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Just curious what this is and what it does.

flexpoint Member Posts: 4
Hello all, first time posting here. I was wondering if any pro could tell me what this is and what it does.

It's just screw on to pipe and its wired to a carlin 60200-02fr relay T T screws .

Does anyone know what it is and what it does for I never seen it before.

Thank you for your time with any insight you can give.

Ken C.


  • Ironman
    Ironman Member Posts: 7,181
    It's a manual reset limit switch. From the looks of your pic, it may be being used as a draft spill switch.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • flexpoint
    flexpoint Member Posts: 4
    Thank you Ironman for responding. My friend sent me these pictures today and asked me. I did not have a clue. I am not a professional or employed in heating industry..I took some classes a couple of years ago Oil burners 1,2,3. My teachers said this was a great place if I ever needed help with something. In class I never seen this discussed or even pictured so curiosity got the best of me. That's why I came here. I just had to know lol. Thank you for taking the time to respond very much appreciate it.

    If you have the free time could you explain what its purpose is and why its used (either a manual reset limit switch or a draft spill switch). I understand if you dont have the time I do appreciate your first response. I just like to learn new things and this one puzzles me.

    Thank you again for your time

    Ken C
  • unclejohn
    unclejohn Member Posts: 1,833
    If the chimney gets blocked the hope is that the hot flue gas will roll over the switch and then break the circuit from the tsat thus shutting down the burner and and keeping everyone alive.
    JUGHNE Member Posts: 10,792
    That looks to be a field installed spill switch, not OEM device.
    Certainly a good idea.
    Often seen on a small angle bracket so the spilled gases would get to it quicker.

    Does anyone know what the limit settings should be for the various fuels?
    I see some old equipment that should have this safety added.
  • flexpoint
    flexpoint Member Posts: 4
    Thanks everyone you guys are awesome. Gave me some knowledge today. Very much appreciate all who responded.

    Thank you 👍👍

    Ken C.
  • Steamhead
    Steamhead Member Posts: 16,263
    edited January 2020
    @flexpoint , the control you mention is used on a Carlin GAS burner, not an oil burner. Does the boiler have, for example, a Carlin EZ-Gas or 201Gas burner on it?

    If so- whoever installed the burner did not change the barometric to the proper double-swing gas type. And that blocked-flue switch is the wrong part.

    Field Controls makes the MG1 gas-type barometric for smaller units:


    and the M+MG2 for larger ones:


    and the blocked-flue switches that go with them. The GSK-3 is most commonly used on smaller units:


    If you tell us where you're located, we might know someone who can straighten that mess out, and test it with a digital analyzer to make sure it's running safely. Or, have your friend post here.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • flexpoint
    flexpoint Member Posts: 4
    I just sent a link to this to my buddy who system this is on. Location long island New York.

    Yes it is a gas fired burner with a carlin burner. He was having problems with his system today and asked for help. I know a little about oil fired burners due to the class I took. I know nothing about gas (except similarity of some parts) I told him he would have to contact a professional because I dont know enough of gas system or want to be responsible for mishaps. His one question was about that part and I never seen it before. So curiosity got the best of me. That is the only reason I asked.

    The good news is he had someone come today and found out what was wrong with his system.....his relay was bad and needed to be replaced.