Electric Radiant Heating System Feasibility (Load calculation/prediction)

[Pengy]

Homeowners of a remodeling project that I have taken on had contacted me about installing some carbon film radiant heating in their house with a floating engineered hardwood floor to provide warmth to their feet around the house. The total square footage of the heated areas would be about 1500 sq.ft and a quote from an installer said that the heating elements use 20w/sq.ft @ 240V which puts me at about 125A of max usage. I know the NEC considers this as constant usage as they are hard-wired and not plugged in, and in order to provide zoning to the different rooms/floors, 10 2-Pole 20A breakers would be preferred with a single 12/2 romex running to each thermostat (10 zones/thermostats). Doing this would require a new subpanel as the main panel has only 4 slots available (GE 200A main panel ~20 slots w/ 4-pole main breaker).

Would a load like this be feasible in this house without requesting another 200A service feed? The heaters would never be used at the same time, however the house does currently have a 50A pool circuit, 40A for AC #1, 30A for the dryer, and a 100A subpanel with 50A for an oven, and 40A for AC #2 and then lighting/plugs for a 3400 sq.ft home.

The installer is also able to wire the heating film in series to halve the amperage, but would take longer to heat up.

 

[Ragin Cajun]

30 KW for 1500 sq ft?!!!!!! NO WAY!

The typical duct heat for a house if 5 KW.

Tell this guy to go back to the drawing board. :thumbsdown:

RC

 

[petersonra]

30 KW for 1500 sq ft?!!!!!! NO WAY!

The typical duct heat for a house if 5 KW.

Tell this guy to go back to the drawing board. :thumbsdown:

RC

5 kw is only 17,000 btu/hr

most homes are closer to 100,000 btu/hr around here.

maybe in warmer parts of CA they don't need as much heat.

125*240 is 30 kw which is about 100,000 btu/hr

if this is the sole heat for the house it does not seem that far off to me.

 

[Pengy]

30 KW for 1500 sq ft?!!!!!! NO WAY!

The typical duct heat for a house if 5 KW.

Tell this guy to go back to the drawing board. :thumbsdown:

RC

I suppose its like comparing an on-demand water heater vs a typical tanked water heater where the output of the on-demand is much much higher than the tanked, but can heat up water instantly where the tank requires time. These pads heat up almost instantly, and when pulsed can provide heat for a whole house.

5 kw is only 17,000 btu/hr

most homes are closer to 100,000 btu/hr around here.

maybe in warmer parts of CA they don't need as much heat.

125*240 is 30 kw which is about 100,000 btu/hr

if this is the sole heat for the house it does not seem that far off to me.

The house does have central heat, but the heating pads allow each room/area to be heated separately.

So any thoughts in whether this is okay? The electrician I talked to said a 200A service is plenty for the whole house and heater.

 

[Sierrasparky]

Electric heat is forbidden in CA except for local supplementary heat.

Electric heat under a wood floor is the worst as far as energy efficiancy. Great for Tile and marble.
I doub't that 1500 sq ft will pass a competent permit tech.

 

[Pengy]

Ok, thanks for the information. I will let the homeowners know.

 

[Sierrasparky]

Oh I forgot.
Welcome to the forum!:thumbsup:

 

[Pengy]

Thanks! I hope to lurk here more often and read up on NEC changes and violations (those are the best part)

 

[Sierrasparky]

Thanks! I hope to lurk here more often and read up on NEC changes and violations (those are the best part)

No problem.
Noticed on your profile that you state you are on the 2008 nec.
If working in CA, we are now on the 2013 CA building codes. The CA electric code is based on the 2011 NEC with some unique changes and rules.

 

[Pengy]

Electrical really isn't my thing, so I just hire electricians to do all of the work, but I will update my profile to 2011 as I wasn't sure which year CA was going off of.

 

[kwired]

5 kw is only 17,000 btu/hr

most homes are closer to 100,000 btu/hr around here.

maybe in warmer parts of CA they don't need as much heat.

125*240 is 30 kw which is about 100,000 btu/hr

if this is the sole heat for the house it does not seem that far off to me.

If it is the sole heat for the house it may not be that far off. According to the op this is "comfort" heat in a new floor that is only 1500 SF of a 3400 SF home.

Seems to me it may likely take over as the primary heat if this high of watt density is used, whether that is intended or not. It may then actually become cold in rooms without this new floor because the rooms with new floor are warm enough the main heating system never cycles.

I think the wattage per square foot is too high for this system and should be re-evaluated, unless it was intended to become primary heat, but then you maybe need to address heating needs in places where no new floor is being installed.

 

[Sierrasparky]

If it is the sole heat for the house it may not be that far off. According to the op this is "comfort" heat in a new floor that is only 1500 SF of a 3400 SF home.

Seems to me it may likely take over as the primary heat if this high of watt density is used, whether that is intended or not. It may then actually become cold in rooms without this new floor because the rooms with new floor are warm enough the main heating system never cycles.

