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Thread: HVAC folks? Furnace won't kick in - thermostat clicks?

  1. #1
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    HVAC folks? Furnace won't kick in - thermostat clicks?

    Yo Creekers. We got any HVAC people here who might have an idea what is going on with my furnace?

    - We have a forced-air natural gas furnace - mid efficiency, probably 20yrs old
    - have a Honeywell Chronotherm III thermostat

    - tonite the furnace won't kick in. The thermostat seems to keep trying - instead of a single click, when the heating cycle starts, it gives a double-click and nothing happens.

    - I can manually turn the fan on.
    - I have been down and pulled the cover off the furnance and it is just sitting there - the pilot light is not kicking in.

    - I think we changed the batteries recently, but I'm not 100% sure. (and as soon as my wife gets home from her errands I'll pop out for a new set just to be sure.)
    "It's Not About You."

  2. #2
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    I suspect you have electronic ignition on the HVAC.
    Batteries usually operate the thermostat and nothing else.
    Does the igniter click, click click???
    Call the man!!
    TJH
    Live Like You Mean It.



    http://www.northhouse.org/

  3. #3
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    There is probably a RESET button inside the furnace.

    Look for something that looks like a button or a switch.

    This happens on one of my furnaces at the flower shop from time to time.

    Your furnace wouldn't happen to be a Ruud would it?

    Joe

  4. #4
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    Hvac

    Art,
    I'm with Tyler (what a surprise) on the igniter. I'm guessing with $50 -100. That happened to me last year and the service guy actually walked in with a new igniter in his hand. It's obviously not an infrequent problem.

    Dale T.
    I am so busy REMAKING my projects that I don't have time to make them the FIRST time!

  5. #5
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    Quote Originally Posted by Tyler Howell
    I suspect you have electronic ignition on the HVAC.
    Batteries usually operate the thermostat and nothing else.
    Does the igniter click, click click???
    Call the man!!
    That's what I thought about the batteries also. Yes, it is electronic ignition.
    And no, the igniter was not clicking.

    And I was figuring I would have to "call the man"... but not at 9pm on a Friday after a serious snowstorm. We'll make the night at least and check in the morning.

    I just killed power to the furnace, and let it "rest" for two minutes, and it ignited immediately. The trick will be to see if it will do another cycle.


    Joe, it is not a Ruud. It is something called a "Clare MegaSave"... I belive that company is RIP.

    Thing is I replaced the fan motor last year. Two years prior we replaced the belt + pulley + gas valve. And also about 7 years ago we replaced the .. oh I forget the name thermocouple?

    On the one hand I know the furnace is an old one. But really -- we've replaced most of the brains/guts of the thing!!!
    "It's Not About You."

  6. #6
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    Turning power off resets it

    Many of the flame safety modules have to be reset after a flame-out. One method of this is to remove power or the demand for heat. This can be accomplished by turning off the breaker and usually also by turning off at the thermostat. A sudden gust of wind that blows down the chimney/stack that puts out the pilot can set up a flame failure event. Hopefully that is your only problem.

    Bill in WNC mountains
    NC Refrigeration Contractor License #2821

  7. #7
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    Go to the furnace and find where the thermostat wires come in, once you find the terminal block find R and W on it, jumper them out and see if the furnace comes on.
    If so, it's probably the stat, chronotherms are not my favorite stat and the three has been updated several times to not always a better stat.

    Anyway, see if jumping R and W does anything, also make sure the blower compartment axcess door isn't off, as there might be a blower door switch that needs to be pressed in for the furnace to function.

    If you have a thermocouple, I doubt you have electronic ignition, but who knows with them Canuck furnaces...

    Try that and let us know what happens.
    btw, R and W should be low voltage but be careful anyway..

    Al

  8. #8
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    Art,
    I'd bet that if you call service at the place that installed the furnace they would walk you through a trouble-shooting sequence no-charge.

    Worth a try, anyway.

