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Posted by 46erjoe on December 8, 2006, 11:39 am
I need to install baseboard electric heating units in two rooms I'm
refurbishing. One will need a 48" 2000 watt unit; the other a 36" 1500
watt unit.
The instructions in each box say that I will need to use a 220v
circuit with "amperage according to local code".
Both rooms are next to each other and I'm wondering if instead of
fishing two wires, I can go with one 10/2 30amp circuit and have both
units branching off the main line. What might be the minimum wiring
and amp circuit? What would be safest? What's the most amperage I can
get out of a 10/2 line?
Related question: I've got tons of 12/3 wiring with ground laying
around unused. Can I turn this into, say, 10/2 by simply clamping
the black and red wires together at the panel and at the end point and
then painting the red wire with black marker pen to indicate power? I
hate to waste wire with the cost of copper these days.
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Posted by avid_hiker on December 8, 2006, 11:58 am
46erjoe wrote:
> Related question: I've got tons of 12/3 wiring with ground laying
> around unused. Can I turn this into, say, 10/2 by simply clamping
> the black and red wires together at the panel and at the end point and
> then painting the red wire with black marker pen to indicate power? I
> hate to waste wire with the cost of copper these days.
Nope
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Posted by Smarty on December 8, 2006, 4:29 pm
Basic Electricity 101: current flows in a circuit, and needs to return back
to the source (in this case let's call it a breaker box) along a 10 gauge
wire as well. Thus, by "clamping" red and black together you get a heavier
conductor only in one direction (from the breaker box to the load) but still
have a light conductor in the return path. You would need to start with 12/4
and "clamp" 2 pairs together to do what you want.
Smarty
>
> 46erjoe wrote:
>> Related question: I've got tons of 12/3 wiring with ground laying
>> around unused. Can I turn this into, say, 10/2 by simply clamping
>> the black and red wires together at the panel and at the end point and
>> then painting the red wire with black marker pen to indicate power? I
>> hate to waste wire with the cost of copper these days.
>
>
> Nope
>
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Posted by Doug Miller on December 8, 2006, 5:50 pm
>Basic Electricity 101: current flows in a circuit, and needs to return back
>to the source (in this case let's call it a breaker box) along a 10 gauge
>wire as well. Thus, by "clamping" red and black together you get a heavier
>conductor only in one direction (from the breaker box to the load) but still
>have a light conductor in the return path.
Right so far...
>You would need to start with 12/4
>and "clamp" 2 pairs together to do what you want.
But that's a violation of the National Electrical Code.
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
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Posted by Doug Miller on December 8, 2006, 12:24 pm
>I need to install baseboard electric heating units in two rooms I'm
>refurbishing. One will need a 48" 2000 watt unit; the other a 36" 1500
>watt unit.
>
>The instructions in each box say that I will need to use a 220v
220, or 240? It makes a difference. If the heater is rated 2000 watts at 220V,
it will produce almost 2400W at 240V -- which is almost certainly the
voltage that you actually have in your house. And never mind the installation
instructions. Look at the rating plate on the heater.
>circuit with "amperage according to local code".
You'd have to talk to a local electrical inspector to find out what your local
code is.
>
>Both rooms are next to each other and I'm wondering if instead of
>fishing two wires, I can go with one 10/2 30amp circuit and have both
>units branching off the main line. What might be the minimum wiring
>and amp circuit? What would be safest? What's the most amperage I can
>get out of a 10/2 line?
Under the National Electrical Code, 10/2 is limited to 30A overcurrent
protection (breaker or fuse), and continuous loads (such as electric
resistance heating) are limited to 80% of the overcurrent rating -- which
would be 24A for a 30A breaker. 24A at 240V is 5760 watts; your heaters total
3500, so one 10/2 30A circuit will be just fine.
>
>Related question: I've got tons of 12/3 wiring with ground laying
>around unused. Can I turn this into, say, 10/2 by simply clamping
>the black and red wires together at the panel and at the end point
NO. First off, that's a Code violation: connecting conductors in parallel is
not permitted. Second, even if that was allowed, that would take care of only
*one* of the two conductors in the circuit anyway. What about the other one?
It would still be 12ga. And don't even think about doubling up the white and
bare wires -- you could wind up making the case of the heater live.
However, if the heaters are rated 2000 and 1500 W at 240V, you don't need a
30A circuit anyway, and you can use 12ga wire: 20A * 240V * 80% = 3840 W,
which is adequate for the heaters you have.
OTOH, if they're rated 2000 and 1500 W at 220V, and you run them on 240V, then
you will need a 30A circuit, because the heaters will produce almost 20% more
power: 2380 and 1785 watts respectively, for a total of 4165 watts -- too much
for a continuous load on a 20A circuit.
This is why I asked above if they're rated at 220V or 240V. It does matter.
>and then painting the red wire with black marker pen to indicate power?
That would be unnecessary -- red is assumed to be power anyway -- but as noted
above, it's a Code violation, and it's not safe.
>I hate to waste wire with the cost of copper these days.
It's come down quite a bit since June. It's still more than double what it was
two years ago, but I saw 250' of 12/2 NM at Home Depot last week for $67...
and just a few months ago, it was over $100.
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
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