Heated Floor Mats - Anyone Tried One?

[CoyoteThistle]

I've been looking for a low-cost option for heating my little camper. I've been looking at the various propane options but due to my confined space, I'd be forever worried about
knocking something over and burning down my rig.

Since my camper is soft-sided and wont hold much heat anyway, I started looking into in-floor heating (radiant) with hot water - at least our toes would be warm. It would be sweet, but pretty expensive. While I was researching that though, I ran into these heated floor mats. Several different brands that appear to be all the same unit more or less. Example:

http://www.globalindustrial.com/p/fo...at-36-l-x-16-w

Seems like they heat up to somewhere between 80 and 125F. That would be useful when it's down below freezing out.

Could run it through my 400w inverter. Looks like it draws about 1.2amps at 110vAC (~12 amps @12vdc is my math is right) - quite a bit, but I have a 130amp house battery that only runs a fridge and some LED's. Would only need it for a few hours in the evening while cooking and what not.

So, anyone have any experience with these?

Thoughts on weather this could work or not?

[mhiscox]

Could run it through my 400w inverter. Looks like it draws about 1.2amps at 110vAC (~12 amps @12vdc is my math is right) - quite a bit, but I have a 130amp house battery that only runs a fridge and some LED's. Would only need it for a few hours in the evening while cooking and what not.

I can't tell you whether this product would work or not, but I'm a bit worried about the extent of the battery drain. Your 12 amp DC estimate is right (figure 10:1 for inverter power), so that might suggest 130/12 hours of running the mat.

However, you don't want to draw down your batteries below 50% in any event, so you really have only 65 amp-hours, so that's 65/12 hours. But your 130 amp-hour rating is at 77 degrees, where you wouldn't need the heat; at freezing (assuming the battery is under your hood or somewhere else external) you'd be down about 20%, so that's about 51/12 hours of heat. Plus your 12 amps/hour is a fast enough discharge to show some Puekert Effect, for which you can look up the equation, but it basically means that you're discharging faster than your battery was rated at and thus you'll only get, in this case, 83% of the power that's available at the rated discharge rate. So now we're down to about (51*.83)/12, or 42/12, or about 3.5 hours of heat.

A 40 liter compressor fridge, as an example, could draw anywhere from 0.5 to almost 3 amps when running, but they don't run all of the time and the colder it is, the less it'll run, and the LED lights are pretty low draws, too. So figure in cold weather maybe an amp per hour for all of your other loads. However, that one amp draw goes on across many hours of the day, so as a rough guess, figure you'd maybe want at least 15 amps available for the non-heat requirements over a day. Subtract 15 from the available 42 amps and now you have only a couple of hours worth of power to run the heat mat at 100% on. (Of course, the heat mat won't run all the time, and since I have no idea how well it works, I don't know what fraction you could divide the couple of hours by to get an accurate running time.)

All of this rough-guess math was put in here only to support the generally-accepted fact that resistance space heating (and air conditioning, FWIW) from a battery bank is real close to impractical for any reasonably sized installation. My Sprinter has 615 amp-hours of AGM batteries and I do have an electric convection heater that works quite well. When plugged into shore power, it's an effective main heat source, but when running off the batteries, it only gets run for 5-10 minutes in the morning sometimes to take the chill off.

[Overland Hadley]

One of my thoughts is that one unit might not put off enough heat. And four units (32x72 inches) would get heavy and need shore power.

[McZippie]

Everything said above plus it's only 125 watts. Imagine trying to heat your camper with a 125 watt light bulb, neither one is not going to do much.

[CoyoteThistle]

Thanks for the breakdown Mike - that's a great way to think about how much battery one really has! Amps are funny little things.

The Puekert Effect is new to me - good one to know though.

Great point Zippie - even if the amperage calculations left any room for argument, that kind of seals the fate of the electric-heater-on-battery-power approach.

Well, back to the drawing board...

Little propane unit outside with some ducting and a fan maybe???

Thanks guys!

[Yellowkayak]

Wool socks and outdoor carpet.....much cheaper and safer!

JJ

[mhiscox]

Well, back to the drawing board... Little propane unit outside with some ducting and a fan maybe???

Time for me to once again make my ongoing pitch for the merit of propane catalytic heaters when used by reasonable people. Quiet, cheap, reasonable fuel cost, and I'm pretty sure you could find a way to mount one to eliminate the chance of it tipping over. Many users (including me) prefer to leave a little ventilation--though most all now have oxygen depletion sensors that would shut off the unit; the ventilation (1 square inch per 1000 BTUs) is an extra precaution. And you have to keep easily flammable materials at least a few inches away. And you may or may not wish to run them when you're asleep, though that might be true for most any heat source.

But assuming there's a flat shelf on your camper, your solution might be something as straightforward as a Mr. Heater Big Buddy heater, which has both ODS and a tipover switch. Add some industrial hook and loop to keep it from going anywhere.

There's a Camco/Olympian Wave 3 heater going into my truck, FWIW.

[Overland Hadley]

Time for me to once again make my ongoing pitch for the merit of propane catalytic heaters when used by reasonable people.

x2, Love my Wave 3.

[Hilldweller]

We ran a buddy catalytic heater in our Conqueror for years without torching ourselves.
15 degrees outside and 70 degrees inside with the windows on the tent open (heat rises nicely).

Dog knocked it over once and it went out.

We bought a new smaller one and tried it in the teardrop. It heated the interior in less than 5 minutes and we had to shut it off ----- tried to light it in the morning for a few minutes but the low O2 sensor wouldn't let it light. The little teardrop is that well sealed that the 3 of us literally sucked the air out of it... ...we leave the windows cracked now.