problem with sump oil bubbling

[seascot]

Dear all,

Anybody have any ideas to why the oil is bubbling in the sump sight glass for a reciprocating compressor in an air conditioning sytem, the system is not operating as normal, can this be the reason?

Thanks

[NoNickName]

What do you mean by "not normal"?
What refrigerant and what superheating are there?

[US Iceman]

Anybody have any ideas to why the oil is bubbling in the sump sight glass for a reciprocating compressor in an air conditioning sytem...

If the system has been shut down for some time, the crankcase may have some refrigerant in it. The bubbling may be caused by the crankcase heater warming the refrigerant.

You did not provide a lot of information, so this is just a guess at this time. I have seen this before though. If the compressor was started, the oil would turn into a foamy texture in the sight glass.

[old gas bottle]

just wondering aboutthis guys, its bloody freezing in scotland at present,is it running at all or is it on heat?

[guapo]

Check exp.valve if it is working properly, you might have liquid carry over to compressor. Check suction temp/ superheat.

eric

[Abe]

Dear all,

Anybody have any ideas to why the oil is bubbling in the sump sight glass for a reciprocating compressor in an air conditioning sytem, the system is not operating as normal, can this be the reason?

Thanks

Change one phase on compressor.
That will solve it.

[NoNickName]

Change one phase on compressor.
That will solve it.

Ooh. This is interesting. :confused: Can you please substantiate?

[frank]

Change one phase on compressor.
That will solve it.
Hi Abe

On a recip the direction of the motor, assuming it is 3 phase, will not make any difference. The pistons still go up and down and compress the gas.

If the oil bubbles it is a sign that liquid refrigerant is "boiling off" out of the oil. It may be that the comp has been off for some time and liquid has been absorped into the oil or it could be that liquid is entering the crankcase during current operating conditions. :)

[Renato RR]

Frank and USiceman have corect answer.

Renato

[chiller563]

Did you put gauges on the unit. I have had instances where the oil foams if the unit runs into a vaccum. These days manufacturers, in the USA anyway, aren't supplying units with pressure controls much anymore. If you have a bad valve or clogged capillary this may be causing the problem. You need to supply more information for an accurate solution.

Chill

[Abe]

Ooh. This is interesting. :confused: Can you please substantiate?


Did you try what I suggested??
On recip, changing phases will make oil pump rotate different dircection

[NoNickName]

Did you try what I suggested??
On recip, changing phases will make oil pump rotate different dircection

Why should I? I'm not the initiator of this thread.
I know what you're talking about, been there, done that, but I don't see the relationship between the oil pump rotation and the bubbling in the sight glass.

[Abe]

Why should I? I'm not the initiator of this thread.
I know what you're talking about, been there, done that, but I don't see the relationship between the oil pump rotation and the bubbling in the sight glass.

I assumed you were the initiator, i checked, you werent, apologies

Read the question, Whos talking about "sight glass" ??

I retort in your manner.......

[phil68]

I assumed you were the initiator, i checked, you werent, apologies

Read the question, Whos talking about "sight glass" ??

I retort in your manner.......
Isn't this thread about oil bubbling observed in the crankcase oil sight glass of a compressor:confused:
It's usually a sign that the crankcase heater is doing it's job of boiling the refrigerant out of the oil when the compressor is off.
If it happens when the compressor is running this is usually normal also, as the oil is moved around by turbulence within the compressor crankcase & also any refrigerant still entrained in the oil boils out.
Need to know more details; is it when the compressor is running & what are the symptoms of the unit not functioning correctly?

[NoNickName]

Abe, the poster asked why the oil is bubbling in the sight glass. Where else could he be looking at the bubbles?
Now, I retaliate: if the oil is bubbling in the sight glass, how this could possibly be related to the oil pump direction?

[Abe]

No Nick Name

With due respect, the poster said.

Sump Sight Glass.

Hope that clears the misunderstanding

:)

[NoNickName]

Well, english is not my mother tongue, but for me sump sight glass and oil sight glass are synonims. Aren't they? Either way, how could rotation be possibly related to the oil bubbles? I'm just curious, no polemic intent.

[mccoolair@yahoo]

Heatcraft in their Tech Topics, mention oil will appear foamy if it is mixing with liquid refrig in the crankcase, of course; or if there is too much oil there will be a tubulence created by mixing with the moving parts of the compressor, and will foam up the sightglass.

[US Iceman]

...or if there is too much oil there will be a turbulence created by mixing with the moving parts of the compressor, and will foam up the sightglass

I would think the oil level in the compressor would have to be above the top of the sump site glass for this to happen.

[NoNickName]

Yes, coolair, most of the time a low SH will cause liquid refrigerant in the oil, that will result in foam

[Davidmac]

Hello i'm a fellow scot and was thinking about you're problem,sounds to me like theres definetely liquid flowing back to the compressor,is the system overcharged?is the suction pipe frosting back?,what superheat is there,it may be an idea to reclaim the gas and use scales to re-charge the system,most a/c's come pre-charged to 30 metres so if the label says eg 3.7 kg's of gas and the piperun is under 30 mtrs then just weigh in that amount,you're pressures should give you a good indication as well,is the evap fan working or the filter blocked?good luck.

[Alex Harvey]

Frank is correct. The oil is foaming due to liquid refrigerant in the sump. You need to consider how this liquid is flowing back to the compressor. If the superheat is not set correctly the refrigerant in the evporator is not evaporating completley and flowing through to the compressor. This can cause compressor burnout. Check your superheat, sizing of the expansion valve and expansion valve orfices. Also head pressure control the system could be 'over condensing' in the cold weather if there is no fan speed control on the condenser fan(s). Check the evaporator fans are operating correctly (blowing in the right direction) and the evaporator and filter is cleen. Poor airflow could cause the refrigerant not to evporate completly in the evporator allowing liquid to flow back to the compressor. Either way this problem should not be ignored as foaming oil will not lubricate correctly.