Is there a Hot air return for furnace?

[oldtool2]

What I would like to do is find a way to use an electric heater that is tied into the floor duct work on my 5er. Right now if I run an electric heater and turn the trailer fan on to manual it is the AC fan that runs. I haven't found a way to run just the furnace fan by itself. The furnace air intake brings in air from the outside. I haven't found a return air duct like I have on my house. The trailer does not circulate the air inside the trailer like a normal furnace does. If it does I haven't found the return air duct yet.

Or am I looking at this furnace wrong. Is the air intake from the outside just for the combustion air? My furnace is located under my stove and oven. There is a nice copper colored grate located there that must be removed to get to the furnace. Behind it is a steel cover that seals the combustion chamber. When the fan comes on it builds up pressure inside this box and forces the hot air out the bottom into the duct work. Does that copper grate act as a return air duct? I don't think so but could be wrong.

Jim

[Crockett]

outside is combustion air. the inside air is drawn through slots in furnace housing. why not go a heat strip in ac?? or something to that effect..

[OldCoot]

The only way I found to run the furnace blower without the burner was to add a switched 12v to the blower fan. I set our Eden Pure electric heater in front of the furnace intake and turn the furnace blower on (sans burner) and it circulates warm air throughout the trailer and underbelly. Works great.

[oldtool2]

Originally Posted by Crockett

outside is combustion air. the inside air is drawn through slots in furnace housing. why not go a heat strip in ac?? or something to that effect..

My first 5er had a heat pump attachment to the AC but this one doesn't and has no provisions to add one. That would have been my first option if it could have been done.

Jim

[DaveSchwartz]

The furnace cold air return is usually a slotted panel in the cabinetry somewhere. Judging by the virtual tour of the 8280 on the FR website, it seems to be to the left of the fireplace (or where it would have been under the entertainment center if you didn't get the FP option - looks like they didn't even have an option for the FP in 2008).

The panel is not ducted to the furnace (would be too much work) but just opens onto the same space as the furnace. Crocket is right that the cold air return in the furnace is just holes in the sheet metal cabinet. Pretty much guaranteed that not all of the cold air doesn't get in through the pretty panel... that space is not sealed well at all - mine can draw from the spaces around all the kitchen base cabinet doors as well as from the basement where the furnace is located behind a ill-fitting carpeted plywood panels.

[DaveSchwartz]

Originally Posted by oldtool2

My first 5er had a heat pump attachment to the AC but this one doesn't and has no provisions to add one. That would have been my first option if it could have been done.

Jim

Mine does have the internal pigtail for a heat strip but I don't know if the thermostat that was set up for a cool-only unit would support it. Anybody know if its possible?

[oldtool2]

Originally Posted by OldCoot

The only way I found to run the furnace blower without the burner was to add a switched 12v to the blower fan. I set our Eden Pure electric heater in front of the furnace intake and turn the furnace blower on (sans burner) and it circulates warm air throughout the trailer and underbelly. Works great.

That is what I would like to do. I was questioning where the return air was. I couldn't imagine a furnace with-out one. I finally found a service manual on line that shows the return air slots. I figured there had to be something I was missing. The way my furnace is installed you can't see them. I now know for sure that the nice copper grill is the return duct.

Now I need to take a good look at this furnace and see how hard it is going to be to get to the motor. Do you recall as to whether you needed to remove the furnace to wire a motor switch in? Or will I be lucky and be able to wire the switch in at the thermostat?

Jim

[TURBS]

Heat strip can be added to a/c only if it's a non ducted unit.

TURBS
08 duramax tuned n modded
2011 32bhok Sabre
2015 camping "24 nights"

[oldtool2]

Originally Posted by DaveSchwartz

Mine does have the internal pigtail for a heat strip but I don't know if the thermostat that was set up for a cool-only unit would support it. Anybody know if its possible?

After installing the heat strip you will need to change the stat. I only used mine once or twice but do remember it had a separate switch to turn on the blower without the compressor coming on. I seem to remember a switch being mounted on the AC unit itself also, to turn the strip on, not on the stat for the strip.

I didn't get any of the manuals for my stat, furnace or AC unit for this trailer so can't be sure. Going to have to see what I can find on line.

Jim

[oldtool2]

Originally Posted by TURBS

Heat strip can be added to a/c only if it's a non ducted unit.

