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Discussion Starter · #1 ·
Hey there, I am wiring a 3 family in massachusetts, and I am not a wiz on residential wiring as I mainly do industrial and commercial. Anyways, my question is How far can my service entrance cable go between the meter disconnect and the panel. It is a 3 family, and I want to put the panels in their respective units, 1st,2nd and 3rd floor. The house panel would be installed in the basement.
 

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OK thats awesome to hear. I was going to use a 4 space meter bank with disconnects for each panel they're feeding. Does the cable need to be in conduit while running through the basement, and up the walls?
 

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If your plan calls for more than 500 foot runs, you may want to rethink the routing. The standard put up is 500' reels, I believe.
 

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Could any of you guys help me out with another question?

Ive done my service calculation for the units, and they will draw max 75 amps, but I know that isn't the case all of the time. Anyways, I figured each unit will have a 100 Amp panel, and for the House panel I was going to install a 60 panel for common areas and outdoor lighting and power. For the meter bank and service drop, do I add up the combined service calculations to get the wire size? or is there a specific calculation I need to use. I have looked endlessly at the code and cannot find the answer I'm looking for.
 

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Could any of you guys help me out with another question?

Ive done my service calculation for the units, and they will draw max 75 amps, but I know that isn't the case all of the time. Anyways, I figured each unit will have a 100 Amp panel, and for the House panel I was going to install a 60 panel for common areas and outdoor lighting and power. For the meter bank and service drop, do I add up the combined service calculations to get the wire size? or is there a specific calculation I need to use. I have looked endlessly at the code and cannot find the answer I'm looking for.
There's a couple ways to calculate multifamily loads. Art 220 allows you to apply demand factors to things like ranges, dryers, water heaters, and stuff like that. There's a table in there somewhere in 220 just for that purpose.

You want to make it real simple?? Think about this - what does the application of these demand factors get you? A little bit smaller conductor group in the riser to the weatherhead. If you added up all your individual demand loads, without the demand factors you could be permitted, you might just buy 20 feet of wire that is heavier than necessary. What a tragedy. See where I'm headed?

It's also unlikely that you'll get much savings using demand factors permitted for only three units anyhow. If you were doing 33, I'd say you definitely need to do that math. The cost savings could be substantial. Three units? Just add them up and be done with it.
 

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Hey there, I am wiring a 3 family in massachusetts, and I am not a wiz on residential wiring as I mainly do industrial and commercial. Anyways, my question is How far can my service entrance cable go between the meter disconnect and the panel. It is a 3 family, and I want to put the panels in their respective units, 1st,2nd and 3rd floor. The house panel would be installed in the basement.
I just want to make sure you understand this part due some meter socket do have bypass lever in there but for your situation it will not be a issue but if you have main breaker below the meter unit then the conductor or cable can be unlimited on distance.

as far for sizing the meter socket unit MDshunk got it on the spot.

but just pay attention to the meter busbar rating that can get ya if not aware of it especially if more than just two sockets like three or more sockets then ya have to watch the busbar rating.
 

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I heard some area they will required the load side of service conductors to be in either MC or in conduit.

I am sure some AHJ are pretty strict with multi family units.
They were going to have us sleeve SER with greenfield on one, we ended up going underground and around. Didn't want one tenant to be able to tap into the others power.
 

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It's not a problem here running SER in from the meter main. I've done it hundreds of times through one unit to feed another. Nothing but jacket and a PVC sleeve where it went through the CMU fire walls between units.

One thing you may have to watch out for is the 60c ampacity rating if you are in the walls with insulation.
 
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