Adding electric heat to coleman Mach3+

Hi myredracer,

I have pillows in the vents and skylights. I have the windows in the rear bedroom covered with Insulbright. But I'm not using most of the other cold weather modifications. The heat strip was cycling while maintaining 72 f.

It is a Canadian made unit, but pretty similar to other class c's which have dual pane windows.

myredracer wrote:
If you can maintain that sort of temp. at freezing temp. on only 1700 watts, that has to be a very well insulated RV! Are Class Cs that much better insulated than TTs?

pianotuna wrote:
Ambient outdoors at 9:48 p.m. 32 F. Inside RV 72 F. Source of heat. Heat strip in air conditioner.

Wattage about 1700 (running fridge on 120 volt).

If you can maintain that sort of temp. at freezing temp. on only 1700 watts, that has to be a very well insulated RV! Are Class Cs that much better insulated than TTs?

Hi Tyandkate,

Be aware that at about -5 F (-20 c) the air conditioner motor starts to complain. I.E. in true cold the heat strip is pretty useless.

If space is an issue then look at electric heated carpets.

Tyandkate wrote:
Thanks for that! I’m confident this heat strip is going to do the job perfectly with gas as a backup. And no heaters taking up the little floor space I’ve got.

pianotuna wrote:
Ambient outdoors at 9:48 p.m. 32 F. Inside RV 72 F. Source of heat. Heat strip in air conditioner.

Thanks for that! I’m confident this heat strip is going to do the job perfectly with gas as a backup. And no heaters taking up the little floor space I’ve got.

Ambient outdoors at 9:48 p.m. 32 F. Inside RV 72 F. Source of heat. Heat strip in air conditioner.

Wattage about 1700 (running fridge on 120 volt).

I use a ceramic heater in our unit, it does a great job for about $20.00
The heat strip does not do an adequate job of heating the unit in cold weather and as stated the warm air comes from the ceiling instead of the floor area.

Okay so I’ve got my plans drawn up and just waiting on Mr UPS to bring one more part to make it happen. I’m relocating my thermostat to a more accurate place. I’m going to install a 2 stage thermostat. First stage is going to be the electric heat if temp isn’t met within a certain time frame it will bring in the gas heat. Here in Texas the temps are typically above 36 degree in the winter months. I’ve just gotta figure out how to route my low voltage wire through the roof to its new location.

westend wrote:

myredracer wrote:
Our TT is comfortably warm and evenly heated from front to rear. An installation like this is not for the average DIY-er tho.

Will the 2000W keep the TT comfortable down to 0f? I know there are a few guys on the Forum that are trying to go pretty much "all-electric". An advisement that a conventional trailer can be heated with appliances and be comfortable at low temps would be a good jumping off point for the DIY'er.

Unfortunately, not a chance, not even close. TTs just aren't insulated well enough. Then if you camp in cold weather and moisture migrates into the insulation (and it will), the R-values go down. Our 2KW of electric heat is only good to around upper 30F and at that point, the heaters are running non-stop. Your lower legs and feet feel start to feel the cold because the furnace isn't making the floor warm. I sealed up all the openings in the floor which helped a bit. Heat loss is a direct/linear function between interior & exterior temp. At 0F, I *think* you'd need over 4-5 KW to maintain about the same inside temp. compared to 40F. You'd need 50 amp service to use electric down to 0F-ish.

One thing about the front-back dimensions of shallow metal outlet boxes is that screws poke out the back 1/4" or so. Carlon has the blue old-work boxes in a shallow version that are 1 1/4" deep. The Carlon boxes are the shallowest I've seen. They won't have much volume in them and may not work in some cases. I recently tried to mount one of the shallow Carlon boxes on an interior wall (in the TT) that was 1" deep but had to furr out the rear of the wall to get a box installed. If you had enough wall thickness, I'm not so sure it's a good idea to have the rear of a box touching or close to the exterior skin as you could get condensation in it?

pianotuna wrote:
No, Not enough BTU's 2k watts is only about 6824 btu's.

No place for "stab" connectors when using electric heat. Even with screw type I don't use 1500 watts per outlet. The limit for continuous loads is 80% so a 30 amp service has 24 amps to "play" with.

Be aware, as voltage drops, heat output falls of fairly dramatically. I do use my autoformer in the winter.

I replaced all but one outlet.

westend wrote:


Will the 2000W keep the TT comfortable down to 0f?

Yes, the typical RV receptacles are ****! It doesn't take much for an untidy installation to wreak havoc with the connections. The SC receptacles are rated for 15 amps but again, wire size and installation can be an issue. It is probable that not all SC receptacles are of the same quality. Here's a Pass Seymour SC receptacle for comparison: PS 15 amp SC receptacle

Fwiw, when I restored the Starcraft, I used shallow new work boxes and conventional duplex receptacles. Don't need problems if I can avoid them.

Hey Don,
Yeah, I thought 2000W would be on the low side but type of enclosure and good implementation may keep everything warm. I hope myredracer checks the thread and adds his experience.

I guess it's a unanimous "no" on the SC receptacles. I don't install or use them so anecdotal experience can be my mentor. A shallow, single gang, old work box has a depth of 1.25" from the interior wall surface. I'd bet that is less depth, in the wall, than an SC device.

No, Not enough BTU's 2k watts is only about 6824 btu's.

No place for "stab" connectors when using electric heat. Even with screw type I don't use 1500 watts per outlet. The limit for continuous loads is 80% so a 30 amp service has 24 amps to "play" with.

Be aware, as voltage drops, heat output falls of fairly dramatically. I do use my autoformer in the winter.

I replaced all but one outlet.

westend wrote:


Will the 2000W keep the TT comfortable down to 0f?

Yes, the typical RV receptacles are ****! It doesn't take much for an untidy installation to wreak havoc with the connections. The SC receptacles are rated for 15 amps but again, wire size and installation can be an issue. It is probable that not all SC receptacles are of the same quality. Here's a Pass Seymour SC receptacle for comparison: PS 15 amp SC receptacle

Fwiw, when I restored the Starcraft, I used shallow new work boxes and conventional duplex receptacles. Don't need problems if I can avoid them.