common neutral on 20/30A ckts

[rob1955]

I had one of my electricians ask me this question today, and I couldn't answer him. Is it a code violation for a 20 amp and a 30 amp branch circuit to share a common neutral? I guess the kicker is the common "tied" breaker, which I've always seen the poles being the same amperage. In this case the two tied breakers would need to be different amperages.

[480sparky]

What kind of load would need 20amps on one side and 30amps on the other?

[iwire]

Is it a code violation for a 20 amp and a 30 amp branch circuit to share a common neutral?

No.

I guess the kicker is the common "tied" breaker,

The breakers may not have to be tied or even beside each other depending on what is being supplied. (This will change in 2008)

What kind of load would need 20amps on one side and 30amps on the other?

In my case a small appliance branch circuit and a 120 volt 30 amp point of use hot water heater.

It was an office remodel and I ended up re-using a 6/3 MC cable that had fed a range.

[480sparky]

Brain fart on my part. I was trying to envision a 120/240v load, not a MWBC.

In that case, yes, you can share the neutie.

[infinity]

It's somewhat common for MWBC's to have different sized CB's.

[LarryFine]

Let's just add that the shared conductor must be sized for the largest breaker.

In my case a small appliance branch circuit and a 120 volt 30 amp point of use hot water heater.

It was an office remodel and I ended up re-using a 6/3 MC cable that had fed a range.Bob certainly complied on that one! :)

[iwire]

Bob certainly complied on that one! :)

LOL....:grin:

The existing 6/3 was about a 125' run from panel to load.

I doubt they will have much VD on the 20 amp SABC. 8-)

[rob1955]

I appreciate the input. And yes, this is two different circuits sharing the same neutral, and the neutral is sized for #10. I looked and looked through the code book, and couldn't find anywhere that said this couldn't be done. Again, thanks!