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10 Seer Evaporator Coil. 13 Seer Cond. coil.

A mismatch guarantees you will not get 13 SEER. Mismatch affects performance, can shorten compresssor life. Extreme cases can give you some of the screwiest readings you have ever seen. With AC you can often get away with it. With a heat pump it is definitely a no-no.


  • JP!
    JP! Member Posts: 5

    I have a system with a 10 seer evaporator coil, though it is brand new, it has a piston for a metering device, and 3/4 3/8 copper line set coming out of it...
    What are the dangers of using a 13 seer condenser coil with a 10 seer evaporator coil? Can it be done?
  • charlie_15
    charlie_15 Member Posts: 6
    gauge reading for central a/c unit

    i am a heating guy with a little a/c experience but my own a/c unit isnt cooling i put my gauges on and they both read the same pressure what does this mean?
  • Jeff Lawrence_25
    Jeff Lawrence_25 Member Posts: 746
    It means

    the compressor isn't running....
  • clammy
    clammy Member Posts: 2,655
    From experence

    From experence when i have ran into mismatch equipment like 12/13 seer condensing units hooked to older low seer indoor units it was not good in some cases the compressors would go into by pass (on scrolls )and or run high head i personally will not do it if it's a a coil on a furnce change it ,if it's a air handler also change it using a lower seer coil with a high seer condensing unit will over time lead to premature failure of the compressor ,in the long and short term it's not worth it and in all liklyhood you will have promblems sooner or later peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • Ranger
    Ranger Member Posts: 210

    > I have a system with a 10 seer evaporator coil,

    > though it is brand new, it has a piston for a

    > metering device, and 3/4 3/8 copper line set

    > coming out of it... What are the dangers of

    > using a 13 seer condenser coil with a 10 seer

    > evaporator coil? Can it be done?

    Hi JP,
    First of all,there is no such thing as a 10 seer coil or a 13 seer condenser etc.,When the evaporator,condenser and other componants are "matched" as per the manufacture/ari,thay have the potential to achieve 13 seer.(or whatever) I have the very same coil that will work correctly with a 10 seer outdoor unit as well as a 15 seer outdoor unit,as long as I follow the mfg. match-up chart & use the recommended metering device for the application.I think the question is will the evaporator on the job function correctly with the outdoor unit that I intend to use and the answer is unless in has been given an ari number for use with that perticular unit there is no way of knowing it's performance.Not to say that aftermarket coils are not subjected to the same testing standards as the oem's (there generally not field tested,but virtually tested on a computer than submitted to ari) I agree with Clammy in that for the cost of an evaproator coil,it's not worth the aggravation of potentially trying to make an existing evaporator coil "work" as it were. Also some mfg. such as UPG/JSI require you also listing the matching ari matched model & serial number of the evaporator coil for compressor warranty.Not having a matched coil is now grounds for voiding the compressor warranty.So bottom line,will it work? Mabie. But now you are forever holding "The Bag".
    Hope this helps,
    Ranger Novrit CM
  • Tammy
    Tammy Member Posts: 1
    air not keeping up with the heat of day

    my air seams to work ok at night. keeps house cool and turns off and on. i keep it at 72. it has felt colder at night though in the past. during the day the temp gets to 80 and runs all day and way up in the night...about 1am before shutting off. this is all a new problem. i had the blower fan cleaned. the inside coil cleaned with acid. the outside coil cleaned with water hose. the coil in the house is NOT cold and wet, but there is water coming out the pipe outside. also inside, sometimes i can hear water gurgling.
    the air coming from vents are cool not cold. what could be the problem with the coil not being cold and wet. oh and i also had the gauges checked out, seemed to be fine.i live in tampa fl. thanks
  • Jeff Lawrence_25
    Jeff Lawrence_25 Member Posts: 746
    a couple of things

    First, a separate post would have gotten you noticed quicker.

    Second, here's an answer.

    I'm a bit north of you, slightly northwest of Atlanta. We are in the middle of a heat wave that hasn't been seen in these parts for many years. Brad White may make a post about heat loads and degree days (love ya, Brad), but the final thing is that it's HOT.

    Design temp for Atlanta is about 92 degrees and it's hitting nearly 100. Cooling systems are sized so that the outside air temp does not get above the 'design' temp 97.5 per cent of the time, but we've had several days of above the line temps.

    I run my AC set at 71 degrees when I leave in the mornings, about 8AM, just so the inside temp will be below 80 degrees when we get home. I've also installed a temp solution of a ten thousand BTU window unit to help the keep the temps in line.

    Does it work? Yes. Is it comfortable? Barely. Is my power bill going to be ridiculously huge for the month? Certainly!

    Another thing to consider. Being that you live in Tampa, Florida, I'd hazard a guess that your ductwork is located in the attic of your house. I'd make sure the duct is tight and not leaking much air, but I'd also make sure that the attic is as cool as possible because the ducting will pick up heat from the attic.

    Good luck.
  • jim lockard
    jim lockard Member Posts: 1,059
    or maybe

    bad gauges or hoses if the compressor is running.
  • John Starcher_4
    John Starcher_4 Member Posts: 794
    Or possibly......

    ....the hoses are hooked up backwards, so the little shrader pokey thingy is on the guage end, not the equipment end.

    Don't laugh---------I saw this happen once!
  • Ken D.
    Ken D. Member Posts: 836

    Has the system ever worked? Is it a new system? It could be, as the previous post suggested, the outdoor conditions are above design. Or it could be short on freon, resulting in low capacity. One or both of the coils could be dirty as could the air filter. The belt could be slipping (if any). The unit could be too small. The duct integrity could be compromised. I have seen many return ducts that have fallen off or separated and 130 degree attic air is sucked through unit (Attics should be well ventilated). Windows or fan openings open in the house that can bring in copious amounts of humidity and heat. Problems with the metering device. Restrictions in any of the refrigerant piping, driers or other components. Non- condensibles. Problems with any of the motors. If the compressor runs hot, that is that much more heat the condensor has to get rid of. The fan motors could possibly not be running up to speed, causing low airflow. Anything that can bring in or produce extra heat and/or humidity in the dwelling (such as ovens, gas grilles or hot tubs). Dampers not set properly, etc. etc.
This discussion has been closed.


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