frosting compressor

[ozonecaire]

hi, im a new member to RE.

i just want to ask if anybody here knows the cause/s of a frosting hermetically sealed-type compressors in split-type units?

when the unit is running, frosting begins to accumulate in the topmost part of the compressor casing then to the evaporator. suction pressure reads 63psi and discharge pressure 290psi going down after 20mins of operation.

evaporator coil is clean, compressor brands are copeland and bristol. i have three units with those situations.

thanks, i'll appreciate any help from you guys!

[Peter_1]

Easy, SH too small.

[ozonecaire]

what's SH sir?

tnx

[Peter_1]

SH = superheat.
Propably overcharged but you can only be sure if you measure the correct SH.
Try to convert your pressures to SI, IP is very ghard to read. (Use Uconeer for free, downloadable on the website of Katmar software)
What refrigerant?

[ozonecaire]

the refrigerant is R22 sir.

what's the normal superheat and how can it be achieved?

tnx.

[davej]

Hi ozonecaire
if your operating on r2 above 55psig you should not be getting frost at the compressor, that would sometimes happen below55 psig. having said that your head pressure seems a little low. what is the ambiant temperature over condenser? if the evap is clean is there good air flow over it?

[ozonecaire]

that's what confuses me coz normally that's the case above 55psi we should not experience frosting in the compressor. our recorded ambient is 35deg cent.

evaporator coils are clean and there is agood airflow.

what really disturbs me is the frost direction, it normally starts from the evaporator to the suction but in our case the frost starts at the compressor housing.

[Peter_1]

http://www.glacierbay.com/Superheat.asp
http://www.longviewweb.com/r22a.htm
And..in IP units :p

[davej]

Could be as peter says , overcharged, maybe you should reclaim refrigerant and re-charge the system, by the way is it on cappilary or expansion valve

[pabs_ref]

hi, im a new member to RE.

i just want to ask if anybody here knows the cause/s of a frosting hermetically sealed-type compressors in split-type units?

when the unit is running, frosting begins to accumulate in the topmost part of the compressor casing then to the evaporator. suction pressure reads 63psi and discharge pressure 290psi going down after 20mins of operation.

evaporator coil is clean, compressor brands are copeland and bristol. i have three units with those situations.

thanks, i'll appreciate any help from you guys!

i have the same experience with locally manufactured
split type r22 aircon units....
it could be an overcharged system due to partial
restriction in the flow control (capillary system) or
filter drier if you have long liquid and suction lines.
Recover, then a good flushing of the evaporator and
condenser coils with nitrogen and cleaning agent
will do and best is to replace the caps and filter
drier...

[greenm&m]

Yes I would like to know does it have long lines? How long are you letting it run? Are you just letting it run for 5 to 10 minutes? Is this on a roof top or on the ground?

[kannanlog]

Hi to all,

Im too facing this problem in 6ton Ductable unit.What the solution for the problem. Can any one explain? We tried a lot,But no good result

[ozonecaire]

sir the expansion device is a capillary tube.

what difference would it make if its a capillary or txv?

tnx

[Peter_1]

A TXV has a sensing bulb which controls something.

[coolflow]

how is the unit installed is it back to back or 5m of pipe?and wot about the size of the unit to the room size, is it matched up ok but as peter has said iwould agree its liquid getting back to comp.:confused:

[Actinide]

Hi ozonecaire

Did you charge the unit, if so have you only charged the correct amount? Does the system have a suction line acummulator?

When you start the unit at what stage does the frosting appear, as soon as it starts, or after a while?

May possibly be over charged... Are you getting a frost anywhere on your evaporator? or just a sweat?

[TSK]

Rember the pressure is slightly higher in the evaporator than at the entry to the compressor (gas flowing from evap to comp) if the pressure is just about the point of freezing water (pres temp relationship then you will see the frost first at the comp end of the pipe, sounds like the evap is a bit marginal or the airflow is.

[Peter_1]

Ozonecaire, is your problem solved now?
Do you know why I mentioned the bulb of a TXV and what its purpose is?

