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Nobby
30-06-2002, 03:47 PM
Ok you guys and gals, here is a dumb question for you. As a newbie I am curious how oil is introduced into a refrigeration system, and how much even:)
I can't find any reference to this in any book I have (Probably so basic they didn't think it needed to be said)

Thanks in advance

Stephen

Argus
30-06-2002, 05:11 PM
Not so. Your actual reasons for adding oil are as valid as the method. Oils should only be added when necessary, either as a result of contamination or catastrophic losses - not when a system is running at low load and without any separation devices for long periods and so refusing to return the oil charge to the sump. In these cases oils will always remain stranded around the system. Adding more will not improve the situation and the risk of compressor damage remains.
The filling method will depend on your system. There are lots of methods. Generally big compressors are straightforward and the addition method is easy.
Regardless of the compressor type, large systems will usually have a sight glass or something similar to indicate oil levels. Generally they will also have a fill plug in the vicinity. You isolate the compressor body and safely relieve the pressure by reclaiming or using the compressor to pump itself down and simply tip the required quantity in usually to half or two thirds the glass, if there is a fill line on the glass. If you are able to draw a controlled vacuum on the compressor sump, you can use the vacuum pump to draw it in if you have a large quantity to add. Another method I used to use was a stirrup-type pump, specially made for refrigeration, which could sit in the oil can and could pump oil directly into the suction service valve when the unit was running. It was OK at low back pressures, but you needed muscles like Rambo on AC systems. It did the job, and I still have it somewhere.
The biggest problem lies with small fully hermetic systems with no indication of the oil charge or even how much remains in the sump. If it is a one piece unit, don?t bother. The manufacturer will have added the correct charge. On split and multi-split systems, providing that you follow the recommendations regarding pipe sizes and length you should be OK ? the factory charge should be sufficient in fact some multiple A/C systems have an oil scavenge cycle built into the controls.
How much oil you put in will be either stipulated by the manufacturer in their literature, with volumetric adjustments for certain conditions, long pipelines, extra components, etc or as I said earlier adjusted to a fill mark. In this instance you need to be as near full load running conditions as you can get and to let the system operate to a stable state, before deciding if you have it right.
Fully hermetic systems, split A/C for example, generally do not need extra oil.
In any case, what ever you do, system hygiene is crucial. If you are using synthetic oils as opposed to mineral, work quickly and avoid prolonged contact with moisture laden air as it is extremely hygroscopic. Always add a meaty drier afterwards.
I almost forgot?.. always pester the manufacturer until they give you the information you want and don?t take no for an answer. If all else fails, read the instructions??????

Hope this helps.
________
religious talk (http://www.religionboard.org/)

Nobby
01-07-2002, 12:08 AM
Wow! What an answer, everything a man would want to know about refrigerent oils but was afraid to ask.

Thanks... Anything I can do for you, Just ask.

Stephen