Electrically Heating TT Underbelly

My trailer came equipped with "ultra heat" heating pads on all tanks. It is a duel system that works from battery power when plugged into your tow vehicle AND turn on the 12 volt switch inside the trailer. When NOT towing and plugged into 120 volt AC power those pads are heated by 120 volt AC power and come on automatically when the temperature reaches a preset number (about 40 degrees). It is safe down to around zero degrees and has the obvious advantage of heating when towing or when living in the trailer. I would NOT advise using the heater when camping off the grid as it would fairly quickly drain your batteries.
Good luck / Skip

Hi GordonThree,

Convection is definitely NOT enough! In fact, my first attempt at preventing freezing was a 1500 watt fan based heater inside the kitchen cabinets. It was set to run constantly on the highest possible heat. That did exactly nothing and the lines still froze. The air was simply not getting to where the problem was.

I did contemplate having a fan only setting for the propane furnace--but the fans are noisy, difficult to service, and expensive to run both from a dollars point of view and amps (9, in mine).

I've not had another freeze up since installing and finding a good set point for the window fans. It works far better than I dreamt. It is quiet, especially on the low speed setting. At -20 c I move to the faster fan setting.

I'm contemplating adding a filter after the fans to reduce the particulates in the air. I have not found one that is the right size, so far, but I've not looked very hard either.

The problem was exacerbated by the fact that the tin wheel wells extend above the floor under the cabinets, have zero insulation over them, and water lines touching them. I did manage to force some 1.8 inch foam board between the lines and the tin.

I've managed to drop the btu's needed for space heating by 50% by doing things such as removing the exterior shower and attempting to insulate what is darn near a hole in the wall. With everything running on electric I need a peak of 6000 watts. That includes operating a block heater for the engine, fridge, and water heater. I do use the inverter charger in winter for house battery charging as it is temperature compensated. In the other three seasons I rely mainly on solar and occasionally the PD 40 amp converter.

I get around the 30 amp limitation by having two auxiliary shore power cords. By careful planning I'm able to have all the outlets live on the OEM 30 am when I do not need the extra power. I have a 50 amp break out box that has a 30 amp breaker protected outlet on one leg, and 20 20 amp breaker protected outlets on the other leg. This allows me to use multiple 15 amp circuits when I'm in a Church parking lot or other location that has more than one plug in.

When I'm on 15 amp only, I can "dial down" the OEM 30 amp to 15 using the Magnum hybrid inverter. The inverter allows me to draw more than 15 amps--and supplies the needed extra amps from the battery bank. In addition it allows me to dial back to 23 amps which is all that the Yamaha 3000 Sieb will output on a continuous basis. That makes my life much easier as I no longer have to load balance.

GordonThree wrote:
regarding warming the water lines, you're saying natural convection is enough to circulate the hot water into the cold, to keep the water lines from freezing up?

I have a couple of portable 1,500 watt heaters with thermostats. Any of them could be used to warm the basement area to say 60F. Normally I might leave one on low heat output, and set it to the warm setting.

I normally have one heater in the back, and keep it in the bedroom at night, and bathroom while I am in there. I heat the living room with a third electric heater.

Because I only have a 30 amp service, I need to have one heater on the power post, while the others are run from the 30 amp service, but only 1 can be on high 1500 watt setting, the other on the low 800 watt setting. If I made coffee, or run the toaster, I would need to shut off one of the heaters, to keep the load below 30 amps.

You might trip a 20 amp circuit breaker inside the RV. If you do, find out what circuits are still "Live" and plug one heater into a "Live" plug, while the other should be plugged into the now tripped and dead circuit. Once re-set, you will only have one heater on each circuit breaker, and not trip it again. NOrmally a 30 amp RV will only have 2 or 3 circuit breakers feeding the receptacles, including one in the basement that feeds the battery charger. (one for the A/C and normally there are no more than 5 total, and a main 30 amp breaker).

With a 50 amp RV, normally there will be several circuits, and dedicated ones to the microwave, kitchen, each A/C unit, and perhaps the basement will have it's own circuit breaker. If you have a optional 'Fireplace heater' it typically will be on it's own 20 amp breaker as well.

50 amp RV's typically have 8-12 circuit breakers, in addition to the 50 amp main breaker.

Have fun camping!

Fred.

pianotuna wrote:
Hi GordonThree,

Nice radiators, thanks for posting them. Any idea what the safe operating temperature is? Are they rated for potable water?

For warming water in the hot water lines put in a valve with pex tubing return to the fresh water tank. No extra pump needed.

hard to say, I imagine selecting one that's ROHS compliant would be pretty safe. I didn't notice, are the in-cab aqua hot radiators advertised as potable?

PC cooling radiators are pretty much all metal, so I doubt domestic hot water would be too hot for them. In a PC applications the water can reach 50-60C, but is usually closer to ambient.

regarding warming the water lines, you're saying natural convection is enough to circulate the hot water into the cold, to keep the water lines from freezing up?

