Electric Baseboard Heat

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Len

Len

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Bucks County
Is their a rule of thumb for btu's per sq. ft. for apartment electric baseboard heat? Ex. 1 bedroom apt. aprox 675 sq. ft.
 
Len said:
Is their a rule of thumb for btu's per sq. ft. for apartment electric baseboard heat? Ex. 1 bedroom apt. aprox 675 sq. ft.
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I used to figure 12 watts per square foot, so a 675 sq. ft. apartment would require 8,100 watts divided by 250 watts per lineal foot of baseboard heat (check with manufacturer's listing) would work out to 34 feet of heat. I never used to put more than 14 feet of heat on a circuit.

Many electricians use 10 watts per sq. ft. Some even use 15 watts per sq. ft. depending of amount and quality of insulation.:smile:
 
peter d said:
Do you apply any adjustment factors to that for things like leaky windows, uninsulated walls, etc?
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No. Reason being is that this rule of thumb works in the worst case scenario. There is no penalty for short cycling of a baseboard heater. Doing a Manual J on the worst case and the average case will often yield the same heater or heaters anyhow. I use the Honeywell Line Volt Pro thermostats exclusively now. It will maintain the heat within 3/10ths of a degree. It "pulses" the heat when it starts to get close to set point, and can predicatively start pulsing the heat when it thinks it's ready for more heat. The #1 complaint about electric baseboard is the differential that all mechanical stats provide. The Honeywell Line Volt Pro makes having electric baseboard really nice.
 
mdshunk said:
Since ceiling heights vary, I use 1 watt per cubic foot.
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I like this method, makes more sense than per square foot. If you are trying to fill a three dimensional container (with heated air), not a two dimensional container, why not use three dimensional measurements?
 
peter d said:
Looks like an Aube product that got folded into Honeywell's line when they took over Aube.
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Yes, but it's the best line voltage heating stat I've ever used. Now, it's the only one I'll use when I have any say. In much the same way that I think motion sensors are a sure-fire callback (so I only use RAB motion sensors to prevent that), line voltage stats have been a constant source of callbacks. The Honeywell Line Volt pro solves the callback problem.
 
peter d said:
That's weird. What are the callback reasons? :confused:
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#1 Calibration. They're notoriously off by as much as 10 degrees right out of the box. I've never installed one that was dead-nuts accurate.
#2 Differential. They have differentials in the 3 to 5 degree range. That can be downright uncomfortable for many people.
 
mdshunk said:
#1 Calibration. They're notoriously off by as much as 10 degrees right out of the box. I've never installed one that was dead-nuts accurate.
#2 Differential. They have differentials in the 3 to 5 degree range. That can be downright uncomfortable for many people.
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I see.

Around here, electric heat is generally done on the cheap for rental property, or supplemental heat. Prior to your post I've never once heard of those problems or encountered a complaint so that is an eye opener.

Now they just need to make one of those Aube stats in inline form. :)
 
peter d said:
Around here, electric heat is generally done on the cheap for rental property, or supplemental heat. Prior to your post I've never once heard of those problems or encountered a complaint so that is an eye opener.
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In the late 60's and early 70's, an all electric home was the "in" thing. The power company would even affix a plaque next to or over the font door, proudly awarding the home the all electric seal of quality or some such thing. There's a heck of a lot of housing stock in my area served by electric baseboard heat. I've had a good many jobs the last couple years where I've replaced a failed thermostat with one of these Line Volt Pro stats, only to have them call me back to do the rest of the house. That's a super-good money maker. Hundred bucks a pop, 6 or 8 stats in a home, couple hours to change out. Good deal. You could legitimately market them as an energy saver, since they'll more accurately control the space temp and enhance the overall comfort.
 
You can no longer make a general assumption as to how much heat to supply to a heated structure based simply on area. There are far too many conditions and requirements to consider.

The applicable requirements are based on adopted building codes (which vary state-to-state, and sometimes by local building departments.)

Common codes currently adopted are: Chapter 11 of the 2003 or 2006 IRC, 1998, 2000, 2003 & 2006 IECC, 1992, 1993 & 1995 MEC; or in many cases a state-written code. Often the state or locals amend the code to make it more stringent. Also makes a big difference as to which year the adopted code is (for example, the 2006 IRC is MUCH more stringent than the previous 2003.)

If you are interested, the DOE has put out a free computer program that is set up state-by-state (by county or city within the states) and all one has to do is input the roof, wall, floor constructions and areas, window and door U values and areas; and it gives you an instant result as to how much heat loss is occurring in the structure.

They can be downloaded (free) from: http://www.energycodes.gov/
For residential choose: REScheck,
for commercial choose: COMcheck

If you run the programs, you can see that the different parts of the country vary widely in the amount of heat needed to be supplied to any given structure.

For example, a 1250 sq. ft home built in Texas might require 63,521,600 Btu/h per hour where that same home in Mn could require 81,115,100 Btu/hour to heat.

Assuming that a 1 watt = 3412 Btu/h, the Tx home would require 18.6 Kva of heating, and the Mn home would require 23.8 Kva of heating.

The numbers are arbitrary (and admittedly low) but are meant offer a graphic example as to why a single figure of watts per square foot is impossible to assume with any degree of certainty.

And also consider that oversizing is no longer considered acceptable. So just assuming say 15 watts/SF will keep them warm may produce a red tag just as readily as undersizing.

I believe that this is definitely a case where you need to talk to one of your local heating contractors for advice.

To properly size (wire) a heated structure, you first need to know the amount of heat loss that's occurring at that particular location. Then divide that by 3,412 watts (the amount of heat produced by 1-watt of electricity) and that will give you the total amount of watts to heat the structure. You can then partition that off room-by-room based on the amount of heat per foot of the individual baseboard registers. (In addition, most heating contractors will go a step further and calculate the heat loss per room; when using individual baseboard heaters.)
 
enigma-2 said:
If you run the programs, you can see that the different parts of the country vary widely in the amount of heat needed to be supplied to any given structure.

For example, a 1250 sq. ft home built in Texas might require 63,521,600 Btu/h per hour where that same home in Mn could require 81,115,100 Btu/hour to heat.

Assuming that a 1 watt = 3412 Btu/h, the Tx home would require 18.6 Kva of heating, and the Mn home would require 23.8 Kva of heating.

The numbers are arbitrary (and admittedly low)

Then divide that by 3,412 watts (the amount of heat produced by 1-watt of electricity)
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enigma-2...I believe that you need to check your math.
Some of those numbers (and terms) that you use are incorrect .

63,521,600 btu/hr to heat a 1250 square foot home? Not likely.
Not even in Alaska..much less Texas.:wink:
The same for the home in Minnesota.

1 watt of electricity equals 3.42 btu, not 3412 btu.

If you're going to quote numbers on this site , they had better be correct, or you will get called on them every time.....ask me how I know.:smile:

steve
 
hillbilly said:
enigma-2...I believe that you need to check your math. Some of those numbers (and terms) that you use are incorrect .
steve
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Ha, ya you caught me, typed in a hurry. (Although the speed of your response did surprise me - cudo's)

In my defense I *did say* they were arbitrary (looking around to see if anyone else noticed....)

Anyway, thanks for the slap, had a brain fart. <big smile>
 
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