The Age-Old 312.8 Question Revisited

[George Stolz]

I am taking an electrical estimating class, and during discussion the instructor and I were talking about how a couple panels next to the MDP on the prints were going to be fed.

He said, "So the panel immediately beside the MDP will nipple to it, and the panel beside that panel will be fed from the MDP, 90'ing into the bottom of it, right?"

I said, "Well, I'd probably look into the feasibility of nippling all the panels together and passing Panel #2's feeder through Panel #1 for ease of installation and neatness."

"You can't do that."

"Au contraire! 312.8 states explicitly that I can!" I said with satisfaction.

"I've been down this road. It has to do with how the panel is listed. They make a panel that has a gutter built into the bottom of it, and if you were to do what you are thinking, you would have to buy that panel, which is outrageously expensive.."

He relayed a story from his past about a difficult inspector that insisted upon this, and also that he had seen the specs for this "gutter panel".

I promised him I would research this, because I don't believe it, and he would love to have proof otherwise.

I have reviewed the UL White Book, and see nothing in QUEY that would tell me that there is any such limitation in normal panelboards.

I was about to start researching in a couple catalogs and see if I could turn up whichever panel he had seen before, and see if there was some stated purpose in this gutter-in-a-panel that was missed.

Anybody ever heard anything like this before?

 

[jwjrw]

There was a recent thread I think about this and taps in a panel. I think the majority of people agree with you!:grin:

 

[eds]

I have had this discussion before and the last code reference cited was 314.28 (A) (1). In my case I had (2) 200 amp disco set on the right side of the meter (our poco will not allow them to be installed on both sides) 2.5 nipple from meter to first disco and 2'' nipple from disco to disco. I discussed this in great detail, new the appeal process would take a while so I changed it to keep the project moving along. I then received a letter stating that there official position is 314.28(A)(1) that disco would need to be 20'' wide. I still don't agree and will probably discuss this on the next opportunity.

 

[augie47]

In the field I have never given it much thought basically using 312.8 and a "guesstimate", but, as with most situations you bring to light, the more one looks at it the more one wonders. I also reviewed UL QEUY and one sentence does make me ponder: "Enclosed Panelboards have been investigated to determine that wiring space is adequate" gives some credence to the instructors thinking. Be worth a call to a panelboard manufacturer is one has a knowledgeable contact.

 

[jim dungar]

I have seen 'riser' panels that have an extra wide side gutter.

 

[iwire]

Yes you can get larger tubs or as Jim mentioned riser panels with a side space but nothing in 312.8 directly requires that.

 

[George Stolz]

I then received a letter stating that there official position is 314.28(A)(1) that disco would need to be 20'' wide. I still don't agree and will probably discuss this on the next opportunity.

I think that section does not apply - the equivalent section, 312.6 does not seem to the size of enclosures that contain conductors that enter and exit the enclosure without hitting a termination along the way.

 

[George Stolz]

So I had another discussion with the instructor yesterday. We didn't exactly discuss this, but he did bring it up in the middle of a sentence and indicated that he was right and that it's a listing issue. I didn't really get a chance to correct him, but such is life.

It was kind of interesting though - the reason it came up was because the mock prints I was bidding called for a 20A circuit for pole lights supplied with two #8's and a #10 ground. When I took it off, I simply entered three #8's, since 250.122 requires the full sized ground when the ungrounded conductors are upsized.

He marked me off for it, asked, and I said, "Well, I figured I'd just take it off to code." It's probably a 100' run in a job large enough that it wouldn't really make a difference. He proceeded to tell me essentially to leave my code knowledge at the door when bidding a job. (ETA: He also added that it was perfectly legal, he had done it forever, etc... )

I figured as I was doing this (and in bidding in general) that if I install it to the prints and got nailed that I would incur more grief than simply correcting it on my end to begin with, making sure it was in the budget, and moving on.

To each their own...

 

[augie47]

It sounds like he would do better to allow your experience to be a part of the course. Just because he has "done it for ever" does not make it Code and it's especially unfortunate that someone in a teaching position won't allow you to challenge that.
He should realize that "leaving your Code knowledge at the door" doesn't fit well with that stamp seen all too often on prints that puts the responsibility of meeting the Code on the installer.

 

[Rockyd]

George,

How sharp are your inspectors in your work region, and do they have a proper interpretaion of 312.8?

As I read it, about halfway through the verbiage seems pretty straight forward unless adequate space space for this purpose is provided. The conductors shall not fill the wiring space to more than 49 percent of the cross sectional area of the space, and theconductors, plices, and taps shall not fill the space more than75 percent of the cross-sectional area of that space.

