Need help with wiring questions

Posted by gwandsh on October 25, 2009, 1:37 am

This weekend I had planned to add a 1000 watt electric heater to an
existing circuit with three similar heaters on it. The other heaters
are 750 watt, wired 240, and draw 2.7 amps each. The circuit is 30
amps, so I expected to pony the new heater (4.5 amps @ 240V) off the
wire to one of the existing heaters, and still not challenge the
breaker.

I was surprised to find the wire to the circuit I planned to pony from
was a 14/2. I traced it back to the junction box, and found each of
the heaters was serviced by a 14 gauge wire. Then I was horrified to
find that the wire from the panel to the main junction box for all
circuits was also a 14 gauge. Even at low amperage, I would expect at
least a 12 gauge, maybe 10?

So, I have shut off the circuit pending some advice on how to wire it
safely. I expect my options are :

1 - Panel->Junction box 10 gauge. Junction box to each heater 12

gauge.

2 - Panel->junction box 12 gauge. Junction box to each heater 12

gauge.

3 - Panel-> junction box 12 gauge. Junction box to each heater 14

gauge.

The final load on the circuit at 240V will be about (if all was on at
full blast) 13.5 amps. We have never turned on any more than two of
the heaters, but I am pretty sure the proper calculation would require
the worst case scenario.

Can anybody tell me what the best wiring combination is? I will ask
my electrician to do the final connection of the panel to the junction
box, but I would like to have the wiring from the junction box to the
heaters in place to save some bucks.

tnx in advance

Posted by on October 25, 2009, 1:47 am

wrote:

>This weekend I had planned to add a 1000 watt electric heater to an
>existing circuit with three similar heaters on it. The other heaters
>are 750 watt, wired 240, and draw 2.7 amps each. The circuit is 30
>amps, so I expected to pony the new heater (4.5 amps @ 240V) off the
>wire to one of the existing heaters, and still not challenge the
>breaker.
>I was surprised to find the wire to the circuit I planned to pony from
>was a 14/2. I traced it back to the junction box, and found each of
>the heaters was serviced by a 14 gauge wire. Then I was horrified to
>find that the wire from the panel to the main junction box for all
>circuits was also a 14 gauge. Even at low amperage, I would expect at
>least a 12 gauge, maybe 10?
>So, I have shut off the circuit pending some advice on how to wire it
>safely. I expect my options are :
>1 - Panel->Junction box 10 gauge. Junction box to each heater 12
>gauge.
>2 - Panel->junction box 12 gauge. Junction box to each heater 12
>gauge.
>3 - Panel-> junction box 12 gauge. Junction box to each heater 14
>gauge.
>The final load on the circuit at 240V will be about (if all was on at
>full blast) 13.5 amps. We have never turned on any more than two of
>the heaters, but I am pretty sure the proper calculation would require
>the worst case scenario.
>Can anybody tell me what the best wiring combination is? I will ask
>my electrician to do the final connection of the panel to the junction
>box, but I would like to have the wiring from the junction box to the
>heaters in place to save some bucks.
>tnx in advance

You are talking about 10.4a or so. (2500w @ 240v = 10.42a)
You do need to size at the smallest conductor on the circuit.
I would just put a 2 pole 15a breaker on that circuit and get on with
your life being perfectly legal.

Posted by aemeijers on October 25, 2009, 6:47 am

gfretwell@aol.com wrote:

> wrote:
>

>> This weekend I had planned to add a 1000 watt electric heater to an
>> existing circuit with three similar heaters on it. The other heaters
>> are 750 watt, wired 240, and draw 2.7 amps each. The circuit is 30
>> amps, so I expected to pony the new heater (4.5 amps @ 240V) off the
>> wire to one of the existing heaters, and still not challenge the
>> breaker.
>> I was surprised to find the wire to the circuit I planned to pony from
>> was a 14/2. I traced it back to the junction box, and found each of
>> the heaters was serviced by a 14 gauge wire. Then I was horrified to
>> find that the wire from the panel to the main junction box for all
>> circuits was also a 14 gauge. Even at low amperage, I would expect at
>> least a 12 gauge, maybe 10?
>> So, I have shut off the circuit pending some advice on how to wire it
>> safely. I expect my options are :
>> 1 - Panel->Junction box 10 gauge. Junction box to each heater 12
>> gauge.
>> 2 - Panel->junction box 12 gauge. Junction box to each heater 12
>> gauge.
>> 3 - Panel-> junction box 12 gauge. Junction box to each heater 14
>> gauge.
>> The final load on the circuit at 240V will be about (if all was on at
>> full blast) 13.5 amps. We have never turned on any more than two of
>> the heaters, but I am pretty sure the proper calculation would require
>> the worst case scenario.
>> Can anybody tell me what the best wiring combination is? I will ask
>> my electrician to do the final connection of the panel to the junction
>> box, but I would like to have the wiring from the junction box to the
>> heaters in place to save some bucks.
>> tnx in advance

>
>
> You are talking about 10.4a or so. (2500w @ 240v = 10.42a)
> You do need to size at the smallest conductor on the circuit.
> I would just put a 2 pole 15a breaker on that circuit and get on with
> your life being perfectly legal.
>

Methinks OP is over in the UK, perhaps? Seeing as how he is running 240
on 14-2? They do some strange (by our standards) things with wiring over
there.

If OP is in UK, he may want to seek out that UK-centric DIY group to ask
in. I can't remember the name, but it has been mentioned on here before.

--
aem sends...

Posted by HeyBub on October 25, 2009, 7:40 am

aemeijers wrote:

> Methinks OP is over in the UK, perhaps? Seeing as how he is running
> 240 on 14-2? They do some strange (by our standards) things with
> wiring over there.
> If OP is in UK, he may want to seek out that UK-centric DIY group to
> ask in. I can't remember the name, but it has been mentioned on here
> before.

The OP is in Portland, Oregon (or environs).

He should have told us to avoid the confusion, but, in case of doubt, one
can look up his IP (76.115.41.158).

Posted by aemeijers on October 25, 2009, 8:03 am

HeyBub wrote:

> aemeijers wrote:

>> Methinks OP is over in the UK, perhaps? Seeing as how he is running
>> 240 on 14-2? They do some strange (by our standards) things with
>> wiring over there.
>> If OP is in UK, he may want to seek out that UK-centric DIY group to
>> ask in. I can't remember the name, but it has been mentioned on here
>> before.

>
> The OP is in Portland, Oregon (or environs).
>
> He should have told us to avoid the confusion, but, in case of doubt, one
> can look up his IP (76.115.41.158).
>
>

What can I say? Way too early in the AM to have thought of looking him
up. And as I often state, I'm no electrician, though I play one at
times. Haven't run across a lot of 2-wire 240 on small-gauge wire in
this part of the country. especially for heaters. (gas is usually a lot
cheaper around here.)
--
aem sends, going back to lurk mode on this thread....

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