Electric baseboard heat VA per foot

[mbrooke]

Ok, new condo construction. 2 questions.


What is the required VA perfoot for electric baseboard heating? Second one is demand factor. Do I factor in them as a 100% continuous load or via a %?

 

[480sparky]

Watts per square foot can depend on how well insulated the building is.

As for service demand, -I think- it depends on how the stats control them.

 

[david luchini]

Ok, new condo construction. 2 questions.


What is the required VA perfoot for electric baseboard heating? Second one is demand factor. Do I factor in them as a 100% continuous load or via a %?

Demand depends on whether you are using the standard method (see 220.51) or optional method (see 220.82(C)).

 

[mbrooke]

Watts per square foot can depend on how well insulated the building is.

As for service demand, -I think- it depends on how the stats control them.

Average insulation. 1,400 square feet. An 80,000 BTU gas forced air furnace would suffice, but Im looking for a general rule of thumb used most builders.

Demand depends on whether you are using the standard method (see 220.51) or optional method (see 220.82(C)).

Thanks! I will look into those

 

[mwm1752]

General recommendations for residential with an 8' ceiling was 10 w per sq ft. not very scientific but it did work well in the real world of 70's thru 90's

 

[mbrooke]

General recommendations for residential with an 8' ceiling was 10 w per sq ft. not very scientific but it did work well in the real world of 70's thru 90's

70s, 80s, 90s construction was less insulated then this, so if it worked then it will work now. Just dont want something undersized or oversized. Thanks!




Will an oversized system drive up the load calcs?

 

[suemarkp]

Yes, oversizing will cause you increased load in the calcs.

80K BTU = 23 KW when using resistance heat. So rules of thumb don't work well. Also, is this North Dakota or Florida? Modern double pane low-e windows, insulated doors, R-13 in walls and R-36 in ceiling, and tight construction should make things better than 20-30 years ago. Having a common wall (e.g. it is up against another condo and not exposed to the outside temps) will also reduce your heat loss. A lot of modern construction requires HVAC calcs (see if a Manual J calculation was done, as that will tell you heating and cooling requirements in BTU). A proper Manual J will be done by room so you would know the BTU needs of each room. There are 3.412 BTU per watt (3412 BTU per KW).

An 80K BTU furnace sounds oversized to me for 1400 sq ft condo. That's about what my 3000 sq ft 1960's house in Seattle had (after upgrades to windows and doors).

See the demand factor in the optional calculation. Put in 4 or more separately controlled units and you get the most demand reduction in the load calc.

 

[mbrooke]

Yes, oversizing will cause you increased load in the calcs.

80K BTU = 23 KW when using resistance heat. So rules of thumb don't work well. Also, is this North Dakota or Florida? Modern double pane low-e windows, insulated doors, R-13 in walls and R-36 in ceiling, and tight construction should make things better than 20-30 years ago. Having a common wall (e.g. it is up against another condo and not exposed to the outside temps) will also reduce your heat loss. A lot of modern construction requires HVAC calcs (see if a Manual J calculation was done, as that will tell you heating and cooling requirements in BTU). A proper Manual J will be done by room so you would know the BTU needs of each room. There are 3.412 BTU per watt (3412 BTU per KW).

An 80K BTU furnace sounds oversized to me for 1400 sq ft condo. That's about what my 3000 sq ft 1960's house in Seattle had (after upgrades to windows and doors).

See the demand factor in the optional calculation. Put in 4 or more separately controlled units and you get the most demand reduction in the load calc.

This is definitely better insulated then 20 years ago. This is up North, but if I oversize I will be forced to put in a larger service. I dont see why the code allows for a partial demand (such as an apartment with 50 ranges) since with an oversized system nothing will be running all at once. But it is what it is.

I found an online manual J calculator and compare that to 10 watts per foot.

 

[mwm1752]

Even if you oversized the heat it would take less time to get to temp preferred & with better insulation long periods in which power is used. Most likely a wash on actual power cosumption. The estmating 1400 x 10 = 14kw of resistance heat.

 

[mbrooke]

Even if you oversized the heat it would take less time to get to temp preferred & with better insulation long periods in which power is used. Most likely a wash on actual power cosumption. The estmating 1400 x 10 = 14kw of resistance heat.

Comes to 48 BTUs per hour. Each room will probably be more or less to factor window losses, fortunately each room is zoned :thumbsup:

 

[kwired]

This is definitely better insulated then 20 years ago. This is up North, but if I oversize I will be forced to put in a larger service. I dont see why the code allows for a partial demand (such as an apartment with 50 ranges) since with an oversized system nothing will be running all at once. But it is what it is.

I found an online manual J calculator and compare that to 10 watts per foot.

Put in all the insulation you want, doors and windows still are loss points, just some are better then others.

Also when it comes to demand factors, cooking equipment is not as likely to run at full load for extended time, it will cycle as needed to maintain desired temp. Space heating and cooling is often sized so that it runs nearly continuously during the most demanding situation it was designed for, no matter what the energy source is. So if a heating system is designed to recover heat lost when outside temp is at -20 deg F, then that system will likely run nearly continuously when the outside temp approaches this level. If the outside temp is only expected to get down to freezing at the worst, then same size and designed space will likely have lesser capacity heating system installed and would only run continuously when outside design temp is occuring.

Of course heat gain from other equipment sometimes is factored in the calculations as well, and even more so for cooling load calculations because if you can not overcome internal gains you will not acquire desired cooling levels.

 

[david luchini]

Comes to 48 BTUs per hour. Each room will probably be more or less to factor window losses, fortunately each room is zoned :thumbsup:

Closer to 48,000 btu/h, I would think

 

[kwired]

Closer to 48,000 btu/h, I would think

48 would give him a smaller service/feeder, and likely would cost less to operate, may be a big difference in comfort level on some of the coldest days though.:happyyes:

 

[mbrooke]

Closer to 48,000 btu/h, I would think

:lol: Got me there. meant 48k, 48,000. My bad.

 

[GoldDigger]

:lol: Got me there. meant 48k, 48,000. My bad.

Maybe the influence of both calories and kilocalories being called calories?

 

[texie]

Seems to me that an electrician sizing the heat capacity with no heat load calcs is about the same as the HVAC guy sizing an electric service.:happysad:

 

[mbrooke]

Seems to me that an electrician sizing the heat capacity with no heat load calcs is about the same as the HVAC guy sizing an electric service.:happysad:

:lol: You got that right :happysad:.