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Hanging furnace Question....

Boring
Boring Member Posts: 42
I have a hanging furnace in my pole barn that doesn't seem to be operating properly...it has me stumped.
It runs and heats, but the burner seems to cycle on and off more than it should. I changed the stat thinking it was the problem, seemed to help, but still cycles a lot. Cleaned the pilot flame sensor / ignitor, pilot orifice .... Also had a leak in my roof that dripped on the control (honeywell 8600c)... wondering if it may be acting up??? Do they act up if they get wet? Main burner shuts off, pilot stays lit, valve clicks, burner comes back on... repeats this sometimes every 30 seconds or so.... Any suggestions ?

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 17,797
    Oh yes. A control that got wet may recover when it dries out. Then again, it may not.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Empire_2
    Empire_2 Member Posts: 2,343
    Very possible. Electronics and water do not get along... Probably some damage to inside of control.

    Mike T.
  • RJ_4
    RJ_4 Member Posts: 484
    Could be cycling on high limit which sometimes is located behind side panel or access panel, what make and model do you have
    RJ
  • RobG
    RobG Member Posts: 1,850
    Are the filters and coil clean? Low air flow will shut it off on high-limit.
  • Boring
    Boring Member Posts: 42
    I thought the Hi limit also.. kind of acted like it might be hot and shutting down.... watched it run this morning and found the sparker wasn't shutting off... i moved the spark wire a little, spark would stop and burner would say on.... I removed the spark wire and tightened up the connectors... now it seems to be working good. The furnace is a 150K btu Dayton purchased through Grainger about 20 years old----First time I've had any issues with it...I think i'm good for another 20 years now.... Thanks for the suggestions....
  • Tim McElwain
    Tim McElwain Member Posts: 4,493
    edited January 2015
    The fact that the pilot was lit and the spark was still continuing indicates a microamp problem. It is either the flame rod needs cleaned or you may have damage internally in the S8600 control. What is the exact number of that control?
  • Boring
    Boring Member Posts: 42
    S8600F....
  • icesailor
    icesailor Member Posts: 7,265

    Oh yes. A control that got wet may recover when it dries out. Then again, it may not.

    And like breaking a bone or having surgery, you never quite completely recover.
  • Tim McElwain
    Tim McElwain Member Posts: 4,493
    The S8600F uses a combination igniter/sensor (single rod). Do you know how to measure microamps? If so you should have between 2 to 10 microamps normal is around 3 to 5. You can measure microamps by placing your meter on the microamp scale and breaking into the GND (Burner) wire and measure your microamp signal.

    You also want to check and make sure you have 24 volts at the module on a call for heat at 24V terminal and 24V (GND). If you do then move one test lead on the meter to the PV terminal on the module, leave the other lead on 24V (GND) you should have 24 volts and the spark should start, pilot should light and then you should have 24 volts at MV to 24V (GND) and the unit should come on and stay on. Leave the meter connected and cycle a few times and see what happens.

    As a temporary measure on the S8600F that got wet use a hair dryer (not to hot) and let it blow on the control for about five minutes to dry out the control. I would still however have it replaced as soon as you can.

    Make sure you have a good ground connection from the pilot bracket to the gas valve is a good ground and you should try that as a final measure and if everything works leave it connected. You can use the screw that holds the pilot to the burner for one end and the other attached to the metal portion of the gas valve.
  • Boring
    Boring Member Posts: 42
    I haven't ever measured microamps... however, I do have a nice fluke that is capable. So you are saying pull the burner ground.... connect one lead of the dmm to the wire and the other dmm lead to the tab on the controller?
  • Tim McElwain
    Tim McElwain Member Posts: 4,493
    Yes that is correct! With the burner running you should have a stable 3 to 5 microamps.
  • Boring
    Boring Member Posts: 42
    Thank you, I'll have to give that a go and see what kind of reading I get... I'll post back, but it may be a big day before I can fiddle with it and respond... Thanks again!
  • Empire_2
    Empire_2 Member Posts: 2,343
    Hi Tim; I believe .9 and up to around 6 is nice. I know all modules are different and I think .9 is the absolute min.
  • Boring
    Boring Member Posts: 42
    Well I was surprised to find my fancy Fluke doesn't have a uA feature....I suppose the mA doesn't have the resolution to measure? Or can you use the mA and move the decimal over a few places? I'll have to keep an eye open for a DMM with the uA feature....
  • BobC
    BobC Member Posts: 5,259
    If it has a 2ma range and it's 3-1/2 digits it will read down to the single ua range.

    Bob
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Boring
    Boring Member Posts: 42
    Borrowed a fluke 87 from a buddy at work. Hooked up and have a steady 6.5 uA... Nice flame, no more issues... At the end of the day, I think I had a bad connection on the spark wire... pilot end. Tightened up both the crimp to wire and the push connector to ignitor.... everything is good now. Replaced a couple roof shingles to cure the water leak... Maybe I'm good for another 20 years.... Thanks again for the lessons.