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mikee72

05:10PM | 11/26/05
Member Since: 02/25/05
42 lifetime posts
Bvhvac
I'm replacing my baseboard heaters with the in-wall/blower style and am curious as to whether it will be cheaper to run three large (4400w) units, or six smaller (2200w) units. The whole house is only 600 sq ft, so I'm not really worried about the "evenness" comparison. (I know that's a lot of heat per area, but each baseboard already has 20 amp 220v) I keep reading that all electric heaters are "100% efficient," but I don't buy that supplying a large coil with "x" watts is going to raise it's temperature as much as "x" watts will heat a smaller one. I realize that the larger mass will give off more energy at the same temp., but I'm not convinced that the net output of the two scenarios will be the same per watt. I have never seen a "BTU/watt" rating on an electric heater, so I'm at a loss here.

mikee72

06:18PM | 11/26/05
Member Since: 02/25/05
42 lifetime posts
Ah, okay, that's confirmation that the heater manufacturers aren't pulling our leg on the efficiency ratings.

As far as the heat requirements go, the house is am all wood "kit" house (cabin) from the 70's whose walls consist of 2x8 car decking, a 1" piece of foam, and a 3/4" x 6" T&G interior. I work 16 hour shifts, and the house will be vacant for that time, so I plan on shutting off the heat while I'm gone and need a large capability to bring it back up to temp after I get home. If there is no efficiency lost by using larger units, I see no reason *not* to run the wattage my house is already set up for. If I'm overlooking something, please let me know.

Billhart

03:48AM | 11/27/05
Member Since: 04/25/05
1915 lifetime posts
"The whole house is only 600 sq ft, so I'm not really worried about the "evenness" comparison. (I know that's a lot of heat per area, but each baseboard already has 20 amp 220v)"

First of all it is 240 volt and that should be used in the calcualtions.

What you are mentioning is the SIZING OF THE CURCUITS, NO THE HEATER.

Look at the nameplate on the baseboard heaters and get their actual wattage.

"I see no reason *not* to run the wattage my house is already set up for."

Load demands are calculated based on the acutal nameplate data, not the rating on the breakers for things like appliances and heaters.

General purpose lights and receptacles are figured at 3 watts/sq ft.


mikee72

04:10AM | 11/27/05
Member Since: 02/25/05
42 lifetime posts
"Load demands are calculated based on the acutal nameplate data, not the rating on the breakers for things like appliances and heaters."

Bill, I'm unclear on what you mean by this. It's my understanding that since I'll be using a 240v/20A circuit, I'll be able to power a heater of 4800 watts or less. (4000w sounds good) The old baseboard heaters are long gone, so I can't look at them to see what they draw. If doing a simple V*A=W calculation isn't enough for this, then I've got it all wrong. Wiring is 12-2, BTW. TIA for your help.


Billhart

07:09AM | 11/27/05
Member Since: 04/25/05
1915 lifetime posts
Actually for long term loads you are limited to 80% of the circuit rating tos you would be limited to 3840 per circuit.

But what I was getting to is that a) you might be install an extremely excess amount of heating b) you might be overloading the service.

Here are a couple of links with information on baseboard heaters.

Commonly 4 ft 240v heaters are 1000 watts and 6ft 1500 watts.

From that you might be able to estimate what was there before.

Also the first link has some sizing and selection info. A google will probably find others.

http://www.cadetco.com/show_product.php?prodid=1004

http://www.houseneeds.com/shop/HeatingProducts/heatingunits/electrical/qmark/qmarkbaseboard220buypage.asp


mikee72

11:08PM | 11/27/05
Member Since: 02/25/05
42 lifetime posts
Bill,

Thanks for setting me straight on the power limits. From the "250w/ft" rule of thumb, it looks as though I was about to nearly triple the wattage in my bedroom. Even with poor insulation and 10ft celings, that's probably overkill.

mikee72

11:19PM | 11/27/05
Member Since: 02/25/05
42 lifetime posts
HK,

Now you have me doubting myself. I was under the impression that the in-wall was the "new-tech" replacement for the baseboard.

One of the things I read on the subject helped contribute to this:

"Another potential problem with baseboard heaters is that if wall insulation is not up to current standards, as it usually isn't in old houses, there can be a high level of heat loss through the back of the baseboard heater through the wall. Also, in areas with a ceiling higher than 10 feet, baseboard heaters may not be the best choice."

Since I fall into both catagories, it seemed like a no-brainer. I'm used to forced air (gas) heating, so I really didn't consider the noise an issue. However, I've never heard an in-wall electric unit, so I don't really know. You have point in that it makes more sense to have the heater on the cold exterior wall than it does on an interior wall, especially on a poorly-insulated house like mine. You may have changed my mind, at least as far as the bedroom is concerned.


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