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T8775A t-stat fried after one day

Hello,

Yesterday I replaced an old mechanical (mercury tube) t-stat with a non-programmable digital power stealing T8775A. It worked fine for about a day. Now, however, the t-stat is showing a partially(?) closed circuit to the R8184G at every setting which causes the igniter relay (?) to click repeatedly, but not ignite the burner, causing lockout.



I had installed the resistor supplied with the T8775A on the lower T and F terminals of the R8184G as specified in the instructions. After the failure I removed the resistor and the same failure occurs. I then replaced the T8775A with the old mechanical t-stat and all is well again.



There are two other wires attached to the two T terminals of the R8184G which come from the box on top of the motor that it is mounted to. This box seems to take cutoff and aquastat control cabling.



I suspect the other controls wired into the R8184G damaged the circuitry of the T8775A.



Anyone know if this might be the case or what the problem might be? I'd still like to get rid of the mechanical t-stat.



Thanks in advance for your help.

Comments

  • sasman
    sasman Member Posts: 32
    t8775

    you put the resistor WHERE?





    unless i was looking at the wrong instruction manual, i didn't see a resistor listed



    i know why they are used on power stealing t-stats, just didn't see in instructions
  • sasman
    sasman Member Posts: 32
    t8775

    you put the resistor WHERE?





    unless i was looking at the wrong instruction manual, i didn't see a resistor listed



    i know why they are used on power stealing t-stats, just didn't see in instructions
  • Electron12
    Electron12 Member Posts: 2
    T8775A t-stat fried after one day

    Thanks.



    I followed the additional instructions provided with the T8775A (bag assembly 50034437-001). It says:



    "use this resistor when installing oil systems using Honeywell R8184 oil primaries"

    and then goes on to say: "connect resistor and transorb assembly to R8184 oil primary terminals T and F."



    The diagram shows the resistor between the lower T terminal and the lower F terminal. That's how I installed it.



    Some more info: I have an aquastat wired in parallel with the t-stat with both going to the TT terminals. Perhaps this is the problem? The t-stat sees no current with the aquastat circuit closes. It's hard to see how this would fry the t-stat though.



    Would a non power stealing t-stat be OK in parallel with the aquastat or do I need more isolation?
This discussion has been closed.