Add electric heat to gas furnace?

[DKB_SATX]

Originally Posted by Llittle54

I’m really interested in this addition as well. We do camp in the winter. Keeping the belly warm to prevent the tanks freezing without going through propane is very appealing. When possible we look for hookups when we ski/winter camp so this system makes sense to me.
I have a 2016 FC fb23. Anyone happen to know which model Cheapheat would work? Anyone done this?
Thanks

They list 3 sizes on the site... 1800 watts (the smallest) would be all you'd want to run on 30A service. The next size up would need 31A at 120v for the heating element alone.

[Hermes]

Originally Posted by MandN

This year we worked on optimization our airstream 2018 25FB FC for winter camping, and successfully negotiated 2months in upstate NY with temps dipping below zero F on a few occasions. We were staying with family so we were able to make this work on a 15 amp circuit, with relatively modest propane use.

When plugged in, space heaters are great, but the problem with space heaters is that they don’t get the warmth to the tanks and pipes, which risks freezing. One of the mods was to decouple the blower on the furnace from the heater, so that you can run the blower fan only and circulate the space heater warm air to the distant compartments.

I have the blower fan controlled by a timer (link below) which allows you to set how often the fan comes on and for how long it stays on. The timer is turned on by a simple on off switch (link below).

We use a tower 1500 watt space heater (link below) which has a nice feature of laying flat which we can then place under the table when in couch position (our usual configuration). It and the cord are out of the way.
In this location, another advantage is it’s proximity to the air intake of the furnace blower fan, so the hottest air is circulated.

We set the parameters on the timer based on the temps in the most vulnerable spaces. I placed three wireless thermometers (link below) in the following spaces: below fridge all the way down below floor level next to fresh water tank; 2) at shower water intake lines 3) bathroom aluminum wall (behind the wood paneling).

Some additional mods relevant to this discussion:

1) made a split from hallway duct (1.5 inch) small tube/duct that shoots air into space where second thermometer is (2nd benefit is that it warms the floor from underneath between fridge and stove).

2) made a split from the duct that heats the bathroom with a 1.5 inch duct that now also runs along trailer passenger side wall right next to the water lines and terminates in the bathroom. The split is in the below sinc behind kitchen drawers compartment

3) the city water intake is very vulnerable to freezing then leaking there are multiple mods for this on airforums, ours allows us to disconnect water from regulator and drain it. In cold weather much better to fill fresh water tank and use pump, don’t have to worry about outside hoses freezing.

4) buble wrap refletix insulation along driver side wall in the shower, water pump compartments as far as your arms can reach and up the entire backside of hallway closet.

5) same insulation along on the inside of metal pan next to where the tank dump valves penetrate. There is a gap there otherwise that can freeze the valve so you will not be able to dump.


Hope this helps.

I asked a local RV tech if he could add a switch to run the fan without firing up the furnace and he said that it wasn't possible because the fan starts the sequence leading to the furnace firing up. Then I found this on a forum which seems to explain it. Any comments?
Here is the link to that forum :https://www.rv.net/forum/index.cfm/f...print/true.cfm

--------------------
Rigging the furnace fan could be done, basically would need to add a 12V SPDT (Single Pole Double Throw) relay in between the fan motor and the control board. The relay basically selects between the control board or direct 12V to the fan motor. Then a simple toggle switch can be used to turn the relay on for bypass.

HOWEVER running the fan by it's self is going to waste your heat. The reason for this is the furnace fan motor does double duty, it not only blows the inside air across the heat exchanger, it ALSO drives a fan on the burner chamber. This means the burner chamber is going to have COLD, COLD outside air being drawn into the burner chamber and PUSHED through the BURNER SIDE of the heat exchanger.

This will CHILL the heat exchanger and the inside air drawn across it will be cooled. Added to this you will be drawing warmer inside air (which in a RV is very humid) and condensing the moisture on the cold heat exchanger. This is going to cause a lot of rust to form on the heat exchanger.

Honestly, I really don't understand why folks who camp in the winter seem to be extremely cheap. SPEND the money on propane and use your furnace the way it was designed...

[MandN]

Originally Posted by Hermes

I asked a local RV tech if he could add a switch to run the fan without firing up the furnace and he said that it wasn't possible because the fan starts the sequence leading to the furnace firing up. Then I found this on a forum which seems to explain it. Any comments?
Here is the link to that forum :https://www.rv.net/forum/index.cfm/f...print/true.cfm

--------------------
Rigging the furnace fan could be done, basically would need to add a 12V SPDT (Single Pole Double Throw) relay in between the fan motor and the control board. The relay basically selects between the control board or direct 12V to the fan motor. Then a simple toggle switch can be used to turn the relay on for bypass.

