Baseboard Heat

Goose

How do I figure how many feet of electric baseboard I can run on a 220 volt 20 amp circuit? I was told that baseboard uses 250 watts per foot. I was told that you can only use 80% of the circuit because its considered a continuous load. I can't find anything in the 2005 nec thats say's anything but figure it at 100%. So whats the proper way to figure it? Do I take the total feet X 250 watts and divide by the voltage to get the amps? Is there anything to this 80% thing?

mdshunk

Any load that is energized continously for longer than 3 hours is considered a continious load, and the circuit should only be loaded to 80%. That being said, properly sized baseboard heat in a dwelling should not run nearly 3 hours at a go. This is certainly an intermittant load since the thermostat cycles the load on and off throughout the day, and the 80% rule would not seem to be required. However, the code does state that fixed electric space heating equipement must be calculated at the load x 125%, which is the same as only loading the circuit 80%. A 20 amp 240 volt circuit will handle 4800 watts at 100%, and 3840 watts at 80%. You can only load an electric heat circuit with 3840 watts of heat. A rule of thumb for electric baseboard heat (if you believe in rules of thumb) is one watt of baseboard heat for every CUBIC foot of space to be heated.

747

Do you have any ideal how expensive that electric base board is going to be to run. Big Big Big money!!!!! You better get put on the payment plan on that electric bill. :Thumbs:

mdshunk

Electric heat makes sense in a number of situations:
1) Locations where installed cost or future maintenance costs must be kept low. This particularly applies to rental units where the tennant pays the electric bill.
2) Locations where the number of days per year in which heating is needed are few. This applies to locations in the south, as well as seasonal cottages and cabins anywhere.
3) Basement remodels where the existing central heating system will not accomodate the additional square footage being adapted for habitation.

Remember, electric heat is the only 100% efficient means of heating (well, 99.99%). Nearly every kilowatt of electricity is converted into heat. Compare this with the most efficient gas furnaces which are only in the 93 or so percent range. The factor making electric heat so expensive is the relative cost of electricity as "fuel" as compared with natural gas, propane, home heating oil, coal, or wood.