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Question DetailsAsked on 7/9/2016

what is the average cost ro replace a ac evaporator core in a doublewide trailer

a widow we know had her ac go out. The evaporator core was icing up. a repairman came out and said it would cost $1100.00 to replace it. She has a very low income and I am trying to see if the repairman was being honest with her about the cost. I do not know the tonnage. I was hoping you would know the average size for a double wide.

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Probably a 2 to 4 ton unit (assuming central air, not a window or spot unit) depending on length of trailer (come up to 90 feet long, after all) and of course on how extreme a climate you are in - could well be a 3-4 ton unit if in the humid and hot parts ofthe deep south or if in the hot desert parts of the country.

For an evaporator not under warranty - meaning not getting the evaporator free or discounted from the manufacturer under manufacturer warranty (typically 1-5 years, rarely up to 10 years but usually prorated if so), $1000+ is pretty much the norm these days for a nominal sized A/C evaporator changeout - commonly $500 or more additional by the time replacement of the gas is included if that all leaked out so can't be recovered and reused (though some contractors will not reuse the gas because it has contaminants and possible compressor metal filings in it so they insist on new oil and gas during full gas refills).

Whether the evaporator needs to be replaced or not is another question, and obviously since I still haven't found my misplaced thoussand-mile-glasses I can't tell from here.

Generally, the evaporator will freeze up in one of six situations, without going into system operating details - and of course not all systems are built the same way so system configuration and design comes into it too :

1) A/C unit running wrong pressures so while the compressor is working right and the high-side (evaporator inlet) pressure is right, the low-side pressure is too low. Might be because of a TXV (control) valve issue or mis-set, or because the unit is running low on refrigerant. This causes excess pressure loss within the evaporator, making it run at or below freezing rather than at the roughly 38-45 degrees F (with most systems) it usually should run at when the system is running at stable conditions.

2) airflow is blocked at the evaporator, commonly because it is dirty or due to mold buildup, so it runs colder than it should because the airflow is not directly contacting the evaporator metal as it should, which warms it. Blocked airflow due to blocked ducts (or vents closed off or down too far) or dirty air handler/furnace air filter can also cause this - you should certainly check that the vents have not been closed down too much (if any recent changes have been made to them) and that the air filter is reasonably clean.

3) air temperature is too low for the air conditioner to be running - either too cold outside so incoming refrigerant is cooling more than it should be, or interior air temp is too cold. Depends on unit, but usually below about 60-65 degrees inside or outside air temp can start causing icing up.

4) evaporator is leaking refrigerant, which cools it the same way a pressurized spray can or fire extinguisher cools when it is rapidly discharged. However, this would normally only last for quite a short time - I have never heard how long this can potentially last under perfect conditions and of course depends heavily on indoor air temp and how often compressor is running, but with a normal household unit (so maybe 4-8 pounds of refrigerant) I would guess not more than a day or so before it ran out of gas in the system. So - icing up of the evaporator due to a failed evaporator would normally be my LAST guess for a reason for it to be icing up - could be, but generally if the icing has been for a period of time I would be looking at the gas pressure in the system and finding out whether it is maintaining the wrong pressure in the system or if there is a leak causing low gas pressure.

5) A/C filter/drier cartridge has plugged up enough to restrict flow of refrigerant in the lines, though usually this would cause inadequate cooling, not overcooling

6) other unusual and rare situations like corrosion blockage of lines, crimped line, mixing of incompatible refrigerant lubricants, condensor (outside) coil blockages (either internally or airflow blockage), evaporator not sized correctly for system can also cause this - but these are rare and mostly require that there have been a recent change in configuration of the system.

Bottom line - I would be asking the repairman to describe EXACTLY what the problem was (probably to you AND to the homeowner, could be done on phone) - i.e. did he actually find a leak in the evaporator, in which case he should be able to show it to the homeowner when he comes to change it out. If not, then evaporator may need cleaning but should not need replacement.

Can't say from a distance, but I have heard of and the press has had a fair amount of coverage on shyster HVAC contractors who are saying A/C evaporators are leaking or bad or that furnace heat exchangers have gone bad when that is not the case. That sort of changeout is a quick $1000+ range repair and one of the most expensive individual repairs on most systems, which type of situation always gives an incentive to the scammers.

Unfortunately, the money for the first inspection is now a sunk cost - say $100-150 range probably. So it comes down to another $100-150 for a second vendor to look at it and give their opinion on the cause PLUS any repair cost (say probably $250-750 range if due to a leak or TXV valve problem rather than a major unit issue, with the higher end ofthe range likely if the gas has leaked out and needs replacement - probably about or under 5 pounds in her case), versus $1100 to replace the evaporator and hope that solves the problem. (It should be clarified in writing too if the $1100 includes refill with gas as needed).

IF the first repairman states that there is a leak in the evaporator, I would get it in WRITING that the $1100 repair WILL fix the problem and get the unit operating normally (not that he will want to sign that) to protect against it actually being from some other cause, because I can see him changing the evaporator out, then being called back the next day because it is still icing up and having to pay him more to find and repair the actual problem causing the icing.

If the first repairman cannot or will not give a coherent and reasonable-sounding explanation of exactly WHAT the problem is, or is not able to show that he checked the operating pressures (both high-side and low-side) and FOUND the problem (which for replacement of the evaporator coil would have to be either blockage in the coil lines - very rare - or a direct leak from the coil itself), then if it were my unit I would get a second opinion with a top-rated and reviewed Heating and A/C contractor. I realize a second opinion payment does not sound like it is going to accomplish anything directly, but it might save on the order of $500 or more of possibly unnecessary replacement cost - plus if the evaporator is NOT the problem additional cost to the first guy to fix it right, which if he was wrong about the evaporator being the problem might be a dubious thing.

The issue of repair cost versus replacement also normally comes into play in evaporator coil replacements - quite a bit of commentary on that issue, and the higher efficiency and new warranty you get with a totally new unit plus the issue of the rising cost of R-22 if this is a Freon-based unit, can be found in the Home > HVAC link in Browse Projects. Realizing the economic issue, but if an older unit (say over 10 and certainly if over 15 or so years) spending $1000+ on a repair versus maybe $2,000-3,000 on a totally new unit might not make economic sense - or the economics might dictate least cost solution regardless of long-term economics of doing so. Basically the old argument of whether to fix an old clunker car or get a new one - sometimes the personal economics dictates the sheaper solution even though in the long run it might cost more.

BTW - kudos to you for helping her out.

Answered 2 years ago by LCD

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