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Missing cad cell

hamp215hamp215 Member Posts: 6
I have a property that I am renovating. It has oil forced air. The system fired up initially and ran well for a while. Then the second time upon attempting to start it would shut down. I checked and noticed that the furnace had no cad cell. Is it possible that the previous owner somehow bypassed the cad cell. Is this possible. I'm thinking of replacing the transformer, cad cell relay and cad cell


  • STEVEusaPASTEVEusaPA Member Posts: 4,103
    edited October 2019
    Would need to see a pic.
    Pretty hard to bypass a cad cell, either the burner would always run or it wouldn't (shouldn't) turn on.
    Maybe the eye was loose and it fell off and is either sitting in the air tube (more likely), or shot into the chamber (less likely).
    I wouldn't just replace all the parts if nothing is wrong with them.
  • HVACNUTHVACNUT Member Posts: 3,265
    Stack relay? I hope not.
    How did it go through a full cycle, and then not?
  • hamp215hamp215 Member Posts: 6
    That's whats confusing. The stack relay is present. I don't believe it was a cad cell present there are no wires coming from the relay indicating that a cad cell was present
  • hamp215hamp215 Member Posts: 6
    I will take a pic & post it tomorrow. Thanks everyone
  • STEVEusaPASTEVEusaPA Member Posts: 4,103
    Never thought of a stack relay, good call @HVACNUT. Almost never see them anymore.
    Well if it's a stack relay, you won't see a cad cell in the burner, the safety is controlled by the ancient stack relay.
    You should have that replaced with a modern 15 second cad cell relay primary control.
    If there is no place to mount the cad cell (like the transformer) you can use one of the provided clips and connect it to the nozzle line.
    You just want to check resistance (ohms) while it's running to make sure you have the alignment and placement correct.
  • HVACNUTHVACNUT Member Posts: 3,265
    > @STEVEusaPA said:
    > Never thought of a stack relay, good call @HVACNUT. Almost never see them anymore.
    For some reason, while I was reading the post, I had a 70's flashback. In my vision I also saw layer upon layer of furnace cement.
  • SteamheadSteamhead Member Posts: 13,764
    @hamp215 , make sure you get some pics of the burner.
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • Big Ed_4Big Ed_4 Member Posts: 1,311
    Hmmm ......Wonder if it was a Blueray
    I have enough experience to know , that I dont know it all
  • STEVEusaPASTEVEusaPA Member Posts: 4,103
    You’re wasting a lot of money up the flue running that burner/furnace.
    Compression fitting isn’t helping either.
    You’re primary safety is thru the stack relay which at best is a 60 second lockout...could be 90 seconds. That’s 60 seconds of un burnt oil going into the chamber without firing, per reset.
    You could pull that out, clean the helix (bimetallic element), reset the control to see if that helps.
    But if you have to keep it, a competent tech should properly service that furnace/burner, replace the stack relay with a 15 sec modern primary, replace the compression fittings with flare fittings.
    Proper cleaning, proper tune up, check the components, check for vacuum leak, proper bleed, and combustion test are needed.
    Or put all that time, effort and money towards a new properly sized, properly installed furnace.
  • hamp215hamp215 Member Posts: 6
    I was definitely thinking of switching to a forced air gas furnace. Thanks for the input.
  • mattmia2mattmia2 Member Posts: 1,173
    what's with the spring? what happened to the return plenum?
    is the supply ductwork graduated?
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