45 year old furnace back to full-power! - Fiberglass RV
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Old 10-04-2022, 09:35 AM   #1
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Name: You can't call me Al
Trailer: 1977 Scamp 13'
Massachusetts
Posts: 717
45 year old furnace back to full-power!

This old gal has been burning regularly since we bought her in 2010.

Initially, the temperature-sensing bulb was broken, so I disassembled the whole gas valve and disabled that feature. I internally set it for half-way, so I can turn the temperature knob and turn on or off the main burner as I see fit. I also had it completely out of the camper so I could give it a thorough check for rust-through and make sure there were no leaks that could kill us.

We don't use it very often, and sometimes, we don't use it at all for a season, but every spring I vacuum and bang on it to keep it clean, then it gets a nice long run to come up to temperature and make sure everything is fine.

This spring I didn't notice, but it must have been burning a little weakly.

Then, last week, we camped in NH and it got to like 40F the first night and when I lit the main burner, it didn't light. :-( I would get an occasional tiny "Fluff" of flame and then nothing for 2-3 seconds, then a tiny foof of flame again. We ran the pilot light that evening to keep the inside barely acceptable. We sleep in a tent, so I wasn't worried about overnight because we KNEW it would be cold.

The next day, I was (barely) able to get the main gas line disconnected and the burner out and disassembled, and I could see through the main orifice, but it was not round. So I stripped a bit of stranded copper wire (always keep tools dedicated to the camper IN the camper!) and I was able to get whatever was in there cleared out and after reassemble/soapy-water-ckecking and gas-power on it burned better than ever before. Nice strong flame, ignites immediately and produces way more heat than previous seasons.

So, I guess it was getting progressively more clogged over the years and eventually didn't let enough gas through to maintain a flame.

Lesson learned. What lesson? Have tools and experience maintaining your old crappy stuff if you're going to camp.

I do love this old furnace and I hope I never have to replace it with a modern powered-fan version.

Bear Brook State Park, NH.
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Old 10-04-2022, 09:45 AM   #2
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Washington
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Glad you got her working again......love the camp picture.....very nice!
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Old 10-12-2022, 02:38 PM   #3
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Name: Darryl
Trailer: Bigfoot
Wisconsin
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Old style gravity furnace working well

Hi Alan,
I had that model furnace in a 1978 Scamp 13.
Iíve replaced its control unit twenty years ago and still heating well.
The new control regulator had a much quieter ping noise when calling for gas ON or OFF, a nice benefit.
Also had to clean tiny white spider nest from main jet later - a common problem when in a no heat condition.
I always closed the windows on the furnace exhaust side when in use for CO safety.
Darryl
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Old 11-28-2022, 08:40 PM   #4
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Name: rj
Trailer: Owner of a 16' fixer Scamp and fixed up 13'
Colorado
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That old style heater seems like such a tank. Why, or do, they make anything like it?
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Old Yesterday, 08:41 AM   #5
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Quote:
Originally Posted by funkgun View Post
That old style heater seems like such a tank. Why, or do, they make anything like it?
Itís a gravity furnace. They were phased out in the late 70ís or early 80ís due to high surface temperatures. Not ignition hot, but high enough to cause contact burns on children and unwary adults.

They remain valued because they are vented (exhaust goes outside the cabin) and heat by convection (no power required to run blowers). There is no modern alternative that provides vented heat without power. Drawbacks include size, lack of parts for repair, and they require a pilot light.
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Old Yesterday, 09:49 AM   #6
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Quote:
Originally Posted by Jon in AZ View Post
Drawbacks include size, lack of parts for repair, and they require a pilot light.
I would debate some of those drawbacks.

Size: Yes, they have a taller and sometimes wider front. However, they are very shallow. This allows them to be installed in front of the wheel well. Typically, this is an almost useless space otherwise.

Pilot light: Since the pilot light is only on when the temperature drops, (other wise the furnace is off) it sort of acts like a low setting. Sometimes the main burner never comes on, and the pilot light keeps the trailer warm enough.

Parts: You got me there. A new gas valve for my favorite brand of gravity furnace, Duo-Therm, costs about half of what a new forced air furnace would cost. Due to different port locations, it is also difficult to install.
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Old Yesterday, 10:42 AM   #7
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Originally Posted by David Tilston View Post
I would debate some of those drawbacks.

Size: Yes, they have a taller and sometimes wider front. However, they are very shallow. This allows them to be installed in front of the wheel well. Typically, this is an almost useless space otherwise.

Pilot light: Since the pilot light is only on when the temperature drops, (other wise the furnace is off) it sort of acts like a low setting. Sometimes the main burner never comes on, and the pilot light keeps the trailer warm enough.

Parts: You got me there. A new gas valve for my favorite brand of gravity furnace, Duo-Therm, costs about half of what a new forced air furnace would cost. Due to different port locations, it is also difficult to install.
The space under my Suburban in front of the wheel well is definitely not wasted.

I can see how a pilot provides a little heat between cycles, but I have gotten used to electronic ignition on gas appliances, much as I have gotten used to fuel injection on my vehicles, and I have no desire to go backward. I've relit enough pilot lights in the cold and dark to last a lifetime!
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Old Yesterday, 11:52 AM   #8
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Name: You can't call me Al
Trailer: 1977 Scamp 13'
Massachusetts
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I love this design for two reasons discussed above:
The pilot light provides enough heat to keep us warm (Well, really, to keep the DOG warm) all night even in 32F outdoor temperatures.
The pilot light provides enough heat to keep the interior surfaces from condensing in the cold.
No power used.
Almost silent. I hear people complain about the noise of the current-design heater/fan wakes them up at night.
No electronics. I've debugged and repaired enough spark-ignition furnaces, stoves, grills etc in my life that I do not want to go forward. :0
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Old Yesterday, 12:11 PM   #9
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One of the things I want to experiment with, when I retire, is how much power I can generate with my Duo-Therm 65512 using Peltier generators:
https://www.amazon.ca/Bolsen-semicon...dp/B07FTJ7XLB/
It seems that 10W per chip is a reasonable expectation. I suspect that I may be able to make on the order of 100W.
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Old Yesterday, 02:43 PM   #10
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Trailer: Owner of a 16' fixer Scamp and fixed up 13'
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Quote:
Originally Posted by Jon in AZ View Post
It’s a gravity furnace. They were phased out in the late 70’s or early 80’s due to high surface temperatures. Not ignition hot, but high enough to cause contact burns on children and unwary adults.

They remain valued because they are vented (exhaust goes outside the cabin) and heat by convection (no power required to run blowers). There is no modern alternative that provides vented heat without power. Drawbacks include size, lack of parts for repair, and they require a pilot light.
Thanks, I knew they phased them out, but never knew why.. Thanks. I know I watched or read about someone’s on here from a Boler. I loved the idea of having heat without power. I bought a catalytic heater for similar reasons as a back up in my trailer. I know it is not exact, and I have to crack a window.
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