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Old 05-21-2007, 02:42 PM   #1
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Subpanel Upgrade


I just removed a very old sub-panel and installed a new 100A Square D 8 breaker panel.....because of the age of the house wiring - there are only two feeders from the main panel - hot and neutral on a 50A breaker - and no ground....question is that four of the new breakers are fed from one bus and that bus is the one that I terminated the hot lead to.....so now I need to jumper from the one hot lug to the vacant lug serving the other four breakers - need to know the size of the conductor to use...I supect it should be rated at 100A rather than just the 50A....?

There are seven branch circuits to the box - four actually feed service, two are dead and are not active and one is actually "hot"......so my second question is should I get the "hot" circuit out of the box or can ir remain as is.....capped off.....?
Thanks......
Rick

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Old 05-21-2007, 04:29 PM   #2
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Just some additional information - the sub-panel is from a double breaker on the new main panel - the black wire is terminated on the breaker and the white wire is terminated on the neutral bar but the red wire is hanging and not terminated - the new black/white meet up with the old feeder cable and that is apparently why there is only one black and one white entering the old sub-panel....the wiring into the sub-panel is the original old cable.....
Thanks,
Rick

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Old 05-21-2007, 05:14 PM   #3
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So if I am understanding without the second hot wire I am limted to four breakers.....? I assume a jumper is not code.....the previous panel did have a #6 jumper......
Thanks again.....
Rick
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Old 05-21-2007, 09:29 PM   #4
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Subpanel Upgrade


I'm not entirely understanding why the red wire doesn't extend all the way from the main panel to the sub. Your feeder breaker is a 2-pole (220V), but with only one of the legs connected to the sub panel, the subpanel only has 110V. If you can connect the red wire to the other lug in the sub-panel, then you can connect the red wire in the main to the second post on the breaker, and you'll have 220V to the subpanel, with each of the individual circuits in the sub getting their 110 Volts.
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Old 05-21-2007, 10:06 PM   #5
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Nate....
Much appreciate the response....I guess what happened (before I purchased the house) - a new panel was installed in the basement and when they went to run a feed to the sub-panel which had to be the first breaker panel ever made (I am sending the panel to the Smithsonian).....they ran into some difficulty as there were only two wires into the sub.....and at that time they decided rather than upgrade the feed all the way to the sub-panel just hook up the black and white to the existing black and white (the run to where the splice from new to old is probably 12 feet).....and thats where I am....I guess I need to call an electrician to see if he can run a three wire feed all the way from the main panel to the new sub-panel......nothing is easy....the house is probably 60+ years old.....
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Old 05-21-2007, 10:16 PM   #6
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Why not just replace the 12 feet of old wire with 3-conductor wire? I assume the splice you're referring to is inside a proper junction box? If so, just replace the 2-conductor cable, and you'll have a proper sub-panel again.
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Old 05-22-2007, 01:51 AM   #7
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Hello Rick


You have a rather big mess with a three wire feeder splicing to a two wire feeder. You are right however in that nothing is easy in these older style homes. It is rather common...unfortunately... to see 120 volt feeds to sub-panels, then jumpering across the lugs putting both busses of the panel on the same leg. I've never understood why people do this but I see it all the time.
Since your messing with the feeder you must bring it up to 2005 or the latest code cycle for your area. That is almost certainly a 4 wire feeder. What you have now is crap and you need to fix it correctly. Your main panel is bonded to the service neutral so you need to bond the metal of the new sub to the fault current path back to the transformer serving your home. It doesnt matter if the branch circuits leaving the new sub have equipment ground or not.
3 wire feeders are no longer allowed to sub panels that are located in the same structure as the service equipment. They must be 4 wire (H-H-N-Grd). Ground will be isolated from the neutral in the sub. If you had an existing 3 wire feeder all the way to the new sub-panel you may have been given an exception to keep it "as existing" by the residential inspector.
As you have things now you cannot make a code compliant new branch circuit out of that square d 8 breaker sub-panel.

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Old 05-22-2007, 11:05 AM   #8
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Stubbie.....
Suspicions confirmed.....when I pulled the breakers on the old panel and did not see two hots and instead the jumper I had that sinking feeling....I want to do this right.....so I will see if I can find an electrician who can homerun a four wire line to the new panel.....you are right it is crap and what is really annoying was the short cut of an electrician to splice into the existing run....Much apprecite your assistance....!!
Thanks,
Rick
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Old 05-22-2007, 04:48 PM   #9
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Hi Rick


First I'm sorry about being so blunt but I dont know how else to explain your situation. You could keep a 120 volt feed to that sub-panel but nothing about it would be right. The circuits will work but it wont be the safest thing on the planet and it will be confusing as heck to anyone who isn't familiar with what they are dealing with. The whole thing is just sub-standard and out dated.
Try not to be to upset with the installation as it was done. You see this type of thing in older homes and newer ones all the time. Be glad that you are making the effort to find out how to do this correctly. The people who came before you didn't. So don't dwell on the what was done in the past, solve the problem and move on. I cant see what you have there or the obstacles you must overcome to get that feeder ran to the sub. There is no way to explain what needs to be done, other than someone local is going to have to look at this and form a plan to get that feeder ran correctly. I have seen where things were so difficult that the feeder had to go outside into conduit then reenter the house close to where the sub was located. So it just depends on what the electrical contractor sees as the best method.

