Split-bus panels not allowed?


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Old 08-28-13, 06:37 AM
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Split-bus panels not allowed?

I think I read in a post here that split-bus panels are no longer permitted. Is there a reason for this? That kind of panel would be ideal for what I have in mind for my cottage where I like to turn off most circuits when I leave-- but leave a couple on (fridge, heat, one light circuit by the door would be nice).

I've already installed a "normal" panel but I'm curious why split-bus is a bad thing...especially since that's what's in my home.
 
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Old 08-28-13, 10:14 AM
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The NEC requires residential services and/or main service panels have a main breaker and have required this for around 25 to 30 years. My opinion is that the cheapy split bus panels were not safe because so many handy homeowners who didn't have a clue about home wiring would get into their panels and get in trouble. I do remember that back in those days, many smaller reputable electrical contractors would absolutely refuse to install one. On the other hand, there were also those contractors who would install nothing but split bus panels to give them a little extra edge on their bids.
 
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Old 08-28-13, 12:31 PM
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My home panel (mid 1970's) has 2 main disconnects--one feeds the 15A group, one feeds the 20A group below. There are also 4 240V service disconnects in the upper section for well, welder, range and workshop. Nothing about it looks "cheapy".
So you 're saying 2 mains aren't allowed anymore? Or is it the split configuration of the panel that's been banned?

I'm just looking for knowledge here. This panel will need to be replaced someday soon and knowing what's wrong with it will help me decide what I should expect for a replacement.
 
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Old 08-28-13, 12:47 PM
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My home panel (mid 1970's) has 2 main disconnects--one feeds the 15A group, one feeds the 20A group below.
Guy, if you turn off the two "mains" in your home panel do you still have power to your 240V loads?

Originally Posted by CasualJor
The NEC requires residential services and/or main service panels have a main breaker and have required this for around 25 to 30 years.
That's one breaker that kills the hot buses in the entire panel.
 
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Old 08-28-13, 05:58 PM
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My home panel (mid 1970's) has 2 main disconnects--one feeds the 15A group, one feeds the 20A group below. There are also 4 240V service disconnects in the upper section for well, welder, range and workshop. Nothing about it looks "cheapy".
Yes, it was a cheapy when compared to a 100 amp, a 125 amp or a 200 amp main breaker panel. Have you ever priced those higher amperage breakers? That was the big material dollar savings when a new home was wired using a split bus panel. In the mid 1970s, a 200 amp split bus panel was probably about $20 cheaper than a Square D 30 circuit main breaker panel that at that time ran around $50.
 
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Old 08-28-13, 07:10 PM
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Kat,
IIRC the service cable lands on lugs that energize the top 6 stabs so it potentially is a 6-throw panel. Each Main feeds an 8 or 10-slot section below.

The NEC is so nit-picky about everything I'm sure there's a reason given for banning these panels. Is it that they require ONE main breaker that kills power to all branches?

I would think split-bus would still be useful for duplexes, MIL apartment, and farm use.
 
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Old 08-29-13, 06:12 AM
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I would think split-bus would still be useful for duplexes, MIL apartment, and farm use.
Split bus loadcenters haven't been manufactured in a long time since they aren't allowed in residential installations and that is where the large majority of single phase loadcenters are installed. The 6 switch rule, however, is frequently used in larger commercial and industrial (non-residential) installations.
 
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Old 08-29-13, 06:19 AM
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I'm sure there's a reason given for banning these panels.
I'm sure there are discussion notes and such from the NEC panels, but my guess would be:

1) The ability to over-fuse the service entry. With a 100A main breaker, the service entry is limited to 100A draw and that's it. With a split-bus, it's easy to overfuse each of the breakers/fuses and pull more than the rated amount through the service entry.

2) The design worked fine when all the house had was an oven, dryer, and a couple 15/20A branch circuits. As electricity demands increased, the design no longer made sense. Even small houses fill up a 30 space panel pretty easily these days.

3) I'm sure some of it also had to do with homeowner confusion as to how to shut power off. Every iteration of the NEC is intended to increase the safety factor based on OSHA/NFPA/etc. incident reports.

