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Old 12-22-2003, 04:15 PM   #1
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Duo-Therm Furnace (MH) repair or replace?

Has anyone had success repairing an old (1985) Duo-Therm furnace? What did it run for part and labor?

I guess a shop would take it apart, clean it, reseal it, put in a new electronic lighter thing, test the board, and check for leaks.

Are the new ones any better? What if you replaced the 30,000 btu's with a lower btu unit? Problems?

New furnaces run $500 and might require some installation components. I plan on only replacing the center furnace. We're in the south and two furnaces would be overkill.
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Old 12-22-2003, 04:47 PM   #2
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Replace it.

You are not talking about $500. You are talking about the difference between whatever the overhaul will cost and $500. Assuming you can get it repaired for $150, you will have a 19 year old furnace that could still fail tomorrow. So at any time you could still be out another $500.

I'm a cheapskate, but to me it was worth it just to know I have a good furnace.

Mark
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Old 12-22-2003, 05:18 PM   #3
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Fred,

While I agree with J54Mark that replacing it is a good idea I have to add this to the equation.

In our 76 MH I replaced the furnace. It would not spin the blower, or light. Found On line for 400.00 (NT30SP) new.

In the 78 the furnace worked, until 2 rallies ago when it quit lighting. I tried all the tricks, to no avail. So last weekend I pulled it and replaced the sail switch and the circuit board. (Again on a NT30SP) Cost 115.00 for the parts. And it works like new. The Sail switch was not necessarily bad, but once you have it out you may as well change it as getting to out later requires all the same work if the board did not fix it.

Most furnaces are simple. I would say invest the diagnostic fee in one of them and see if the shop can give you an estimate. They may just say replace it. If they do say to replace it, I will scrounge up the place I got my last one from. They seem to have the best prices.

I do understand your feeling on the need for only one, but is the one you are replacing the one that heats your tanks?

Smaller BTU output will save you some money, but the savings will be offset in the extra run times that the furnace needs to heat the coach as well as the fact that the BTU output and air CFM (cubic feet per Minute) are taken into account when the duct work was installed. a lower CFM unit may not have enough back pressure to close the sail switch and then it won't light either.

If it is that when the furnace does not light the gas valve stays on then it is one of 3 things. A bad gas valve, a bad ignition sensor/igniter, or a bad board.

Have you considered taking the two units and trying to get one good one?

Lastly if you are not comfortable with the furnace repair take it to a pro and follow their advice. I would hate to have anything happen to you or your family just to save a few $$$.
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Old 12-22-2003, 07:20 PM   #4
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Question Should you NEVER use an old furnace?

My furnace did not work when I purchased my trailer.

I removed the guts. Rebuilt the bad motor, cleaned out the mudd dauber nests, cleaned the electrical connections. etc...

I put it back in the trailer and other than having to light it manually it cycles and works fine.

However, after reading post after post of not using an old furnace, your family's life is not worth it, etc...

I am scared to use it. I did install an LP and CO detector.

So what's the deal? Do I buy a new one even though the old one works?

What's the difference to know the new one is safe?
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Old 12-22-2003, 07:34 PM   #5
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Tim,
Nothing will guarantee that the new one is safer, you have taken a great step in installing the CO detector. Some of the old furnaces have had a recall due to the crossover pipe leaking which could allow combustion fumes inside (CO). As long as the furnace is operating safely and your CO detector is good, IMO you shouldn't have anything to worry about. We used to live in an older house that had the orginal floor furnace in it. Some people up the street swore the thing was dangerous and had theirs taken out, and a brand new central system installed, unfortunately it was installed wrong and they had a near miss with CO poisoning. When we were popup camping we used a Mr Heater Buddy Heater for heating the popup. There were people that told me to my face that I was stupid for using it due to the possiblity of CO poisoning(IN A POPUP?) the only people to die in a campground that winter were in a high dollar MH where the heat exchanger had cracked and allowed CO to enter the coach. Unfortunately they did not have a CO detector. BTW I do, in my popup, AS and at home.

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Old 12-22-2003, 07:40 PM   #6
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That's kind of what I was thinking. A new CO detector and a 30 year old furnace, is better than a 30 year old CO detector and a new furnace

I did replace the crossover hose during my repairs. I used a high temp heater hose from Napa auto parts. It was difficult to replace as it was a tight fit. But that's the point.

I have run it several times at home with all the vents shut for a test ( I would leave a vent/window open in actual use) and the detector never made a sound.