good Luck

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Old 05-23-2007, 11:43 AM   #10
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Stubbie.....
Didn't mean to dwell.....hope to have an estimate sometime today or tomorrow.....and you don't have to apologize for being blunt - I appreciate the honesty....I would rather have this done right than jerry rig the panel and have an unsafe condition....I do a lot of home repair work and nothing is ever straight forward - I feel for the contractors who run into this stuff every day.....! Just had the roof redone and the previous roofer had left a gaping hole under the shingles at the peak which the current roofer, who has been in the business for 25 years had never seen anything like it before......Anyway.....much appreciate your help with this -
Thanks,
Rick

PS The house is in otherwise excellent condition......
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Old 05-23-2007, 11:30 PM   #11
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Hello Rick

Just a figure of speech didn't mean anything by it. Give us an update when all is well with the project. BTW what kind of walls does the house have as far as the finished surface...ie.. drywall, plaster lathe etc..?

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Old 05-29-2007, 05:17 PM   #12
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Stubbie....
Walls are plaster but behind the plaster is not lathe but horizontal wallboard.....
I had an electrician friend of a friend come over and make some recommendations - because the sub panel only serves upstairs lighting 40A should be plenty.....so he suggested a run of 6/3 AL cable with new breaker - the one installed is a 50A......he suggested that I lay the cable and he will tie it in to the panels to save $$....so that is what I am doing - 28' is in place - now just need to fish the wall.....but to get to the wall space I had to remove two layers of sheet metal duct work to gain access - the first layer was easy - the second layer I had to use nips to cut it away - old home with heavy gauge sheet metal- still have to open a bit more - just time consuming.....so I am about to fish the wall - I think that I will have to open a hole in the wall to make it a lot easier....
He had also suggested that I could just run a #6 ground from panel to panel and also a #6 jumper across to energize the second bus and that would meet code....but since I have to run a cable anyway I thought that I should go ahead and run the 4 conductor wire - it is not that unwieldy......
Again thanks.....
Rick
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Old 05-30-2007, 10:06 PM   #13
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Stubbie....
Fished the wall....OMG what a project to drill through the floor up from the basement with a 12" extension because of the sheetmetal in the way and some arm cuts to prove it - (finding the right spot was a pain as the wall upstairs is curved - so measurements from three walls) and then to make sure I poured aome water on the one and only cable coming up which I had calculated to be on he oher side of a stud......anyway the cable is pulled through all the way - used some WD40 to help push from below....I will cut power to the panel and dress it all in tomorrow...all the branch circuits and the feeders...I have to tell you there are lots of repairs to the plenum panels and some work on the walls....oh well at least it is done correctly....is anything easy....?
Sincerely appeciate all your help with this project....
Rick
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Old 06-07-2007, 10:32 PM   #14
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Subpanel Upgrade


Stubbie....
New 40A breaker in the main and red/black/white/ground between the boxes....looks great....some small wall repairs.....but electrically 5 15A breakers are now in service in the sub and all outlets/lamps work.....really appreciate your help with this.....
Thanks again.....
Rick
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Old 06-07-2007, 11:09 PM   #15
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Hi Rick

Sorry it's been a while since I checked here at this forum....beeeen busy of late.

You did absoultely the right thing with running a new cable. A 6/3 Grd cable is just fine. Being aluminum it was probably an SER cable and that is great. This cable will have an ampacity of 50 amps. A 40 amp breaker is good for your needs.

Some things to double check.......

You need to use an anti-oxident paste on the stripped ends of the aluminum cable before inserting in the lugs of the breakers or lugs. This prevents corrosion when the al gets exposed to the air.

The ground wire of the feeder cable and the branch circuit grounds will not go with the white wires at the sub-panel they will land on their own seperate ground bar that is bonded to the metal of the sub-panel. The neutral bar will take all the white wires. This is the one on the insulated stand-offs and always comes factory installed. Do not install the bonding means (probably a green screw) that came with the sub-panel. You do not want the neutral bar bonded to the metal of the sub-panel only the ground bar is bonded to the panel metal... so if a bonding means was installed when you bought the panel remove it. Square d uses a green screw other manufacturers may differ in design and the bonding means may be a metal strap or jumper.

You do not want the sub panel metal bonded to the neutral bar as this will allow the neutral current from the branch circuits to split and flow on the feeder ground wire and the feeder neutral wire.

At the main panel you want the neutral bar bonded to the metal of the main panel, this is the only place you want this done.

Congragulations on a job well done, it wasnt easy but it is done right and you can sleep knowing you dont have a sub-standard installation of that sub-panel.

Stubbie


Last edited by Stubbie; 06-07-2007 at 11:12 PM.
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