Main Breaker Use

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Old 04-12-13, 04:17 AM
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Main Breaker Use

I'm thinking not but let me ask here.
Can the main breaker of a subpanel be used as a feeder or connection point (i'm not sure of how to word this) to power another subpanel, physical wire size permitting of course?
 
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Old 04-12-13, 06:24 AM
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The lugs are listed for use with only one conductor.
 
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Old 04-12-13, 05:50 PM
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With what you are trying to do, all you need to do is plug a breaker into the first subpanel to feed the second subpanel.
 
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Old 04-13-13, 02:16 AM
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After spending some time looking on line, this looks to be called double tapping and from some postings i've looked at doesnt seem to be 100% allowed in current code books.
 
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Old 04-13-13, 06:11 AM
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Unless the lug states usage with multiple conductors, only one can terminate in the lug.
 
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Old 04-13-13, 11:47 AM
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this looks to be called double tapping and from some postings i've looked at doesnt seem to be 100% allowed in current code books.
The lugs that I've seen that allowed double tapping not only stated that, along with the wire size range and conductor material, in the information stamped into them, they also had wire openings that were clearly made to accept two conductors. Kinda figure-8 shaped.

Why do you want to do this anyway? Getting the overcurrent protection and feeder sizes right for the whole string is going to be tricky, at best.

Originally Posted by CasualJoe
With what you are trying to do, all you need to do is plug a breaker into the first subpanel to feed the second subpanel.
 
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Old 04-13-13, 01:06 PM
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How about using split bolt connectors in a wire trough to split the cable going to a second panel? Is this something that is common or is this a no-no.

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Old 04-13-13, 01:56 PM
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There's a good deal in the code book about that.

Let's back up for a minute. What's your goal? Not your already-imagined solution, but your goal.

Why do you want to add any subpanels? What will that enable you to do?
 

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Old 04-13-13, 02:12 PM
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What you propose is done quite frequently, and would be acceptable if done properly. If this is your main service, you would not be installing a sub panel, you would be doubling the capacity of your service. All equipment and wire before the main breakers would need to be sized accordingly. (Meter socket, feeder, taps, raceways, etc.)

The information you are looking for in is section 240.
 
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Old 04-13-13, 03:02 PM
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It would be much simpler just to add a 2 pole breaker in the panel off the bus just like a branch circuit.
 
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Old 04-13-13, 06:46 PM
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Something like this is what is in place now...except for the wiring feeding the 2 panels that I am asking about so that I can make it somewhat more code compliant.


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Old 04-13-13, 06:50 PM
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You can do that. The feeder conductors need to be sized for the loads. The feeder also needs to be 4 wires.
 
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Old 04-13-13, 07:12 PM
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Assuming from viewing the pictures this is a 200 amp service, what is the amperage rating of each main breaker in the two subpanels?
 
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Old 04-13-13, 07:45 PM
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Something like this is what is in place now...except for the wiring feeding the 2 panels that I am asking about so that I can make it somewhat more code compliant.
Do you already have two subpanels that you're considering whether there might be a better way to feed, or you thinking about adding one or two new subpanels?

What are you trying to accomplish?
 
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Old 04-14-13, 06:30 AM
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Do you already have two subpanels that you're considering whether there might be a better way to feed, or you thinking about adding one or two new subpanels?

What are you trying to accomplish?

These circuit breaker panels (subpanels) were used to replace 2 fuse panels that were originally there.
I think the branch wiring was also too short when it was done so it was decided to replace and stay with 2 instead of just 1. I believe there are a total of 38 breakers in the 2 boxes. These 2 panels feed 3 other slightly smaller subpanels (kitchen, attached garage, laundry room and large extension). There are a total of 5 or 6 subpanels in the house. The house has gone through 3 or 4 major changes including extensions in its 80 or 90 year existence.
The meter is for 100 amp service. the disconnect breaker is 100 amps the feeder wires to the 2 big panels that are about 40 feet away are 1/0 copper. The 2 big panels that we've been talking about have main breakers that are 200 amps. What do I want to accomplish? I am doing a little maintenance work on the house and noticed the double tapped main breaker, so I figured I'd ask. If its not a lot of work, I may just give it a try to correct anything that is not copacetic even if it includes replacing the 2 subpanels with 1. I hope this info helps in helping me with information. Thanks to all posting here.
 
