furnace open to storage area...

fixithud · 03-22-2014, 10:52 AM

Our fifth wheel is new to us and I am learning quite a bit.

I have noticed that the area where the furnace is located is open to the underneath storage area of the trailer. Also, the return grille inside the trailer just covers the area where the furnace is, there is no ducting back to the intake of the furnace.

It seems to me that I would want to enclose the furnace area from the storage area. I also realize that sometimes a little warm air underneath, around the water lines and tanks and such, isn't always bad, but it seems that should come from the supply side,

I just think my furnace would be more efficient if it was returning just the air from the living space.

Am I on the right path?

It would really be awesome if I could capture the air coming from the burner exhaust. Holy Smoke that is a nice hot jet of air coming out of the side of the trailer!!
Hud

therink · 03-22-2014, 11:19 AM

I have the same setup with furnace return grill under steps to bedroom on the door side and the furnace is on the street side in the basement utility area. The basement utility area serves as one large return air duct. I like it because I can barely hear the furnace when it is running. It heats he entire living space well. The other advantage is that it keeps the water works in the basement from freezing and the bathroom floor is usually warm.

canesfan · 03-23-2014, 06:31 AM

Hmmm, I'm on the opposite side of the fence, my furnace is right under the steps and the return air grills are on the face of the steps. My furnace is horrible loud and I'd love to isolate it from the inside but am afraid it would overheat if I blocked the return air grills. Also, it struggles to heat the coach. I'm debating having a larger one installed. I checked all (one) of the ducts and don't see anything kinked or loose or anything. Like you said, it's too bad we can't get some of that hot air that's blowing outside and put it to good use besides a hand warmer on a cold day.

Bob Landry · 03-23-2014, 07:18 AM

Quote:

Originally Posted by canesfan

Hmmm, I'm on the opposite side of the fence, my furnace is right under the steps and the return air grills are on the face of the steps. My furnace is horrible loud and I'd love to isolate it from the inside but am afraid it would overheat if I blocked the return air grills. Also, it struggles to heat the coach. I'm debating having a larger one installed. I checked all (one) of the ducts and don't see anything kinked or loose or anything. Like you said, it's too bad we can't get some of that hot air that's blowing outside and put it to good use besides a hand warmer on a cold day.

You are correct in not blocking the return air to the furnace. Those like AC units require a certain amount of supply and return area. You might try lining the area that it is in with some kind of sound dampening material, but the fan is what is generating the noise on these units. If you are having issues heating, I would look at adding duct and floor resisters. You said it had one duct. That's odd to me and I don't see how you can hope to get good air distribution from that. The furnace should have the capability of more outputs and dropping the coroplast on the bottom would make everything pretty well accessible.
At this point, there are two possible drawbacks to going to a bigger furnace. If you have a less than adequate air distribution system, a bigger unit buys you nothing there except possible overheating and damage to the unit. Also, the larger unit may require larger ducting to get the required amount of air flow and that may or may to be possible, depending on construction.
I don't understand why they put the return air access from the storage compartment. That doesn't sound like a very efficient setup, but then, I didn't design the trailer and maybe they had a good reason for doing so. I install mating air conditioning and the return air is always taken from the interior space that's being cooled.

canesfan · 03-23-2014, 07:51 AM

Thanks for the input Bob.

The furnace is under the steps, which is open to the entire underbelly behind the pass through compartment wall. So everything under there, furnace, water pump, converter, etc that makes noise enters the coach from the return air vents.

I've thought long and hard as to how to solve the noise issue but haven't come up with anything.

As for the one duct, there is a single flex duct coming out of the furnace going to the rigid duct that runs under the floor. There are 5 vents from the rigid duct. If you put your hand on the duct closest to the furnace, the air is warm at most. Vents farther away are naturally worse. My last rig you could almost cook on the vent closest to the furnace.

Sorry, I don't want to hijack the OP thread.

canesfan · 03-23-2014, 07:58 AM

As to the OP, is yours like mine, under the steps but open to the entire underbelly? If so, I am wondering if we could close off the furnace from the rest of the underbelly with some sheathing? It would get return air from the living area that way. In my case though it would probably make it even louder being in more of an enclosed space, although with it closed of I could maybe then use some dampening material like Bob suggested.

Don't know, just thinking out loud.

And yes, some warm air under there can be a good thing.

fixithud · 03-23-2014, 08:36 AM

I do not think that blocking the return air GRILLE is at all a good idea. Just like in a house, the return air, in my opinion should be air from the living area.

I just want to know why keystone lets the furnace intake cold air from the storage rather than only from the living area.

If you want to keep your storage area 'warm', it needs to be done with the supply air.
Hud

canesfan · 03-23-2014, 09:10 AM

Hud, where is your furnace located within the underbelly? Mine is under the steps on the door side with the grills under the steps. If yours is similar I don't see why you couldn't wall off that part of the underbelly from the rest, isolating the furnace in its own "compartment". Then it would have only the return air from inside the coach. I don't see this as an issue as long as the return air grills from inside the coach are the right size. Mine are, I found the specs in the manual and measured the grills. I don't know anything about HVAC and don't know if that would solve anything for you. Someone with more knowledge might want to chime in.

Bob Landry · 03-23-2014, 09:27 AM

The furnace really needs to be closed off so that all of the return air is being drawn from the living spec. The theory on airflow is the same as air conditioning but in reverse, and until you do that, you are going to be chasing your tail. This is obviously, along with many other things, a poor design on the part of Keystone, but it shouldn't be that hard to fix. You could instruct a box to enclose the furnace from the outside area and get some similar material as the storage space from an upholstery supply house that would closely match and end up with a nice looking job.

BTW, if your furnace is under steps and there is a wooden grill in front of it, that will supply adequate return air, just isolate the furnace from the storage area and you'll be good.

therink · 03-23-2014, 09:32 AM

Like I said above, my furnace is on other side of basement than the return grill under steps on door side. It is quiet and heats the unit very well. I like this set up as it is quiet. Personally I think it is a good design in my rig.

fixithud · 03-23-2014, 09:42 AM

Quote:

Originally Posted by canesfan

Hud, where is your furnace located within the underbelly? Mine is under the steps on the door side with the grills under the steps. If yours is similar I don't see why you couldn't wall off that part of the underbelly from the rest, isolating the furnace in its own "compartment". Then it would have only the return air from inside the coach. I don't see this as an issue as long as the return air grills from inside the coach are the right size. Mine are, I found the specs in the manual and measured the grills. I don't know anything about HVAC and don't know if that would solve anything for you. Someone with more knowledge might want to chime in.

My furnace is to the left of the steps, if you are in the trailer. Under the Ent center. Nice big grille at least 16x14. I think I am more than okay to do this, I just didn't understand why it was like this.

Thanks for the reply
Hud

canesfan · 03-23-2014, 10:18 AM

Quote:

Originally Posted by fixithud

My furnace is to the left of the steps, if you are in the trailer. Under the Ent center. Nice big grille at least 16x14. I think I am more than okay to do this, I just didn't understand why it was like this.

Most likely because it saved Keystone $ from not using a couple more sq feet of sheathing. You should do what Bob suggested then, build an enclosure for it and channel your return air to it. I may try that and try to insulate it with some type of non flammable material to see if I can deaden some of the noise.

My last rig had the return air up at the ceiling and the furnace was on the street side, nice and quiet and actually heated the coach. This one stinks both noise wise and heat wise. Plus it has a high pitched whine on top of the motor/fan noise.

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