Never Mind What Oil, How much is the Question?

[Grizzly]

I can't speak for other areas of Refrigeration.
But certainly within the Chiller and Industrial Applications. I am coming across more and more Compressors that have been overfilled with oil.
Or is it just me?
A awfully lot of people seem to think that a full sight Glass is a good thing. With scant regard to the consequences.
There has been a lot of helpful information on the forum lately about Lubricants. So I thought I would just add for the few that may not know.
Overfilling can cause
Hydraulic locking leading to catastrophic mechanical failure.
Can cause serious quantities of oil being carried over into the system. Basically the Compressor becomes an oil pump (on recips anyway)
Increased internal oil pressures cause seal and bearing wear.
To name just a few problems.
Hopefully the guys can add some more?
If anyone is in doubt fill to 1/2 a sight glass, or in the case of dual sight-glasses 1/2 top glass maximum when Running and 3/4 glass when standing. No more and some manufacturers recommend even lower levels.
Grizzly

[frank]

If anyone is in doubt fill to 1/2 a sight glass, or in the case of dual sight-glasses 1/2 top glass maximum when Running and 3/4 glass when standing. No more and some manufacturers recommend even lower levels.
Grizzly

Good points grizzly. It's also important to spend time with the equipment when adding oil as it can appear to be correctly charged one minute then can be over filled as oil is returned to the compressor under certain operating conditions.

[The Viking]

Good points grizzly. It's also important to spend time with the equipment when adding oil as it can appear to be correctly charged one minute then can be over filled as oil is returned to the compressor under certain operating conditions.

+1 to that...
And never add oil to a system where you are not 110% sure that it has a full charge of refrigerant.

I lost count of how often I seen compressors overcharged with oil after refrigerant leaks have been repaired and the system re-gassed.

[US Iceman]

If you are working on an ammonia system, any oil added should should also be taken out in the oil drains.

It must all be accounted for somehow or you run the risk of filling up the evaporators or vessels.

[monkey spanners]

I took three times the correct oil charge out of a newly fitted L'unite 5hp comp once, this had come from the two 'dead' comps sat next to the unit. This was on one of the rare occasions when i had time to go back and check on the compressor i had fitted the day before, couldn't see a level in the glass and took about 3L out before a line appeared! Changed the lot for fresh oil.

Jon

[get the gauges]

I took three times the correct oil charge out of a newly fitted L'unite 5hp comp once,
Jon

I did the same once(in my earlier days) when i came to a 7.5hp prestcold that had no oil in it so i put a load in it just to make the oil pressure switch.20 mins later i had the customer on the phone saying the compessor was moaning like the millenium falcon, you live and learn.

[Lowrider]

When changing the oil weigh or measure the amount of oil you take out and only put the same amount in plus up to a max of 10%. Run the system at least one hour in full load and check oil level according to the manual (running or standing still).

Never ever put the standard amount in after an oil change! You'll overfill it for sure!

[Grizzly]

Run the system at least one hour in full load and check oil level according to the manual (running or standing still).

It's also important to spend time with the equipment when adding oil as it can appear to be correctly charged one minute then can be over filled as oil is returned to the compressor under certain operating conditions.

And never add oil to a system where you are not 110% sure that it has a full charge of refrigerant.

I lost count of how often I seen compressors overcharged with oil after refrigerant leaks have been repaired and the system re-gassed.

All the above are relevant because to explain.
When a compressor/ system runs for a long time unloaded. Oil is "carried over" into the system but!
Because the swept gas volumes are low the oil is not returned to the compressor.
Basically ( AS ALREADY STATED) never assume a system is short of Oil, especially if it runs unloaded for long lengths of time and Always fully load a system before any maintenance checks / diagnosis is carried out.
Sight Glasses, Oil or Refrigerant are useless until full load conditions are achieved especially true on Chiller Systems.
Hopefully someone has benefited from this info?
Cheers Grizzly

[Springbok]

I've seen where on refrigeration systems,especially multi-plex systems,(of maybe two compressors or more),a fault lies in the system.For example the oil seperator float is blocked/stuck/faulty,the compressors trip on oil safety switches.Engineers just come and top up the compressors!

After about a few visits and constant topping up,when someone actually does find the actual problem and repair it,you find the system completely overcharged with oil.You can imagine the damage the poor compressors have to suffer,let alone to say how long it takes to remove all that oil again!

[iScream]

When I was working for ICI, I would only fill / check and ensure that the Reciprocating Compressors (Propane) were 75% and no more than 80% full of oil. when returning next day I always found that someone had filled them 'Full' And these idiots were reporting me for not ensuring the compressors were full. I couldn't convince management that they were the stupid ones.
(Sydney, Australia)

[techie]

i agree its redicously stupid,it should be 3/4 full

[Springbok]

True that!

[The MG Pony]

i agree its redicously stupid,it should be 3/4 full

when in the off state one should specify, 50% whilst running!