EMT Conduit capacity?


Old 03-02-06, 01:38 PM
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Join Date: Mar 2006
Posts: 4
EMT Conduit capacity?

I'm new to this forum and have a do-it-yourselfer question for any electricians out there:

I recently bought a old house, and I'm in the process of installing an electric heating system in the dormer/attic, since channeling-up the furnace ductwork was not a practical option.

Based upon the calculated heating requirements for the area, I have 2 1600W/240volt wall heaters installed, which will run off of a direct-line thermostat that has a 16 Amp capacity. I furthermore, calculated that this heating system can safely run off of a 20Amp/240volt circuit, which I intend to hire an electrician to install in the house's panel (and yes, there is room in the panel to do this).

I would like to do as much of this myself as possible to save money, and consequently I have started to lay the wire/EMT conduit myself. The Manufacterer's directions recommend 10ga copper wire for the heaters/thermostat.

I am accordingly using 10ga solid copper wires, and for areas where I 2 wires running, I fed it through 1/2 inch pipe conduit, and for areas where there are 4 wires running between the heaters/thermostat, I used 3/4 inch conduit. No span of wire is more than 30 feet without a junction box pull-through.

First off, is what I have done so far acceptable/safe?

Secondly, and more importantly is the question I need an answer for. Currently, there is a 1/2 inch conduit pipe running from the panel up to this dormer, containing 2 12gauge solid copper wires, running on a 20 Amp circuit that supply the romm's electrical outlets.

Rather than trying to run a whole new conduit line down to the basement, which would be very difficult and expensive, I'm sure (something I would like to avoid), would it be safe and possible for me to wire-in the conduit I have layed so far into this existing conduit line?

So in other words this 1/2 inch conduit would contain 2 12guage wires for outlets, and then the 2 10 guage/240V wires powering the heating system, which would run about 30-40 feet down to the basement.

Is it possible and safe to run these 4 wires in 1/2 inch conduit, or does it need to be expanded to 3/4 inch?

Many Thanks!
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Old 03-02-06, 03:51 PM
Join Date: Sep 2000
Location: United States
Posts: 18,497
The answer depends on exactly which of the many kind of conduit you are using, and which of the many kind of wire you are using. But most likely the answer to all of your questions is yes (except the last one after the "or").

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