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Old 05-10-2009, 02:44 PM   #1
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Distance of Conduit from Radiator / Heat Source


Question:
Is there a distance you should keep away from a radiator or heat source when running conduit?

Background:
The work is residential. I am wiring a room with EMT conduit which will be exposed (because it is a masonary wall with plaster over it). The circuit in question powers the wall outlets for the space. The walls of the large room have steam heat radiators along the wall. I would like to run conduit along this wall, but it would have to run in the small space between the wall and the radiators; it would be basically touching the radiators (they are 2' long and spaced about every 12'). The conduit is 1/2" EMT and there are only 3 12-gauge wires running through it (black,white,ground). I have other options, such as dropping down into the basement for each outlet, but it would be most cost/time effective to just go along the wall.

Any input?? Thank you ahead of time

John

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Old 05-10-2009, 04:52 PM   #2
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Distance of Conduit from Radiator / Heat Source


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Originally Posted by jjohanson View Post
Question:
Is there a distance you should keep away from a radiator or heat source when running conduit?

Background:
The work is residential. I am wiring a room with EMT conduit which will be exposed (because it is a masonary wall with plaster over it). The circuit in question powers the wall outlets for the space. The walls of the large room have steam heat radiators along the wall. I would like to run conduit along this wall, but it would have to run in the small space between the wall and the radiators; it would be basically touching the radiators (they are 2' long and spaced about every 12'). The conduit is 1/2" EMT and there are only 3 12-gauge wires running through it (black,white,ground). I have other options, such as dropping down into the basement for each outlet, but it would be most cost/time effective to just go along the wall.

Any input?? Thank you ahead of time

John
Hmmm... I'd try my best to avoid doing that. However, if you do it, you will have to derate the wires according to the ambient temperature. At the radiator, the temp will most surely be above 30C. The ampacity of #12 is based on that temperature. You either need to avoid the radiator or install larger wires if you do the necessary temperature calculations.

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Old 05-10-2009, 05:29 PM   #3
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Distance of Conduit from Radiator / Heat Source


Thanks for the response.
Do you know where to find instruction, information, or tables on those calculations?
I did a search through the NEC handbook and didn't find anything.
John
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Old 05-10-2009, 05:40 PM   #4
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Distance of Conduit from Radiator / Heat Source


Quote:
Originally Posted by jjohanson View Post
Thanks for the response.
Do you know where to find instruction, information, or tables on those calculations?
I did a search through the NEC handbook and didn't find anything.
John
Look at the ampacity table 310.16. At the bottom is a chart showing a multiplier based on ambient temperature. Whatever it is, you multiply the conductor ampacity by that to get the new ampacity at the adjusted temperature. And you derate from the 90 column, even though you use the 75 column for selecting breakers.

For example, let's say you have #12 THHN. It is rated for 30 A in the 90 column. If the radiator gets to a temp of let's say 70C, the table at the bottom gives a multiplier of 0.58. This makes the ampacity of #12 at that temp 30 x 0.58 = 17.4 A. You would either need to use #10, or put the circuit on a 15 A breaker.
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Old 05-12-2009, 11:39 AM   #5
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Distance of Conduit from Radiator / Heat Source


OR....run the conduit at baseboard level where it's cooler
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