Put furnace blower on a separate switch?

[EMD_Driver]

The holding tanks in our fifth wheel are heated, via furnace ducting to the underbelly. Whenever possible, we use the campground electric to heat the camper. This leaves no heat for the underbelly.

I'd like to (If safely possible) tap into the furnace blower's hot wire and be able to run it from a separate switch. That way, I would still have warm air circulating to the underbelly area. My question is: Would anything prohibit me from doing that?

Here's a wiring diagram for our furnace. I would like to tap into the red wire, going to the blower motor.

[mainah]

Are you hoping to just use the blower to circulate heat from inside to heat the basement? I would not back feed power to the controller if it's a solid state switch you could kill it. You could do it with a single pole double throw switch. Cut the fan wire join it to the common lead on the switch join the cut end (the controller wire) to either of the other terminals and the added power wire (could come from the breaker in the heater) to the other terminal one way heat the other fan. I think you are going to find the blower will cool you off too much just moving air. You could add an other thermostat in the basement and set it to 40 degrees the only problem there is making the camper too hot.

[EMD_Driver]

Something else I was told, was that the heat exchanger would work in reverse. It would take heat from the coach and force it outside... Guess I will do something else.

[Jim-Bev-2363]

The larger computer power supply cooling fan, or two, placed in the right place might work good. Maybe? I'd put a LED reminder light in the circuit to know it/they are werkin.

[EMD_Driver]

Originally Posted by Jim-Bev-2363

The larger computer power supply cooling fan, or two, placed in the right place might work good. Maybe? I'd put a LED reminder light in the circuit to know it/they are werkin.

Great minds think alike!

They are very low power draw and would be easy to use!

I also use them to blow air past the cooling unit fins, on the fridge. I mount them behind the access cover and wire them to the fridge 12v power supply... They work great!

[Jim-Bev-2363]

[Trailblazer]

A few years ago I read about someone using a footwear dryer similar to the one in this link to help pump heat into the trailers underbelly:

Footwear Dryer | Canadian Tire


Unfortunately I can't find my link to the photos but basically he drilled four holes through the floor into the underbelly just large enough to fit the four hoses. He then sealed around the hoses with caulking to help hold them in place and prevent air leakage back into the coach. Basically this unit allowed the poster to provide heat to the underbelly while not having to run the propane furnace. If I remember correctly the guy said that you are not trying to bring the underbelly temp up to 70 degrees Fahrenheit, but just trying to keep it about freezing.

[mainah]

Originally Posted by EMD_Driver

Something else I was told, was that the heat exchanger would work in reverse. It would take heat from the coach and force it outside... Guess I will do something else.

That is correct the blower also supplies air to the combustion chamber and exhaust so you will lose some heat to the out side.

[mainah]

Originally Posted by Jim-Bev-2363

The larger computer power supply cooling fan, or two, placed in the right place might work good. Maybe? I'd put a LED reminder light in the circuit to know it/they are werkin.

You also could use a line voltage thermostat in the basement to turn them on and off they are pretty cheap and would work fine on 12 volts.

[Jim-Bev-2363]

Why not just carry a Porta-Potti and potable water bottled inside the camper? Then all systems could be left winterized. Using winterized systems means they need to be refreshed from the winterized condition and winterized after the trip is over. That would mean a lot more work than just emptying a porta-potti, using water from bottles and emptying the potti as needed. You might even feel like you have really been "roughing it". Can't you see the stories around the campfire now? I remember when we had to use a portable toilet to go camping. That would be alright until JohnB tells of pooping behind a small bush. . LOL!



Edited to add: I can see a problem now. This would remove a modification and not acceptable.

[EMD_Driver]

Originally Posted by Jim-Bev-2363

I can see a problem now. This would remove a modification and not acceptable.

Which is why I had this as my avatar!

[frank]

Gary,

An alternative for routing some warm air down there might be a bilge blower. They come in a bunch of sizes and prices, a small/inexpensive one would likely move plenty of air. They also run on 12v and are sized for hose, so connections would be pretty easy to make. Just a thought.

