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

[Art Mulder]

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.)

[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!!:(

[Joe Mioux]

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

[Dale Thompson]

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.

[Art Mulder]

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!!! :mad::mad:

[Bill Turpin]

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

[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.

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...:D

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

Al

[Frank Chaffee]

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

[Art Mulder]

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...:D


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... :rolleyes: 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

[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?

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

[Bill Turpin]

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

[Art Mulder]

Bill,
Here is my "Chimney". Sorry for the blurry photo, shot through the window.
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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?
...
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. :D
(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.

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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.
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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.
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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).

[Al Willits]

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

[Art Mulder]

... 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.

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- 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! :D

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... :rolleyes::cool:

Happy Weekend, folks!

[Al Willits]

"""""""""""
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... :rolleyes::cool:
""""""""

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

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

[Art Mulder]

When you said in your first post the pilot wouldn't light, was it the pilot or the main burner??

Pilot.

The way the thing normally works, is that the thermostat will give a click, and the yellow "system" LED will light. This causes the furnace to light, and 10-30 seconds later you hear the muffled "whump" as the main burner kicks in. Then another 30-60 seconds(?) after that the fan kicks in.

(I know, you know all this... :) )

With my problem yesterday evening, the thermostat would give the initial click, but then immediately give another click, so what I'd hear would be "click-click". The display would blink at the same time, and then nothing would happen for about 20-30 seconds and then it would try again. (so the system light did NOT light up.)

thanks again, Al.

[Larry James]

Art, hope you have it working - if not, here is some additional information.

This looks like a White-Rogers gas valve and ignition system - often called pilot-relight when used with a thermocouple. You have a version designed for induced draft furnaces.

The basic generic sequence is ...

1- Thermostat calls for heat, circuit between R (24 hot) and W (switched 24) energizes a relay and the relay (large silver box with terminals) starts the vent blower motor. Power may also be switched to the spark ignitor at this time, but gas is not yet following. Note: the gas valve does not have a pilot position, only on and off for this system.

2-When the vent motor up to speed and the combustion air switch ( the round control mounted to the right of blower in your picture) senses that combustion air is flowing and closes a switch proving air flow before the gas valve is allowed to open. Note: this switch may have 2 or 3 terminals. Also, the system may have a time delay to allow blower to purge combustion chamber before ignition.

3- After air flow is proven, the spark will light the pilot burner and the mercury sensor will heat up. The black control on the end of the sensing tube is plugged into the gas valve, as Al mentioned. This control usually (?) has a single pole double throw switch (SPDT) inside - like the switching action of a 3-way light switch that you likely have in your house.

4-When the sensor has heated up, proving there is a pilot flame available, the main gas valve is energized by the sensor switch. The pilot should light should ignite the main burners.

5-After a delay that allows the heat exchanger to warm up the blower should circulate warm air. Note: The blower may have a time delay as well as a bimetal sensor - the blower may turn on in this system even if the burner is off.

Al noted, "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?" This could be related to what is called a holding circuit that holds the pilot on after the mercury switch changes position (or not). EDIT: more on yellow wire-this setup may be used to supply 24 volts to the thermostat in the off cycle.


There were many variations to this system. That's why I called it "generic." I haven't repaired furnaces for over 25 years, but I repaired many systems with the mercury sensor. The most common problem was with the sensor, or quoting Al again, "...more common, is the pilot gets a bit dirty and won't always heat the cap tube hot enough."

I also give information under the:
"Art Mulder, hereby indemnify" clause. And how about this: "I, Art Mulder, hereby indemnify Larry James 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...

Best to find a "old timer" to repair the system, cause like I used to tell customers - "I can't fix them over the phone."

Let us know what the problem was when you have it working.

Keep warm, Larry

[Al Willits]

Art, you ever get the furnace looked at??
Just wondering how it went.

Al

[Art Mulder]

Art, you ever get the furnace looked at??
Just wondering how it went.

Al

Not yet... got a salesman coming by tomorrow to scare me with a quote on a new one. After that we'll probably go running back to our corners... :eek:

[Rich Konopka]

I had somethig similar happen with my Thermostat clicking and cicking and the Furnace false starting. I was he thermostat. I had a fancy digital programmable Robert Shaw Two zone switch. Replaced the battery and tightened the connections and it has been fine. Have you double checked the thermostat?

[Art Mulder]

Finally this morning I got the time to see about blowing out the pilot line. The furnace seemed to work for about 2 days at a stretch, then the click-click-nothing would happend and we'd have to reset it again.

