Installing a second furnace for the basement

noteven · November 3, 2015

Has anyone installed a second propane furnace to heat the basement only when using a radiant heat source in the living space?

Wrknrvr · November 5, 2015

We use to have a 39' Nuwa Hitchiker with one furnace. I used all available duct openings on the furnace. Where I could I removed the round vent covers and converted to standard 4x10 household duct opening and install oak vent covers on the wall.

The extra vents from the furnace were directed into the basement area, then I cut several 4" holes into the floor under the bed and installed a household prefinished vent on the side of the bed towards the hitch. The air could flow all around , up under the bed and out the vent.

What difference in comfort and cost as now there was a balanced flow of air.

We now have a 42' Teton with two furnaces. I added one vent in the living room as that is all the heater tubing I could fish towards the rear.

The second furnace only had four vents used. So I installed four vents into the front basement area. And left the other two that already in the bath area alone.Then there is a open space under the cabinets at the foot of the bed so I cut 4-4" openings, installed4" computer fans that are hard wired into the furnace. So when the front furnace is on the floor is about 3degrees warmer than the thermostat setting.

I like warm feet.

In addition to the propane furnaces I also installed a hydronic system in the rear of the fifth wheel where the spare tire use to be. That heats the rear floor area very nice.

I get bored real easy so the second winter we had the Teton along with installing tha hydronic heating system, all metal that was exposed to the outside was covered with 2" of styrofoam and then cover with frp and sealed for possible water intrusion. Where 2" styrofoam would not fit then 3/4" was used.

Then since I was down under doing things and had some commercial heat tape for down spouting that fit into the lower box tubing in the frame it was installed also.

So the is things that can be done to help with a heating system in an RV.

Using it all as we are in Missoula Mt for another day or two.

Safe Travels, Vern

noteven · November 6, 2015

Thanks Vern.

Wrknrvr · November 6, 2015

You can do a simple test to help the efficiency of your system. When everything is going to be constant as in outside temperature, get the tools to remove any round heater vent covers that is in your system. Then time how long it takes for a heat cycle. No door opening or other things to change the time for a heat cycle.

Heat cycle is from the time the furnace comes on till it starts again. With no other changes in the RV.

Now as soon as you have the time with the vents on, then remove the vent covers and get that time for the heat cycle.

also note if there is more air flow with the vent covers off.

With the vents off there may be more air flow. That is why I installed household vents if I could get the 4" vent line converted to a rectangular duct of the proper size.

You just need to look and see what can be done to improve what you already have.

Although a second furnace will be nice if the original quits at a inconvenient time.

Safe Travels, Vern

noteven · November 7, 2015

Hi Vern - those are some great ideas. Our furnace now is 35,000btu heating the living space & basement of a 39ft C-Force toyhauler. Vents are residential type. Much below 5F / -15C and it is no longer maintaining the basement above freezing. Right now in the toyhauler return air is from the living space, but some heated air gets supplied to the basement as well as the living area...I was thinking of redirecting the return air so that air flows from the living space to the basement through some additional vents then returns to the furnace.

Our truck camper is ducted this way with an additional heat duct to the tanks and under the shower floor and that area runs warmer than the main space, especially on the feet . Once we were parked during a storm at the Flying J in Great Falls, MT. Temp 0F and wind 35mph-45mph. We found the 16000btu camper furnace heating 9ft plus the overhead to comfortable temp wearing long sleeves was running 20 minutes then stopping for 8 to 10 mins then running 20mins... basement/tanks were in no danger of freezing but we considered that to be maximum low temperature operation conditions. The toyhauler would have 4 to 5 times the heat loss vs the camper but only 2x the heating output...

I am also thinking about other heat sources in the living space such as marine solid fuel, diesel, or propane stoves with a second furnace dedicated to the basement only. On chilly rainy days or cool nights a single 1500watt oil filled electric radiant heater will provide more comfort (7500btu?) than the 35,000btu unit going through it's blow cool air down your neck cycles... in this scenario a second furnace to maintain the basement at safe temps would be nice...

lappir · November 7, 2015

My thought is to someday do a retrofit of a radiant hot water heat in my trailer. (unless I can swing a rebuild). A dual zone with the ability to set the basement at 40 while keeping the living area comfortable too. If NukeE get's his solar panel cooling/water heating idea worked out maybe it could be tied into the system too. I have had that idea in my mind for quite a while. I helped an inlaw take down his solar water heating panel several years ago and moved that panel at least twice wanting to set it up somewhere for use. Never did. Was amazed at how quickly it heated up. plumbed it with a garden hose for a test one afternoon in the south Florida sun and in less than 5 minutes I had water at 160 degrees coming out of the other end. Someday someone will harness the power of the sun and the wind with an effective storage bank so it won't take combustion generated power to support our lives. Ok, maybe I'm dreaming.

Rod

Wrknrvr · November 7, 2015

You have some good thoughts on what to do. It really depends how you can get the best air flow to the most places.

The other thing to do is think if your RV was a boat would it sink from leaks from the underneath.

I did a repair on a DRV and found several places where air and water from the road could get in easy.

Safe Travels Vern

outwestbound · November 16, 2015

You have some good thoughts on what to do. It really depends how you can get the best air flow to the most places.

The other thing to do is think if your RV was a boat would it sink from leaks from the underneath.

I did a repair on a DRV and found several places where air and water from the road could get in easy.

