#8 Too Small For Sub Panel Lugs

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Old 10-01-07, 03:04 PM
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Question #8 Too Small For Sub Panel Lugs

I have #8 copper feeder in conduit serving my condo and a 50 amp breaker outside at the meter. (Double checked wire rating in a previous post.) I bought a 12-24 load center to replace my existing sub-panel. The load center's main lugs are sized for #6 and larger cables.

To attach my #8 feeder should I install a two-pole 50 amp breaker in the panel, filling in 2 spaces? Would this interfere with the sub-panel requirement that the neutral bus must be separate from the ground?

One suggestion I got was to strip the #8 back a little further and fold it over so that the lugs will make contact. This sounds like it would cause a hot spot and is probably a bad idea.
 
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Old 10-01-07, 03:21 PM
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No, you should not fold over the conductor to increase its size.

Before you backfeed the breaker you should see if a backfeed lock clip is available and listed for use with that panel. If one is not listed for use you cannot backfeed your new panel.

Backfeeding a panel would not change the requirement to keep the grounds and neutrals separate.

Why are you replacing the panel and is it legal for you to do?
 
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Old 10-01-07, 03:32 PM
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I'm remodeling my kitchen with a permit. The new circuits required for all the appliances etc. exceed the existing panel space I have. Several electricians said upgrading my service would be too costly and one said "buy a new house". So I'm just using a panel with more space, existing feeders, and checking my load calculation very carefully. I understand it is legal in California for the homeowner (that's me), family members, or licensed electricians to do the work. Which is all inside the house.
 
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Old 10-01-07, 03:39 PM
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I would first contact the supply house or panel manufacturer to see if a different lug kit is available. Next, I would check a different panel manufacturer to see if they make a 12/24 panel which accepts #8. If neither of those pan out, I would backfeed a 50A breaker, assuming you can get a breaker hold down clip for the panel.
 
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Old 10-01-07, 03:44 PM
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Thanks, I will talk to the supply house again. The panel is a Cutler Hammer BR1224L125DG.
 
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Old 10-01-07, 03:54 PM
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The BR1224L125DG do have a backfeed main breaker kit the number is BREQS125 that is the hold down kit and make sure you noticed that this box the tie down useally be upperleft hand corner part of the panel box and this do come with seprated grounding bar as well [ normally have to buy it separted ]

this is one of few very common box i ran into.

I did double checked my catalog book about this and now the other question is the #8 wire i feel the 50 amp is little too large for this wire normally the #8 copper [ THHN/THWN and TW wires type] useally are rated for 40 amp breaker

most BR double pole breaker can take #8 wire with out issue there [ larger than 30 amp size btw ]

Merci, Marc
 
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Old 10-01-07, 04:10 PM
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The feeder is labeled '8 AWG Type THHN or THWN E14656K (UL) Gasoline and Oil Resistant II 600V' and it is in conduit. I checked with my building inspector and he said it's OK for 50 amps although he hasn't been out to see it yet.
 
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Old 10-01-07, 05:58 PM
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I hate to rain in your prade in a min but one question it may irrated the building inspector a little what tempture chart he did used ??

that part be prepared for his remark normally just about all resdential area normally are marked for 60C or 75C termation rating and to use the 90C rating this will get very compated matter [ kinda little out of the diy scope ]

i just checked my catalog book for verifcation with the rating and it do listed for both 60C and 75C rating

sorry to shake the " tree " a little but this part i am condering about the rating issue there the other reason why i was condersing is the distance from the subfeed to the main breaker box that part i am condsering about this one

Merci , Marc
 
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Old 10-01-07, 06:43 PM
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There are eight meters with 50 amp breakers at the main disconnect. Installed in 1987. The #8 feeders run in conduit underground. The meter is roughly 100 feet away if the cable is running straight.(They would have wanted to save money on cable right?) Or 132 feet away if it runs out to the street and makes a 90 degree turn.
 
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Old 10-01-07, 09:02 PM
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Copper #8 THHN in conduit is good for 50A using 75C terminations per table 310.16. Although given a 100' distance, I think it's overloaded or at least bumping against the ceiling. At 50A load, you've got 3.2% voltage drop which is outside the recommended tolerance for feeders. I guess it would depend on what the load calc shows.
 
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Old 10-01-07, 09:39 PM
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Ibpooks ,,

thanks for catch that number i did miss that part and i just recheck my caluations if fully loaded 50 amp that get pretty good droppage there.

IMO for that distance it should have #6 instead of #8 the votlage drop will be at 2 %

Merci, Marc
 
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