Electric Heat Concept

[snoobler]

I did a brief search and couldn't find anything.

Context: Applicable only to a unit with insulated basement and heated via furnace to prevent pipes/takes from freezing such as my Montana with Arctic insulation package.

While some units may have the ability to use electric heat via heat pumps, this becomes increasingly less effective as it gets colder. Additionally, for temperatures below freezing, it may not be acceptable at all since heat is not being circulated in the belly to prevent freezing of the pipes, etc.

It's my understanding that the furnace air intake is through the vents in the stair risers. If this is not the case, please disregard.

Idea:

Place a 1000-2000W space heater at foot of stairs.
Set propane furnace to 50°F.
Close propane valve.

In this situation, the space heater would provide the heat, and the furnace would cycle on and off according to the thermostat. Placement at the stair risers encourages the heated air to be drawn in by the furnace and distributed throughout the trailer.

Alternatively, since the space heater in the interior may keep the interior sufficiently warm to prevent the furnace thermostat from triggering, it might make sense to locate the heater inside the basement, though it should be thermostatically controlled itself to something reasonable like 70-80°F, so it's not running full time in a relatively tight space.

While it's arguably horribly inefficient, that's not the concern here. The assumption is that propane is not readily available, but electric power is cheap and plentiful.

This idea is inspired by the prior owner. He would spend 1-2 weeks at various sites in this unit in very cold climates, and he didn't want to make regular propane runs, so he ran the electric fireplace and supplemented with space heaters. As a result the black tank valve froze and was damaged.

Setting aside safety implications, does anyone have any thoughts on this concept? My main concern is if the furnace would cycle normally in response to temperature changes even if the furnace isn't firing.

[chuckster57]

If the propane is shut off, the furnace won’t run long enough to move much air and it may go into “lock out” and not run until you reset it.

[snoobler]

Originally Posted by chuckster57

If the propane is shut off, the furnace won’t run long enough to move much air and it may go into “lock out” and not run until you reset it.

Thanks!

I wondered if that would be the case. In another unit, I've ran out of propane overnight, and the blower just kept going all night.

If that's the case, is there anything preventing me from manually wiring the blower to run with a separate circuit?

[bobbecky]

If it’s that cold to worry about plumbing freezing, a small electric heater won’t provide anywhere close to enough heat as a substitute for the heat from the furnace. A common 1500 watt electric heater only puts out a little over 5,000 btu of heat. The furnace is usually rated 35,000 btu in these rigs.

[snoobler]

Originally Posted by bobbecky

If it’s that cold to worry about plumbing freezing, a small electric heater won’t provide anywhere close to enough heat as a substitute for the heat from the furnace. A common 1500 watt electric heater only puts out a little over 5,000 btu of heat. The furnace is usually rated 35,000 btu in these rigs.

Thanks. Agree. If I get more serious, I'll track how often the furnace runs and size it to an equivalent BTU/h. Based on 35,000 BTU/h, assuming 50% duty cycle, I'd need 4-5kW continuous.

Prior owner was able to maintain some level of comfort with a couple of space heaters.

I'm primarily looking for the conceptual flaws like the one pointed out by chuckster57.

I'm sure I'd need to implement skirting for any chance of being successful at lower power.

[travelin texans]

Originally Posted by snoobler

Thanks!

I wondered if that would be the case. In another unit, I've ran out of propane overnight, and the blower just kept going all night.

If that's the case, is there anything preventing me from manually wiring the blower to run with a separate circuit?

If you have the fan switch on the tstat set to hi or low then the A/C will run nonstop but the furnace fan will not.

[snoobler]

Originally Posted by travelin texans

If you have the fan switch on the tstat set to hi or low then the A/C will run nonstop but the furnace fan will not.

Thanks! Understood. I would wire a custom switch to manually turn the furnace blower on.

[JRTJH]

There's a lot of confusion about "insulated basement storage", "floor insulation" and "the space above the coroplast".... They are three entirely different areas and three entirely different"'levels of insulation"....

The basement storage area is usually "insulated" but not as well as the trailer interior. There are those 1" insulated access doors and often spaces or cutouts where plumbing runs and openings go from the "insulated area to the belly *uninsulated area*... All that "air leakage makes the "basement storage area insulation" significantly less "warmth retaining" than the main cabin area. Those "stairway vents" on the steps do allow heat into the basement storage area, but they also allow cold into the main cabin area.

