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OT: gas fireplace problem

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  • OT: gas fireplace problem

    I have an in-wall gas fireplace. I shut it off during the warm weather, but this time it isn't coming back correctly. The pilot light lit and burns fine. The fireplace is controlled by a wall switch. But when I switch it on, nothing happens. That is, the pilot is lit but the main gas valve doesn't seem to be opening.



  • #2
    Is the pilot flame hitting the sense tube? Is the other end of the tube screwed tightly into the valve?
    Southwest Utah


    • #3
      I assume that after lighting the pilot, the control valve dial has been turned to the "normal operation" position.

      I ask, as I had to replace the wall heater this past winter and the new unit has the control knob turning the opposite way of the old device after lighting the pilot. I had to read the instruction card that is hung on a chain from the control unit.

      Cold air coming, frost tonight. Time to get these heaters going!


      • #4
        That sense tube is normally a thermocouple, when the flame hits it, it generates a small voltage, and operates a device that allows the main valve to open in the control. If that does not operate, the main gas valve cannot stay open, and the unit will not work.

        The thermocouples go bad after a few years, since they are at a near red heat for the whole season, and may need replaced. They also may be located in the wrong spot and not get hot enough to work. I have moved them as little as 1/16" or 1/8" lengthwise, and had them start working. Ditto for how far they are sideways into the flame.

        You can try moving it, or just replace it. They are not expensive, and the box stores have them.
        CNC machines only go through the motions


        • #5
          If the thermo couple is defective, the pilot will NOT remain lit. So that is out.

          But, if the device is mis-located, Or if there is draft in the area due to a leaking sight window seal, the burner may not light even though the pilot is burning.


          • #6
            Remove the thermocouple connector and buff up the contact, put back on. This has worked for me more than once.
            I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-


            • #7
              I've seen (at the neighbor's) a mis-located thermocouple put out the pilot even though it was seen to be burning when checked. It was out when checked later. The thing would heat up but then quit. Moving it fixed the problem.

              If the pilot is truly seen to be lit WHEN the thing will not light, then there is a different issue, yes. If it was lit and then after a bit it would not light the main burner, then re-check the pilot.

              If the pilot stays lit, is still lit when the refusal to turn on is noted, then the valve may have a problem, the burner is messed up (obstruction in the jet), etc.

              DO YOU SMELL GAS even though it does not light? If you do, then there is some foulup in the mixing tube, and you won't like it when it does light!

              If you do not smell gas, then.......

              The power to the valve may not be on

              Power to the valve may be interrupted by a bad wire, bad connection, etc.

              The orifice may be plugged.

              The gas valve may be defective
              CNC machines only go through the motions


              • #8
                Originally posted by CalM View Post
                If the thermo couple is defective, the pilot will NOT remain lit. So that is out.


                • #9
                  Originally posted by A.K. Boomer View Post
                  As noted ONLY if it is observed to still be burning when the thing won't light. Refer to my post above....

                  It appeared that he lit the pilot OK, but I am not certain he observed it to be still lit later.
                  CNC machines only go through the motions


                  • #10
                    Well, metalmagpie did say "The pilot light lit and burns fine. The fireplace is controlled by a wall switch. But when I switch it on, nothing happens. That is, the pilot is lit but the main gas valve doesn't seem to be opening."

                    Seems like he made sure it is lit and stays lit.
                    Location: Saskatoon, Saskatchewan, Canada


                    • #11
                      Originally posted by J Tiers View Post

                      You can try moving it, or just replace it. They are not expensive, and the box stores have them.
                      80 bucks or so for some. Half that for others. I suppose that is not expensive, but more than I care to spend on a guess.


                      • #12
                        Most of 'em are 5 to 12 bucks, at least for my furnace or water heater.


                        But first we need to be sure

                        that the pilot has been lit for sure when the thing won't light

                        That power is on for the valve.

                        Whether or not he smells any gas (seems like he would mention that)

                        If that stuff is OK, it's pretty much down to the valve unit or a blockage.
                        CNC machines only go through the motions


                        • #13
                          Would cost at least $75 in the UK for a Gas fitter to tell you "It can't be fixed, obsolete, you will need a new fire at $600 fitted". Theoretically, pain of death if you try to fix your own gas faults over here.

                          Regards Ian.
                          You might not like what I say,but that doesn't mean I'm wrong.


                          • #14
                            You need to dig a little deeper and give me more information for me to help you. I fix Green house gas unit heaters every year for the last 35 yrs. In the green house environment working when turning off doesn't mean they will work again when you go to turn them on the next year.

                            You can rule out your thermo couple. If you ever have issues with it, like someone mention before, unscrew it from the valve and rub the end on your flannel shirt or a paper towel and put it back in. This fixes 99% of thermo couple issues. I find they rarely go bad.

                            Do you normally hear a soft 'click' when the valve opens? Do you hear it now? Stick your ear down by the valve and listen while someone else flips the switch.

                            If the valve clicks -Do you smell gas? Spiders can raise all kinds of hell inside dormant gas piping. They can plug the closest part to your pilot light while the other area fills with gas. This is dangerous. Clean your burner manifold or hire someone to do it for you.

                            There must be a power supply to your valve. Here (US) they are 24v. Make sure that you have voltage to your valve.

                            I find gas valves that have sat around for a period of time get sticky. Sometimes all I have to do it turn the switch on and off several times. You should hear a click when they open. Other times they get permanently stuck and need replacing. This requires shutting off the gas, changing the valve, bleeding the system, leak testing, and firing it back up. If you have never done this, or have been shown how by a professional I would call someone. Replacement valves come usually come with extra parts for LP and NatG. Some have internal gas pressure regulators and pilot flame adjustments, not to mention the ability to fit the space and have places to hook up all the safety devices.

                            Another thermo-couple related issue which I don't think you have but here goes for anyone else. ECO - Emergency cut out - An extra safety device you will find on some valves. It sits between your thermocouple and your gas valve. I find them to be extra sensitive and a bit fussy. They have 2 leads that go to a sensor. I find the two leads where they connect to the valve to be the trouble spot. You can test this by jumping across the contacts. If your pilot light works you have to trouble shoot that circuit.

                            You will need to get your hands on a wiring diagram. Depending on the age of your system there should be safety circuits. Overheat shut down, CO, and maybe one or two more, it just depends. Safety circuits, (EDIT)- if 'open' ( a short circuit could bypass the safety device) will prevent your valve from opening. This is a good thing like cars that can't start are better than cars that can't stop.

                            Gas is serious if you don't know what you are doing. There was a downtown building here locally that blew up due to a gas leak last week. 2 1/2 stories and now a pile of rubble. Took out most of the windows of the buildings around it too. 8 people injured no deaths.
                            Gas guys have some really terrifying stories. If you can't find a simple fix call someone.
                            Last edited by Abner; 10-25-2016, 08:59 AM.


                            • #15
                              The circuit breaker supplying the wall switch may be tripped.