I think the wattage per square foot is too high for this system and should be re-evaluated, unless it was intended to become primary heat, but then you maybe need to address heating needs in places where no new floor is being installed.

Infortunately a Electric resistance heat system is not permitted in California any longer due to Energy codes unless the home was originally all electric and there is no natural gas available. However if there is already propane or natural gas you may not change fuels.

These new energy codes are comming to a city near you. Just as the 100 watt incandescent went away

 

[kwired]

Infortunately a Electric resistance heat system is not permitted in California any longer due to Energy codes unless the home was originally all electric and there is no natural gas available. However if there is already propane or natural gas you may not change fuels.

These new energy codes are comming to a city near you. Just as the 100 watt incandescent went away

Just another thing I do not understand about CA and the reasoning behind some laws they have. Electricity is environmentally clean, Californian's you would think would be on board with that, how it is generated may be another story, but how is that a consumer problem? The powerhouse emissions can be regulated, probably at a cost that will be passed on, yet it is ok to put in millions of smaller gas furnaces that are not as closely regulated:huh:

When it comes to space heating a BTU is a BTU, electric resistance heat is 100% efficient. Any problems they have with using electricity as a heat source has more to do with generation issues then the real efficiency of the heating unit. Building insulation issues apply no matter what the heat source is. The cost of energy alone could be something to deter one from wanting to use resistance heat though, just so happens that electric energy is pretty cheap in these parts - especially in the winter months and that is part of the reason we see as much resistance heating as we do around here. Right now it may cost less to heat with natural gas, but a few years back when gas was higher it may have cost less to heat with resistance heat.

 

[Sierrasparky]

Just another thing I do not understand about CA and the reasoning behind some laws they have. Electricity is environmentally clean, Californian's you would think would be on board with that, how it is generated may be another story, but how is that a consumer problem? The powerhouse emissions can be regulated, probably at a cost that will be passed on, yet it is ok to put in millions of smaller gas furnaces that are not as closely regulated:huh:

When it comes to space heating a BTU is a BTU, electric resistance heat is 100% efficient. Any problems they have with using electricity as a heat source has more to do with generation issues then the real efficiency of the heating unit. Building insulation issues apply no matter what the heat source is. The cost of energy alone could be something to deter one from wanting to use resistance heat though, just so happens that electric energy is pretty cheap in these parts - especially in the winter months and that is part of the reason we see as much resistance heating as we do around here. Right now it may cost less to heat with natural gas, but a few years back when gas was higher it may have cost less to heat with resistance heat.

Gotta love it in CA. :lol:

Yea it's a bit crazy here. too much sometimes.
Electric resistance heat may be 100% but that is at it's usage point. When you count in the production and the fact we have shortages in this state I think that is what it is all about. When I say shortages we buy a lot from outside the area. If CA had to rely on our own electricity there could be issues. I think we have much of our own Natural gas within the State.

 

[kwired]

Gotta love it in CA. :lol:

Yea it's a bit crazy here. too much sometimes.
Electric resistance heat may be 100% but that is at it's usage point. When you count in the production and the fact we have shortages in this state I think that is what it is all about. When I say shortages we buy a lot from outside the area. If CA had to rely on our own electricity there could be issues. I think we have much of our own Natural gas within the State.

CA probably can't build any power plants because nobody wants the environmental impact they may provide, but they still want the energy.:roll: But it is that way in more then just CA, if they were to propose a new power plant around these parts it would get a lot of public resistance no matter if it were coal, NG, nuclear, etc., people just don't want to deal with the potential environmental impact, but they do complain when energy rates go up.

 

[Sierrasparky]

CA probably can't build any power plants because nobody wants the environmental impact they may provide, but they still want the energy.:roll: But it is that way in more then just CA, if they were to propose a new power plant around these parts it would get a lot of public resistance no matter if it were coal, NG, nuclear, etc., people just don't want to deal with the potential environmental impact, but they do complain when energy rates go up.

Actually CA can build new power plants. Permitting can be long time to get. I bet the biggest problem is NIMBY.

CA would really like to see more Geothermal Heating and cooling systems. The energy input is far less than the net heating or cooling than you get out. See GEO does not make energy it moves it from one source to the other.

 

[kwired]

Actually CA can build new power plants. Permitting can be long time to get. I bet the biggest problem is NIMBY.

CA would really like to see more Geothermal Heating and cooling systems. The energy input is far less than the net heating or cooling than you get out. See GEO does not make energy it moves it from one source to the other.

Well aware of what GEO is - have one on my own home.

 

[curt swartz]

CA doesn't want electricity used for lighting or HVAC but they are pushing everyone to get electric cars.

 

[kwired]

CA doesn't want electricity used for lighting or HVAC but they are pushing everyone to get electric cars.

With lighting and air conditioning in them as well