Adding a subpanel in a really old house

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  #1  
Old 12-10-10, 07:39 AM
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Question Adding a subpanel in a really old house

Hello,

I purchased a rental and was going to add an overhead service drop from the house to a detached garage but this thing is quickly turning into a bigger and bigger project!

I was going to add a service mast, weather head to both ends until I noticed that the breakers in the main panel with the two meters supplying both units looked a little funny. One breaker is 40 amps and has two thick wires feeding a subpanel in what I will refer to as the "remote" unit. The other breaker which is 60 amps has 4 sets of smaller gauge wires shoved inside its terminals presumably feeding the branch circuits in this, the immediate unit because I cannot locate a subpanel in this unit.

The right thing to do is is to add a subpanel which I thought would be easy enough to do by pulling the wires off the breaker and pulling into the room immediately behind the existing main panel. The problem is that the main panel is directly behind a closet. So even if I pull the wires into the house, I can only pull them into the closet. The house was built in the 30s I believe and this bedroom and closet were and addition. Much of the wiring in the house is older and brittle but the wiring to this panel appears to be new which would be consistent with it being an addition. My questions are:
  • What is the easiest, quickest way to approach adding a subpanel that meets code?
  • Keep in mind that after installing this subpanel I still have to add the overhead to supply power to the garage for a garage door opener. (which was previously being powered by and overhead extension cord from the neighbor's!)

Thanks,
Jorge
 
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  #2  
Old 12-10-10, 08:24 AM
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Originally Posted by banterer View Post
One breaker is 40 amps and has two thick wires feeding...
What is the approximate age and make/model of these breakers and panel? Can you post a picture of it? Sometimes the very old stuff is not standard so it's hard to understand what's there without seeing it.

What is the easiest, quickest way to approach adding a subpanel that meets code?
With a very old service there usually isn't much you can do to modify it safely. Often the best course of action is to rip it out and install a new service. What size (amps) is the existing service? How many breakers are in the main panel and how many open slots are there?

Keep in mind that after installing this subpanel I still have to add the overhead to supply power to the garage for a garage door opener.
Are you set on overhead? Outbuildings are usually much better on an underground feeder. If you install a single circuit using 12-2g UF-B cable on a 20A GFCI breaker the trench only needs to be 12" deep. Whereas if you do the aerial you need 10' of ground clearance for undeveloped land or 12' of clearance for driveway/parking areas.
 
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Old 12-10-10, 08:56 AM
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Red face

Hi ibp and thanks.

I have images but I only see how to insert a url. I do not see how to attach images.

It is a Square D and it only has two slots for breakers, no additional. One is for one unit and the other for this unit.

I'd have to sawcut through about 20 feet of concrete to go underground, I figure overhead is faster/easier.

Jorge
 
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Old 12-10-10, 09:09 AM
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Old 12-10-10, 09:11 AM
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Yeah unfortunately they don't host images here, but you can upload to one of the free image hosts like photobucket, imageshack, flickr, etc. and post the url here.

The overhead makes more sense given all that concrete. Are the house and garage tall enough to get the 12' ground clearance? That means the attachment points will need to be about 14' up to get the right sag in the line.
 
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Old 12-10-10, 09:43 AM
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Pics

Ok here are links:






 
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