HOWEVER running the fan by it's self is going to waste your heat. The reason for this is the furnace fan motor does double duty, it not only blows the inside air across the heat exchanger, it ALSO drives a fan on the burner chamber. This means the burner chamber is going to have COLD, COLD outside air being drawn into the burner chamber and PUSHED through the BURNER SIDE of the heat exchanger.

This will CHILL the heat exchanger and the inside air drawn across it will be cooled. Added to this you will be drawing warmer inside air (which in a RV is very humid) and condensing the moisture on the cold heat exchanger. This is going to cause a lot of rust to form on the heat exchanger.

Honestly, I really don't understand why folks who camp in the winter seem to be extremely cheap. SPEND the money on propane and use your furnace the way it was designed...

Excellent points, thank you, the condensate-rust issue is something I did not think of. Is there anyway you can think of that might decouple the the double duty that the blower fan does so that it is not drawing cold air into the heat exchanger? BTW it is not the cost that was driving this mod but rather convenience, as the nearest propane refill place was about an hour away and those 30lb tanks don’t last very long in cold weather. I know I can get more/bigger tanks but we don’t have room for them as full timers.

[Hermes]

Originally Posted by MandN

Is there anyway you can think of that might decouple the the double duty that the blower fan does so that it is not drawing cold air into the heat exchanger?

If I get it right, there is only one fan. When starting up it is pulling in air from the outside into the burner chamber without firing but that is for a short period of time until the sail switch says there is lots of air blowing and it's ok to fire up, then the ignition fires up to heat the RV, then after the thermostat shuts off, it keeps running to push the remnant heat from the heat exchanger into the RV and it cools down the burner chamber by pulling in external cold air.

Unless the additional proposed relay which would connect the fan motor to a direct 12V source (or bypasses to the board) also activates a damper on the air intake to the burner chamber to close off the cold air intake, I don't see a simple solution.

An idea is to add an additional fan (like this Attwood marine inline Blower H20 3" bilge blower fan found on Amazon) activated with a switch/timer, connected to the furnace plenum which would pull air from the RV interior and push it into the ducts, thereby bypassing the the furnace/fan/control board. This could be a straightforward alternative to rigging the furnace.

It would be a matter of cutting a 3" opening into the plenum to connect the fan; and with a 3" flexible ventilation duct connected to the fan intake, you could pull in the warm air closer to where it is generated, for example the fridge area. The thing to check is that by pushing air into the plenum you are not losing it through the furnace air intake!

A fan like this is most likely not as powerful as the furnace fan, but since it only pulls 2.6 Amps, you can leave it running for longer periods. It may also be a lot quieter. And beyond pushing warm air to the belly pan, it would recirculate air in the trailer. But I haven't examined this solution yet.
Keep us informed!

[MandN]

Originally Posted by Hermes

If I get it right, there is only one fan. When starting up it is pulling in air from the outside into the burner chamber without firing but that is for a short period of time until the sail switch says there is lots of air blowing and it's ok to fire up, then the ignition fires up to heat the RV, then after the thermostat shuts off, it keeps running to push the remnant heat from the heat exchanger into the RV and it cools down the burner chamber by pulling in external cold air.

Unless the additional proposed relay which would connect the fan motor to a direct 12V source (or bypasses to the board) also activates a damper on the air intake to the burner chamber to close off the cold air intake, I don't see a simple solution.

An idea is to add an additional fan (like this Attwood marine inline Blower H20 3" bilge blower fan found on Amazon) activated with a switch/timer, connected to the furnace plenum which would pull air from the RV interior and push it into the ducts, thereby bypassing the the furnace/fan/control board. This could be a straightforward alternative to rigging the furnace.

It would be a matter of cutting a 3" opening into the plenum to connect the fan; and with a 3" flexible ventilation duct connected to the fan intake, you could pull in the warm air closer to where it is generated, for example the fridge area. The thing to check is that by pushing air into the plenum you are not losing it through the furnace air intake!

A fan like this is most likely not as powerful as the furnace fan, but since it only pulls 2.6 Amps, you can leave it running for longer periods. It may also be a lot quieter. And beyond pushing warm air to the belly pan, it would recirculate air in the trailer. But I haven't examined this solution yet.
Keep us informed!