- Frank

[Jim-Bev-2363]

Gary, What I said was said kidding. Of course I never thought my post would deter a man with such determination, LOLOL!

On a more serious note. What about moisture? Would heating the underfloor without having air transfer cause potential damage?

[JohnB]

Hi Gray,

See this post if you have not. I had to hunt to to find it.
http://www.sunlineclub.com/forums/f7...pics-9497.html

I could not get a straight answer on extended season camping and how cold one can go with enclosed tanks. So I installed a temp sensor so I can get my own readings

After my upgrades and adding Reflectix to the tank area this is an excerpt from that link.

Outside air temp: 11 deg F
Camper inside temp: 68 F (Hunter digital furnace T stat set to this)
Lowest tank compartment over night: 40 F
Highest tank compartment over night: 78 F

Tank compartment temp in middle of afternoon before I turned on furnace: 41F, (outside = 30F)

The radiant heat off the furnace ducts shocked me that it went so high. Seeing temp in the 60’s and 70’s was unexpected. And seeing it only get down to 40F made me a happy camper with it being 11F outside….

We now go "wet" all the time. And as you may remember I have the camper setup to be blown out after each camping trip. I had to do some redoing but I can blow out the camper now in about 10 to 15 minutes as we are unpacking the camper and feel good I will not have any freeze ups. I then blow down the drains and put RV anti freeze in the drains and we are good to the next campout.

You have already worked through that the blower is a twin blower. You turn it on and the gas side starts blowing the same as the inside. So what little heat it sucked from the living space just convected out side passing over the combustion chamber.

At night we turn the T stat down to 63 so we can sleep... If not the furnace will run you out of there. We too use qty 2 electric heaters. One an oil filled and the other a ceramic blower. Did not have to do this on the T2499 but on this T310SR with all the windows and slide... you need more BTU's as it is convecting out of the camper. We even have the windows covered with shrink film which really helps.

My thoughts on your tank situation. When the furnace runs the ducts really heat up and convect off into the tank compartment. I have seen it reach 90 F in the tank area.... As such the water in the gray tank is probably 55 maybe 60 deg F. Washing dishes and taking showers puts hot water in the gray tank. The potty tank, well it may be more like 45 to 50 maybe a little more. Never measured that one yet.... An IR gun for sure....LOL So the water convects some level of heat into the compartment. Again I have added above and beyond what Sunline did and I have better insulation so take my figures realizing I upgraded. I also have a frost free fresh tank drain and I dealt with the outside shower, the HW drain hose and the P trap in the shower from freezing.

If all you are doing is blowing 68F heat down there verses convecting off 80 to 90 F heat from a duct, you are really going to need a large volume of 68 degree heat. The only way to really know is put a sensor down there like I did and measure it to see what you are up agasint.

Unless the 5er is insulated better then the TT's odds may be you need to run the furnace a few times to keep the living space comfortable. Do you have double pane windows? Single pane convert a lot of heat and the slides do too.

I have found that during the day the sun shines in and the electric heaters keep the majority of the heat in enough that the furnace does not run a lot. If it is above freezing outside then there is no tank concerns. At night we turn the heat down to 63 , put the oil filled near the bedroom and the ceramic blower one way out in the living area. You have to vent the camper for moisture so some heat leaves through the vent. The furnace may turn on 2 to 3 times and that is enough to keep the tank compartment in the 40 or above range. My sensor has a max and min feature so I can see how low it made it to. Come time to get up and cook breakfast and that 63 is cold out in the living area so the furnace runs a good 15 maybe 20 minutes to bring the camper up to 68/69 and then the electric ones keep it in check.

Again back the the sensor in the tank compartment. If you put one in then you know what you have and fix as needed and go from there. Your camping area may be warmer then ours up here and just the camper heat loss may be enough to keep you OK. In a camper of that size, some where along the day you are going to run the furnace.

Hope this helps.

John

[EMD_Driver]

Thanks for all the info John,

My concern is that when we run the electric heaters, the furnace does not run at all (At least not in the F-311) I did not want to risk the underbelly getting too cold. Perhaps the F-344 will be different, since it has two slides.