    Frank

  9. #9
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    Quote Originally Posted by Al Willits
    Go to the furnace and find where the thermostat wires come in, once you find the terminal block find R and W on it, jumper them out and see if the furnace comes on.
    If so, it's probably the stat, chronotherms are not my favorite stat and the three has been updated several times to not always a better stat.
    ...
    If you have a thermocouple, I doubt you have electronic ignition, but who knows with them Canuck furnaces...
    Al,
    you're right, it wasn't the Thermocouple - that was on the furnace at the last house. It was the Gas Valve + auto pilot. (I just read the service listing which is on a sticker on the furnace).

    It's been running fine the past hour, so it seems that turning it off and letting it rest a moment reset something or other. But I'm taking notes in case it acts up again.

    Bill, there is no chimney. It is a power vent out the side of the house. East side too, so out of the prevailing wind. I'd be real surprised if any wind gust could make it past the baffle, down the pipe, past the elbow, and past the power vent van... But I suppose anything is possible.

    Al,
    I just checked inside the furnace, and up top where the the thermostat (and the 120v line) enter the furnace there is a block with 5 terminals, marked R W C Y G - however the W is the one that is NOT hooked up to anything. However, if I pop the faceplate of the thermostat, there IS a R and W back there that is wired up. Can I jumper it from the Thermostat end?

    thanks for the advice,
    ...art
    "It's Not About You."

  10. #10
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    Art, if W isn't connected to anything I might want to be a bit careful with that, not a W2 is there?
    What color wire goes to W on the stat and what does it connect to on the furnace?

    And it sounds like your right, most electronic ignitions will reset themselfs if you either break power or turn the heat off and on again.

    This is a gas furnace right?
    Do you know if its a glow style ignitor or does it spark to light?

    I'll hang around a bit if your gonna be online.

    Al

  11. #11
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    Power vent fans are usually used when the flue configuration does not create enough negative pressure to insure proper exhausting of combustion products, ie CARBON MONOXIDE. Draft is created by enough vertical rise vs. horizontal run and the rising of heated air. If you are venting out the wall there is very little rise, therefore little draft. That is why you have the fan. These fans are referred to as "draft boosters", not draft suckers. If properly installed and sized they work well. However a several second wind gust of 40/50 mph can overcome them. This is usually not enough to cause gassing your house but it can still cause nuisance trips of flame failure detector. My original statement was a guess to help you understand some of the possibilities that might not be anything being broken.

    Bill

  12. #12
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    Bill,
    Here is my "Chimney". Sorry for the blurry photo, shot through the window.
    chimney.jpg


    Quote Originally Posted by Al Willits
    Art, if W isn't connected to anything I might want to be a bit careful with that, not a W2 is there?
    What color wire goes to W on the stat and what does it connect to on the furnace?
    ...
    Do you know if its a glow style ignitor or does it spark to light?
    Thanks, Al, for all your great help. Here's a "photo tour" of my furnace.
    (I love digital cameras!)

    Here's the guts of my furnace - bottom section. There is the black blower fan - to exhaust the flue gasses out the side of the house. Above that is the heat exchanger in the back, and above that the silver gas valve (only 4yrs old). Oh and it is a spark ignitor, not a glow igniter -- when the furnace works, I can hear it clicking repeatedly before the pilot lits.

    furnace-guts-bottom.jpg

    Here is the guts of my furnace - top section. Up top is where the power and thermostat wires enter and hook up. The grey box below that is -- I don't know the official name, limit switch? That kicks on the fan after the heat exchanger heats up.
    furnace-guts-top.jpg

    And here is a closeup of that block where (some of) the thermostats wires hook up. I labelled it, as the letters were a bit blurry.
    furnace-guts-top-closeup.jpg

    On the thermostat end of things we've got a W (white wire) G (Green wire) R (Black wire) Rc (Red wire) Y (Yellow wire).
    "It's Not About You."

  13. #13
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    That helps, thanks.

    Ya, looks like a spark to light pilot, with a capillary style safety, meaning that thin tube that goes from the valve into the furnace, is filled with mercury/freon/whatever and when the pilot is lit by that orange wire (spark lead), it heats up the end of that tube, which is probably sitting in the pilot flame.

