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#130805 - 02/14/07 08:51 PM Radiant heat vs BTU's?  
WFO  Offline
Member
Joined: Sep 2005
Posts: 202
Cat Spring, TX
OK, everybody has seen the new energy saver fluorescent bulbs that try to compare their light output to the old traditional incandescent bulb by stating its wattage. So the package says it's a 60 watt bulb, even though it's only consuming a fraction of that in actual wattage.

So how do you compare the radiant heaters? I see one rated at 1200 watts of heat, but on the back it says 120 volt, 10 amp.
How is this any more efficient than old fashioned strip heat?

More to the point, is there a way to compare the efficiency of a radiant heater to its actual watt use? I've never seen a BTU rating on one.


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#130806 - 02/15/07 06:56 AM Re: Radiant heat vs BTU's?  
SteveFehr  Offline
Member
Joined: Mar 2005
Posts: 1,213
Chesapeake, VA
If you put 1200 Watts into a cheap electric heater of any type, you're going to get 1200 Watts out. A radiant heater may produce more radiant heat than convective/conductive heat, but it's still just as energy (in)efficient as any other electric resistance heater.

If that radiative heat is focused on a person, I they would feel warmer despite the room being colder, so you might see some energy savings there. But it won't heat up the room any faster or slower than a ceramic heater or any other resistance element heater.

1200 Watts is 4100 BTU/hr
1500 Watts is 5120 BTU/hr

So, you're looking at about 1/3 ton of heating.

[This message has been edited by SteveFehr (edited 02-15-2007).]


#130807 - 02/15/07 10:18 AM Re: Radiant heat vs BTU's?  
winnie  Offline
Member
Joined: Sep 2003
Posts: 649
boston, ma
1 watt hour = 3.41214163 BTU
or equivalently
1 watt = 3.41214163 BTU per hour

This is true for all electric resistance heating.

-Jon


#130808 - 02/15/07 07:03 PM Re: Radiant heat vs BTU's?  
WFO  Offline
Member
Joined: Sep 2005
Posts: 202
Cat Spring, TX
So, is the only efficiency here in that the radiant (i.e., infrared) heat can be absorbed directly by an object (including yourself) rather than disbursed with a fan and rising by convection to the ceiling?


#130809 - 02/15/07 10:23 PM Re: Radiant heat vs BTU's?  
winnie  Offline
Member
Joined: Sep 2003
Posts: 649
boston, ma
Exactly, the improvement in performance, if any, is not from an improvement in efficiency, but from an improvement in usage.

I don't know from experience if radiant heating actually makes a difference. Do people tend to keep thermostats set lower, for example?

-Jon



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