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Question DetailsAsked on 7/21/2016

Why can you flush the copper lines of R22 and move to 410A, but you can't flush the lines in the evaporator coils?

my R22 condenser coils have another leak, and A/C service says I have to replace with new condenser coils, new compressor, & new evaporator coils, but they flushed the copper lines in between and reused them. If they can flush the copper lines, why can't they flush the evaporator coil lines? I can see on the side of the old evaporator coils that the unit can use 410A coolant...

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Voted Best Answer

You can flush condensor and evaporator coils like linesets - though with some models you have to remove them to do it.

All the parts have to match the system for it to work right, so if a replacement condensor [if you actually meant the condensor (outside coil) rather than the evaporator (inside coil) which is usually what goes out] was not available that fit that unit's cooling and pressure requirements, say because parts are out of production and also out of stock nationwide, then you might have to replace the entire unit.

Changing from R-22 to R-410a generally (not always) also requires replacing all components - putting in a totally new system with normally only the electrical, thermostat, base pad, and lineset being reused - because while the coils might be rated for the higher R-410a pressure, they would likely not produce the correct heat transfer and pressure changes for the system when running R-410a. Just because it says it is rated for R-410a does not mean for your system - that might be for a different sized and rated unit, because basically speaking (with some exceptions for higher-end units) putting R-410a into an R-22 unit will result in about 15-20% less heat transfer for the same running time. Therefore, the unit would likely be undersized even if you could just flush the lines to remove the incompatible lubricating oil and change the gas out, which would overwork it in many cases unless it was oversized in the first place.

Sounds like this has already been done so you are out probably at least $2-4,000 for a new unit and possibly more. All you can do at this time, since it is too late for bids from another contractor, is if you have the part numbers from the old unit or the model number of the entire system, would be to check yourself if replacement condensors (might be several that fit your unit) are available. If so, you might have a claim against the contractor for fraud for saying you had to get a whole new unit when just a part changeout (and replacing any lost gas) would have done the job. Unfortunately, too late to get a second opinion on exactly WHAT was wrong with the unit - whether the coil was actually leaking or it was just a fitting or tubing or such that could be easily fixed.

Answered 2 years ago by LCD


Correction - in my answer, which I was reviewing to provide as a link to another question, I noticed a minor error in the first paragraph - I said -

You can flush condensor and evaporator coils like linesets - though with some models you have to remove them to do it.

Only the evaporator coil unit and sometimes condensor coil has to be removed in some cases to properly flush them - if just a flat panel unit with coiled uniform diameter lines with the high-pressure (inlet) on the top and the low-pressure (return) on the bottom, it can just be flushed with the lineset connected. If a unit which has varying diameter interior openings in it like cast "radiator" type (like some condensors and a few much older evaporators) rather than continuous tubing type or the flow in the lines is bottom to top, normal flushing equipment will not necessarily get gooey or sludged oil and debris out of the lower parts of the coil, so it should be removed and positioned where it can be turned properly to flush out such material from top to bottom.

The lineset does NOT have to be removed, as could have been implied in the above response - can be flushed in-place, though if it has a significant dip in elevation below outside unit level (rare except common with rooftop and wall-mounted mini-split units) you have the same risk of assumulated material not being lifted up out of the low areas in the lines. Commonly, controlled pressure-flushing using higher pressure compressed air would be used to drive out such sludge and debris after an initial solvent flush to loosen it up. This commonly is not safe to do on coils because they commonly cannot accomodate the higher pressure that the lineset can - depends on manufacturer, and commonly the evaporators do not even have a pressure rating on the manufacturer's plate or label so safer to do it with lower-pressure liquid solvent cleaning, taking the unit out as needed to be able to ensure it is all cleaned out.

One thing I may not have put enough emphasis on - removing and cleaning the evaporator coil (if it has to be removed), even if reusable in a R-410a system which is unlikely, is likely to cost a quarter to half the cost or so of replacing the coil, so not worth doing maybe with an older coil (say over 10 years old or so). Condensor coils are generally a lot easier to remove so not such a big deal - and also generally longer-lived and much cheaper in the first place so not such an issue there.

Answered 2 years ago by LCD

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