Jump to content
Sign in to follow this  
Brandon Whitmore

Sub Panel Q's

Recommended Posts

I ran into something that I'm not sure I've seen before, so I figure I'll ask in the hopes for a quick answer prior to looking it up.

Today's house had a main panel with a sub panel directly below (inches below). The sub panel had a combination of 240 and 120 v. circuits installed. There was only a 3 wire feed to the sub panel (wrong I know), but here's the odd thing. There was only 1 grounding conductor and 2 neutrals attached to the terminal bar. All of the rest of the neutrals and grounds were secured under the main panels terminal bar, while the hots were extended down into the sub panel. I'm positive this is wrong (ok, not 100%). Can someone explain to me why this is wrong, and give any code cite for why it is wrong?

Thanks.

Share this post


Link to post
Share on other sites

What about this cite from the 2006 IRC?

E3703.8 Single conductors. All conductors of the same circuit

and, where present, the grounded conductor and all equipment

grounding conductors shall be installed in the same raceway or

shall be installed in close proximity in the same trench.

Marc

Share this post


Link to post
Share on other sites

I ran into something that I'm not sure I've seen before, so I figure I'll ask in the hopes for a quick answer prior to looking it up.

Today's house had a main panel with a sub panel directly below (inches below). The sub panel had a combination of 240 and 120 v. circuits installed. There was only a 3 wire feed to the sub panel (wrong I know), but here's the odd thing. There was only 1 grounding conductor and 2 neutrals attached to the terminal bar. All of the rest of the neutrals and grounds were secured under the main panels terminal bar, while the hots were extended down into the sub panel. I'm positive this is wrong (ok, not 100%). Can someone explain to me why this is wrong, and give any code cite for why it is wrong?

Thanks.

Perhaps you're thinking of 300.3(B):

Conductors of the Same Circuit. All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1) through (B)(4).

When you run the hots without the neutrals near them, you have electromagnetic fields that can cause cause inductive heating of the enclosure.

- Jim Katen, Oregon

Share this post


Link to post
Share on other sites

What about this cite from the 2006 IRC?

E3703.8 Single conductors. All conductors of the same circuit

and, where present, the grounded conductor and all equipment

grounding conductors shall be installed in the same raceway or

shall be installed in close proximity in the same trench.

Marc

That particular reference only applies to underground installations. In the IRC, I'd use 3701.3

In Oregon, though, we don't use the electrical section of the IRC, just the NEC.

- Jim Katen, Oregon

Share this post


Link to post
Share on other sites

Correct me if I'm wrong, but sub/distribution panels don't HAVE to have four wire feeds. Can't the metal conduit also act as the EGC?

Yes, you're correct.

- Jim Katen, Oregon

Share this post


Link to post
Share on other sites

Speaking of subpanels, I recently (Wednesday)inspected a home with a 15kw standby generator- enough to run the whole house so the transfer switch was a big solenoid that switched the distribution panel from line to generator automatically.

Line came into the distribution panel, passed through the panel and went to one side of the generator transfer switch. Then, line came back into the distribution panel from the transfer switch and fed the main breaker.

That made the transfer switch the service equipment, and the 200 amp distribution panel, a sub panel.

I failed to report it that way- it took me until this morning to figure it out- I've known something was wrong since I did the inspection and I've been ruminating on it ever since. Luckily, I called my client in time for him to address the issue with the seller. The distribution panel will need to be reconfigured as a sub.

Share this post


Link to post
Share on other sites

Doesn't sound quite right. The transfer switch is not the main disconnecting means since it doesn't necessarily de-energize the panel. It just moves it from one power source to another.

Marc

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...