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-   -   Load center vs. bottom fed Panel Board. Ugh. (http://www.diychatroom.com/f18/load-center-vs-bottom-fed-panel-board-ugh-43081/)

wmldwilly 04-23-2009 06:25 AM

Load center vs. bottom fed Panel Board. Ugh.
 
I've read a few other posters running into similar problems as this but not quite this annoying. :furious: or take this long to explain.

Here's my project: I'm changing over to a new 200a service from a 100a service thanks to a large multiple story add on. I won't go a mile deep into the details but I need to find the following:

Nema 3r ("Outdoor", or "Rain Tight") load center, 200a main breaker.
No meter - the meter is on a rear building
*BOTTOM FED* - the feeds will come underground from the aforementioned meter on a rear building and up into the box.

Possible Square D model just for example:
QO140M200RB (or QO130..., or QO120...)

Conduit from all over the house will converge and enter the load center from both under the house/into the bottom of the box and out a soffit space/down the sidewall/into the *top* of the box. I showed my inspector a bucket full of Red Dot brand rain tight field add hubs and he said they're fine (i.e. rain tight enough) for top exit on an outdoor box as long as I punch the right size holes. (Like, Duh. Thanks for that.)

Here's the fly in my particular ointment:

It seems that *nobody* makes a Nema3, Main Breaker equipped load center with a rotatable inner buss frame like in so many Nema 1 (indoor) panels. I went so far as to get on the tech support line with Square D and the very nice phone person even read to me from a tech note they have been given on this very subject. Words to the effect of "The Nema3 version of Square D QO120, 130, and 140 do not feature rotatable inner panels for bottom fed applications - the gutterways to the left and the right of buss frame are wide enough to accomodate feeder cable in addition to normal wire entry".

Oh. Really now. I've heard that one before - and I end up trying to make it all fit and put a huge 180 in the 3/0 feeder? So I call my local elec. trade supplier I like to buy from (NOT a big box home center...) and he makes the phone rounds too. Same answer. Square D, Cutler-Hammer, Murray-Siemens, etc. don't let you spin the insides of a 200 amp panel around in a nema 3 box. So, he's got for me a price on a Panel Board that does what I want it to do - put the main breaker/lugs at the bottom of the damn box. However it's only available with bolt-on breakers. That doesn't scare me and they even sell the breakers at "oem" prices which are only a little bit over retail if you order them with the box and they bolt them in at the plant.

So here's my question to the wise and experienced among us: What am I missing? Does everybody really NOT offer a Nema 3 200amp breakered load center that you can cleanly feed from the bottom? Is the Square D tech support note really true and the gutters are plenty roomy to allow the mains to travel up and around and not interfere with the regular work that has to go on in there? I just find that so hard to believe what I need doesn't exist but I sure can't find a retail/residential solution.

Please don't tell me "just fly the feeds to the weatherhead like normal and feed thru the top" because it's a long story why the cables have to be reworked to come off the pole and stop at the rear building, hit the standalone meter, then come to the main house underground.

The punchline to this little joke this project is playing on me is this: The ordered-to-spec panel board price from Murray-Siemens is actually about $250.00 cheaper than the suggested retail on the Nema 3 40 space 200 amp QO loadcenter I mentioned above.

Egads, and sorry for the novel of a post.

William

InPhase277 04-23-2009 07:50 AM

Now that you mention it, I guess I haven't seen alot of bottom fed outdoor panels. But really, there is enough room in the wireways to allow the feeders to come from the bottom and land on the breaker up top. I've done it hundreds of times. It's only three wires, two if you can move the neutral lug to the bottom. Shape your wires, starting with the one furthest from the side you are entering on. Some panels have small metal protrusions in the back of the can that are meant to be used for tie downs or zip ties. Use a couple of zip ties to bundle the cables together, then zip tie them to the panel to hold them out of the way.

micromind 04-23-2009 08:55 AM

It helps to run the feed conduit on one side or the other, not in the middle. It looks sorta odd on the outside, but it sure makes wiring the inside easier.

Rob

wmldwilly 04-23-2009 02:50 PM

Quote:

Originally Posted by micromind (Post 264445)
It helps to run the feed conduit on one side or the other, not in the middle. It looks sorta odd on the outside, but it sure makes wiring the inside easier.

Rob

Hmm...but with a consumer box i'd have to punch my own 2 1/2" hole at the left or right corner, amongst all the little pre-punched holes and probably make a mess of it. it seems the retail boxes only provide a small-to-huge knockout ring right in the middle. everybody's Nema3 boxes seem to have a full knockout ring at the bottom corners on the sides (facing outwards rather than downwards) but I can't imagine getting feed cable to make that tight of a corner (in a condolette or something).

time to look at everybody's bottom knockout patterns...

HouseHelper 04-23-2009 03:05 PM

Never really had a problem with this, and I usually do it with 4/0 Al. With a center feed, send one hot and the neutral up one side, the other hot up the other to give you a little more room. The Al wire shapes easily.

220/221 04-23-2009 06:11 PM

In new panels, which generally have loads of room in them, there is plenty of room to run your feeders up an into top lugs.


If I can't flip the bus I just run the feeders up and over in the can.

Actually, you can always flip the bus. The dead front can be a whole nother issue. :laughing:

micromind 04-23-2009 07:35 PM

Another option is to run the feeder conduit up to the side of the panel, and use an LB to enter the panel on the side, near the top. Depending on how fussy the inspector is, you might have to enter the panel with a close nipple and a Meyers hub.

There likely won't be any factory knockouts on the side of the panel, you can drill one in with a holesaw. This would also be a good spot to reduce to 2", or even 1-1/2". It's much easier to holesaw a smaller hole.

Rob

InPhase277 04-23-2009 07:46 PM

Quote:

Originally Posted by micromind (Post 264745)
Another option is to run the feeder conduit up to the side of the panel, and use an LB to enter the panel on the side, near the top.

Rob

LB's work, but it is one of my pet peeves. I think it just looks tacky to have an LB where an LL or LR would more appropriate. Just me though...

micromind 04-23-2009 07:48 PM

Agreed. The cover plate out front looks like someone actually planned it that way!

Plus, it's easier to get big wires into an LL or LR.

Rob


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