[ozonecaire]

tnx guys for your views.

sir peter, the problem is not yet solved coz im still on leave vacation im gonna be back 2 days from now, y did u mention the bulb of the txv sir?

additional information for you guys, the units i've mentioned are still original installations, they have never been repaired that's why its not gonna be possibly overcharged coz we haven't added any refrigerant yet.

they are all capillary tubes, piston-type compressors, no liquid line accumulators installed. evaporator & condenser coils are all clean.

[TSK]

You have mentioned the ambient temperature at 35C, could you then take the evaporator inlet and outlet temperatures and post these in the forum so all can see whats going on.

[frank]

additional information for you guys, the units i've mentioned are still original installations, they have never been repaired that's why its not gonna be possibly overcharged coz we haven't added any refrigerant yet.

A very scary statement.
The original installer could have over-charged from day one.

[momo]

Had similar symptons/problem with "White-Westinghouse" 2+1 multisplit R22 unit, after about 4 years use: complaint was not cooling as before...the single compressor unit with a 5m+ horizontal & 1.5m vertical drop - after some checks etc gave readings of Head pressure 17bar Suction 3.5bar (0C.) with a measured suction line T of 7C. Air T out of indoor unit 12C after 15 minutes: OK !
Conclusion: leave working as is -with frost- owner was unlikely to pay for new gas, capillary change etc especially lost patience of trying to braze on a windy roof !

[setrad7791]

you should check your reversing valve ie heat pump models! you may find it is leaking refrigerant back to the compressor!

[mohamed khamis]

tnx guys for your views.

sir peter, the problem is not yet solved coz im still on leave vacation im gonna be back 2 days from now, y did u mention the bulb of the txv sir?

additional information for you guys, the units i've mentioned are still original installations, they have never been repaired that's why its not gonna be possibly overcharged coz we haven't added any refrigerant yet.

they are all capillary tubes, piston-type compressors, no liquid line accumulators installed. evaporator & condenser coils are all clean.

Hi ozonecaire

I suggest u check the air filter of the condenser ...may it is some blockage inside....Or check the location of the outdoor unit is subject to sunny location or something halt the discharge hot air from the condenser to be freely off and be diverted again to the condenser. In addition the condenser fan is properly working without any breaking in its speed. ALL that account to ur system condenser suffers from a high condensing pressure and in turn, the capillary tube overfeed the evaporator as a result of the difference between the condnesing and evaporator pressures, thus the compressor has a flood back liquid and got frosty.

best regards

[BigJon3475]

Amperage draw on the compressor's? Should be really high if overcharged as opposed to what it should be. What Bristol compressor and what Copeland compressor model numbers?

You can go to http://www.bristolcompressors.com/ homepage and find the operating conditions for your particular compressor here is an example this is one I had to replace 3 days ago (clip on Bristol Recip's on the menu):

http://www.bristolcompressors.com/prftablecals.aspx?ModelNo=H23B243ABC&CylRunning=2&Frequency=60&Standard=E


You can go to Copeland @ https://www.emersonclimatecontractor.com/webapp/wcs/stores/servlet/ctp/cs/ToolsProviderIndex_cs.jsp?RedirectURL=WelcomeIndex_CS.jsp but you have to sign up and it may take up to 24 hours to get logged into to be able to down load the compressor calculator.



My compressor was running but it was drawing really low amperage for operating conditions and it had the appearance of being overcharged. It was a bad compressor with leaking valves and a low compression ratio.

[ernestlin]

when the unit is running, frosting begins to accumulate in the topmost part of the compressor casing then to the evaporator. suction pressure reads 63psi and discharge pressure 290psi going down after 20mins of operation.

evaporator coil is clean, compressor brands are copeland and bristol. i have three units with those situations.

Hi, ozonecaire, from your reading data, I calculate ur unit worked at approx. 2.0 C degree (if the SH is zero) evaporating temp. and 54.0 C degree condensing temp., if there isn't a overcharge or liquid flooding in ur system, it sounds good and should never take frosting. Possibly, the evaporator is not big enough or the unit is overdesigned. And, u'd better install an accumulator to separate the liquid from return gas in the future.