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dznf0g · 12-10-2010, 11:36 AM

Quote:

Originally Posted by Jammer

Both the 2" ducts to the tank area, just hang down below the belly and are open at the end.

If I remember correctly, the easiest way to get to it is to remove the drawers below the microwave. There's another hole in the floor there, much like the one below the closet.

Thanks, Did you fashion some sort of closure panel to block of those holes in the floor? It seems to me that a lot of the het intended for circulation within the tank areas would just find it's way back up into the trailer. If so, what did you use?

Jammer · 12-10-2010, 11:52 AM

I left it alone and don't plan to change it.

I don't know exactly what's down there, but the basic strategy of having the duct pointing down and letting the return air rise through the floor seems sound. There has to be some path for the air to get back to the furnace, and since the inside of the kitchen cabinets more or less serve as one big return plenum for the furnace (with maybe 2/3 of the air coming through the opening below the sink cupboard and 1/3 coming in through the louvers around the microwave), it's a reasonably functional design. The air has to go somewhere and closing it off would probably lead to it mostly blowing outside.

dznf0g · 12-10-2010, 12:19 PM

There was another discussion relative to desired airflow to warm the tanks in the Classics. I was told that the airflow would be curbside fresh water tank (of course where the ducts enter), around the fresh water tank, through the punch outs in the frame member between the tank enclosures, into and around the black and gray tanks, finally exiting the bulk of it around the sewer pipes and valve pull handles. Of course there are plenty of leaks along the way. If we have most of that air simply returning through the hole from which it came, we're not doing much to prevent freezing, particularly black and gray valve area, are we?

However, to your point, with all that air from two 2" ducts not returning to the trailer interior, we'd be sucking more outside cold air in through...well everywhere, making the interior harder to heat. Hmmmmmm.

Jammer · 12-10-2010, 12:55 PM

The current service manual doesn't have a drawing but from the parts list it seems like the basic arrangement is unchanged since the 1970s or perhaps earlier.

In essence the tanks are insulated with styrofoam on the sides, ends, and bottom, and the duct just provides the idea of some heat over the tops.

dznf0g · 12-10-2010, 01:09 PM

Quote:

Originally Posted by Jammer

The current service manual doesn't have a drawing but from the parts list it seems like the basic arrangement is unchanged since the 1970s or perhaps earlier.

In essence the tanks are insulated with styrofoam on the sides, ends, and bottom, and the duct just provides the idea of some heat over the tops.

I thought I had seen, somewhere, pictures that showed there were a few channels or gaps in the foam sheets where air can move from side to side and end to end in the tank compartments. Not so?

I guess you have to be at Jackson Center on a Friday to see frame flipping and fitting. I was there on a Thursday. Has anybody seen Classic inerds?

dznf0g · 12-10-2010, 01:11 PM

Or, I should say frames partially built up...nobody there on Friday to flip and fit!

Jim Foster · 12-10-2010, 01:19 PM

When I replaced the furnace in the Excella, located under the stove near the entry door, there was a 2"hose going through the floor, attached to the old furnace just behind the removable panel. I cut a hole in the new furnace so that that hose could be attached just like the old furnace.

Now I am wondering just where that 2"hose goes. I know for sure that it doesn't furnish warm air to the 50 gal fresh water tank located between the axles, as that tank has it's own steel cover and there is no hose to it. Does that hose or the heat from it somehow get clear to the rear of the trailer to heat the gray and black tanks, or does it just warm the floor under the living room?

dznf0g · 12-10-2010, 02:01 PM

Quote:

Originally Posted by Jim Foster

When I replaced the furnace in the Excella, located under the stove near the entry door, there was a 2"hose going through the floor, attached to the old furnace just behind the removable panel. I cut a hole in the new furnace so that that hose could be attached just like the old furnace.

Now I am wondering just where that 2"hose goes. I know for sure that it doesn't furnish warm air to the 50 gal fresh water tank located between the axles, as that tank has it's own steel cover and there is no hose to it. Does that hose or the heat from it somehow get clear to the rear of the trailer to heat the gray and black tanks, or does it just warm the floor under the living room?

Don't know, I believe Jammer's and mine would have that duct disappearing through the floor ahead of the front of the fresh tank too, if the hole is behind the microwave. I haven't seen it yet. Jammer? What do you think?

Jammer · 12-10-2010, 02:49 PM

I'll take a look tonight and post back.

Ag&Au · 12-10-2010, 03:46 PM

I just have a comment:

Our 31 has a heat vent in the bedroom.

However since you have the twin beds, I am guessing that is why you don't. Our is a queen.

The vent is on the wall between the storage drawers that are just aft of our closet and the bedroom. In other words, just to the curb side of the bedroom door.

Ken

Jammer · 12-10-2010, 04:10 PM

I do have a heat vent in the bedroom. The way it works with the 30' twin layout, the area between the door and the wall is boxed in, so they put the heat outlet on the side of the box facing towards the center of the bedroom.

It's just that it doesn't give off enough heat.

Jim Foster · 12-10-2010, 05:36 PM

The furnace in our Excella, like some others, has four round outlet holes. One is blocked off. One has a short hose to the living/kitchen area, one a longer hose to the center twin area, and one very long to the bath.

All air is being pushed by the fan in the furnace. Since air is much more easily pulled than pushed. the short hose to the living area supplies the most air. Less to the center bed area, and far less to the rear bath.

