furnace ignitor

[2fifty2]

Any ideas where I can find a furnace ignitor for my Carrier furnace on a Sunday afternoon?

Yesterday a thermal fuse blows in my dryer now this morning my furnace locks up in safety mode. I cleaned off the flame sensor and removed the circuit board and looked for any damage - none found...Then I saw my ignitor-black and white soot and a crack in one wand...

Ever feel like you are taking things apart more than using them? *sheesh*

Oh, for those who helped me with the basement drain - thanks - it all went well and the sink drains like a champ.

252

 

[jsfinn]

Re: furnace ignitor

I don't think you're going to find one on a Sunday afternoon, sorry.


Your best bet may be to order it somewhere online - it'll be less expensive and you can probably have it Tuesday if you pay for the overnight shipping.

Good luck with it.

 

[roscoe]

Re: furnace ignitor

In the mean time, you can do as I did.

When the furnace tries to ignite, light it with a long match or a long lighter.

Crank the furnace up to 78 and get the house good and warm, let it cool down to 60 or so, then do it again. It should take 2 or more hours between cycles.

 

[gonefishie]

Re: furnace ignitor

OK, this got me interested as it could happen to me too. I know little to nothing about the hvac stuff. Few questions, if the ignitor goes bad, does it take out the pilot flame too? If the flame goes out then what happen to the gas that keep the flame going? It would goes unburn and causes fire/explosion? is there seperate feed for the actual burners and pilot? If there isn't, do you have to adjust the valve for a proper gas input? I mean, you wouldn't want to turn it to full blast and stick a flame in it, do ya? I thought the pilot flame stays on as long as there is gas and it didn't get blown out? how do you know when the darn thing try to ignites anyway?

 

[2fifty2]

Re: furnace ignitor

There is a sensor that detects heat to make sure the furnace is lit. If the furnace trys to light three times and senses nothing going on - it locks out for something like 90 minutes then tries again. That sensor has a common issue with getting dirty and giving false readings so the furnace will not lite.

 

[MikDee]

Re: furnace ignitor

OK, this got me interested as it could happen to me too. I know little to nothing about the hvac stuff. Few questions, if the ignitor goes bad, does it take out the pilot flame too? If the flame goes out then what happen to the gas that keep the flame going? It would goes unburn and causes fire/explosion? is there seperate feed for the actual burners and pilot? If there isn't, do you have to adjust the valve for a proper gas input? I mean, you wouldn't want to turn it to full blast and stick a flame in it, do ya? I thought the pilot flame stays on as long as there is gas and it didn't get blown out? how do you know when the darn thing try to ignites anyway?

I've had a propane (LPG) powered hot air boiler in a mobile home, and had the ignitor go out because it cracked after awhile. The ignitor is used with electronic ignition, it is basically just a "glowstick" a glowing rod like you find on a surface burner of an electric stove, or in an electric water heater, in place of a lighted flame. Either way, the pilot flame, or ignitor has to be on all the time, & anytime, the burner is working to keep it lit, just to ease your mind, there is a device called a Thermocouple (independently mechanically operated by a bi-metallic switch)
on gas burners, that will automatically safely shut off the gas flow, if it doesn't sense heat from the pilot flame, or ignitor.
I've also had pilot lights on gas water heaters, that ocassionally would blow out in windy weather, with no ill effects, except you have no hot water, and have to re-light the pilot.

 

[Xcusme]

Re: furnace ignitor

OK, some basics first. If you have a furnace with a standing pilot, that pilot flame impinges on a thermocouple. The thermocouple sends a small electrical signal to the gas valve telling the gas valve that the pilot is lit. When the thermostat calls for heat, the gas valve opens and the gas to the main burners is opened. Since the pilot is lit, it fires off the main gas and the furnace works.

If you have a newer furnace, the standing pilot is replaced with a spark ignition system. When the thermostat calls for heat. The controller board supplies a high tension spark to the pilot and turns on the pilots gas supply. When the pilot lights, the flame impinges on a sensor wire. The sensor wire sends a small signal voltage to the controller board, in effect, telling the controller board that the pilot is now lit. Controller board now sends a signal (voltage) to the main gas valve to open. The main burners are then fired by the now lit pilot and the furnace heats the house.
This is a simplification of the process, but I hope you get the idea.

