Sooty Evaporator!

[daddymac]

Thanks to a burnt out compressor, I have an evaporator coil which is now full of soot so it needs a clean out before I do anything else! What product is the best for doing this? I don't seem to have acid... just soot!
Any Ideas?
DM:confused:

[Argus]

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That is most likely to be burnt oil and wax, not soot, and it probably has a very high acidity.
For example, many small split systems actually become diesel engines during the immediate burn-out process.
(Heat + Pressure + Fuel-Oil = diesel cycle). This may even continue after the power has been turned off until the oil is exhausted.

There are commercial cleaners available - you'll get plenty recommended here.
It is unlikely to ever come as clean as you'd want, but you have to ask where the krud they remove goes - usually it's just shifted to somewhere else in the system unless you continually flush it out with clean fluids.


Your probable best course of action (apart from a new system) is repeated anti-acid measures in the first few weeks after the repair.

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[daddymac]

Thanks for the advice... would a burnout drier protect the system?
The only anti acid measure I've heard about is acidaway which seems to get a mixed review. Are there any others??:)

[paul_h]

OK, I've seen this done, and I'm open to any ideas why it wouldn't be recommended, but it seemed to work:
Isolate the contanimated parts, sweating off or welding in 1/4" access points if necessary.
Using an oil pump, pump through methylated spirits until it flows clean through the other end.
Blow through with dry nitrogen until no more moisture comes out.
Add extra driers. ie., split with TX in outdoor unit fit biflow drier on the liquid line, or a system already with a liquid line drier, fit oversized liquid line drier and fit suction drier.
Replace compressor, then give a good and long evacuation.
It worked for a system we went to that had a burnout, then succesive burnouts time and time again.
Back then I was new to the game, and that's what my bosses told me to do, and they've been doing refrig since the '60s, so I just followed their instructions. I'd never heard of it before, but it seemed to work.
edit: From what I can gather, the metho isn't magical stuff, just something that evaporates easily, dissoles oil and doesn't leave a residue. While it's liquid and you're pumping it in under pressure, it flushes everything out.

[NH3LVR]

For example, many small split systems actually become diesel engines during the immediate burn-out process.
(Heat + Pressure + Fuel-Oil = diesel cycle). This may even continue after the power has been turned off until the oil is exhausted..

This is a new one on me, although I do not work on small systems much. I would have assumed that Oxygen would have been required. :confused:

[Argus]

I would have assumed that Oxygen would have been required. :confused:

Yes.

Inadequate evacuation or a low-pressure side leak that results in a vacuum dragging air in will give this combination.
It's uncommon, to say the least, but the internal results when the insides are examined are quite dramatic. The oil and internal parts can be incinerated.

These little split units are not equipped with pressure switches, and the thermal cut-out on the compressor is self resetting, so that a prolonged stop-starting cycle on an unattended machine will provide these conditions.

In a previous role, I worked for one of the multi-nationals who churned these out by the million. Occasionally a burned out unit would arrive with a demand for an explanation. Removing the top of a compressor would usually provide sufficient visual evidence to convince even the most sceptical installer.

In my view, it’s futile to try to repair these things. It's best to change the lot, including the pipework.

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