So I disconnected it and blew it out.
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Then I put it back together, and then the furnace wouldn't ignite the pilot. The exhaust fan would start, but that was all. I checked the flue outside and it was not obstructed.

This was odd, I hadn't touched anything but the pilot line and the igniter wire. I wondered if I'd jostled the wire loose, as it did have two cracks in it.

Called a few places, but neither one had the pilot relite part (it is a white-rogers). THe one guy told me that this is an old no-longer-made furnace and he would have to wait until monday to call his supplier to see if he could get a part. Even if I called a furnace repair guy, that guy probably wouldn't have the part either. Argh!

So I went back down and disassembled it again. This time I found a possible loose wire on one of the vacuum sensors. (this is connected to what looks like a temperature probe above the opening to the pilot area. Not sure what that would be for) I tightened that, and also had a look at the ignitor wire end. I wondered if I could cut out the cracked part and resolder it to the end. Can't do it though, as the connection is embedded in a ceramic shield.

But I put it back together and now the furnace sparks. I can hear it clicking. But now the pilot STILL won't light. ARGH! What could I have done?

I dunno what now. I just wanted to write, in case anyone had a brilliant idea.

...art

ps: FYI for any Canadians out there... I had a furnace quote: just a touch under $6000 for a new furnace. 60,000 BTU Armstrong (made by Lennox) with DC variable speed motor, and dual fire, (that is installed, with humidifier, taxes in, NO a/c). $600 less for no variable speed, and another $600 less for no dual-fire. :eek::mad::( (where's the fainting icon?) Better get a few more quotes...

[Al Willits]

Make sure the sparking is at the pilot and not to somewhere else, with the cracked insulator it could be arcing to chassis before it gets to the spark rod.
6k sounds a bit high, I think I'd get that second bid too..
Can you hear if gas is coming out of the pilot?
If so, I'd think that the spark is not at the rod or strong enough to light the pilot, maybe.

Al

[Art Mulder]

The guys are right now replacing my furnace.

And BOY am I glad we made that decision, because this is the heat exchanger in that old unit.
529475294652945

With all those holes we are really puzzled as to why our CO2 detector was NOT sounding.

These are all way at the top also, which would have made detection pretty tricky as well.

I'm going to sleep a lot better tonight.
...art

[Ken Fitzgerald]

Art...........There's little that I don't fix at home. I install and fix MR scanners, CT scanners, x-ray equipments for a living. In the Navy I installed and maintained all the equipments used in air traffic control centers...and equipments aboard nuclear powered subs..........I had a house burn down due to a gas leak when I was 6 years old. I don't ....I DON'T do anything related to natural gas....water heater...I'll relight the pilot.....furnace...I'll turn off power ....wait a while...turn it back on....That doesn't do it......I call the PROS! I do my own plumbing, carpentry, electrical........I don't do gas....... except for the gases (helium) used in the cryogen systems of supercooled magnets used with MR scanners......

[Al Willits]

Popular misconception that all furnaces with holes in the chamber produce CO, not true.
That's why your CO detector didn't register, assuming it was working correctly.
Most manufactures recommend a yearly inspection of their furnaces, and it is a good idea.

Good thing they found the bad chambers though, when the exhaust gases go back into the house and get burned again, you will/can start to get CO, or if the holes get big enough to cause flame distortion that will/can cause CO.

Al

[Art Mulder]

Hey Al, one last thing...


The guys ripping out the furnace also discovered that the condensate drain line was plugged somehow. This meant that it wasn't draining properly, and the exhaust blower was sitting in water, and probably not generating enough suction.

Yet the technician we had out on Saturday completely missed that. I can't really blame him either. Who would check that?

[Al Willits]

Loaded question, but you'd think the first guy would have caught it, did the furnace run for the first guy?
If so, that could be why he missed it.
If it didn't, I'd say he missed the boat here, remember I wasn't there and asking second opinions over the iner net is chancy.

I will say plugged condensate lines are/can be common, and should be checked from time to time.
If the furnace didn't come on because the combustion air motor was running to slow, jumpering the pressure switch out would have probably shown that, least wises the probalem was in that circuit.

One of the basic checks for a chamber having holes or cracks in it, is to run just the blower (house air, not combustion blower) and not the burner, then stick a match into the chamber, if you see flame distrortion, good chance a chamber is bad...not in concrete, but a good indication.

Good part is that you are now headed for a new furnace and safe.

Al