Lewis.

What were the outdoor tempretures when you observed this fault condition?

I had a similar fault on a ducted package system last year, and in my case it turned out to be low on gas.

What type of system are you working on....close circuit, package, or is the condensor fan assy on the roof and the evap/compressor located internally?

The readings you gave, were obviously low for R22 (depending on the outdoor temps). The other factor to consider other than the expansion valve (as already mentioned by others) being the compressors-suction side.

Fans running ok on the evaporator/coil ok? Check external condensor fans & confirm all is well!

Any filter driers on the system?

Ideally you need to reclaim the gas to work on the TEV. If you weigh it out, you can calculate the charge if it's low or whatever..............kill two birds with one stone!

J.

[majo]

Is it possible that this one is a regular domestic a/c unit? Ice building up on the coils and tev is a frequent problem of standard units placed in serverrooms. The units qualified for this have higher fan speeds and, so does daikin say, have other room sensors due to the low humidity. They also need some sort of head pressure control/condensor fan speed regulation to maintain a high pressure when cooling in winter. Once we I had an intervention like this on another company's a/c unit that was also freezing up. The guys from Daikin sent us a PCB that had to be placed at the inside unit to compensate the readings of the probes inside. No problems here after...

[taz24]

TEV's do freeze up somtimes.
Think how they work they restrict the refrigerant flow. The exit of the TEV is colder than the air temp around it.

Is the system running ok?
Is the system displaying any signs of a problem?

If not just remove the ice and put some armaflex over the valve to insulate it.

Cheers taz.

[N.Lewis]

Thank you guy's for all your inputs, as i stated, last night i heated exp valve and got a whoosh of ref flowing through, blockage yes!!, this morning checked unit, all ice has cleared and unit running v.nicely:). Will monitor unit and if it happens again will keep you posted.

Thanks..:D

[paul_h]

Sounds like moisture in the system. Before the whole system breaks down due to acid etc, I'd reclaim, change drier, evacuate and recharge.

[taz24]

Sounds like moisture in the system. Before the whole system breaks down due to acid etc, I'd reclaim, change drier, evacuate and recharge.


It does indeed.
I agree with Paul.
But I would just change the dryer for now.
Does the sight glass have a moisture indicator on it.
R22 is a very forgiving refrigerant and if you change the dryer fit a sight glss with a moisture indicator on it. Then let it run for a month or so and change the dryer again. It should recover.

The one thing you need to find out though is how did the moisture get in.

In my opinion we are the worst culprets for allowing moisture in:D.

Has there been a leak?
Has sombody done some work to it recently in the past?

All the best.
Cheers taz.

[paul_h]

Oh yeah, I forgot about r22 over there. Can you still get it easily and cheaply?
If not, just change the drier. (edit: leaktest though as well)
R22 is so cheap and common over here it's not worth any effort to try and keep the refrigerant already in the system
It's better to reclaim, pressure test with nitrogen, then get a good evac on the system when you suspect moisture, which means reclaim and recharge.
If it's a pump down system and flare TX, then leak is probably on the TX if the cut out LP is set below 0 kpa ;)

[philjd26]

hi
head pressure seems sufficient but would like subcooled temp, however might wanna check the return temparture and set point and see if all ok, there maybe very little r/h there and sometimes it struggles to get down to temp due to load from equipment, which in turn causes constant operation.remember tev is trying to maintain superheat.....r/h i.e latent heat can bring up the back pressure by increasing load...

rgrds phil