1978 boler furnace

[suedolpe]

I have had a gas guy working on my original boler furnace to insure safety.
He has discovered that when the thermostat hits the desired temp the heating unit turns off with a click but there is still a small fire burning.

The only way to get this fire to go out is to turn the red nob to pilot.
Is this normal?

The gas guy thinks there may be a very small internal leak but he has never worked on one of these furnaces before.

Any input would be really appreciated folks.

Sue

[Mark Bradley]

Hi Sue,
I own a 1976 Boler and I have used the furnace a number of occasions. When the red knob is turned to pilot and pushed in a small amount of propane will be emitted through the pilot nozzle. This propane will then be lit with a outside source. This is the small flame that you see burning and will stay lit as long as the furnace is on. There is also a device called a thermocouple that is located above the pilot nozzle that will be immersed in this flame. This thermocouple is a safety switch that is connected to the main gas valve. If ever the pilot light goes out and there is propane gas being emitted into the burner box the thermocouple will cool off, and close the main gas valve.

After the pilot light is lit and the thermocouple heats up the red knob can be turned to on. Then the main burner nozzle will be lit with the emitting propane and will cycle on and off according to where your thermostat is set. The pilot light will always be lit in order to light the main burner propane.

I hope this helps and if you are successful with this furnace be sure to install a CO Detector.

[Eric Frye]

Before you spend much time on that issue you really need to make sure the burner box is solid. My 77 Airstream furnace looked like the night sky when it was fired up. The pin holes were not detectable to the naked eye in normal day light.

[Doug Arthurs]

1978 furnace. I would think about replacing it. I replaced the one in my 1979 Bigfoot a couple years ago with a safe modern unit.

[RogerDat]

The older propane appliances would have a small flame on a tube that was the pilot to light the burner when the thermostat opened the valve for the main burner. A small thermocouple (copper heat sensor rod) would shut off the gas flow to the pilot if that small pilot flame went out.

Modern would have an electric ignition with some gizmos to open gas valve to burner AND start component sparking or glowing to ignite the burner in response to thermostat. Furnace will shut off gas if it doesn't detect burner ignition. Burner has the same sort of copper probe thermocouple that when heated generates small amount of current.

So there would always be a small flame burning in an old style furnace until know is turned to pilot. In pilot position one can push in the knob to open the pilot gas flow and light it. Holding it for a minute or two until the sensor gets hot. I think on some models in the pilot position if the knob isn't being pushed in the gas flow to the pilot gets cut. Same as off. It sounded like OP and gas guy were describing that. Knob at pilot and the little flame goes out.

The burner is essentially a fire in a box that has a vent to pull in outside air for combustion and an exhaust vent to take the combustion gases outside. Won't use up the air inside to support the combustion and won't dump the CO from combustion inside.

The room air gets warm by flowing around the box with it's vents to the outside. Like a wood stove if the wood stove had a pipe in the back that brought in air for combustion and the door sealed air tight.

If that box has rust holes or cracks at the welded seams the leaking CO can kill you so hat is why checking the box for CO leaks is important professional service item. When it looks like the stars in the sky when lit in the dark you have a lot of holes. Also why finding a spot for a CO detector in your camper is important.

Having a 77 Scamp I have given some thought to the furnace age. Thought about 2 things.

Doing bodily harm to the engineer who put the dang hot box right next to the bed where sheets and blankets can fall against it. The outer metal shouldn't get hot enough to ignite cloth but I am sure I don't want it melting my expensive sleeping bag either.

That there are pro and cons to the old vs new furnaces. Convection furnace has no blower, thus draws no power from battery. It might use a bit more gas because it cycles slower but I have days worth of propane, not days worth of battery.

Low oxygen sensor. Modern furnace has that thermocouple positioned where if the oxygen level is low it causes the pilot flame to be smaller and it won't keep the thermocouple hot so furnace shuts down. Supposed to be a safety feature, if the fire box leaks and starts contaminating the atmosphere with CO and using the oxygen the furnace quits.

On the other hand above 7,000 feet there isn't as much oxygen as it takes to make the flame reach the thermocouple and the furnace cuts out. Not being able to keep furnace lit on a chilly night in the mountains sort of stinks.

My furnace works, smells like burning dust since the vent pipes are covered in dust and I never use it but I do test it annually. I would be inclined in a small camper like mine to get a little cube heater for when I have electric available and a small propane heater that I can set on the counter that aims outward. You can take the chill off in the morning by making a pot of coffee and gain 10* or more over outside temperature from a burning candle.

Would take very little btu's from a portable heater to make things fine for sleeping. Cody Wyoming snow on the car in the morning and a small electric cube heater had no problem keeping it warm all night.

If you are going to use a candle make sure it is in a sturdy, stable, fire proof container. I would consider setting a long burning candle in a metal coffee can in the sink safe. But I'm a bit of a... well not sure what but have done that. Have also slept burrowed into a mound of snow with a candle lantern hanging from a branch shoved into the wall of the snow cave so... I have standards but not ones everyone will share.

