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rehab old dirty hvac unit

ohscrifle | Posted in Energy, Heating & Insulation on September 9, 2010 10:11am

Bought a house with an old HVAC unit that’s been run w/ no filter. Gonna replace it eventually, but not yet. HVAC tech says it needs an “acid wash” to clean out the caked on dirt from components in the air path. Quoted about $400.

What’s a fair price to clean out the inside unit (60k btu furnace & 1.5 ton cooling system)? What’s the correct way to do it?  Location is ATL

thanks

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  1. davidmeiland | Sep 09, 2010 11:30pm | #1

    All right pardner...

    how much we gonna spend on nursing this damn thing along 'fore it's cheaper to replace it with a 95 percenter? The gov'ment is giving good rebates, some of the manufacturers are too.

    1. DanH | Sep 09, 2010 11:45pm | #2

      Of course, in ATL he uses the heater about 2 weeks a year, so a 95% unit is a waste.  Would make more sense to install a heat pump.

      (In fact, hard to see why a 60K unit would be required.  That's what we have here where it hits 30 below sometimes.)

      1. davidmeiland | Sep 10, 2010 11:04am | #5

        If he needs a furnace

        I don't think I'd spend anything repairing the one he has. Isn't it the one that also needs makeup air?

      2. Tim | Sep 10, 2010 11:23am | #6

        Not knowing any details

        about the house or construction makes it more than "hard" to see why the unit is sized as it is.  KIA BS only goes so far.......

  2. DanH | Sep 09, 2010 11:48pm | #3

    I think I'd just get the AC "A" coil washed -- should probably run about $100, unless they have to bleed the system and pull the coil.  Any efficiency loss at the furnace heat exchanger is negligible, given your climate.

  3. Tim | Sep 10, 2010 09:19am | #4

    Two things to clean,

    the cooiling coil and the fan. Both can be cleaned easily by most homeowners, no acid required. $400 is not bad if they do a thourough job, but not well spent money, IMPO.

    You can brush and vacuum out the fan compartment and fan with a standard "furniture"brush attachment on a canister vac.

    The coil will have a removable cover, usually on the side with the piping, but not always. Remove the cover and with a steel brush, carefully remove the caked on dust and debris from the upstream side (the "inside" of and upflow "A" coil). A little compressed air through the coil after brushing (and straightening and bent fins) completes the cleaning.

    The "acid" or coil cleaner that is commercially used is a lazy, quick and rather messy way to do this. Save your money and spend a few hours and do it yourself. Then get a good pleated filter and keep it changed regularly.

    1. ohscrifle | Sep 10, 2010 01:25pm | #7

      Excellent. Sounds like a fun filthy weekend project - but a necessary one for sure. I suspected the same regarding the "acid", also wondered if that'd just end up getting flushed out thru the condensate drain...

      The home warranty folks want me to have it cleaned within 30 days & they send old 'camo shorts & t-shirt mechanic' to come back out confirm its no longer having maintenance deferred.. which I have to do in order to have any future mechanical failure covered & not blamed on no poor maintenance prior to my ownership.

      1. Tim | Sep 10, 2010 02:51pm | #8

        The coil cleaner will

        get flushed through the condensate drain (and pump if you have one) along with all the "stuff" that comes off the coils and out of the pan. You can buy the stuff and do it that way yourself as well. Most any HVAC supply stores like Ferguson (there are several in the ATL area) will sell coil cleaners, as well as almost any dealer/manufactrer parts department. Most will do "cash" sales. 

        DiversiTech is one of the more popular brands and is available in either acidic, akaline and other "types".  Google and read what they say.

    2. ohscrifle | Sep 13, 2010 12:31pm | #9

      3 fun hours in the crawl space

      cleaning out the fan unit & AC coil... and I'm done with the downstairs system. Attic unit will be much easier now that I know what I'm doing.. just have to wait for the right weather conditions to start that all over again. 

      Man there was some filth inside the air handler, all over the return air plenum box and the worst was on the windward side of the cooling coil.  All clean now - it is truly amazing that any air could flow through the cooling coil with all the muck that I removed.  The amount of added static pressure must have been enormous - and the fan must be breathing a sigh of relief.  Hopefully the dirt removal by screwdriver doesn't spoil its perfect balance & kill the motor.

      Underside of the fridge was no picnic either.

      1. Tim | Sep 13, 2010 02:02pm | #10

        By screwdriver?

        I don't remember recommending that particular cleaning instrument......

        1. DanH | Sep 13, 2010 08:45pm | #11

          Yeah, you're supposed to use a 2" wood chisel.

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