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Old 02-17-2015, 07:43 PM   #1
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Default Explanation of Main Panel Circuitry/Design

As the title states I am creating this post because I would like to better understand how a panel I came across is designed.

The panel is a Square D QO Load center, Model# QO-16-408, Series: A-10.
I tried looking up information on the panel via google but couldn't find any relevant search results.

Based on what I see when I remove the panel cover it looks like the two hots(single phase 120v/240v) are connected to a double pole breaker. It isn't a typical setup with a main breaker above the bus bar and two hots connected to the lugs above it.

The two hot service conductors are 4 AWG, there is another 4 AWG that is tightened to a lug above the bus bar A and goes behind some breakers and I can't see the other end. There also is a sticker inside the panel stating it doesn't use a neutral, which seems odd because it has a neutral bar with the service neutral in it along with all the branch circuits neutrals as well.

So based on my limited description does anyone have an idea of what exactly is the reasoning behind this type of panel design and how it works?

I mean I can understand that the two hots going to the double pole breaker basically function as a Main Breaker. But I don't understand why there is another 4 AWG which almost seems like its a jumper between the two bus bars. I also don't understand what the previously mentioned sticker about no neutral is referring to. I will take a picture later if need be.

[IMG]"http://s690.photobucket.com/user/badreligion9265/media/IMG_20150217_1851387731_zpsf7dcbb80.jpg.html[/IMG]

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Old 02-17-2015, 07:47 PM   #2
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A pic would be good. The wire in the middle is the neutral that runs behind the buss itself. The others are hot conductors. If the panel states 240/120 then it has a neutral.
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Old 02-17-2015, 07:57 PM   #3
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Yeah pic please
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Old 02-17-2015, 08:09 PM   #4
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[IMG][/IMG]


From the pics you can see that there are wires in the main lugs that go behind the breakers. And the two Hot service entrance conductors go to a double pole breaker. I want to know what those other 4 gauge wires are going to and why the panel is set up like this.

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Old 02-17-2015, 08:12 PM   #5
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maybe those wires from the lugs are feeding another panel?
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Old 02-17-2015, 08:13 PM   #6
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Quote:
Originally Posted by papaotis View Post
maybe those wires from the lugs are feeding another panel?
There is no other panel, this is from my house, so I'm pretty certain there is no hidden sub-panel. It looks like they either go directly to the bus-bar or to a breaker(s). It just seems like a weird design either way.

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Old 02-17-2015, 08:17 PM   #7
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It looks like someone used a SqD MLO as a feed through panel

~CS~
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Old 02-17-2015, 08:23 PM   #8
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its a split buss panel. the wiring diagram is right on that label
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Old 02-17-2015, 08:26 PM   #9
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oh, I see what happened...someone is a meathead
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Old 02-17-2015, 08:29 PM   #10
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Can you guys elaborate a little more please, I don't understand what Chicken or Jack is saying really.
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Old 02-17-2015, 08:33 PM   #11
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Jack thinks it's a split bus, good eyes if so

I thought FPE ran than market into the ground...>>>




~CS~

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Old 02-17-2015, 08:40 PM   #12
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see how the wires on the lugs are all jacked up? they used to go on that 2 pole 60. That's the lighting main breaker, it feeds the bottom half of the panel

look at that label on the side under the yellow wirenut
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Old 02-17-2015, 08:57 PM   #13
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Okay so I think I get it now. It used to be so the SE cable fed the top two buses and then that double pole fed the bottom bus.

But now it is wired so that the 60 AMP double pole truly acts as a Main breaker because the SE cable's ungrounded conductors are connected to it, feeding the top bus which then has jumper wires connected to the top bus feeding the bottom bus. But those jumper wires are downstream from the 60 Amp breaker so if it is off the bottom bus is off as well.

Does that sound right?

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Old 02-17-2015, 09:02 PM   #14
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Definitely a split buss. You are allowed 6 handles to disconnect the building. The top of the panel has room for 6 dp one of which feeds the bottom half of the panel
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Old 02-17-2015, 09:12 PM   #15
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Thanks for the pictures and explanations guys! So based off the confirmation of this being a split-bus panel is what I wrote in my last post correct about the 60Amp double-pole now acting as a main by cutting power to both top and bottom buses?
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Old 02-17-2015, 09:19 PM   #16
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Quote:
Originally Posted by badreligion9265 View Post
Thanks for the pictures and explanations guys! So based off the confirmation of this being a split-bus panel is what I wrote in my last post correct about the 60Amp double-pole now acting as a main by cutting power to both top and bottom buses?
yep, and you got two neutrals under one screw in a couple spots, just tear it all out and start over
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Old 02-17-2015, 09:19 PM   #17
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It looks that way, but it wasn't designed for that. Those top lugs should be fed

Someone 'effed it up ....

~CS~
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Old 02-17-2015, 09:20 PM   #18
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Jack, you win the kewpie doll in this thread.....~CS~
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Old 02-17-2015, 09:23 PM   #19
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Quote:
Originally Posted by badreligion9265 View Post
Can you guys elaborate a little more please, I don't understand what Chicken or Jack is saying really.
no one really understands what Chicken is saying
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Old 02-17-2015, 09:28 PM   #20
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Quote:
Originally Posted by Jack Legg View Post
no one really understands what Chicken is saying
lol well his picture certainly helped alot of what I didn't understand.

Ya I don't understand why this panel wasn't replaced because during hurricane Sandy the weather-head was knocked off the house and that along with the meter-pan got replaced. Would seem like a good time to replace the panel as well but for whatever reason it wasn't. Landlord supplied the electrician so I guess probably just a money factor.

Last edited by badreligion9265; 02-17-2015 at 09:51 PM.
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