75 percent was always described as how much would be ently persuaded to go into the box with the rubber end of the hammer. That may be a bit extreme, but conductors neatly ran across the bottom of a panelboard should easily be well under 40 percent I would think?

 

[jimport]

I have seen discussions in HI forums that unless adequate space space for this purpose is provided. to mean that somehow that space needs to be delineated. Their sticking point seems to be the for this purpose.

 

[Dave58er]

I am taking an electrical estimating class.......

Sounds like maybe you should be teaching, not taking, this class. :roll:

Or maybe you could tutor your instructor on the side. Just show up a little early, go over his lesson plan, and explain to him which parts he has no idea what he's talking about. They really appreciate that kind of input you know.

 

[charlie b]

He proceeded to tell me essentially to leave my code knowledge at the door when bidding a job.

He is right about that, or at least he is right when you are in a classroom/test question environment. If you want to get marked as getting the answer right, which actually helps when it comes to passing the test, then give the answer that the test question's author believes to be the right answer.

Now, in real life, I (as the design engineer) would rather see a prospective bidder ask the question before the bids are submitted. Send in an RFI, stating that you believe the EGC needs to be #8, so that all bidders can get the same answer before any of them submit their bids.

 

[infinity]

I have seen discussions in HI forums that unless adequate space space for this purpose is provided. to mean that somehow that space needs to be delineated. Their sticking point seems to be the for this purpose.

That sounds like a big stretch. It says unless adequate space has been proivded and the next sentence defines what that space actually is. Seems pretty clear to me.

312.8 Enclosures for Switches or Overcurrent Devices.
Enclosures for switches or overcurrent devices shall not be used as junction boxes, auxiliary gutters, or raceways for conductors feeding through or tapping off to other switches or overcurrent devices, unless adequate space for this purpose is provided. The conductors shall not fill the wiring space at any cross section to more than 40 percent of the cross-sectional area of the space, and the conductors, splices, and taps shall not fill the wiring space at any cross section to more than 75 percent of the cross-sectional area of that space.

 

[cadpoint]

Give a a parting gift, a big yellow Mike Holt sticker :grin:

 

[George Stolz]

How sharp are your inspectors in your work region, and do they have a proper interpretaion of 312.8?

Never had the discussion, myself.

I have seen discussions in HI forums that unless adequate space space for this purpose is provided. to mean that somehow that space needs to be delineated. Their sticking point seems to be the for this purpose.

Home Inspectors? That's all you got?

Sounds like maybe you should be teaching, not taking, this class. :roll:

You're too funny. I just lost a bid by bidding $94k to the low bidder's $44k. Since my lights and gear were more than $44k, I feel a little better, but I'd still like to be comfortable when I submit a commercial bid. I am currently 0 for 10, I think.

Or maybe you could tutor your instructor on the side. Just show up a little early, go over his lesson plan, and explain to him which parts he has no idea what he's talking about. They really appreciate that kind of input you know.

Especially this fellow.

He is right about that, or at least he is right when you are in a classroom/test question environment. If you want to get marked as getting the answer right, which actually helps when it comes to passing the test, then give the answer that the test question's author believes to be the right answer.

Well, I'm not sure what happens if I fail - maybe I get a refund?

Now, in real life, I (as the design engineer) would rather see a prospective bidder ask the question before the bids are submitted. Send in an RFI, stating that you believe the EGC needs to be #8, so that all bidders can get the same answer before any of them submit their bids.

If the answer is small, I'd just as soon skip it. I can't get in trouble for doing it right, hopefully.

That sounds like a big stretch. It says unless adequate space has been provided and the next sentence defines what that space actually is. Seems pretty clear to me.

I agree.

 

[mivey]

If you want to get marked as getting the answer right, which actually helps when it comes to passing the test, then give the answer that the test question's author believes to be the right answer.

Hear! Hear! You tried.

"But if any man be ignorant, let him be ignorant"

 

[benaround]

George,

The 'leave your code knowledge at the door', might be sound advice for an estimating

course Instructor to give. IMO, some of the best Estimators are the ones' that have no

field experince, little code knowledge, and have a tuff time with tools. They bid it right off

the plans, they don't miss any needed parts and they use 'shop' man hour units.

I know you only 'fixed' that one item, but-- you know where I'm going from here. What's

even worst is that they feel real comfortable with their bid because they don't fret over

all the things that 'We' know can go wrong. Last thing, the way the EI's inspect to the

plans, in this area anyway, I've seen the code get left at the door, its madning (sp).