Hi GordonThree,

Nice radiators, thanks for posting them. Any idea what the safe operating temperature is? Are they rated for potable water?

For warming water in the hot water lines put in a valve with pex tubing return to the fresh water tank. No extra pump needed.

GordonThree wrote:
Those aqua-hot things reminded me of something related in my computer hobby, called water cooling radiators.

The price is a lot better:

example, clicky

bigger radiator (room for 2 fans) clicky

I keep my water lines from freezing while heating 100% electrically by replacing the return air grill for the furnace with dual window fans controlled by a mechanical thermostat. The placement of the thermostat is under the cabinets close to the outside wall. This, happily in my case, does push some air through the heating duct work.



I developed this method because when I was trundling down the road in my class C the furnace would not cycle because of heat from the cab, so the water lines would freeze, even though the living quarters were at 20 C (68 f).

Dual Window Fans

The fans draw a scant 23 watts, so are easily run by a small inverter. This has been used at -34 C (-30 f).

The waste tank area is enclosed but unheated, so I added a 120 volt outlet and run 200 watts of heat controlled by a thermostat. This has been live tested to -27 C (-16.6 f), with no other heating of the RV.

If you plan to camp in extreme temperatures do not forget to protect the fridge. There is a great thread on Winter Camping in the full time forum.

It is important to not use a computerized thermostat as they reset to off when power is interrupted for a second or two.

Those aqua-hot things reminded me of something related in my computer hobby, called water cooling radiators.

The price is a lot better:

example, clicky

bigger radiator (room for 2 fans) clicky

RoyB wrote:
A couple of guys I know are using the HYDRONIC method of using the 6-gallon hot water heater to route hot water to heat exchangers for the tanks and pass-thru storage areas using this heat concept...

Roy, what sort of pump is used in this application? I don't think I'd be installing radiators in my rig, but I would like to install a small hot water pump under my kitchen sink (farthest from the WH), to keep the water moving when the temps are down in the teens.

A couple of guys I know are using the HYDRONIC method of using the 6-gallon hot water heater to route hot water to heat exchangers for the tanks and pass-thru storage areas using this heat concept...


SMKETTNER is doing something like this as well for his under belly tanks...

Another guy on the JAYCO FORUM did the same idea to replace his Propane Furnace and his install looks like this.



I have been thinking about doing something like this mod configuration for my OFF-ROAD POPUP.



I would use the AQUA HOT 100 or 200 model for my heat exchanger which has built-in axial fans. This heat exchanger would fit in the original propane furnace hole in my cabinets.


You could add separate heat zones by just routing more PEX water lines to different areas you want to heat up.

One of our Canada friends on here uses this idea to heat the floors of his bath room using special floor tiles. You can run different heat zones around the trailer walls using this type of heat exchanger


The theory is the hot water heater will use less propane to keep the hot water flowing in a closed loop. Obviously this is alot less heat being produced as compared to the propane furnaces. My furnace runs us out of the small floorplan of my off-road POPUP anyway. It is hard for us to maintain a even temperature.

Also the 12VDC AXIAL fans run much quieter than the 12VDC Propane Furnace loud fan. My furnace fan does the very loud GRRRRRR noise. wakes me up every time it kicks in...

Just showing a couple of different ideas you may want to look into. For smaller trailers I really think this method of heating has some merit...

Roy Ken

West Texan wrote:
Has anyone made or found a way to electrically heat the enclosed underbelly of a travel trailer? We just finished a trip to Ruidoso during which the temperatures were below freezing for much of it, down to single digit one night! Of course I was prepared to and did run the furnace as I have a heated and enclosed underbelly to prevent freezing underneath. We did burn through the propane, which I figured we would, but didn't expect quite as much as we did.

This got me to thinking, if we are hooked up to shore power, about how to heat underneath electrically. I was thinking about maybe some type of compartment heater to heat it separately, or maybe even a small ducted fan to just pull cabin air and send it underneath.

We don't winter camp much, and this was about the first time below freezing, but I just kind of want to be prepared for the next time, or maybe some emergency reason I may need to camp in freezing temps.

Has anyone really experienced water freezing underneath down to 15-20 degrees while camping, which is all we typically encounter in Texas, and has anyone found a good or productive way to heat electrically?

If I were to do something like you're suggesting I think I would install some floor access from the interior of the trailer in the areas of the tub and water pump since they generally have some floor space aorund them and are near either water lines or tanks and then use some sort of fan/squirrel cage motor to blow warm air from inside the trailer into the underbelly. Not sure how efficient that would be, but I would think it would work for temps down to close to the single digits.

In generall I don't think this is a big issue since most electric heat is only good to the high 20's when you have to have some supplemental furnace type heat anyway and thus things freezing up in the underbelly should not be an issue as long as it has some heat from the furnace that gets there when the furnace is used.

Larry