TURBS
08 duramax tuned n modded
2011 32bhok Sabre
2015 camping "24 nights"

My 05 5er had a strip and had ceiling ducts. It worked OK as long as it didn't get below freezing. Any colder than that and it needed help.

Jim

[OldCoot]

Originally Posted by oldtool2

That is what I would like to do. I was questioning where the return air was. I couldn't imagine a furnace with-out one. I finally found a service manual on line that shows the return air slots. I figured there had to be something I was missing. The way my furnace is installed you can't see them. I now know for sure that the nice copper grill is the return duct.

Now I need to take a good look at this furnace and see how hard it is going to be to get to the motor. Do you recall as to whether you needed to remove the furnace to wire a motor switch in? Or will I be lucky and be able to wire the switch in at the thermostat?

Jim

Had to remove the unit and 2 items were difficult, 1 is to remove the outside vent tube as it is a very snug fit into the furnace 2 is on our unit, it is difficult to disconnect the propane line due to lack of wrench clearance. I also sealed all the seams on the furnace with alum tape before reinstalling.

[Hank2355]

Good thread. I'm a full timer and plan to add a small wood stove in mine as soon as the warranty expires. I also plan to use the furnace fan to circulate the warm (hot) air throughout the TT.

[KAS]

Wouldn't it be easier to just plug in a fan (12V if you have no shore power) to circulate the air? You could direct it towards the ceiling to turn over the air better.

[magpi26]

I have had four TTs over the years and none had a cold air return duct per se. The air coming out of the furnace is distributed via hot air ducts and the cold air return is a grill or grid located at or near the furnace itself. The air returns to the furnace via the door ways and under the doors.

[OldCoot]

Originally Posted by KAS

Wouldn't it be easier to just plug in a fan (12V if you have no shore power) to circulate the air? You could direct it towards the ceiling to turn over the air better.

Doesn't circulate thru the underbelly into the basement which is what is wanted on a cold night.

[Bpenn]

Is there a filter on the cold air return like in a house?

[Crockett]

maybe just boost to the cold areas with these...

Suncourt Inductor 4 in. In-Line Duct Fan-DB204 - The Home Depot

[oldtool2]

Going to reply to a couple of replies at one here.

Originally Posted by KAS

Wouldn't it be easier to just plug in a fan (12V if you have no shore power) to circulate the air? You could direct it towards the ceiling to turn over the air better.

A fan in front of the heater is not needed, just buy a heater with a fan. If it blows then just turn on the ceiling fan for better heat circulation. Yes it would be but as someone else mentioned it won't heat the under belly at all. This would defeat part of what I would like to do.

Originally Posted by Bpenn

Is there a filter on the cold air return like in a house?

No, there is no filter but probably is not needed. The returned air goes right into the combustion chamber. I would think any, or at least most, dust drawn back to the furnace would burn up there. You could place a filter in front of the decorative grill but I wouldn't, you may restrict the air flow too much if you used a good filter. The grill will act as a leaf catching filter. (cheap filter)

Originally Posted by Crockett

maybe just boost to the cold areas with these...

Suncourt Inductor 4 in. In-Line Duct Fan-DB204 - The Home Depot

I have been thinking about a booster fan, actually two of them. I would place one under the kitchen sink and just crack that door open an inch or so. That would supply more heat to the underbelly than it would normally receive. I have a decorative grill under my tv set. This is where I considered placing the second one. This would supply better air circulation in the area where the water pump is.


A better solution to the water pump might be using a heat tape on the pump and plumbing in that area, or a small electric thermostat controlled heater. Jus need a little heat to keep any water in that area from freezing. Nothing else in that area really needs any heat.


Jim

[OldCoot]

Originally Posted by oldtool2

...No, there is no filter but probably is not needed. The returned air goes right into the combustion chamber. I would think any, or at least most, dust drawn back to the furnace would burn up there. You could place a filter in front of the decorative grill but I wouldn't, you may restrict the air flow too much if you used a good filter. The grill will act as a leaf catching filter. (cheap filter)..Jim

Correction: Combustion air is drawn in from the outside, not from the inside of the trailer.

[deebarjay]

x2 ....oxygen depletion...that's why the warnings when using gas range for heat supplement...."you feeling sleepy too dear"