For portable propane heater consider models with some care and test, make sure that if you place it on counter it doesn't overheat anything like counter or rising heat getting the overhead cupboards. I'm not going to suggest a brand or model because frankly that is a pretty contentious issue. Some folks use outdoor heaters inside, others are aghast at such behavior they consider dangerous. I can only say it would have to be fairly cold to need more than 5,000 btu's

A propane lantern on low can keep a 4 man tent warm in Michigan winters. Getting up to use the bathroom means leaving the sleeping bag and that is not pleasant but it does stay above freezing through the night.

[steve67]

I would be suspicious of your gas guy if he doesn't recognize a pilot light flame on a gas furnace... Granted newer equipment comes with electronic igniters requiring no pilot flames, but that's standard on older units.

[NigelW]

Guys
Reread the original post. Sue says the only way to get the flame to go out is to turn the gas valve to PILOT not off. I’m not a gas guy but from the description it sounds to me like the gas valve is not turning the burner completely off.

Nigel

[suedolpe]

Originally Posted by RogerDat

The older propane appliances would have a small flame on a tube that was the pilot to light the burner when the thermostat opened the valve for the main burner. A small thermocouple (copper heat sensor rod) would shut off the gas flow to the pilot if that small pilot flame went out.

Modern would have an electric ignition with some gizmos to open gas valve to burner AND start component sparking or glowing to ignite the burner in response to thermostat. Furnace will shut off gas if it doesn't detect burner ignition. Burner has the same sort of copper probe thermocouple that when heated generates small amount of current.

So there would always be a small flame burning in an old style furnace until know is turned to pilot. In pilot position one can push in the knob to open the pilot gas flow and light it. Holding it for a minute or two until the sensor gets hot. I think on some models in the pilot position if the knob isn't being pushed in the gas flow to the pilot gets cut. Same as off. It sounded like OP and gas guy were describing that. Knob at pilot and the little flame goes out.

The burner is essentially a fire in a box that has a vent to pull in outside air for combustion and an exhaust vent to take the combustion gases outside. Won't use up the air inside to support the combustion and won't dump the CO from combustion inside.

The room air gets warm by flowing around the box with it's vents to the outside. Like a wood stove if the wood stove had a pipe in the back that brought in air for combustion and the door sealed air tight.

If that box has rust holes or cracks at the welded seams the leaking CO can kill you so hat is why checking the box for CO leaks is important professional service item. When it looks like the stars in the sky when lit in the dark you have a lot of holes. Also why finding a spot for a CO detector in your camper is important.

Having a 77 Scamp I have given some thought to the furnace age. Thought about 2 things.

Doing bodily harm to the engineer who put the dang hot box right next to the bed where sheets and blankets can fall against it. The outer metal shouldn't get hot enough to ignite cloth but I am sure I don't want it melting my expensive sleeping bag either.

That there are pro and cons to the old vs new furnaces. Convection furnace has no blower, thus draws no power from battery. It might use a bit more gas because it cycles slower but I have days worth of propane, not days worth of battery.

Low oxygen sensor. Modern furnace has that thermocouple positioned where if the oxygen level is low it causes the pilot flame to be smaller and it won't keep the thermocouple hot so furnace shuts down. Supposed to be a safety feature, if the fire box leaks and starts contaminating the atmosphere with CO and using the oxygen the furnace quits.

On the other hand above 7,000 feet there isn't as much oxygen as it takes to make the flame reach the thermocouple and the furnace cuts out. Not being able to keep furnace lit on a chilly night in the mountains sort of stinks.

My furnace works, smells like burning dust since the vent pipes are covered in dust and I never use it but I do test it annually. I would be inclined in a small camper like mine to get a little cube heater for when I have electric available and a small propane heater that I can set on the counter that aims outward. You can take the chill off in the morning by making a pot of coffee and gain 10* or more over outside temperature from a burning candle.

Would take very little btu's from a portable heater to make things fine for sleeping. Cody Wyoming snow on the car in the morning and a small electric cube heater had no problem keeping it warm all night.

If you are going to use a candle make sure it is in a sturdy, stable, fire proof container. I would consider setting a long burning candle in a metal coffee can in the sink safe. But I'm a bit of a... well not sure what but have done that. Have also slept burrowed into a mound of snow with a candle lantern hanging from a branch shoved into the wall of the snow cave so... I have standards but not ones everyone will share.

For portable propane heater consider models with some care and test, make sure that if you place it on counter it doesn't overheat anything like counter or rising heat getting the overhead cupboards. I'm not going to suggest a brand or model because frankly that is a pretty contentious issue. Some folks use outdoor heaters inside, others are aghast at such behavior they consider dangerous. I can only say it would have to be fairly cold to need more than 5,000 btu's

A propane lantern on low can keep a 4 man tent warm in Michigan winters. Getting up to use the bathroom means leaving the sleeping bag and that is not pleasant but it does stay above freezing through the night.