We are on the same page, that’s the route I’m currently exploring the plenum has some unused 3 inch cutouts, I like the idea of a quieter fan as well.

[Hermes]

Originally Posted by MandN

We are on the same page, that’s the route I’m currently exploring the plenum has some unused 3 inch cutouts, I like the idea of a quieter fan as well.

If the plenum connection isn't feasible because the pushed air comes out through the air exchanger intake, then a duct Y splitter combined with a spring loaded backdraft damper (example: https://www.amazon.ca/dp/B0822VQMHM/...kZXRhaWw&th=1)
connected to the duct that feeds the belly pan would be an alternative.

[gypsydad]

Use a space heater; get one that is efficient; likely much cheaper. Plus, you can use it other places if needed...a tent, a cabin, your living room...

[richard5933]

Originally Posted by gypsydad

Use a space heater; get one that is efficient; likely much cheaper. Plus, you can use it other places if needed...a tent, a cabin, your living room...

I think the interest of many people, myself included, in the concept of adding electric heat to the furnace would be the ability to circulate that heat into the belly pan to keep the tanks warmer. An electric space heater is ideal in many ways, but not this one.

[Hermes]

Originally Posted by richard5933

If you've room to add it, I see it as a great addition to the system.

I checked and I have less than 3" of space at the back of the furnace, which is half of what the additional CheapHeat plenum requires for its installation.

I didn't see any videos of an Airstream installation (mainly class A MH). Aware of an Airstream installation?

[gypsydad]

Originally Posted by richard5933

I think the interest of many people, myself included, in the concept of adding electric heat to the furnace would be the ability to circulate that heat into the belly pan to keep the tanks warmer. An electric space heater is ideal in many ways, but not this one.

Good point. Wasn't considering the bellypan. Understand the goal now...dahh...

[MandN]

Originally Posted by Hermes

If the plenum connection isn't feasible because the pushed air comes out through the air exchanger intake, then a duct Y splitter combined with a spring loaded backdraft damper (example: https://www.amazon.ca/dp/B0822VQMHM/...kZXRhaWw&th=1)
connected to the duct that feeds the belly pan would be an alternative.

Hermes, here is another idea, see what you think. So as you know we have a bypass switch that is on a timer to run furnace fan only. You correctly pointed out that this is both inefficient and potentially detrimental to the furnace because the furnace blower fan is also designed to pull cold air from the outside and circulate it through the heat exchanger and back out which cools the indoor air and can cause excessive condensation and rust on the exchanger. Yet, even with this built inefficiency we were able to keep the coldest belly compartment above 34 degrees at night with outdoor temps dipping into the teens without using furnace heat and only using just one 1500 watt space heater as we were plugged into a 15 amp circuit. Now I did add an additional y split to the belly and bathroom side wall which I’m sure helped. So here is the idea, With the furnace off why not just seal the furnace out-intake valve to the outside with one of those cheap outdoor winter faucet foam covers (or something like it)? I know it’s kind of radical and you Must keep the furnace off but that area is so cold at baseline because there is a direct connection to the outside. So not only will the blower fan now not pull from the outside but there is added insulation which stops the direct connection to the outside. Thoughts?

[zapper]

I was stuck in Denver Co one winter and was able to rent a 100lb propane tank from a local propane distributer. The tank was placed on the ground adjacent to my existing 30lb tanks and the connection was made to one side of the regulator. a 100lb tank would last us about a month or so. Just thinking that this might be an alternative if you are full timing with winter coming on.

[MandN]

Originally Posted by zapper

I was stuck in Denver Co one winter and was able to rent a 100lb propane tank from a local propane distributer. The tank was placed on the ground adjacent to my existing 30lb tanks and the connection was made to one side of the regulator. a 100lb tank would last us about a month or so. Just thinking that this might be an alternative if you are full timing with winter coming on.

Approximately how much $ was it if you remember?

[gypsydad]

Originally Posted by MandN

Approximately how much $ was it if you remember?

I have always my on board furnace set at 40 with propane here in TX; but 2 years ago we had that 2 week freeze and I was afraid I was going to run out of propane All the business' were closed because the roads were closed down for the most part for about a week. No one had propane because the trucks could not get thru to replenish the dealers tanks. I panicked, so last year I blew out my lines for the first time last year, and winterized with a bit of antifreeze in the drains also. Worked well. If I was winter camping in the North with my AS, this solution using an electric alternative as mentioned may make sense. Propane ain't getting any cheaper...something else to consider if you don't winterize...