    That causes a bellows on the other end (at the valve) to trip a switch that allows main burner to come on.

    Not sure how far you want to go into this, but that tube (pilot safety) can sometimes get weak, or what's usually more common, is the pilot gets a bit dirty and won't always heat the cap tube hot enough.

    Trick of the trade was to remove (furnace off) the pilot line from the valve and using a aspirator bulb, blowing though the pilot line, 9 out of ten times it would clean the pilot well enough to function again.
    Compressed air will work, but it doesn't take much.

    That gray box is your fan and limit control, chances are if you pull that white knob out, the blower will run continuously.

    Looks like they're running the W on the thermostat to the Y on the furnace...haven't a clue why, sorry.
    Y is usually used for A/C, wondering if they use it to energize a relay or something?
    If your on Natural gas, can you see the pilot when it lights?
    Is it blue or is there some yellow to it?
    Orange is OK, just stuff in the air.
    Propane may have a bit of yellow tipping on the pilot, but it shouldn't be very much, if it looks like a candle, its probably dirty.

    PLEASE, if your not sure of what your doing, get a service tech out there, add all the numbo jumbo about me not taking any responsibility (wonderful world we live it...suing at the drop of a hat).
    Do not change anything, and be careful, if in doubt, stop and either get back to us or call someone.

    It doesn't sound serious, but I doubt it'll get better.

    Al

  14. #14
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    Quote Originally Posted by Al Willits
    ... with a capillary style safety, meaning that thin tube that goes from the valve into the furnace, is filled with mercury/freon/whatever and when the pilot is lit by that orange wire (spark lead), it heats up the end of that tube, which is probably sitting in the pilot flame.
    ...
    Trick of the trade was to remove (furnace off) the pilot line from the valve and using a aspirator bulb, blowing though the pilot line, 9 out of ten times it would clean the pilot well enough to function again.
    ...
    If your on Natural gas, can you see the pilot when it lights?
    Is it blue or is there some yellow to it?
    Hey Al,
    - Yes it is Natural Gas
    - Yes the pilot is blue (with some white), no yellow as I recall.

    furnace-guts-annotated.jpg
    - Here's another photo, just double checking my understanding of things
    A- is the capillary saftey - yes I know it has mercury, it is labelled as such
    B- is the Spark lead - red wire that ignites the pilot
    C- is the pilot line that you are wondering about blowing out
    D- is the off switch for the gas. I'd turn that off as well as power before trying any of this!

    Just to reassure you that while I am not a licensed gas fitter, I am a pretty handy guy who has worked on electronics and hardware like this over the years. I just did't know what all the parts do, just some of them.

    And now that you mention it, I remember seeing a furnace tech in previous years using a bulb to blow out things on the furnace

    And how about this: "I, Art Mulder, hereby indemnify Al Willits from any responsibility. If I do anything, I accept responsibility for my own actions." Whearas and so forth and the party of the first part and habeus furnace-us...

    Happy Weekend, folks!
    "It's Not About You."

  15. #15
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    """""""""""
    And how about this: "I, Art Mulder, hereby indemnify Al Willits from any responsibility. If I do anything, I accept responsibility for my own actions." Whearas and so forth and the party of the first part and habeus furnace-us...
    """"""""

    I'll copy that and keep it in a safe place...

    Looks like you got it.
    Not sure about the white, must be the Canadian gas...hehe

    That mercury safety probably just unplugs from the valve btw.
    If ya want, try blowing the pilot line out and see if that white disappears, that safety has to get fairly hot to work.

    It could also be in the venting of the furnace, but what I've suggested are things I think you might be able to check, key word here is free, if these don't work I might get someone out to check the pressure switch and combustion air motor, also the vent going outside, like say by someone else, its possible a wind could cause problems.

    I don't know how many times your furnace will try to relight, but usually wind will cause only intermittent problems.
    When you said in your first post the pilot wouldn't light, was it the pilot or the main burner??

    Al

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