So, as long as I leave a window or vent open and have the CO detector, I should be safe to use it. Right?
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Old 12-22-2003, 08:13 PM   #7
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"the only people to die in a campground that winter were in a high dollar MH where the heat exchanger had cracked and allowed CO to enter the coach"

This is the real danger, of course. All heat exchangers will eventually fail. While it could happen to a new one, it WILL happen to an old one. When? It is impossible to say. I argue that a 20 year old unit is not worth the risk or the expense.

"So, as long as I leave a window or vent open and have the CO detector, I should be safe to use it. Right?"

Why not have somebody qualified to check it out? It will cost less than a refill on your LP bottles.

I am not sure what help an open window will be with an RV furnace. If there is any benefit, I'd appreciate a post from someone who knows.

Mark
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Old 12-22-2003, 08:40 PM   #8
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Quote:
Originally posted by j54mark
"I am not sure what help an open window will be with an RV furnace. If there is any benefit, I'd appreciate a post from someone who knows.

Mark
The open window will provide some fresh air, reducing the concentration of CO should it occur. Hopefully giving you time to get out allive. Also the open window will help reduce condensation which can be a real problem in an RV. Course the down side is you will lose some heat

Aaron
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Old 12-22-2003, 08:46 PM   #9
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"....the only people to die in a campground that winter were in a high dollar MH where the heat exchanger had cracked and allowed CO to enter the coach………

All heat exchangers will eventually fail. While it could happen to a new one, it WILL happen to an old one. When? It is impossible to say. I argue that a 20 year old unit is not worth the risk or the expense.

I am not sure what help an open window will be with an RV furnace. If there is any benefit, I'd appreciate a post from someone who knows………."

Hard to imagine a question more loaded with liability……but……

ANY air exchange, no matter how slight, will mitigate CO poisoning. Quantitative mitigation? Impossible to say. CO is about the same molecular weight as N2 and O2 (the main constituents of air), so it mixes really well -- and stays mixed -- it does not migrate in any appreciable amounts to either the ceiling or the floor. Therefore ANY CO is a potential risk.

But, then again, getting in the car to go to the local convenience mart is a risk. How much are you willing to take?

You have to put a certain amount of trust in your own common sense and abilities.

Personally, I would pull the unit down myself and check it out, I trust my abilities for most mechanical repairs and natural gas related inspections -- that’s what I do. Would I trouble shoot a known defective e-board and attempt a repair? -- No way.

Bottom line, we all have to make judgment calls as to what is “safe” or “unsafe”. It’s great to have this forum to exchange ideas, opinions, and repairs, but to ask “is it safe?” goes way beyond the intention of free information exchange.

The only “safe” answer to a “safety” question is to pay for an opinion, hopefully by someone who is adequately insured if your own common sense or luck fails.

Don’t mean to ‘diss anyone, but personal safety is the sole responsibility of the person taking the action. On the other hand, opinions are part of the forums, but, being free, that’s all they are, right, wrong, or indifferent, they are only opinions.
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Old 12-22-2003, 09:03 PM   #10
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Fred's Original Question

Fred stated that he thought that both furnaces in the south would be overkill.

At Blanco (mid south Texas), during the recent mid December mini-rally, overnight temps were in the upper 20's.

I can truthfully state that having both furnaces operational made things MUCH more comfortable, especially when both sleeping areas were occupied.

I don't think that there is enough air exchange between the front and the back of the 345's for one furnace to adequately (comfortably) heat both areas.

You could try leaving the rear AC heat strip on to help mix the air in both areas, but, in my opinion, that creates a lot of unnecessary noise since it (the AC/heat strip blower) runs continuously.
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Old 12-22-2003, 09:40 PM   #11
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I appreciate the comments and concerns about safety and I agree that it is top priority regardless of expense. We also have a CO detector on-board at all times.

My rear furnace heated the bedroom and made the bathroom a sauna. Way too hot. (Before it stopped working)

I have noticed that the new units have the exterior access panel. My DuoTherms have the two vent tubes.

1) Does a new furnace require changes to the coach wall or will a replacement unit use the existing vents?

2) What units work and which ones would not?
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Old 12-22-2003, 10:30 PM   #12
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Is this it??

http://cgi.ebay.com/ebaymotors/ws/eB...tem=2449744405

I would be hesitant to cut a hole in the coach. If you can get an exact replacement that is what I would do. Especially since the the Aluminum exterior covers would need to be ordered from Airstream
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Old 12-30-2003, 03:47 PM   #13
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The old Duo-Therm went to the dump today with the garbage truck! My wife does not want to spend $$ on labor but rather hard goods (i.e. new furnace and yours truely installs it).
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