Another Subpanel Question

Installing 100A subpanel off of 200A main panel. Running #4 copper off a 100A breaker in main panel. Where do I connect my #4 neutral conductor on the main panel? The neutral bus bar is full, besides I don't think #4 cable would fit in those small holes. Since the neutral and ground are bonded together in the main panel, can I install a mechanical lug directly to the main panel (metal to metal) and connect my neutral conductor to this? Would it have to be isolated?
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Tying a neutral to the chassis would not be an ideal solution. Do you have a common ground/neutral bus? If so, can you double or triple up grounds of the same gauge into the same hole? Neutral wires cannot be doubled up. The only other way to get more holes is to add a ground bus and screw it to the (hopefully existing) holes in the panel chassis. Tie this into the neutral/ground bus with a #4 or #6 copper wire and relocate all the grounds to this bus. Hopefully, this frees up a bunch of holes in the neutral bus.
If none of those solutions work, you could split bolt it to the existing neutral service wire or perhaps install a double lug where the neutral comes in. Or lastly, take the largest neutral off the bus and put a 1/0 copper wire segment in its place. Then split bolt the wire you took off and the new #4 to this 1/0 segment. This segment with the split bolts must be properly taped and colored white when you're done. You must make sure that common wire has an ampacity equalt to the sum of all circuits that you split bolt to it, or has the ampacity of the whole service (probably close to 200A which means a 1/0 or 2/0 copper conductor).
-- Mark Kent, WA
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Check the labels inside the panel's cabinet to see what size and combination of wires will fit in the holes on the neutral buss bar. In most of the panels I've seen the terminations will take two or three Equipment Grounding Conductors (EGC) in one hole. Also most neutral busses have larger terminations that will take number four American Wire Gauge conductors.
You could also install an additional buss bar and move the EGCs to that bar thus clearing spaces on the Neutral Buss. It is a generally bad practice to use the equipment cabinet as a regular current carrying neutral conductor. Since the add on buss bar mounting screws bond it directly to the cabinet and the Neutral Buss is bonded to the cabinet via it's main bonding jumper they will both be electrically functioning as bonded grounded conductor (neutral) buss bars but it will still be better practice to move the EGCs to the new buss bar and leave the identified grounded conductors on the original neutral buss bar. If you find it necessary to use the new buss bar for current carrying grounded conductors then install a bonding conductor between the buss bars.
If the neutral buss bar does not have terminations that will except #4 AWG conductors you can buy an add on lug that will attach to the buss bar to accept that conductor. -- Tom
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Exactly what I wanted but didn't know they made such a thing. I went to the Depot but couldn't find one. Until they directed me to the light bulb area. Never thought to look there. Finally asked. Now if I double up a couple of grounds I'll have 2 empty slots. Kind of like Walmart. They have the rat poison next to the cat food. Which, after thinking about it, is where it should be!!!! Thanks.
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NO THATS WHERE YOUR DINNER SHOULD BE!! THANKS, TONY D.
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