Again, just my guesses.
 
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Old 08-29-13, 06:30 AM
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My interest in this--and the reason I ask about having 2 disconnects--is because my previous cottage had a 4-space box near the meter that contained the main disconnect and 1 other breaker that went only to the fridge. This was incredibly convenient and I never had to worry if I left anything on when I left. Is there a way to legally duplicate this convenience?
 
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Old 08-29-13, 07:21 AM
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Yes, you can add one or more sub panels.
 
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Old 08-29-13, 09:35 AM
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Ahead of or in parallel with the main disconnect?
 
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Old 08-29-13, 10:47 AM
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Neither, after.

.
 
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Old 08-29-13, 12:48 PM
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Then you don't understand my point. One switch to cut power to everything except the fridge.
 
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Old 08-29-13, 12:57 PM
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Or you don't understand me. Put the fridge and subpanel breaker in the main panel and everything else in the sub. Just shut off the subpanel breaker in the main panel to kill everything but the refrigerator.
 
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Old 08-29-13, 07:18 PM
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THAT'S what i was hoping for.
So it is permitted to have more than just the main breaker connected to the meter in the 1st (main) panel. That's how my previous cottage was wired and that's how I would prefer my new one to be. I thought I was hearing that I could only have one main breaker in the main panel and nothing else could be connected in parallel to the meter. The diagram shows a main disconnect in the subpanel but that's optional and not present in mine.

 

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Old 08-29-13, 08:09 PM
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So it is permitted to have more than just the main breaker connected to the meter in the 1st (main) panel. That's how my previous cottage was wired and that's how I would prefer my new one to be. I thought I was hearing that I could only have one main breaker in the main panel and nothing else could be connected in parallel to the meter.
No, your main panel can have either no main breaker or one main breaker. Period. Full stop.

At your cottage, IIRC, your main panel is a subpanel fed from a main overcurrent protection device (main breaker) located just inside from the meter base.

But it doesn't matter. Either way, the service feeders go to a MOPD first. Everything else is downstream from that. Nothing else in your system is on that level.

The 240V 60A (or whatever size) breaker that feeds the sub-subpanel (if you will) with all of the breakers for the circuits that you want to kill when leaving is just another branch circuit breaker. It's on the same level, schematically, as the breaker for the receptacle your fridge is plugged into.

If you turn your main breaker off you will kill everything, including the fridge and the sub-subpanel. If you turn off the branch circuit breaker for the fridge you will kill that circuit. If you turn off the breaker right across from it, for the sub-subpanel, you will kill that load. They're equivalent, and none of this is "in parallel to the meter." Or it all is.
 
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Old 08-29-13, 08:18 PM
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But you can have a subpanel feeding a subpanel. In the first subpanel you would have only the breaker for the second subpanel and the breaker for the refrigerator.

The situation Nash is referring to with the first OCPD device in a box with no other breakers is one I don't see much in my area and I was referring to what I am familiar with, the first OCPD in the main panel with all the branch circuit breakers.
 
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Old 08-29-13, 08:25 PM
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Or use a meter/main panel combo with feed-thru lugs and a main breaker panel as the subpanel inside.
 
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Old 08-30-13, 07:09 AM
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This is getting more complicated than it needs to be.

So it is permitted to have more than just the main breaker connected to the meter in the 1st (main) panel.
No. My opinion is that your first disconnect, which I think is just an enclosure with a 100 amp breaker, should be a 100 amp main breaker panel with perhaps 6 to 8 spaces. AFTER that main circuit breaker in this main panel, you could have the branch breaker to feed the subpanel and another branch breaker to feed the refrigerator. In this configuration, the refrigerator branch must be AFTER the main breaker.
 
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Old 08-30-13, 08:56 AM
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Ray were you wrong in the post I got all geeked about or is this a jurisdiction/interpretation thing?
Justin Smith

Or use a meter/main panel combo with feed-thru lugs and a main breaker panel as the subpanel inside.

ray2047

But you can have a subpanel feeding a subpanel. In the first subpanel you would have only the breaker for the second subpanel and the breaker for the refrigerator.
The Meter Socket/Main breaker combos I've seen have been huge & I didn't leave that much space for one.

