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Question DetailsAsked on 6/25/2017

Do I have to replace the whole system if there is a leak in the evaporator coil?

If the tech found a leak in the coil, can't it be fixed? I was told the whole system needed to be changed.

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1 Answer


R-22 (Freon) systems run at a significantly different pressure than R-410a, so while there are some some variable-gas capable systems out there able to run both, pretty rare at residential level and getting rarer as the years go on. So, if your coil goes bad, here is basically where you are at:

1) unless it is just leaking at the inlet or outlet fitting, which some locktite/permatex thread sealer or a replacement bushing may fix, generally they are not repaired - both because there are few shops who know how to do it these days AND the repair cost is generally (with the "modern" aluminum and copper mixed metal evaporator coils) as much as or more than a new replacement one. Also, you almost certainly will not find a shop who will warranty a rebuilt or repaired unit, nor a contractor who will warrant the work for more than a few weeks or a month or so at most. Unfortunately, most of the modern ones are so thin and made of mixed copper and aluminum (very much a no-no in metallurgy but they do it to make them cheaper), so traditional brazing or heliarc wleding repair is not at all common like it used to be - you used to be able to get a coil repaired or go to a shop and get a rebuilt/repaired one as easy as getting a rebuilt clutch for a car.

2) you generally cannot mix and match R-410a parts with R-22 because they are designed to work at different pressures and particularly at a different pressure drop and flow rate through the coil, so it would not perform the same - generally degrading the cooling capacity by at least 50% even if the different lubricants did not trash the compressor.

3) if you can no longer get a replacement R-22 coil for your size unit, then you have two choices:

a) see if a specialty HVAC distributor can provide an R-410A rated one that is ALSO rated by the manufacturer for your unit - doable but not easy, especially if not in a large city, and most manufacturers do not even cross-rate the evaporator coils for different systems, even if they could work - plus many coils these days do not come with replaceable expansion orifices (the fixed metering fitting which regulates the pressure drop at the coil) so you cannot change orifices for a different gas liek you used to be able to.

b) replace the entire system with a new R-410a unit

4) if you CAN get a replacement coil rated for your unit and R-22, then you have the options of

a) replace and refill with R-22 (commonly a $1000-2000 exercise),

b) replace and change to one of the replacement gases for R-22, when can potentially cut your gas cost to about half or so that of R-22 (though still commonly 50-100% more than R-410a)

c) figure the unit is too old to be worth putting that sort of money into repairing (usually if over 10-15 years old) and get a new R-410a unit anyway rather than potentially putting good money after bad.

Unfortunately, R-410a (the "new" gas for residential HVAC units) is also goingto start going away, just like R-22, under the global warming environmental laws, so by the time a new unit is getting old you will be looking at the exact same fiasco again.

You should talk to several HVAC contractors about your options and costs for repair/replacement, and you can find quite a few previous questions with answers and ballpark costs and discussions of the relative merits and costs and life-cycle cost/benefits of the repair vs replacement options, but generally unless the unit is under about 10 years old AND you can get a matching coil for the existing system, you are looking at a total system replacement for from a few thousand (a reasonable cost for a normal size house in normal A/C country) on up to the $5000 range for larger house or higher efficiency unit, and more for extreme efficiency or combined heating/cooling heat pump units (now available up to about 20-25 SEER versus the normal 14-16SEER unit normally being installed today).

Answered 3 years ago by LCD

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