Shared Neutral

BobSmitt · 09-20-2011, 07:07 PM

Quote:

Originally Posted by Sunny B.

If you were to use 30 amp breakers, the breakers isn't gonna trip if something is pulling 25 amps. Which is dangerous when your wire, and recepticals are only rated for 20 amps. This will cause a fire so don't attempt it

The wiring is already handling 30A, or at least that's how it's been set up since the 1960's without any apparent incident. I was just making sure that there wasn't some special property of switching from a single 220V circuit to two 110V circuits with a shared neutral that all of the sudden decreased the amperage carrying capacity of the wire. It seems like as far as the wire is concerned nothing's changed, each leg still carries 110V and taps the same neutral.

Sunny B. · 09-20-2011, 08:40 PM

Quote:

Originally Posted by Code05

That only became code in the 2008.

Ok well I didn't even know that it was code to do so. I just thought we did it because it was idiot proof "laughing"

Code05 · 09-20-2011, 09:56 PM

Quote:

Originally Posted by Sunny B.

Ok well I didn't even know that it was code to do so. I just thought we did it because it was idiot proof "laughing"

Class time, you got a code book handy? 2008.

Gigs · 09-21-2011, 11:39 AM

Quote:

Originally Posted by BobSmitt

The wiring is already handling 30A, or at least that's how it's been set up since the 1960's without any apparent incident.

Being running that way for years without incident doesn't mean it was ever right.

If it was 12 AWG wires on a 30 amp breaker, it might run 100 years that way without apparent incident. It also might eventually (after many years) cook the insulation and make it more brittle than it would be otherwise.

It's about having a safety margin built in.

BobSmitt · 09-21-2011, 12:09 PM

Quote:

Originally Posted by Gigs

It's about having a safety margin built in.

Absolutely. How much extra does it cost to run 10AWG instead of 12AWG? 50% more? The way I approach the analysis is to ask myself if I'd spend an extra $50 or $100 for that increased safety margin over the next 20+ years. YES!

I'm so conservative that I'm saving up to have my wiring updated to current code.

Sunny B. · 09-21-2011, 03:20 PM

Quote:

Originally Posted by Code05

Class time, you got a code book handy? 2008.

Not at the moment. But I have the "NEC CHANGES" app on my phone. But it's for 2011

Sunny B. · 09-21-2011, 03:26 PM

Quote:

Originally Posted by BobSmitt

The wiring is already handling 30A, or at least that's how it's been set up since the 1960's without any apparent incident. I was just making sure that there wasn't some special property of switching from a single 220V circuit to two 110V circuits with a shared neutral that all of the sudden decreased the amperage carrying capacity of the wire. It seems like as far as the wire is concerned nothing's changed, each leg still carries 110V and taps the same neutral.

How do you know what the wire is carrying?

Sunny B. · 09-21-2011, 03:26 PM

Quote:

Originally Posted by BobSmitt

The wiring is already handling 30A, or at least that's how it's been set up since the 1960's without any apparent incident. I was just making sure that there wasn't some special property of switching from a single 220V circuit to two 110V circuits with a shared neutral that all of the sudden decreased the amperage carrying capacity of the wire. It seems like as far as the wire is concerned nothing's changed, each leg still carries 110V and taps the same neutral.

Did you put a tester on it?