1500 watt heater. Enough?

myredracer wrote:
In colder weather, you need to ventilate the interior to remove moisture laden air. If you don't, you can end with issues like mold, rot and delamination. An electric dehumidifier may be needed if you plan to use your camper often in cold weather. Cracking vents and windows and/or running a fan means you lose some heat. Don't seal everything up with in an effort to retain heat.

Very true of the propane furnace, which can put out a lot of moisture. An electric space heater will actually dry out the area, not introduce more humidity.

Chris Bryant wrote:

afidel wrote:

Chris Bryant wrote:
Fwiw, if you are hard wiring it, you can go up to 1800 watts on that 20 amp circuit.
Actually, I believe you can go even higher, like 1920 watts.

1800W is correct for a heater as it falls under continuous load so the circuit needs to be derated by 20%.

I thought 1920 was 20% down- 20 amps times 120 volts equals 2400 watts, less 480 watts (20% of 2400) equals 1920 watts.
Or is there an additional derating due to constant load? My NEC is still packed :)

Interestingly, in Canada we can run wire on fixed space heaters at 100% of it's rating while breakers must be derated to 80%. Heaters are considered non-continuous loads in buildings. Nothing burns up here, including our house which is part electric heat. AFAIK, the NEC still considers heaters to be continuous and requires derating of wire and breakers by 80% for fixed space heating. Fixed heaters in an RV are going to be a different thing because they won't cycle on/off like in a building (which will have good insulation and properly sized heaters) and I would def. not exceed 1440 watts on 15 amp wire and breaker or 1920 watts on 20 amp wire and breaker. Plug-in portable heaters are a different matter and can be rated at 1500 watts and have 16 ga. cord wire and be plugged into a 15 amp recept.

You don't say what you have which may or may not make a difference. I installed recessed heaters in our TT and can add some comments.

It depends somewhat on how well your camper is insulated. Many are not plus they can leak like a sieve. We had lots of holes in the floor in ours, including one about 8x8" and I sealed them all up with foam. Having run lots of various wiring through the ceiling, I've found the insulation workmanship in the ceiling cavity to be terrible and in some locations there isn't any.

Your floor will feel uncomfortably cold in colder temps. You may want to wear thicker socks. If you have an enclosed underbelly, tanks and piping won't get any heat so if the temps. will drop below 32, something could freeze up.

You will need to maintain the required safety clearances on all sides of the heater. Can be a challenge to find a suitable spot. I installed a semi-recessed heater on the ceiling in a previous TT because there was no other place - worked fine.

In colder weather, you need to ventilate the interior to remove moisture laden air. If you don't, you can end with issues like mold, rot and delamination. An electric dehumidifier may be needed if you plan to use your camper often in cold weather. Cracking vents and windows and/or running a fan means you lose some heat. Don't seal everything up with in an effort to retain heat.

I'd get a heater with a squirrel cage blower instead of a propeller fan because they're much quieter. These heaters aren't cheap and don't get the cheapest one you can find. You don't need to share the circuit for the AC unit, Just get tandem breaker and run a new circuit back to the panel. You'll never run the heaters and AC together (and if you did, you'll just trip a breaker). Wiring can be run 100% concealed via ceilings, interior walls, cabinetry, under shower, etc. It will take longer to get the interior up to a comfortable temp. when you get to a new site but can always use the furnace at first. I'm an EE and have never run into a heater that doesn't put out it's rated wattage and they must meet a UL standard that specifies output requirement. Note that ratings are at 120 volts and heat output varies as the square of the voltage so try and have good voltage. If you can, install a wall mounted t'stat because they function better compared to an integral built-in one on a heater. I'd suggest two smaller wattage heaters in different areas for more even heating.

We have a 29' TT and I installed two recessed heater like the OP shows plus a 1KW recessed kickspace heater below the stove and have it set up at 2,000 watts total. One heater is above the bed, one is in the bathroom and one is at the rear of the TT in the kitchen. Provides even and comfy heating from front to rear. I used King Pic-a-watt "PAW" heaters which have adjustable tap settings from 250 to 1500 watts in 250 watt increments. I made my own demand controller using a current sensing relay that automatically shuts off the heaters when something gets plugged in that exceeds 30 amps total into the TT. I used wall mounted low voltage thermostats for better control. 2,000 watts isn't quite enough below 40F as the heaters run continuously, esp. the one in the kitchen as it covers a larger area. I did this a few seasons ago and haven't had to use the furnace since - not sure if it still works, lol. And yes, these heaters put out their rated wattage.

afidel wrote:

Chris Bryant wrote:
Fwiw, if you are hard wiring it, you can go up to 1800 watts on that 20 amp circuit.
Actually, I believe you can go even higher, like 1920 watts.

1800W is correct for a heater as it falls under continuous load so the circuit needs to be derated by 20%.

I thought 1920 was 20% down- 20 amps times 120 volts equals 2400 watts, less 480 watts (20% of 2400) equals 1920 watts.
Or is there an additional derating due to constant load? My NEC is still packed :)

Chris Bryant wrote:
Fwiw, if you are hard wiring it, you can go up to 1800 watts on that 20 amp circuit.
Actually, I believe you can go even higher, like 1920 watts.

1800W is correct for a heater as it falls under continuous load so the circuit needs to be derated by 20%.

A friend has installed one simular in his 30’ fifth wheel and has said it works well.

Chris Bryant wrote:
Fwiw, if you are hard wiring it, you can go up to 1800 watts on that 20 amp circuit.
Actually, I believe you can go even higher, like 1920 watts.

JMO but for better heat distribution in a larger rig one would be better off using 2 heaters running 900 watts each, located in different areas, and powering each by plugging them in to 2 different circuits, rather than a single 1800 watt heater sitting in just one location.

Should be fine with a 1500 watt heater. We usually use one in our 31 foot camper with bunkhouse and a slide. We will turn it on in the main room under the AC unit and turn on the AC fan to distribute the heat throughout the camper. Works great!

Fwiw, if you are hard wiring it, you can go up to 1800 watts on that 20 amp circuit.
Actually, I believe you can go even higher, like 1920 watts.

prichardson wrote:
1500 watts is 1500 watts whether it is portable and set on the table or mounted on the wall. The heat produced by either is the same.

Rarely is any so-called "1500 watt" electric heater actually drawing 1500 watts, in fact the actual draw can be all over the map. I own several and on HIGH actual consumption runs all the way from a low of ~ 900 watts to ~ 1400 watts, which in turn obviously means their heat output varies considerably. Once you've measured any heater's actual draw you can then calculate it's energy output in BTUs according to the formula 1 watthour = 3.412 141 479 9 BTU.