The floor insulation is typically fiberglass and is placed "above the frame rails, wrapped in DARCO, along with the "center heat duct" and parts of the plumbing run. that space, top to bottom, is the carpet/vinyl, floor decking, floor joists, aluminum heat duct, insulation and the bottom is the DARCO wrap. All that rests "above the frame rails"....

Then there's the "belly".... That space is typically the frame rails and the cross members that keep them aligned. Through that area you'll find 2 or 3 "meandering, dryer vent type heat ducts", the holding tanks much of the plumbing run/sewer runs, dump valves and most of the electrical runs for trailer 12 volt and 120 volt electrical systems. That space, top to bottom is the DARCO floor wrap, open space with ducting, wiring, PEX tubing, holding tanks and valves. Below that is a sheet of mylar bubble wrap and a coroplast belly liner. When you consider that the steel frame rails are filled with holes (take a look at yours if you think otherwise) with no insulation on the frame rails, that space, below the "insulated floor" is honestly "uninsulated except for "feel good measures"....

So, going from "most insulated to least insulated":

1. Interior cabin, usually with single pane windows, R value somewhere around 7-9 (a better roof R value is negated by the windows in the walls) You can "pack" only so much insulation in 2" thick walls and what's advertised as "R-30 *effective rating* in the ceiling is honestly useless in reality.... Think about how warm you'd be if you have a "nice warm cap on your head" and take off your coat, exposing your arms and chest to only being covered by a tee shirt.... What's in the roof doesn't keep the walls warmer....

2. Basement storage/front passthrough storage, possibly heated, R value around 5 or 6 because of the 1" foam core doors that leak air around the metal framework.

3. "insulated belly" that's really a "polar package or artic package" JOKE...

There's a reason why current sales gimmicks include 12 volt heating pads on the holding tanks and still have warnings to run the furnace (remember that ineffective 2" dedicated duct)...

Truth be told, if a S&B home were built/insulated like an RV, it would cost 10 times as much to heat as it currently does... Does that mean an RV is 10 times less insulated ??? No, but when you consider that most home furnaces are in the 50K-75K BTU range and heat 2000 to 2500 sq ft of space and an RV furnace is 35K BTU, augmented by a 5K BTU electric fireplace for a total of 40K BTU's of heat source and is expected to heat around 200-250 sqft of space, it becomes pretty clear just how "uninsulated" any RV really is.

Most are "liveable during moderately cold weather" but few, if any are going to keep occupants "warm and toasty" when the temps fall below freezing, and those that do, will "burn through propane at a rate 10x greater than the average S&B home with significantly less "delivered comfort".....

As far as wiring a switch to turn on the furnace fan, most people find that fan to make more noise than most people would/could endure for more than a few minutes every hour... The furnace fan is about as annoying as trying to watch TV while vacuuming the floor....

[snoobler]

Originally Posted by JRTJH

[snip]

So, going from "most insulated to least insulated":

1. Interior cabin, usually with single pane windows, R value somewhere around 7-9 (a better roof R value is negated by the windows in the walls) You can "pack" only so much insulation in 2" thick walls and what's advertised as "R-30 *effective rating* in the ceiling is honestly useless in reality.... Think about how warm you'd be if you have a "nice warm cap on your head" and take off your coat, exposing your arms and chest to only being covered by a tee shirt.... What's in the roof doesn't keep the walls warmer....

2. Basement storage/front passthrough storage, possibly heated, R value around 5 or 6 because of the 1" foam core doors that leak air around the metal framework.

3. "insulated belly" that's really a "polar package or artic package" JOKE...

There's a reason why current sales gimmicks include 12 volt heating pads on the holding tanks and still have warnings to run the furnace (remember that ineffective 2" dedicated duct)...

Excellent. Thank you for the detailed response. I am only moderately familiar with this particular rig, and I greatly appreciate the deep(ish) dive. I have never regarded RV insulation to be particularly effective; however, our '99 Newmar American Star appears to be dramatically better insulated on the belly than the Montana. It's single massive slide seal is complete garbage!

I only recently noticed the gaping holes in the Montana frame beams for the slide rods while assessing how rodents are getting in. I didn't equate it to gaps in the insulation, but that totally makes sense. Thanks for connecting those dots for me. All the more important to address them now.