 

[Caveman Charlie]

Re: furnace ignitor

OK, some basics first. If you have a furnace with a standing pilot, that pilot flame impinges on a thermocouple. The thermocouple sends a small electrical signal to the gas valve telling the gas valve that the pilot is lit. When the thermostat calls for heat, the gas valve opens and the gas to the main burners is opened. Since the pilot is lit, it fires off the main gas and the furnace works.

If you have a newer furnace, the standing pilot is replaced with a spark ignition system. When the thermostat calls for heat. The controller board supplies a high tension spark to the pilot and turns on the pilots gas supply. When the pilot lights, the flame impinges on a sensor wire. The sensor wire sends a small signal voltage to the controller board, in effect, telling the controller board that the pilot is now lit. Controller board now sends a signal (voltage) to the main gas valve to open. The main burners are then fired by the now lit pilot and the furnace heats the house.
This is a simplification of the process, but I hope you get the idea.

The real new gas furnaces. like my two year old one. no longer use a spark to ignite the gas. They use a glowing stick thing that starts to glow before the gas valve is opened. The rest is the same as your explanation.

 

[2fifty2]

Re: furnace ignitor

That glow stick is what took a dump in my furnace - it had a bunch of white residue on it and a small crack that looked like a chunk had been worn out of it. Got the part today for 15 bucks and had it installed and fired up in 10 minutes. Heat is good in 20 degree weather - the house stayed in the upper fifties all day with nothing on...

 

[MikDee]

Re: furnace ignitor

Isn't this what I went into detail about, a glow stick, or glow rod! Duh

 

[gonefishie]

Re: furnace ignitor

OK, so if the pilot goes out the gas that feed the pilot get shut off automatically? to light the pilot, you just stick a lighter in and that's it? My water heater has a push putton to provide spark to light the pilot. My furnace, however, have no such thing and it seemed that I have to stick some source of flame in it. It's pretty ancient. So, is the glowing stick is what make new furnances more efficient since it doesn't have to stay on all the time?

 

[MikDee]

Re: furnace ignitor

OK, so if the pilot goes out the gas that feed the pilot get shut off automatically? to light the pilot, you just stick a lighter in and that's it? My water heater has a push putton to provide spark to light the pilot. My furnace, however, have no such thing and it seemed that I have to stick some source of flame in it. It's pretty ancient. So, is the glowing stick is what make new furnances more efficient since it doesn't have to stay on all the time?

Yes, When the Thermocouple senses no heat from the pilot, it shuts the gas flow down. Yes, to light the pilot you follow the procedure listed, and use a source of flame (long match, lighter, etc.). Actually the glowstick does stay on all the time to keep the burner lit, it comes on whenever it calls for heat it's just a bit more convenient, then having to light it manually with a flame. I've replaced them myself in previous places I've lived, It's not hard to do, and they run about $15.

 

[Caveman Charlie]

Re: furnace igniter

Re: furnace igniter

Yes, When the Thermocouple senses no heat from the pilot, it shuts the gas flow down. Yes, to light the pilot you follow the procedure listed, and use a source of flame (long match, lighter, etc.). Actually the glow stick does stay on all the time to keep the burner lit, it comes on whenever it calls for heat it's just a bit more convenient, then having to light it manually with a flame. I've replaced them myself in previous places I've lived, It's not hard to do, and they run about $15.

I think I know what you were trying to say but, you made that a little confusing.

The old style furnaces used a pilot light to light the gas when the thermostat called for heat. If the pilot light went out a safety device called a thermocouple shut off all the gas to avoid a fire/explosion. To relight this type of furnace you had to hold a button down to bypass the safety feature until the thermocouple got hot enough. The furnace will not fire up until the thermocouple is hot enough to hold the gas valve open. Some furnaces had a gas control valve where you had to turn it to a different position and then hold the valve down until the pilot was lit and the thermocouple was hot enough to work. Then you turned the valve to open or run and everything worked normally after that.

