Number Of Wires Under One Neutral Bus Bar Terminal Screw? - Electrical - DIY Chatroom Home Improvement Forum


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Old 07-12-2007, 03:16 PM   #1
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Number of wires under one neutral bus bar terminal screw?


I was looking at our main panel today (residential, 100A service) with the cover removed. I noticed that in a couple of places, more than one neutral or ground is terminated under a single terminal screw on the neutral bus bar. Is this kosher? I don't know if there's a "one terminal, one wire" type rule regarding the neutral/ground bus bars.

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Old 07-12-2007, 03:31 PM   #2
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Number of wires under one neutral bus bar terminal screw?


For neutrals, it's one wire per screw. For grounds it may be 1,2,or 3 depending on the panel manufacturer. There should be a label either inside the panel or on the door that will tell you how many are allowed on the ground.

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Old 07-12-2007, 03:53 PM   #3
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Number of wires under one neutral bus bar terminal screw?


Thanks House, I'll look that up!
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Old 07-12-2007, 10:37 PM   #4
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Number of wires under one neutral bus bar terminal screw?


How did they use all the terminals up? They usually have enough for full capactity of the "skinny" breakers...
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Old 07-13-2007, 07:55 PM   #5
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Number of wires under one neutral bus bar terminal screw?


I put a new breaker panel in at at our house last weekend and I had to double encumber a few of the lugs because there simply wasn't enough slack in the wires to reach the next lug down. I thought it made more sense than making a splice inside of the panel.
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Old 07-13-2007, 08:13 PM   #6
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Number of wires under one neutral bus bar terminal screw?


Better to put a splice than chance a loose neutral due to more than one wire under a screw. There is no restriction to wirenutting two wires together inside a panel as long as there is enough space to do so. Most modern panels have that space.
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Old 07-13-2007, 08:50 PM   #7
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Number of wires under one neutral bus bar terminal screw?


Househelper, thanks for the info. I'll wirenut them asap.
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Old 07-14-2007, 09:43 AM   #8
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Number of wires under one neutral bus bar terminal screw?


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Better to put a splice than chance a loose neutral due to more than one wire under a screw. There is no restriction to wirenutting two wires together inside a panel as long as there is enough space to do so. Most modern panels have that space.
This might resolve my first issue. I was checking to see if there's space to swap out the bedroom breakers for AFCI breakers, and to swap two other breakers for a SSP. I know the pigtails for the AFCIs and the SSP /must/ be as short as possible. So, I could if necessary splice a few other lines together to make room? Or is it better to get a longer length neutral bus bar and install it?
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Old 07-14-2007, 11:16 AM   #9
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Number of wires under one neutral bus bar terminal screw?


You do NOT want to be combining several neutrals under one wire nut with a pigtail to the buss: you risk overloading the pigtail. And most neutral bars are not replaceable.
For each AFCI breaker you add, you will be removing a neutral from the bus (it will now go to the breaker). If the breaker pigtail won't reach the now open hole, just add a short length of white wire to the pigtail to extend it.
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Old 07-14-2007, 12:28 PM   #10
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Number of wires under one neutral bus bar terminal screw?


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You do NOT want to be combining several neutrals under one wire nut with a pigtail to the buss: you risk overloading the pigtail. And most neutral bars are not replaceable.
For each AFCI breaker you add, you will be removing a neutral from the bus (it will now go to the breaker). If the breaker pigtail won't reach the now open hole, just add a short length of white wire to the pigtail to extend it.
Right, what I meant was that if there is a ground wire in a spot I need on the neutral bus, I could move that ground wire into a shared spot with another ground wire. Assuming my particular panel allows more than one wire under a screw in the neutral bus, that is. The neutral wire coming from the AFCI breaker would not share a hole. The idea being that I could move a ground wire to another spot if doing so would allow the neutral wire from the SSP to be take the shortest path possible.
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Old 07-14-2007, 09:48 PM   #11
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Number of wires under one neutral bus bar terminal screw?


Well when you put it that way, that is a good plan as long as this is a main panel (you said it was) and the neutral and ground buses are the same.
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Old 07-15-2007, 04:07 PM   #12
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Number of wires under one neutral bus bar terminal screw?


Would a licensed electrician be able to install a longer neutral bus bar if the existing one is already at safe capacity?
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Old 07-17-2007, 04:56 AM   #13
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Number of wires under one neutral bus bar terminal screw?


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Would a licensed electrician be able to install a longer neutral bus bar if the existing one is already at safe capacity?
Yes, but I think adding a ground bar and moving the grounds to it would be easier and cheaper. The end result (more room on the neutral bar) would be the same.

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