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Furnace Reinstallation


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Hi, I just bought my first RV, an '85 Sunrader. The previous owner was part way through a remodel. The old furnace has been removed, but I still have it, and there's a brand new replacement furnace. Since I didn't remove it I'm not quite sure how it's supposed to be mounted. Based on the ducts and exhaust, it seems like it should be obvious, but I don't see how the previous unit was secured.

I was wondering if someone would be gracious enough to post a picture of theirs to give me an idea.

Thanks in advance!

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Thanks, I do have the manuals. I was just trying to see how it had been mounted in this particular vehicle, but I'm sure I can figure something out from the manuals.

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Is your old furnace stuck or haven't you tried to remove it yet?  All that holds it in (usually) is a few screws in the front-bottom where it is attached to the floor.  Just take out those screws (two in most cases), unhook the gas line (hex flare nut), and disconnect any wires and pull straight out.  The chimney is supposed to be a slip fit and it just comes unattached as you pull.  Sometimes they get rusted stuck.  Most small RVs I've seen have no ducts other then the front grill..  When they do it is just 3" or 4" flexible hose used for heat, and no cold air ducts.  

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I think my description was unclear, sorry about that.

I have a new furnace and the old furnace, neither is installed. Since I've never seen them installed I'm uncertain on how they're supposed to be secured.

The new furnace appears to be an exact match for the old one.

The compartment for the furnace is larger than the furnace itself. If I put the new furnace in so that it matches up with the ducts and exhaust there's no obvious way to secure it. My best guess is that I'm putting it in incorrectly or there used to be some sort of bracket that it could be screwed into.

I can try to get some photos later as an illustration.

Thanks!

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pix would help.  not least since you may be having to fabricate something up.  I like the sound of oversize compartment...seems like you'll have options for mounting bracket.  would angle brackets or some aluminum L channel work w/o looking too bozo?

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Attached photos of the space and the new unit roughly in place.

I suppose I could try putting a screw and washer through the bottom metal plate into the plywood. Might be enough to secure it along with the exhaust connection in the back. Or I could put some sort brackets on the sides.

IMG_2415.png

IMG_2416.png

IMG_2417.png

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from the pix, looks like the unit was designed to mount to a faceplate cut tightly around it.....that looks like a mounting flange, screw holes and all.  or if that would put it too far forward (sticking out of the hole), make a "frame" to fasten the flange to.

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I agree, just wish I knew how the original was installed since it's more or less identical to the new unit and I don't see any evidence of a faceplate having been in there previously.

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Can't be certain. It's what I was told by the previous owner, and some parts (duct flange, part of the gas connection) were still attached to the old one.

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49 minutes ago, Kale said:

I don't see any evidence of a faceplate having been in there previously.

one nice thing about a 30 yr old motor home is that you don't need to be wedded to the way it was done at the factory....i feel safe in saying that no matter what make, lots of stuff was done kind of half arsed at the factory, so just do it right as you define it.  any pix on the Dometic web site that might shed some light?

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6 hours ago, Kale said:

The compartment for the furnace is larger than the furnace itself. If I put the new furnace in so that it matches up with the ducts and exhaust there's no obvious way to secure it. My best guess is that I'm putting it in incorrectly or there used to be some sort of bracket that it could be screwed into.

I've never seen one with any mounting bracket, regardless if it is a Suburban NT , Hydraflame, etc.  Just a pair of wood screws go through the sheet metal of the furnace at the front-bottom.  Just like shown in this diagram.

suburban furnace mount.jpg

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8 minutes ago, linda s said:

You've got west coast Sunrader paneling. Only suburban furnaces used. There's the problem.

Linda S

That would certainly explain my confusion. The suburbans appear to have very different dimensions.

I just went and looked at the thermostat, which says hydro flame. Maybe this furnace has been replaced more than once. Possible that they didn't properly secure it when it was replaced. Doesn't seem smart, but people do odd things.

So I suppose my question now is whether it's alright to use this one or should I get a different furnace.

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I'm not sure where your concern lies.  The furnace, regardless of make, gets fastened to the floor, hooks to a chimney, gas line, and a 12 volt power source  Size of the hole it is going in doesn't matter as long as there is the require air-clearances around it. Make of thermostat does not matter either, assuming they are both mechanical.  It is possible that the extra furnace that was not originally installed in your RV might not match the chimney vent and if not - you'll need to buy one if you need to install it.   I'd try hooking up which ever one is wanted  - to power and propane and make sure it works before installing it.

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I didn't see your photos before.   That Hydroflame looks like a nice furnace and puts out more heat that the OEM furnace did.  Here is a diagram showing the chimney and air box in back that it needs.

atwoodhydroflame7920.jpg

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18 minutes ago, jdemaris said:

I'm not sure where your concern lies.  The furnace, regardless of make, gets fastened to the floor, hooks to a chimney, gas line, and a 12 volt power source  Size of the hole it is going in doesn't matter as long as there is the require air-clearances around it. Make of thermostat does not matter either, assuming they are both mechanical.  It is possible that the extra furnace that was not originally installed in your RV might not match the chimney vent and if not - you'll need to buy one if you need to install it.   I'd try hooking up which ever one is wanted  - to power and propane and make sure it works before installing it.

The hydro flame doesn't have mounting holes on the bottom, they're on the sides. I can certainly drill some in the bottom though. I'm not concerned about the thermostat, I was just trying to figure out how the furnace was originally installed and why the two hydro flames don't quite line up in the existing space. The thermostat brand was a clue as to what had been installed last.

I'm very new to this. To me it seems perfectly fine to use the hydro flame I have, but I don't know much about RV furnaces. I figured it would be safer to ask before doing something that I might later regret.

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The last Sunrader I worked on was a 1983 and that had a Suburban NT-16 furnace in it.  I have no idea if it was original or not.  Suburban chimneys are quite different from Hydroflames.  Any Sunrader literature I've seen shows a Hydroflame 16K BTU input furnace.  The newer one you show in the photos is an 18K BTU input furnace that should physically be the same size as the 16K.  

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I think I'm going to be able to make this work. I took jdemaris's suggestion and hooked it up to power and gas, it fired right up, so at least that's some small progress.

Have to wait until some parts arrive to finish the install. But that's ok because there's a "new" air conditioning unit that won't turn on and an oversized refrigerator sitting right in the middle of the rig that I need to build an enclosure for.

Thanks for everyone's help!

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  • 4 weeks later...

Some are also held in with screws through the exhaust flange. That is some thing you really want to make sure is correct you don't need any exhaust fumes inside. The pipe is coaxial it also brings in make up air for the furnace if you have to fabricate inside duct work that's not a real issue the worst it can do is loose a little heat..

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