Gas boiler down , cant get repair service.

[Seasoned Oak]

Got a boiler down for a week now and cant get a service tech for another week. Its been off a week already.Apparently they dont usually take new customers during the busy season. It starts and fires for about 5 seconds then shuts down. Thats the length of the test phase. My best guess is a defective flame sensor, or a weak gas valve not able to open fully. Its a direct vent lo mass with electronic ignition. I have a general knowledge of oil and gas furnaces but this baby has a lot of new safety devices on it and its a bit complicated.
Any ideas.?

 

[nate379]

Pull the flame sensor out and clean it.

 

[basod]

I'd guess it's flame sensor as well.
My propane furnace is old-schoool pilot with thermostatic switch.
Could be a relay on the control board as well, does it have a schematic print or do you have a link to site?
Might be able to walk you through testing it

 

[rwhite]

My NG furnace does this every now and again. I just pull the cover, vacuum all the dust and wipe all the sensors down. Good as new.

 

[Seasoned Oak]

I'd guess it's flame sensor as well.
My propane furnace is old-schoool pilot with thermostatic switch.
Could be a relay on the control board as well, does it have a schematic print or do you have a link to site?
Might be able to walk you through testing it

It does have a control board. Thats were im finding the testing sequence. At this point it seems the furnace fails the flame on test. Even though the flame does come on.

 

[MasterMech]

Sounds like a blind cad cell (flame sensor) to me.

+1 on cleaning the cad cell & trying again.

 

[Seasoned Oak]

Sounds like a blind cad cell (flame sensor) to me.

+1 on cleaning the cad cell & trying again.

I dont think there is a cad cell like device on this furnace,but there is a flame sensor of some kind. I will be removing the gas gun monday or tuesday.
In the meantime im going to tie in an oil burner which is nearby to giver this guy some heat while i wrestle with his gas furnace.

 

[basod]

I thought you said it was turning on for 5secs and then failing test, above you said there is no flame.
Are your hereing the igniter? or does this have a purge timer(I'm guessing forced hot-air)
Do you have the type of gas valve with a manual overide? Where you can turn it to pilot and push it down for gas flow?

I had one of my tenants call me because they had no gas heat once, went over there tried all kinds of stuff, until I realized there was no gas!
It had been shut off for non-payment, I fixed that by tacking it on the rent, and keeping all utilities in my name.

 

[mrfjsf]

The problem is likely your flame rod, If it is lighting then almost immediately going out. If the flame proving rod, is very dirty or just plain broke, it will not send a signal to your ignition board to keep the gas valve open, which will close the gas valve. Trace the wire from the board to the flame rod. The terminal on the board will likely be noted "FS" or "F", it will be one single wire, typically yellow in color, probably 16 awg. Find your flame rod, pull it out and clean it very well with abrasive sand cloth or 200 grit sandpaper, whatever you have. Put it back in and try it. If it still doesnt work, you can check to see if the flame rod is sending a signal to the board. Most send a mVDC signal. If you have a multimeter, set it to mVDC, pull the flame rod wire off the ignition board, place one lead on the flame rod wire, the other on the flame rod terminal on the ignition board, then try to fire the boiler. When it fires, you should get around a 15 mVDC signal, if not, your flame rod is junk, if you are getting the signal, and it is still dropping out the gas valve, then it is likely that your gas valve is shot.

Hope this helps.

 

[Seasoned Oak]

I thought you said it was turning on for 5secs and then failing test, above you said there is no flame.
Are your hereing the igniter? or does this have a purge timer(I'm guessing forced hot-air)
Do you have the type of gas valve with a manual overide? Where you can turn it to pilot and push it down for gas flow?

I had one of my tenants call me because they had no gas heat once, went over there tried all kinds of stuff, until I realized there was no gas!
It had been shut off for non-payment, I fixed that by tacking it on the rent, and keeping all utilities in my name.

Yes the flame does come on for about 5 seconds the length of the test.

 

[Seasoned Oak]

I fixed it ,Thanks guys most of you were on the right track. It was the shroud that covers the ignite r rusted away and what was left was so thin it sagged down from the heat and was partially laying on top of the igniter causing it to send the wrong signal back to the controller shutting down the furnace. I Cant get the part anymore,dicontinued burner model, but stove works fine after i removed the metal fragment from the igniter.

 

[heat seeker]

Way to go! Thanks for the update!