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Old 04-14-13, 08:16 AM
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The meter is for 100 amp service. the disconnect breaker is 100 amps the feeder wires to the 2 big panels that are about 40 feet away are 1/0 copper. The 2 big panels that we've been talking about have main breakers that are 200 amps. What do I want to accomplish? I am doing a little maintenance work on the house and noticed the double tapped main breaker, so I figured I'd ask. If its not a lot of work, I may just give it a try to correct anything that is not copacetic even if it includes replacing the 2 subpanels with 1
Your two subpanels with 200 amp main breakers don't appear to be very old. Unless there is something wrong with them I cannot see, I'd keep them. 1/0 copper is larger than necessary for a 100 amp feeder and I'd bet it was not easy to double lug two 1/0 conductors in the 200 amp main breaker's lugs, but that is where I'd make changes. If you can remove the double lugged connections and use a trough or junction box to make those connections, as was discussed earlier in this thread, I believe you would be fine. Are you sure the conductors are #1/0 and not #1? I am not sure a #1/0 conductor will fit in the lugs on a 100 amp breaker. Of course, you'll have to remember that those panels are not good for 200 amps and share a total of 100 amps of capacity.
 
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Old 04-14-13, 01:07 PM
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The meter is for 100 amp service. the disconnect breaker is 100 amps the feeder wires to the 2 big panels that are about 40 feet away are 1/0 copper. The 2 big panels that we've been talking about have main breakers that are 200 amps. What do I want to accomplish? I am doing a little maintenance work on the house and noticed the double tapped main breaker, so I figured I'd ask. If its not a lot of work, I may just give it a try to correct anything that is not copacetic even if it includes replacing the 2 subpanels with 1.
Assuming the two primary subpanels are fed with #1 AWG copper and not #1/0 AWG, I would install a new 100A 240V breaker in the main panel and move that feed to that breaker, as suggested in several replies in this thread.

Note that the existing double tap, if it is in the lugs where your power comes in from the meter, will always be hot unless there is an outside disconnect or the meter has been pulled. Moving the feeders under those conditions is a job for a licensed electrical contractor.

The 200A main breakers in those two panels can remain. They only function as convenience disconnects.

Note also that, in every subpanel, the grounds must be kept together and bonded to the EGC from the main panel and to the subpanel enclosure. The neutrals must also be kept together, separately, and isolated from any connection to ground, including the panel enclosure. This usually requires the installation of a separate, bonded ground bar.
 
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Old 04-14-13, 02:46 PM
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Note also that, in every subpanel, the grounds must be kept together and bonded to the EGC from the main panel and to the subpanel enclosure. The neutrals must also be kept together, separately, and isolated from any connection to ground, including the panel enclosure. This usually requires the installation of a separate, bonded ground bar.
Do you have a drawing you can post here?
 
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Old 04-14-13, 03:55 PM
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Do you have a drawing you can post here?
Somebody may, but I don't. I'll be glad to explain it though, if you'll tell us what it is that you don't understand.

Simply put, an electrical subpanel needs to have a ground bus that is mechanically and electrically bonded to the enclosure (the can, the box, etc.). Some of us go so far as to use a wire brush in a drill to remove the paint from the inside of the can when we're installing an auxiliary ground bar, if the electrical bonding is to be achieved by direct mechanical contact.

Regardless, all of the grounding conductors - for the branch circuits and from the feeder source, plus any new bonding conductors needed just for that panel, are terminated to that bonded bar. All of the neutrals are terminated to a bar that is held off the inside of the enclosure with insulating supports.

You do have 4 wires feeding the subpanels, don't you? You need 2 hots, a neutral and a ground to each.
 
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Old 04-14-13, 04:46 PM
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Old 04-14-13, 05:49 PM
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Cool. Thanks, Ray .
 
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