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asenada 11-05-2011 06:05 PM

90-year-old Furnace Burners won't light
 
4 Attachment(s)
Hi. I have an old furnace at least 90 years old. A few days ago, it was working fine (although hadn't been used in for several months). Then all of the sudden the burner won't light. The pilot seems fine although slightly split flame veers off to toward the left.

I shut off the pilot supply and main supply, then looking closely, I notice what looks like a couple inches of baked copper wire is sitting on the burner so I pick it up and it crumbled. I thought maybe that was the thermocouple and bought a new one, but now comparing them, I don't think so. I think the thermocouple is what is hooked to the pilot from below, then what are the two wires that hover above the burner and would one of them burning off and getting shorter affect the burner not lighting?

Attached are pics of the General Controls B60 gas valve two the unidentified wires hovering above, and the pilot assembly, which I can't figure out how to remove or if I even need to.

I'm not sure what to do next. Any help or advice appreciated!!

yuri 11-05-2011 06:40 PM

You have a very old outdated millivolt gas burner. Those 2 tubes are vents. One vents the main press regulator and the other the valve. The valve may have finally failed or the pilot generator is weak or any of a about a dozen other problems which can happen to those old units. The pilot generator needs to produce between 600-750 millivolts for that system to work. The gas valve is obsolete and replaced by a single valve instead of a 3 piece setup like yours. Furnace is less than 50-40% efficient so I would recommend a new one.

how 11-05-2011 06:52 PM

The wire from the top of the gas valve to the underside of the pilot assemble looks like it belongs to a power pile. (thermocouple on steroids).
The thin wires that go directly up from the gas valve will go to your thermostat.
The two lines that exit at the edge of your burners are vent lines and are fine.
I believe the entire system works on a 1/2 volt and is vulnerable to anything less than perfect connections( connections not tight enough at the thermostat or the gas valve) or just the increasing resistance of aging thermostat lines..
Take a long tube and blow air at the bottom of the pilot assembly( pic 4 ) because I believe this one has air vents that can get plugged with dust.
I would tighten all your wire connections and relight your unit. Tap the underside of the pilot assembly with a large screwdriver to see if pilot debris is partially obstructing the pilot output. Do not strike the thermopile lines while doing this. If your unit doesn't work after 5 minutes try crossing your thermostat connections at the thermostat. If that doesn't work then try removing those two thermostat wires from the gas valve and pigtail directly across those two thermostat connections on top of the gas valve.
Let us know what you find out.

asenada 11-05-2011 08:06 PM

Thanks! For the step where I cross the wires at the thermostat, can I do that at the valve instead?
And I don't understand the piggyback step. (Sorry, not sure what that means when it comes to wiring.)

biggles 11-05-2011 08:24 PM

remove the white and red wire that is the stat from the space take a short piece of thin wire and jump the 2 terminals the wires came off your simulating the stat calling for heat the burner should light...the pliot has to be lit and covering that power element thats what produces the power to run the main gas valve.that system is antiquated,:wink: but you always have heat because there is no electricity required to run the heat

how 11-05-2011 10:29 PM

Taking the (two) wires off the thermostat and twisting the bare ends tightly together will test if the thermostat is faulty or causing too much resistance to let the rest of the system work.
Taking the thermostat lines off the two gas valve scews and then tightening a wire across those same two screws will test out if the thermostat and the wires are the problem.
I would blow and then do the pilot tap first to try and raise the voltage generated by the powerpile as high as possible.
What you tell us happens from those tests determines the next steps to take..

asenada 11-06-2011 12:01 PM

I blew, tightened, and relit, tapped the underside of pilot and waited.

Then crossed wires, nothing. Then pigtailed both terminals and burners lit fine.

Then tried with red and white thermostat wires, nothing. Reversed them, nothing. Just when I was giving up, voom, burners lit! Yay!!

Thank you so much!

biggles 11-06-2011 12:05 PM

so it does light at the valve with the jump LEAVE IT the stat hookup seems "Faagazzie"...warm the place up then we'll do a test on the wires from there up to the stat...OK :wink:

how 11-06-2011 12:51 PM

After getting the best volt output from the thermopile...
When you crossed the thermostat lines at the thermostat and it didn't operate the furnace, you verifyed that the thermostat wasn't the problem.
When you got the furnace to work by pigtailing across the thermostat conections at the gas valve you established that the main problem is with the thermostat lines. Too much electrical resistance, too far to carry the required current, bad marretted connections some where along the line, or almost broken anywhere.
If you can get it to work with the thermostat and gas valve connections back where you originally found them ..then great but I'd have enough new thermostat wire on hand to replace it all if it happens again.
Note..Most thermostat wire problems with old thermostat wire occurs within the first few feet of the gas valve. I'd remove a foot of wire from there and re attach before replacing the entire length.

biggles 11-06-2011 01:40 PM

want to proff out the stat run up to the stat itself...if the place is warmed up remove the 2 wires up on the stat and leave hanging in the air...reconnect them as originally were before you jumped to heat the place so the jump is removed and the white and red are back on....might take a small piece of sand paper and just clean the gas valve termials where the white/red go if the screw comes out all the way...now go up to the STAT with all the power ON and put the 2 stat wires together go down and see if you get a heat run... if it does run or not touch the red and white wires want to see if the main burner bounces...when touched...lets hear back...:whistling2:

guyinsb 10-23-2012 11:04 PM

I also have an older General Controls B60 gas valve. When I disconnect the thermopile from the valve,
the pilot lights keep burning. Is this standard operation for the B60? Or is there a pilot valve that is stuck open?

hvactech126 10-23-2012 11:22 PM

Quote:

Originally Posted by guyinsb (Post 1036855)
I also have an older General Controls B60 gas valve. When I disconnect the thermopile from the valve,
the pilot lights keep burning. Is this standard operation for the B60? Or is there a pilot valve that is stuck open?

IF you have the same setup as shown in the previous posts on this thread then there is no 100% shutoff pilot safety. This is unsafe and should be updated to a 100% shutoff system. Something this old should be serviced by a professional to verify correct and safe operation.

To answer your question - Yes this is standard (unsafe) operation on that type of setup. If you follow the pilot line back you will find a small manual shutoff valve.

biggles 10-24-2012 04:23 AM

the pilot is the source to generate the power(millivolts) to run the gas valve and is always a direct standing item.the only benny of this type of system if it is a "steam heat boiler" application you have heat in a black out...the millivolt generator can weaken over the years and as stated the stat wire run can drag on the valve opening

sammy37 10-24-2012 10:04 AM

Quote:

Originally Posted by biggles (Post 1036887)
the pilot is the source to generate the power(millivolts) to run the gas valve and is always a direct standing item.the only benny of this type of system if it is a "steam heat boiler" application you have heat in a black out...the millivolt generator can weaken over the years and as stated the stat wire run can drag on the valve opening

We had a simillar setup in a house once with a 1964 carrier furnace in the hall closet and the owners manual gave instructions on how to run that thing in a power outage, pretty scary for a forced air unit.

biggles 10-24-2012 01:37 PM

forced air i would like to hear about how air moved in a black out...heat rises but jessssssssss


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