[JohnB]

Originally Posted by EMD_Driver

Thanks for all the info John,

My concern is that when we run the electric heaters, the furnace does not run at all (At least not in the F-311) I did not want to risk the underbelly getting too cold. Perhaps the F-344 will be different, since it has two slides.

H'mm, not at all, nada, never? How cold outside is it? or how warm do you have it inside?

Maybe the 5ers' are insulated better then the TT's, or it is warmer in your area. There is no way my 2 1,500 watt heaters can keep up in ours if we are targeting 68 with it below freezing outside. We end up with stratified pockets of heat and cold. But ours may have a lot more glass then yours. We have 16 windows and a roof vent open to let the moisture out.

I was thinking about a low set point T stat in the tank compartment. Put a single pole double throw switch on the T stat line and flip between the 2. But it would need a real long heat anticipation setting. As once the furnace fires up the heat given off by the ducts is a lot. Since most T stats are targeting 1 degree of setpoint it might go off real quick and still leave the compartment cold on the other areas.

H'mm the air temp sensor may be the need to see what it is your up against in the right spot. Maybe 1 fan blowing down from the cabin might be enough.

John

[EMD_Driver]

When we went camping with Teach at New Year's, we had the fireplace 1,500w fireplace on. We also had the rear most vent cracked open. The "Downstairs" portion of the 311 stayed very warm. Warm enough, that the furnace never came on. We had the sliding door shut, to keep the dogs out of the bedroom. The bedroom got quite cool, but the downstairs never went below 70* and that's where the thermostat was set.

Kitty is very sensitive to the cold, due to her chemo treatments. I had to open the sliding door and turn the furnace up a bit, so she could even get out of bed. The electric blanket kept her warm enough, that I didn't have to leave the door open.

We were there for three nights. Friday night/Saturday morning temp was 37*.. Saturday night/Sunday morning temp was 30* and Sunday night/Monday morning temp was 28*... There are 8 windows and the entry door, in the downstairs of the 311. It also has a bigger slide than the TT's, if you remember..

I cannot include the 344 in my observations since the only night we stayed in it, the furnace quit working around 4am. The furnace in the 344 seems to stay on a lot longer though. We've been using it a lot, since we have been busy modding and un-packing.

[JohnB]

Hi Gary,

Well, you had 9 windows including the door to our 16 and the outside temperatures do not get as cold. In addition, yes your slide is bigger! Longer and taller. We have no problem going down to 20 F, sometimes colder. The days high may stretch up to 40. The wind or lack of makes a really big difference.

Since our portable heaters are in the living area the bed room does get cold... in fact we turn the sheets down, jack the furnace up to 72 to get it to run and then warm up the bed room. Then once it is bedtime, we move the oil-filled heater into the hall in the bathroom just outside the bedroom. With the furnace at 63 and the oil filled, we do not have a problem sleeping.

I wonder if the fiberglass siding cuts the wind better then the aluminum? It should just due to the fact of less little spaces in the siding itself.

Interesting how this turns out.

John

PS. Oh. I know what it is. The 2 dogs!!! You have 2 more heaters. Well, OK Harley does not heat much….

[Trailblazer]

Gary,

I think what you are wanting to try and do is similar to this new product that can be retro fitted onto your propane furnace. It is called Cheap Heat

I had thought this unit would have been a great idea until I saw the cost of it. Now in your case since you are just trying to circulate the warm air from the coach into the underbelly, maybe you can figure out how to to accomplish what you want to do by looking through some of the documentation on the site.

[Murphie]

Hi Gary,

I have another option which might work for you. There is a post I read on the Forest River forum where a guy with a 15k Coleman Mach AC added a heating unit to his AC . The unit either comes with or you buy it separately a new stat that has a electric heat setting on it. This engages the blower and would send the heat through your plenums including your basement if your furnaces is ducted that way. He phoned the manufacturer and got the model numbers of the heating element and the stat. I was always under the impression that it wasn't possible with ducted heat but with the electric heat setting activating the blower it sounds like the cats meow. If your interested I can dig up the link to the post. Sound similar to what you wanted to do. He said that his cost was 200 dollars. Hope this helps.
Richard