Originally Posted by JRTJH

[snip]

As far as wiring a switch to turn on the furnace fan, most people find that fan to make more noise than most people would/could endure for more than a few minutes every hour... The furnace fan is about as annoying as trying to watch TV while vacuuming the floor....

LOL. This is primarily for unattended operation, and I would make an effort to make that switch thermostatically controlled via an Arduino controlled relay.

I had originally intended to run wall and ceiling calculations with R8 and floor of R4. The goal isn't to stay comfortable - it's to keep stuff from freezing. HOWEVER, thanks to the insight of those responding, this is rapidly transitioning to a "not particularly effective and more trouble than it's worth" status.

Thanks again!

[flybouy]

There is a company that makes an adapter to install a 240vac electric induction element to the furnace. Can't remember the btu capacity perhaps a forum search will reveal it.

JMHO but campers make lousy permenant housing in non-temperate climants. Compensating for hot climate is easy, add more a/c units with a 50 amp service the energy is available. As warm weather is the most traveled/used time it only makes sense. Fewer people choose to live in a camper (full time) in cold climates so the LP furnace compensates for that at yhe cost of high propane usage. Anyone considering that option should consider dome type of skirting or wind barrier and havjng a propane company set a bulk tank with auto rifill scheduled.

[snoobler]

Originally Posted by flybouy

There is a company that makes an adapter to install a 240vac electric induction element to the furnace. Can't remember the btu capacity perhaps a forum search will reveal it.

JMHO but campers make lousy permenant housing in non-temperate climants. Compensating for hot climate is easy, add more a/c units with a 50 amp service the energy is available. As warm weather is the most traveled/used time it only makes sense. Fewer people choose to live in a camper (full time) in cold climates so the LP furnace compensates for that at yhe cost of high propane usage. Anyone considering that option should consider dome type of skirting or wind barrier and havjng a propane company set a bulk tank with auto rifill scheduled.

Thanks! Didn't know about the heating element.

Yep. And both of those are being considered.

[rhagfo]

Originally Posted by flybouy

There is a company that makes an adapter to install a 240vac electric induction element to the furnace. Can't remember the btu capacity perhaps a forum search will reveal it.

JMHO but campers make lousy permenant housing in non-temperate climants. Compensating for hot climate is easy, add more a/c units with a 50 amp service the energy is available. As warm weather is the most traveled/used time it only makes sense. Fewer people choose to live in a camper (full time) in cold climates so the LP furnace compensates for that at yhe cost of high propane usage. Anyone considering that option should consider dome type of skirting or wind barrier and havjng a propane company set a bulk tank with auto rifill scheduled.

Originally Posted by snoobler

Thanks! Didn't know about the heating element.

Yep. And both of those are being considered.

We have that system it is produced by RV Comfort Systems and called Cheap Heat.
We can heat with either gas or electric simple flick of the switch, it runs both on 120 volt 30 amp service or 240 volt 50 amp service. At 30 amp you get 1,800 watts of heat on 50 amp 5,000 watt of heat or 17,050 BTU. Keep in mind that your 35,000 BTU furnace is about 80% efficient where the electric is 100%.

https://www.rvcomfortsystems.com

[rhagfo]

Originally Posted by snoobler

Thanks. Agree. If I get more serious, I'll track how often the furnace runs and size it to an equivalent BTU/h. Based on 35,000 BTU/h, assuming 50% duty cycle, I'd need 4-5kW continuous.

Prior owner was able to maintain some level of comfort with a couple of space heaters.

I'm primarily looking for the conceptual flaws like the one pointed out by chuckster57.

I'm sure I'd need to implement skirting for any chance of being successful at lower power.

As stated before we full time in the PNW, we see temps in the high teens. We have a 2005 Sprinter Copper Canyon 32’ 5er, we can keep the 5er at 68 to 70 degrees with the add on unit down to 40 degrees on a 30 amp circuit. When we have 240 volts and 50 amps no issues at all down to the teens.

I hate using space heaters as the 120 volt wiring in RV’s isn’t really designed to carry high loads for extended periods of time, just not really safe.

[gearhead]

There's somebody over on the the Bigfoot forum crowing about converting his propane furnace to a diesel furnace. He camps a lot in very cold temps.
If you really need cheap fueled heat, maybe look into that.

[snoobler]

Thank for the input everybody.

Lazy wins. I'll just winterize every visit.

Thanks again!