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VS820A1245 problem

Mr_TAMr_TA Member Posts: 40
Hi all,

I have an old SlantFin gas water furnace which uses subject valve with a standard pilot light and powerpile setup. The electric scheme is very simple, as it's a very old model.

Last spring, the powerpile went and I replaced it with a unit that I bought from a local plumber for $45. The valve is supposed to operate on 750mv from the powerpile, however the powerpile that I bought produces 550mv or something around that. I asked the plumber 2-3 times and he assured me that it's the right powerpile and that he would use it too if he was doing the repair himself. I installed it and the system worked fine. (On second thought, it may have been that the powerpile had produced around 550mv when I tested it before it died and the new one was 750mv and I was worried that the voltage is too high, don't remember exactly now)

Today, my tenant tried turning the heat on and sure enough, it doesn't work. Upon cursory inspection I found that: the powerpile works, the pilot light is on, the water pump works, the electrics are fine. The only thing that doesn't happen is the main gas doesn't come on, which obviously points to the valve. Note that it worked only 6-7 months ago with the same powerpile.

- Is the voltage difference acceptable?

-- If yes, is it possible that the lower voltage that the new powerpile produces somehow damaged the valve over the period of recent months? I seem to recall that when insufficient voltage is supplied to a magnetic coil, it may spoil the static magnet inside the valve assembly (assuming that's how it operates).

--- If this is the case, is the valve dead or there's hope for it, if I find a powerpile with the right voltage?

-- If not, is it more likely that the valve died on it's own, due to it's age?

- In any case, if I do need to replace the valve, is this the correct item?

- Is this the correct powerpile?


  • Mr_TAMr_TA Member Posts: 40
    Cheaper valve?

    Is this the right replacement? Is VS820A the only significant portion? What about the last 4 digits? Mine is 1245, these ones online are 1047 and 1045, any difference?

  • Tim McElwainTim McElwain Member Posts: 3,893
    Do not just change the valve

    do some troubleshooting first. The system does use a 750 millivolt powerpile generator. For procedure to check this out go to "Resources" above then "Library" look for Tim McElwains Closet. The procedure is listed as Procedure for Troubleshooting Powerpile Systems.
  • Mr_TAMr_TA Member Posts: 40
    Will do

    Just to clarify: the circle on top in those drawings is the thermostat/relay/switch/we that closes the circuit, correct?
  • Tim McElwainTim McElwain Member Posts: 3,893
    Is this a steam

    system or a Forced Hot Water system? The circle in the illustrations indicates a thermostat but can be any switch which is going to bring on the burner circuit. The exception is that a Powerpile Thermostat with a fixed anticipator will have a size-able millivolt drop across the thermostat in the range of 115 to maybe 130 millivolts. A switch however should be no more than a 10 millivolt drop across the switch.
  • Mr_TAMr_TA Member Posts: 40
    Hot water, regular thermostat

    The thermostat is the most basic kind, with mercury (or whatever that liquid metal is) bring the circuit into contact.

    I'm going out there tomorrow with my tools to do a proper inspection of the system, will post what I find. Thanks for the help.
  • Tim McElwainTim McElwain Member Posts: 3,893
    You have a

    forced hot water system which I imagine has a relay which brings on the burner when the call for heat takes place. The contacts on the relay which are connected to the gas valve will only allow a 0 to 10 millivolt drop across the contacts. What is the make and model of the relay? If it is an aquastat relay it will typically have B1 and B2 as the switch to bring the burner on. If the pilot is staying lit then the pilotstat on the gas valve is fine. Your problem is either poor millivolt output from the pilot generator or the valve coil itself. The procedures I directed you to will find this problem.
  • Mr_TAMr_TA Member Posts: 40
    Looks like the powerpile

    I read 240mv with open circuit, couldn't test completely disconnected. Given 750mv desired output, isn't 500mv a big drop for just pilot valve?
  • Tim McElwainTim McElwain Member Posts: 3,893
    Why can't you disconnect the

    generator from the gas valve? Just put the valve on pilot and hold down the pilot on off knob and connect the meter to the two leads you will read the output of the generator.
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