Hmmm... what do you think of this?
 

www.eheat.com

Your thoughts?

Pete

Looks like an interesting idea, but how much can a single 400 watt electric heater really heat an average room if it is well below freezing out?

Anyone know how much they cost?

Like $80 or somthing... the link is on the page to buy it on their site. They have been all over the media, etc. I agree, how the heck can 400 watts heat a friggin room that size...

Sure sounds interesting.

Seems like a rehash of an old idea,nichrome resistance wire sanwiched between 2 panels,but with obviously thinner wire,hence the low wattage needed.

The best electric heat I ever saw was installed in a local estate in the '50's I think.

These were wallmounted units,very flat with opaque glass panels that had resistance wire inside and a reflective mirror coating on the rear,I think they were called Glassfire or something,thermostat regulated.

The devil is in the details.

400 watts of resistance heating is 400 watts of resistance heating, no matter how you advertise it. It is no more, or no less, efficient than any other 400 watt resistance heater.

Heat pumps can be more efficient, though.

Is 400 watts enough heat for a 10x10 room? It depends on how hot you want the room, how cold it is outside, how many times the air in the room is exchanged with outside air and how good the wall and ceiling insulation is...

If it sounds too good to be true, it is too good to be true.

I agree with Jim.

Sometimes I use those oil filled radiators for supplemental heat. 900W can raise the temp in the room by about 10°F. when the ambient temp outdoors is about 30°F. I'm quite sure that 900W would be insufficient as the primary heating source for a 10 x 10 room.

I don't see how 400W can do much unless the ambient temp is 50°F. or above. Then the losses to the exterior of the building are minimal.

Thanks for the vote of confidence, Brian.

For further thought, those of us in colder climates, a 100,000 BTU output furnace could be considered 'typical' for 1,500 square foot home.

100,000 BTU is 29,300 watts, so that works out to about 19.5 watts/square foot. At that rate, the 400 watt heater would cover a room 4'-6" square. :eek:

Oh, and if I'm off by a factor of 2 on the heat input needed, the room could be a whopping 6'-6" square... :D

That same 29,300 watts would require 73 of those $80 heaters, or a cost of $5,840, house wiring not included...

The devil is in the details.

Man, I appreciate clear thinking!

Thanks.

B

I agree with all the calculations.

I'm curious to know if you have ever had a 100,000 BTU furnace running flat out in MI? Meaning that the house was losing 100,000 BTU/hr.? If so, what was the ambient temperature? I'm guessing that it had to be lower than -15°F.??

The furnace that I have has an output of about 80,000 BTU with the smaller .80 nozzle. It has approached a 75% duty cycle at 0°F. ambient. The house is standard 2 x 4 constuction without any additional insulation.

If it's just -15 its no big deal but if you add wind to that your furnace can work hard. Last year my I was installing a NG line for my generator and my furnace was off for 6 hours and the outside temp was -6 and it was clody with light winds my house droped from 72 to 69 in that period of time...and thats with the workers going in and out. I have 110,000 btu 90% efficency furnace.

Something is not right. Are you stating that the house dropped three degrees in six hours, without any furnace in operation, with an ambient of -6°F?

Either you have some unbelievable insulation in that house or there is some truth being stretched. 2 x 6 walls with R-19 would not be able to hold a house to a .5°/hour temperature drop at -6°F. ambient.

In fact, at this temperature, the average 2,000 sq. ft. house in MI would be sucking down somewhere around 70,000 BTU/hr. If you are losing 70,000 BTU/hr, the house is going to drop by much more than .5° per hour.

No, that's never happened, even on the coldest days. It's working hard when it on 10 minutes, and off 20 minutes, or 33% duty cycle.

I don't think any HVAC contractor wants to risk that a furnace will fall 10% 'short' on the coldest days, so they upsize the rating.

That, or running the blower fan 24/7 would burn it out.

I would think that a 50,000 BTU unit, with a 2-speed fan, low for heating, high for cooling, would be a bit more efficient, since you would not have the losses of the heat up/cool down portion.

It's a very well insulated house if it only uses 33,000 BTU/hr (presuming 100K unit) on a day that is -15°F.

Since they size the unit for the lowest temperature, I'd bet that a typical house would use twice this much. Do you have any solar heating? Will the house maintain the 33% duty cycle at night or does the duty cycle climb without the sun??

the appliances, lights generate heat plus the material in the house holds heat like the concrete basement walls, drywall, insualtion, even the couch.

The heating/insulation tech even commented that it should a a degree less than that.

roof insulation is R-40. Interior walls are R-12.