This is great information. Thank you so much.
To clarify, although I think you got me, when I turn the nob back to pilot, the fire goes out and the pilot stays lit. The gas guy thought that the white thermostat nob that has Low, medium, high on it, should turn the flame off automatically when a certain temperature is met. This does not happen. The only way for the flame to go out is to turn the red nob to pilot. He thought this meant the unit was not functioning safely.

[suedolpe]

I think I replied in the wrong spot - Im really struggling with this forum.
These replies were so helpful.
Roger Dat. I think you got me.
To clarify though. When I turn the nob back to PILOT the flame does go out and the pilot does stay lit. The gas guy thought that when the unit was fired up the thermostat (the white nob with the high,med,low on it), should automatically turn the flame off when the temperature gets to a desired temperature. I understand you to say that these old furnaces do not work that way and that the only way to turn out the flame is to turn the red nob to PILOT. This does work. When I turn the red nob to PILOT the flame does go out. The blue pilot light stays lit until I turn the red nob to OFF.

[TBlevins]

It's possible that the white knob is not installed properly. If you unscrew the knob and pull it off, you'll see there's a stop that protudes from the body of the metal unit. There's a corresponding stop on the knob. When these two connect it makes the knob stop. It prvents the knob from spinning around and around. If it's not put on at the correct spot (i.e., rotated a few degrees in either direction) the stop could be preventing the knob turning all the way off. Just a guess.

[Roy in TO]

Originally Posted by suedolpe

This is great information. Thank you so much.
To clarify, although I think you got me, when I turn the nob back to pilot, the fire goes out and the pilot stays lit. The gas guy thought that the white thermostat nob that has Low, medium, high on it, should turn the flame off automatically when a certain temperature is met. This does not happen. The only way for the flame to go out is to turn the red nob to pilot. He thought this meant the unit was not functioning safely.

Originally Posted by NigelW

Guys
Reread the original post. Sue says the only way to get the flame to go out is to turn the gas valve to PILOT not off. I’m not a gas guy but from the description it sounds to me like the gas valve is not turning the burner completely off.

Nigel

There are 2 thermocouples in these furnaces.
1 is near the pilot light - when it gets hot enough it will keep the gas flowing to the pilot light.


The other is near the bottom of the furnace either inside or outside - looks like a fine metal tube with a thicker bulbish tube at the end of it. The latter controls your temperature. Since it relies on thermal expansion it is not as sensitive as an electrical control and takes a little while to respond. It is a common inexpensive part that is easy to change. If you gas guy does not know this, find someone that it experienced.


If you can locate that bulb, fire up the furnace, turn the white knob down to low and heat the bulb with a hair dryer. It should turn your flame off in a minute or so.



I see from another post that you are in or near Lindsay. If so this guy is fairly local and has been around long enough to know the equipment.
How to Contact Us - Stevenson RV Sales & Service


If you want to drive a little further, contact Mark at Panda Propane in Holland Landing. He refurbished our propane systems years ago. Expensive but worth knowing it was safe. He would not let us take the trailer back until we could both demonstrate we knew how to do things properly.
https://canada411.yellowpages.ca/bus...o/3984558.html


I'll PM you another # for Panda Propane.

[Josh Robinson]

Hi Roy, lots of great facts in here, I just wanted to correct you on the above.


There is only one thermocouple, the other thing is a capillary tube or hot capillary thermostat.


The thermocouple controls gas flow to the pilot light only, and in effect "proves flame" and puts out milliamp current to hold the gas valve open to the pilot light position.


The other thing that is mounted outside the furnace, is a capillary tube filled with fluid that expands and contracts with changing temperature outside the furnace. It controls the gas valve position to allow gas flow to the main burner.


Thanks everyone for contributing here, our "new" 74 13' needs a lot of work and this forum has already been an invaluable resource.





WRT to the OPs question, if the main burner is staying lit when the thermostat is not calling for heat, that is definitely a problem. It's not dangerous as long as the function of the thermocouple is normal (ie if the pilot light goes out, the gas valve shuts off completely). But it is wasteful and providing heat when you aren't asking for it.

[Borden]

We replaced ours with a new furnace.
The vents went horizonal instead of vertical had to use the cutout part to fill old hole and then gel-coated the surface.
The furnace required an extension due to our cupboard depth but was so worth the trouble and cost; works awesome. No pilot light, great heat and instant start.
We still have fill lines using the stove first and then turn on the replacement furnace and water tank.

[John A]

I would think the 'capillary tube bulb' unit has gone bad. I've seen that more often than not, but I haven't found them available as a replacement part. On mine, I replaced the entire gas valve assembly along with it's capillary tube. Good peace of mind, as the gas valves can fail over time too. Nice to have it all new. it's called a 'hydraulic snap action gas valve'. I mounted mine outside the furnace to give it more space for the gas plumbing. On the replacement valves, you typically need to replace its regulator with one for Propane- they come set up for Natural Gas.
I always run a carbon monoxide detector.

[Jan Dyke]

Question. Is the low temp setting on.the white knob all the way to the left or the right?