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  • Thermo Coupler

    what exactly is there purpose? i was never really trained on reparing water heaters always replaced them. now im learning as i go. so i was wondering if you guys wanted to throw your 2 cents in on trouble shooting and repairing water heaters.
    Mike
    Clark County Plumbing And Drain
    www.plumbinginclarkcounty.com

  • #2
    Re: Thermo Coupler

    The thermocouple makes a very small voltage when heated to let the gas valve know the pilot lite is working. I think the voltage magnatizes something to hold a valve open to the burner. Get a digital volt meter and some aligator clip jumpers. to test the thermocouple if your interested I'll tell you how. Testing beats replacing when you don't have to. Especially with the sealed combustion W/H.

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    • #3
      Re: Thermo Coupler

      A Thermocouple junction or Thermocouple for short is a flame proving device.

      Heat from the pilot flame acting on the thermocouple generates a millivolt signal which when present allows the main gas valve to open on a call for heat from the thermostat.

      Over time dirt, rust, and soot will build up on a thermocouple insulating it from the heat of the pilot flame, when this happens the pilot valve will close and the main gas valve will not open on a call for hot water (Common no hot water service call especially the day after high winds)

      Clean a thermocouple off with steel wool or for the few dollars they cost just replace.

      Be careful of left hand thread thermocouples on Craftmaster and Whirlpool units. If you run into these you will be required to install a retrofit kit. (can't buy left hand thread thermocouples anymore)

      TMP valves will drip when the water does not have a place to expand to (expansion tanks are a good thing and may be required in your area)
      Sometimes a simple lift and release will allow a TMP to seal otherwise change it out (This can be done without draining)

      Combo thermostat and gas valve. If you are having temperature control issues change it out. If you can't get the pilot to stay lit after you have replaced thermocouple and checked any other safeties change it out. (This can be done without draining)

      A leak from any other point except the TMP is a changeout "A leaker"

      That's the basics...

      Okie
      Last edited by OkieBill; 04-20-2009, 06:48 PM.

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      • #4
        Re: Thermo Coupler

        Some water heaters require changing the entire pilot assembly if the thermocouple goes bad.

        Comment


        • #5
          Re: Thermo Coupler

          so lets say no wind, if you hold the pilot light button down the pilot will stay lit but if you let go it gos out even if you hold it down for two minutes. but other times it will stay lit and then at random go out?
          Mike
          Clark County Plumbing And Drain
          www.plumbinginclarkcounty.com

          Comment


          • #6
            Re: Thermo Coupler

            Originally posted by haycad View Post
            so lets say no wind, if you hold the pilot light button down the pilot will stay lit but if you let go it gos out even if you hold it down for two minutes. but other times it will stay lit and then at random go out?
            A properly functioning pilot light, provided there is fuel, should in theory never go out.

            Hold the button for two minutes with the thermocouple in the flame-let go of button-flame goes out.....typically faulty thermocouple.

            Pilots should not "at random" go out but there are situations where venting & high winds can make this happen.

            Good pilot/thermocouple systems should be fairly stable in their operation.

            J.C.

            Comment


            • #7
              Re: Thermo Coupler

              Originally posted by haycad View Post
              so lets say no wind, if you hold the pilot light button down the pilot will stay lit but if you let go it gos out even if you hold it down for two minutes. but other times it will stay lit and then at random go out?
              Try cleaning like okie said. To test the thermocouple you need a volt meter. Disconnect the copper lead from the gas control valve. Tape or clamp a probe to it. Then put the other probe on the top of the part that came out of the gas control valve. Light the pilot. The volt meter should show 12 milli amps dc as the thermocouple heats up the voltage should go up to 14 or 15 milliamps. If not it is bad. Sounds like a gas control valve problem to me though.

              Comment


              • #8
                Re: Thermo Coupler

                You guys are a mountain of knowledge keep it coming
                Mike
                Clark County Plumbing And Drain
                www.plumbinginclarkcounty.com

                Comment


                • #9
                  Re: Thermo Coupler

                  What brand and year is the Water Heater?

                  May have a quirky brand one of us knows.

                  Okie

                  Comment


                  • #10
                    Re: Thermo Coupler

                    I think he is just looking for general knowledge as he or his company is adding service work like others.

                    J.C.

                    Comment


                    • #11
                      Re: Thermo Coupler

                      Ahh I get it...

                      Sorry, was a long day of under the house crawlspace repipe...My abbs are killing me!

                      Time to crash

                      Comment


                      • #12
                        Re: Thermo Coupler

                        I found out recently that some thermo couples have an inbuilt safety device so that if the flame goes back from the burner onto the lead of the thermo couple it stops the thermcouple from working rendering it useless and stops the potential of flames coming outside of the unit.

                        Simon

                        Comment


                        • #13
                          Re: Thermo Coupler

                          the one i was reffering to was an ao smith pro max. ive been doing service for a long time but with water heaters i was never taught to diagnose just replace so im just trying to learn some new stuff. thanks for the feedback
                          Mike
                          Clark County Plumbing And Drain
                          www.plumbinginclarkcounty.com

                          Comment


                          • #14
                            Re: Thermo Coupler

                            mike, keep in mind that fvir (flamable vapor ignition resistant) heaters, last 5 years require the thermocouple assy to be changed as an assembly. the combustion chamber is a sealed unit and swapping just the thermocouple will usually compromise the integrity of the fvir.

                            most heater companies will send you the parts for free. most supply houses don't stock the parts here

                            the american appliance heaters were the ones that were the left hand threads. they had the high limit built into the thermocouple.

                            they were also the first co. to perfect the fvir type heater.

                            rick.
                            phoebe it is

                            Comment


                            • #15
                              Re: Thermo Coupler

                              http://www.hotwater.com/products/res...chBulletin.pdf

                              http://www.hotwater.com/lit/FlameArr...enCleaning.pdf

                              These two links may help.

                              Comment

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