I can do meter-main-sub-sub ( or meter-bigger main-sub) if that's the only solution. Yes it's that important to me. Is there a "disconnect" that fits in the space of a 240 breaker but is not a breaker? I don't like the idea of all the redundant breakers but I'm betting if there is such a thing it'll cost more than a common breaker.
 
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Old 08-30-13, 09:51 AM
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A breaker is a disconnect. Almost all modern breakers are also rated for use as a switch.

Ray were you wrong in the post I got all geeked about or is this a jurisdiction/interpretation thing?
No, just a difference in the way things are done. I have modified one of your drawings t show how it is often done here.

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Old 08-30-13, 08:57 PM
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Does anyone make a "Mini Main" that would have 2 spaces at the top for a 100A Main breaker + 4 spaces below for another "main" (that would kill the sub-panel) + 2 branch breakers?

The big boxes don't have anything like that but is it a catalog item I can get from a supply house?
 
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Old 08-30-13, 09:02 PM
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A sub panel is never fed from a "main". It is fed from a branch circuit breaker. There is nothing that prevents you from using only two breakers in an eight space panel.
 
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Old 08-30-13, 09:43 PM
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There is only one main overcurrent protection device (main breaker) in any electrical system. Everything after that is a branch circuit breaker. It doesn't matter how big it is or what it supplies.

I've installed breakers that fed entire electric rooms. Those were branch circuit breakers.

On a different but relevant note, the main distribution panel in a house I renovated for my family in the eighties had space for more than 30 full-size breakers in it. In addition to the main breaker, It had 6 breakers in it when it was complete, as I recall. One each for the subpanels on the first and second floors.One for the A/C condensing unit, one for the outdoor receptacles, one for the furnace and one for the lights and receptacles in the basement.
 
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Old 08-31-13, 06:25 AM
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Let me re-phrase that...
Does anyone make a "Mini Main" that would have 2 spaces at the top for a 100A Main breaker + 4 spaces below...?
 
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Old 08-31-13, 08:02 AM
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Let me re-phrase that...
Does anyone make a "Mini Main" that would have 2 spaces at the top for a 100A Main breaker + 4 spaces below...?
To find exactly what you are asking about would take searching through manufacturer's catalogs, but I am fairly certain you could find something to fit the bill. I believe what you are asking is basically the same thing I suggested in Post #19. You are asking for 4 slots, here is a panel with 8 slots that still has the 100 amp main.

Eaton 100 Amp 8-Space 16-Circuit BR Main Breaker Loadcenter-BR816B100 at The Home Depot

Here's another way you could do it. Install a 8 slot main lug only panel and install a 100 amp backfed main breaker with main breaker retaining kit. That leaves you a total of 6 additional slots.

Eaton 125 Amp 8-Space 16-Circuit Type BR Main Lug Indoor Load Center with Door and Ground Bar-BR816L125SDP at The Home Depot
 
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Old 08-31-13, 08:28 AM
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I chose eight as the magic number after a search of mosts common small size 100a main breaker panels. If you find anything smaller it will probably cost more then an eight space because of limited sales. The main lug Joe mentioned is another solutioa but I didn't mention it because it won't physically be much smaller and may cost more. Main breaker panels usually include the main breaker. Main lug by their nature don't. So to the cost of the main lug you must add the cost of the main breaker and a hold down kit.

Why do you find the number of unused spaces so important?
 
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Old 08-31-13, 12:56 PM
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Why do you find the number of unused spaces so important?
I'd like to think it would make the panel smaller. This is on the wall right next to the back door where space is tight.

I did some browsing the manufacturer's sites to see if they make a small main breaker panel that HD. Lowes or Menards don't carry. I came close to the size & function I want in a trailer park panel--but it's an outdoor enclosure.

I think I've beaten this idea to death. I think I'll give it a rest and coast on to my service inspection Wednesday. After that I have plenty of time to consider how elaborate and/or compliant I want to get.
 
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Old 08-31-13, 01:43 PM
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This is on the wall right next to the back door where space is tight.
So is there room outside under the meter?
 
 

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