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GuitarJack 08-24-2009 02:02 PM

Replacing 2 Sub Panels with 1 Larger Panel
3 Attachment(s)
Hi, I would like to describe my panel arrangement and see if anyone would like to offer any advice, ideas or opinions. I have an indoor, main shut off box which has the meter attached and contains two 70 amp BUSS fuses. This also has a large handle that can be pulled down to shut off power to the entire house. This main shut off box says 100 amps on it and it does not contain any circuit breakers.

Currently there are two small sub panels that come directly off the Main shut off box along with a third feed to the main circuit breaker panel. These two smaller panels are within a couple feet of the Main shut off box. One of these small sub panels contains a 30 amp, 240 Volt breaker for the Clothes dryer. The other small sub panel contains one single 20 amp breaker for the dish washer. There is another double breaker in this panel that has a line out and leads to a box that is not attached to anything. All three of the panels are being fed from the same connection inside the Main shut off box. In other words, each of the bolt down type connectors in the main shut off box has three wires attached, to supply the three separate panels.

The main circuit breaker box is about 20 feet away. It is a bulldog pushmatic type Panel rated at 100 amps. It has spaces for 14 Circuit breakers and it is full. It has worked well over the time Iíve lived here and I have replaced about 4 of the breakers. The house is not that big and we have plenty of electrical devices running with no problems. Breakers have rarely tripped. Maybe once every couple years when someone manages to turn every thing in the kitchen on at the same time. In other words I donít think I need more than 100 amps. I know many will say I should replace the pushmatic panel. I donít want to replace the Bull Dog panel because it is mounted in a very difficult spot within the wall of the basement stairway. It is a nightmare getting wires in and out of that box from behind that wall. There is about 4 inches of clearance behind the wall before you hit cinderblock. I think it might be a pretty big job because of the difficult location.

Right now none of the panels has a main breaker. They all rely on the 70 amp BUSS fuses in the Main shut off box. Iím going to read the local code book here but I suspect that it might not be allowed to have three panels feeding off the main shut off box.

The solution I am imagining is thisÖ

  • Remove the two small sub panels.
  • Replace them with one new larger 100 amp panel. Then, instead of having 3 direct feeds coming from the main shut off box there would be only one.
  • Put a 100 amp breaker in this new panel that will feed the bull dog panel.
  • Move a few of the circuits away from the Bull Dog over to the new panel.
  • The end result would be a neater layout with less congestion on the bull dog panel. Also there would be several empty spaces on the new panel for future needs. I should note that I am not planning to add any more circuits than already exist in the current setup.

Iím planning to do this work myself followed by inspection by an electrician and local inspector. Iíve done work like this before on several homes I previously owned with no problems.

By having a 100 amp panel feeding off of another 100 amp panel would my house now be considered to have 200 amp service? Also since the Main shut off fuse box is rated at 100 amps would that be considered an overload? As I said, Iím not planning to add more appliances than currently exist.

Do I need a main breaker in the new panel or can I rely on the Buss fuses?

Thanks in advance for any enlightenment you shine my way! :thumbup:

220/221 08-24-2009 03:23 PM

Pictures are worth thousands of words, especially in your case.

It sounds like you can do what you want but there are a LOT of details involved. The first issue is how the panel feeders are tapped on to the main disconect. Probably incorrectly/illegally.

I would suggest that you install a new panel (with as many spaces as you need plus some) next to the disconnect switch. Install 100 amp wire to feed the new panel and install 100 amp fuses in the disco.

Drop your feed (to the Bullgog panel) into the new panel and land it on the appropriate sized breaker. To stay code compliant you will have to re feed the Bulldog panel to keep the neutrals/grounds separated.
Run the rest of your circuits into the new panel and terminate them properly.

All grounds and neutrals must be separated beyond the disco.

GuitarJack 08-24-2009 03:59 PM

Anlother Pic attached
Thanks for that, I have attached a new picture of the connection in the Main disconnect. I was pretty sure this was not code and that is one of the reasons I'm doing this changeover. Also I forgot to mention that I noticed that none of the panels have a ground bar. All of this work was probably done over 25 years ago. It was my dad's house so I'm pretty familiar with the history. The separation of neutrals and grounds is something I want to clear up with this work.

junkcollector 08-24-2009 09:15 PM

If you do as you propose,

You say that that old A base meter disconnect box is rated for 100A, but be sure that the incoming SE cable is OK for 100A. If we use NEC 310.15(B) 6 You would need an absolute bare minimum of a #4. That old SE usually has RHW insulation on conductors inside. It is tinned copper.

I wonder why they used the 70 A fuses? That basically means that you have a 70 A service right now. They probably stuck them in there because the the size of the conductors going over to the pushmatic panel. Hopefully, and not because the incoming conductors are rated at that.

You'll need to run 4 conductors between the meter/ main and your new panel. I see that there is a large knockout on the lower left hand side right below were one of the smaller AC cables leave. I would punch that KO out and run a conduit nipple over to your new panel. I would use #3 THHN copper for both hots and a neutral. You can use a # 6 for the ground. Then you should be able to replace the 70 A with 100A fuses.

And as 220 stated, no questions asked you will need to replace the existing feeder to the pushmatic panel to a 4 wire setup.

Remember to post "after" pics!

GuitarJack 08-24-2009 10:21 PM

Good Point
Thanks Junkcollector. I will certainly post "after pictures". That's a great idea. Your point on the rating for the incoming conductors is well taken. Those incoming wires are the same line that is coming in from the street. I didn't know that those would vary in size. They are probably the origonal wires that were installed in 1948.

First of all how do I get an accurate measurement on them without getting electrocuted?

Secondly, if they are only rated for 70 amps would the power company pick up the tab on replacing them? Just a little wishful thinking.

junkcollector 08-25-2009 12:37 PM


Originally Posted by GuitarJack (Post 318951)
First of all how do I get an accurate measurement on them without getting electrocuted?

The only thing I can tell you is what I do, and that is a visual inspection. I sorta "know" how big wires are just by looking. If you are unsure, You could compare the size to scraps of new wire using them as a gauge.


Originally Posted by GuitarJack (Post 318951)
Secondly, if they are only rated for 70 amps would the power company pick up the tab on replacing them? Just a little wishful thinking.

Most likely not. I assume that you have overhead service? If so, their responsibility most likely ends where the overhead service drop attaches to the house and is spliced to your SE cable. If a whole service change is needed, you would need to install a new service with an outside meter socket and then and cable / or conduit feeding new panel inside. (your job, or the job of an electrician.)

Underground service is different. For the most part, their responsibility ends at the meter. (It does in my area, but different in others!) Best just to give them a call and see what they say.

220/221 08-25-2009 08:56 PM

I'd like to see a straight on pic of that meter/disco.

I have not seen that configuration.

GuitarJack 08-25-2009 09:43 PM

Pic Added
No Problem. Thanks for asking too. If you want any further close-ups or other shots just let me know.

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