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Suggestions on new A/C unit

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  • #31
    Re: Suggestions on new A/C unit

    Hi Bob, that is exactally what my sons A/C buddy said last night! I mean, just how hard is it to wire up 4 color coded wires! LOL
    Congratulations to Mr. "the sky is falling" Al Gore, nominated the new Village Idiot!

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    • #32
      Re: Suggestions on new A/C unit

      There should be an inline fuse on the low voltage side of the transformer. I add those to most systems that dont already have them.

      It sounds to me like W is going to gound. The wire could be pinched somewhere. I have seen houses framed with metal studs where someone puts a drywall screw through the Q539 subbase of a T87 and the head of the screw touches the metal of the subbase and shorts it out. I have also seen bad spots in brand new rolls of stat wire. It could also be something mis-wired inside the unit from the factory. Thats about all I can think of. I'm sure the tech will figure it out.

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      • #33
        Re: Suggestions on new A/C unit

        At this point I would install a fuse holder for a 3AG 1/4 x 1-1/4 fuse and a proper fuse (Try a Bussman MDL2 or AGC3 fuse) inline with the transformer secondary. Be sure to keep a few spare ones handy just in case.

        As Bob stated it sure seems to me like a wiring problem. To solve this once and for all, havel brand new 5 conductor thermostat wire wire run from the furnace to the T-stat and disconnect the old. It very well may be damaged. I would also get rid of the fancy thermostat for now and use a T87 with proper sub-base (Have them look it up carefully). They can take the fancy T-stat back to the shop and check it out there.

        Here's an idea: Any half good HVAC tech should have an AC Ammeter with a 0-2 or 0-3 range or a digital with a 10 Amp AC range. Have them connect it in series with the transformer. If they blow it up (Their meter), that's their problem and proof you have a short circuit issue to fix before going farther. You normally shouldn't have more than 1 Amp current draw at any time. This is with the control circuit only.

        Rather than my going PLPLPL anymore, I suggest that you take a look at this site and print it out. My bet is they goofed connections or there is bad T-stat wire. 50 feet of 5-18ga T-stat wire doesn't cost much so growl and howl that they must replace it. Your son has been through enough and so have you.

        http://home.howstuffworks.com/home-thermostat3.htm

        Keep after them until it is fixed and is working well. A tech that runs from a problem is not helping you. Maybe they will hopefully send someone else soon.

        I have seen where people need 5 conductor T-stat wire and have used 4 conductor. It sort of works (sometimes) but not properly and causes some strange issues. Maybe that's what is wrong there. Be sure they do not use a staple gun and use only insulated staples and just tap them in enough to hold it in place. Driving in a staple too far = short circuit. Also look for anything sharp that may cut into it. If the wiring is on the older side, just install new and cut the ends of the old back so no one will ever connect it up again.
        Last edited by Woussko; 09-23-2007, 07:02 PM. Reason: Found some goofs with wording.

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        • #34
          Re: Suggestions on new A/C unit

          Just wanted to post back the "fix" on my sons new A/C unit. If you recall, when switched to heat to program the thermostat, it kept blowing the transformer. (which one, I don't know, but assume the low voltage one)
          After a few months and 4 transformers, they replaced the circuit board and all is well. Not sure if that was all that was wrong but it now works and he has heat. I tried to get him to demand new wire from the thermostat to the unit but I don't think that happend. Oh well.

          Mark
          Congratulations to Mr. "the sky is falling" Al Gore, nominated the new Village Idiot!

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          • #35
            Re: Suggestions on new A/C unit

            You got a lot of good advice already, but I thought a few more items should be brought up.

            Higher efficiency means reduced energy cost per BTU of heat moved! If units are oversized, they will short cycle and not remove humidity. If you can find a 2 speed compressor, you will have the world by the tail. Runs at low speed during mild weather and stays on to keep humidity down but can kick it up a notch when it gets really hot.

            I am in Wisconsin and Heat pumps get used up here because they save on fuel costs, until it gets below 20 to 30 degrees depending on how the unit was sized. Your fuel costs will dictate which heating system is better.

            R-22 is being phased out because of the EPA and Global Warming, not because of Dupont and the rest of the refrigerant manufacturers. The cost increase on R-12, R-502, and coming soon on R-22 is almost all in Taxes.

            It was 14 below zero last night so I better go find the wife and have her throw another log on the fire!

            Good luck.

            Warming, HUH!!!

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            • #36
              Re: Suggestions on new A/C unit

              I'm glad we're not the only ones who are making the clamshell vs. tubular argument. We USED to sell Lennox furnaces until we started seeing cracks in 3 year old heat exchangers. We sell Rheem and Amana; both use stainless tubular heat exchangers. We used to sell York, and since they changed to Tubular heat exchangers in 1996 (mild steel) we haven't seen a failure, lots before that, though. (P2UDD = cracked)

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