I just tried my bath roof vent fan idea, and it didn't seem to make any improvement. I think the answer will be the bilge blower. I would install the blower as close to the bath register as I can. By the time the air gets that far, temperature may not be an issue. If it does take out the blower, oh well. After all, the engine compartment on a runabout boat, where these blowers are used, can get plenty warm.

Worst case, I spend an hour or so, $25-$30 and get poor results. Best case, toasty showers in the winter.

I may just give it a try.

Jammer · 12-11-2010, 12:39 AM

Jim I think it's a worthwhile experiment. They are cheap.

If you have problems with noise you could wrap the duct with acoustic foam.

Gene · 12-11-2010, 11:42 AM

Someone said long ago they had a return, but I haven't seen one in our trailer. Perhaps the motorhomes or the 30+ trailers have them. My belief is the heating system is quite primitive and the design is to use brute force—lots of BTU's—to make up for it.

When there's an imbalance in home heating forced area system, there are usually (except in the cheapest ones) diverters inline to direct more or less flow where ducts split off. There should be diverters available for these ducts, but there may not be space for them.

This is an interesting thread. It seems that opening the belly pan is the only way (aside from taking up the floor) to see just what ductwork is around the tanks and how they are insulated. I expect, given Airstream's lack of HVAC knowledge, that heating and insulation are poorly done.

Gene

Jammer · 12-11-2010, 05:30 PM

Quote:

Originally Posted by dznf0g

Don't know, I believe Jammer's and mine would have that duct disappearing through the floor ahead of the front of the fresh tank too, if the hole is behind the microwave. I haven't seen it yet. Jammer? What do you think?

OK, it's actually a little farther forward, under the aftmost portion of the sink. I have no idea where it goes, but it doesn't pull out easily so perhaps it twists around and goes... somewhere? I don't quite understand what's down there that needs heat -- the tanks are farther aft, and the plumbing is above the floor at that point. Maybe it warms the floor. Maybe it comes out under the dinette. Who knows.

Jim Foster · 12-14-2010, 01:40 PM

Found out how the heat gets to the gray and black tanks at the rear of the trailer.

The register box for the rear bath is located at the bottom of the curb side closet, beneath the false floor. I removed the trim door at the front of that area and found that the register box is fed by the 4' hose from the front of the trailer, as thought, but there are two 2" hoses out of that register box, one to the black tank area, one to the gray tank area. So, that one 4" hose is doing double duty. That may be why there is not a lot of warm air going into the bath. About half of it is going to the tanks. The bilge blower in the 4" hose may be a good idea.

The small hose from the furnace does heat the fresh water tank between the axles.

Sure glad I got that figured out, I guess.

Aage · 12-14-2010, 05:00 PM

Have you tried partially blocking the short hose that heats the lounge area?

Since it's the shortest, it's logical that it is the path of least resistance, therefore, with the heaviest load at the very rear, it is allowing the bulk of the hot air into the lounge.

Block it partially and see what happens. Can't hurt, won't cost anything...

dznf0g · 12-14-2010, 05:04 PM

Quote:

Originally Posted by Aage

Have you tried partially blocking the short hose that heats the lounge area?

Since it's the shortest, it's logical that it is the path of least resistance, therefore, with the heaviest load at the very rear, it is allowing the bulk of the hot air into the lounge.

Block it partially and see what happens. Can't hurt, won't cost anything...

If I understand your statement correctly, I think that's covered in earlier posts, both from the standpoint of the installation manual as well as Jammer's temp. numbers showing a level of heat at the furnace plenum which he felt was unacceptably high.

Jim Foster · 12-14-2010, 06:06 PM

Quote:

Originally Posted by dznf0g

If I understand your statement correctly, I think that's covered in earlier posts, both from the standpoint of the installation manual as well as Jammer's temp. numbers showing a level of heat at the furnace plenum which he felt was unacceptably high.

I am somewhat concerned with blocking off part or all of the register in the front of the trailer, as it is only about 12" long from the furnace, and the air at that point is very warm. However the air coming out at the bath is much, much cooler so using the bilge blower at that point should not be an issue. That air really cools down on the 18' journey through the hose along the floor, along the outside wall. Granted, turning the blower on should bring air a little faster, and perhaps a little warmer, but that is the point of the blower.
Also, the blower can remain off until warm air is needed in the bath. The fan blades in those blowers seem to have plenty of room for air to pass through when off.

Hey, if this doesn't work, I can install the blower inside the fridge vent near the roof to help there in warm weather.

How 'bout that? I know, that's another thread.

dznf0g · 12-14-2010, 06:18 PM

Quote:

Originally Posted by Jim Foster

I am somewhat concerned with blocking off part or all of the register in the front of the trailer, as it is only about 12" long from the furnace, and the air at that point is very warm. However the air coming out at the bath is much, much cooler so using the bilge blower at that point should not be an issue. That air really cools down on the 18' journey through the hose along the floor, along the outside wall. Granted, turning the blower on should bring air a little faster, and perhaps a little warmer, but that is the point of the blower.
Also, the blower can remain off until warm air is needed in the bath. The fan blades in those blowers seem to have plenty of room for air to pass through when off.

Hey, if this doesn't work, I can install the blower inside the fridge vent near the roof to help there in warm weather.

How 'bout that? I know, that's another thread.

I think so too. "robbing" air from the LR vents by sucking more out to the rear should keep the plenum temps at or below their designed level. You would just be negating the friction of that long run to the BR or bath.

I'm not sure if the heat will hurt the bilge blower, or computer fan like in another post, but let us know how it works out.