Safe Travels Vern

You really know your stuff on this. Thanks for sharing. I just started fulltiming in my 37' fifth wheel. The HVAC system is terribly inefficient and poorly designed, which you've overcome it looks like. I'm looking to install a CheapHeat electric add on to my 40,000 btu gas surburban furnace. I winter in parks with 50 amps, so I'm thinking having an electrical option on the central system may help especially with the furnace serving the ducts in the double walled tanks.

Have you heard anything about "CheapHeat" add-on electrical elements? RV Comfort Systems makes them. I was thinking if I did the cheapheat element, I'd try to quit down the furnace fan, which is obscene. My return is in the bulkhead wall by the refer and direct draws to the furnace mounted horizontally 30" away, so the noise is just stupid. If I built a return air hard board plenum (if that's the correct term) that connected to the in-wall grill, then I wonder if I could then box in and insulate the furnace to kill the nose. However, that may not help because the return is still 30" away and the nose travel through that. The other option may be to let the return pull from my basement area, but I don't know whether that's a good idea. One thing about this Cheapheat thing is that it is just an add on to the gas furnace, so the gas furnace fan still has to run.

Any thoughts on this CheapHeat product and/or how to quit down the furnace would be great. I have plenty of work area around my furnace. It's about 40" between the basement and the bulkhead wall at the kitchen.

Wrknrvr · November 16, 2015

There is another source of heat in a RV that could be utilized. It will take some thought but if done correctly it would be great.

If the water heater was plumed correctly and used a mixing valve for tempering the house water. Then you could use higher temperature water for heating.

There are RV water heaters that are made with the mixing valve in place. But probably needs replumbed to do a heating source.

You would need to install a circulating pump to circulate hot water to heat exchangers and return, then install 12vdc powered fans to get heated air moving. Liquid lines are a lot easier to fish through tight places than 4" ducting.

The other thing would need to be done is to sence when domestic hot water is being used to allow for the energy to go towards that use.

This would take some planning but I think it would doable.

Electric or gas, or both for heat source. No or very little noise. If the underbelly is sealed good and insulating well a warm floor would make an R V a lot more enjoyable to be in when it is cold outside.

Safe Travels, Vern

DJohns · November 18, 2017

I know this is old thread but getting heat out of the hot water heater sounds neat. My 35 foot New Horizon has only one furnace and will no way heat if the outside temps were 10 degrees. I am thinking of adding a second furnace but has anyone done the hotwater heater thing Wkrnrvr suggested

alan0043 · November 19, 2017

20 hours ago, Dan Johnson said:

I know this is old thread but getting heat out of the hot water heater sounds neat. My 35 foot New Horizon has only one furnace and will no way heat if the outside temps were 10 degrees. I am thinking of adding a second furnace but has anyone done the hotwater heater thing Wkrnrvr suggested

I am interested in knowing more myself.

Al

GlennWest · November 19, 2017

My previous house in NC was heated with a gas hot water heater. Heat exchanger, pump, thermostat. It was a 75k btu though. Done a good job. We were cozy. Burned right much propane.

DJohns · November 20, 2017

I know this is old thread but getting heat out of the hot water heater sounds neat. My 35 foot New Horizon has only one furnace and will no way heat if the outside temps were 10 degrees. I am thinking of adding a second furnace but has anyone done the hotwater heater thing Wkrnrvr suggested

I was just thinking. If my propane/ electric HW heater will not keep up just put in a 5 or 10 gallon electric HW heater like in prevost?

I'mdonewiththis forum · November 20, 2017

One thing to keep in mind with using the water heater for heat is the time it is not used for heat. The water in the lines can and will become stagnant unless the water is circulating through them. That is the reason a regular water heater cannot be used for both domestic hot water and hydronic heat according to code. There are water heaters made for that, but they have a heat exchanger built in so that the water in the two systems remain separate.

ALLOY · November 20, 2017

If a 2nd loop is added there will be a stagnation issue but stagnation can be dealt with if the heating loop is inline with a sink or shower. This will provided a secondary heat source but when the extra heat is not need there will be heat loss from longer piping.....six of one...half of another.

The link below is a temperature controlled HW tank re-circ system. I chose not to use the HW tank for heat because my $0.02 thinks the HW tank is less efficient than the furnace. i uses a similar system to save water using a timer instead of a temp. controller.

http://roadtreklife.blogspot.ca/2016/03/rv-hot-water-recirculation-system.html

For secondary heat I added a Propex 2800 and I'm considering replacing the electric fireplace with a Rinnai direct vent wall heater.

https://www.rockymountainwesty.com/Propex_HS2800_Heating_Unit_p/hs2800.htm

https://www.rinnai.us/gas-home-heating/direct-vent-furnaces

The Propex is is ducted into the trailer (shoulder season heat) as well as (with 4" slide gates) a boot/glove drying locker that is vented (reduce condensation) outside. By removing a couple of clamps it can be swapped from the drying locker to heating the tanks.

To make the heater more efficient all the 4" flex hose has been replaced with 4" and 6" galv. steel ducting. The warm air from the Surbuban heater now enters the trailer as far away from the return air intake as possible. All the ducting as well as the cage of the heater has been sealed with a duct mastic. The registers in the floor are upgraded from 3" x 10" to 4" x10" that can be closed. The heating duct for tank heat has been increased to 4". This duct can be closed when it isn't necessary to heat the tanks.

My first choice for hot water and heat (for sure if I was building new) was a Bosch Buderus boiler (or similar with 96% efficiency) but it would have been 3X the work to pull out the floor insulation and install 3/8" radiant loops.

https://www.bosch-climate.us/products-bosch-thermotechnology/boilers/residential-boilers/gas-condensing-boilers/ssb-residential-models.html

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