The glow stick on a new furnace means that there is not pilot light and it does help with the newer furnaces being more efficient. There are other factors that come into play too though.

 

[MikDee]

Re: furnace igniter

Re: furnace igniter

I think I know what you were trying to say but, you made that a little confusing.

The old style furnaces used a pilot light to light the gas when the thermostat called for heat. If the pilot light went out a safety device called a thermocouple shut off all the gas to avoid a fire/explosion. To relight this type of furnace you had to hold a button down to bypass the safety feature until the thermocouple got hot enough. The furnace will not fire up until the thermocouple is hot enough to hold the gas valve open. Some furnaces had a gas control valve where you had to turn it to a different position and then hold the valve down until the pilot was lit and the thermocouple was hot enough to work. Then you turned the valve to open or run and everything worked normally after that.

The glow stick on a new furnace means that there is not pilot light and it does help with the newer furnaces being more efficient. There are other factors that come into play too though.

Nothing confusing about it Charlie, I was just answering the question in a clear concise way, (notice I said, "to light the pilot follow the procedure listed") rather then go into more confusing detail like yourself, plus that's basically what I stated in an earlier post.

 

[SS MAYFLOAT]

Re: furnace ignitor

Proper term for the glow style is "Hot surface ignition" the old type with the pilot/thermocouple is "Standing Pilot" For further note, the hot surface ignitor does not stay on after the main burners are on. If they do, it causes them to burn out prematurely. After the main burners are on, they are what shows proof of flame. On all gas fired appliances (for indoor use), it is a reqirement by code to have a flame proofing system. There is also a hi-limit switch which is a very important item. This will shut the unit down if something happens to the main blower and keeps the unit from over heating which could cause a possible fire. Never bypass this saftey.

My experience with hot surface ignitors is to always have a spare. When they first come onto the market, they were prone to failing. The newer styles have been improved, but I still insist that a spare is kept on hand.

 

[Caveman Charlie]

Re: furnace igniter

Re: furnace igniter

Nothing confusing about it Charlie, I was just answering the question in a clear concise way, (notice I said, "to light the pilot follow the procedure listed") rather then go into more confusing detail like yourself, plus that's basically what I stated in an earlier post.

Sorry, I didn't mean to offend. :redface:I should have said that "I" was confused not that it was confusing. Remember us caveman get confused easy.

 

[MikDee]

Re: furnace ignitor

Proper term for the glow style is "Hot surface ignition" the old type with the pilot/thermocouple is "Standing Pilot" For further note, the hot surface ignitor does not stay on after the main burners are on. If they do, it causes them to burn out prematurely. After the main burners are on, they are what shows proof of flame. On all gas fired appliances (for indoor use), it is a reqirement by code to have a flame proofing system. There is also a hi-limit switch which is a very important item. This will shut the unit down if something happens to the main blower and keeps the unit from over heating which could cause a possible fire. Never bypass this saftey.

My experience with hot surface ignitors is to always have a spare. When they first come onto the market, they were prone to failing. The newer styles have been improved, but I still insist that a spare is kept on hand.

Yes, I definitely agree a spare is handy, the one doublewide I rented, used to burn them out at the worst times! Till I found out that a previous tennant had broken a baffle (heat sheild) over it, causing it to get fried ocassionally, once I replaced that (easy, & cheap) no more problems. Correct me if I'm wrong here, I was under the impression they need to be on all the time the burners running, because what else would keep the flame lit?

 

[gonefishie]

Re: furnace ignitor

, because what else would keep the flame lit?

The flame itself.

 

[rickdb1boat]

Re: furnace ignitor

because what else would keep the flame lit?

The flame sensor rod serves the same purpose as the thermocouple on electronic (Spark) ignition systems in keeping the flame lit. The ignitor serves as the flame prover on hot surface ignition systems. Also, when replacing the ignitor, never touch the element with bare hands or the oil from your fingers will cause hot spots and it will fail prematurely.

Flame sensor: