Feeders to 3-plex residense

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tbakelis

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Hi All,

I'm installing new 100 amp feeders on a 3-plex where a 400 Amp service has already been installed. The 3-plex is uniquie in that the three individual units don't share any walls. In other words it's like 3 tiny individual homes on same property.

So in order to get from the 400 Amp service (on unit 3) to the furthest unit (lets call it unit 1) there will need to be 2 trenches installed (one trench between unit 3 and 2 and another trench between unit 2 and 1).

My PVC conduit will be 18" deep between structures, and the houses are on a raised foundation. So my question is... am I allowed to drill an 1 1/2" hole through the foundation 18" down and send my PVC directly through so I can avoid installing 5 LB's??? I'd like to strap the PVC to the joists under the home and then just sweep down and through the holes drilled in the foundation and then so on.

This is in Cupertino California... I know I know... ask your jurisdiction. I was just wondering if anyone had some insight on this so I could avoid a trip down there at this moment.

Thanks!

Ted
 
I don't see any issue with the install however I prefer not to drill below grade because of possible water infiltration. If you do it then make sure you seal the hole well.

Are you sure 18" down is not going to land you in the footer?
 
Hi Dennis,

What's the footer? I've never actually drilled through foundation 18" below grade. Just trying to think if it would be an easier way of doing it than having to install all those LBs for 150' worth of wiring. If I had to seal the holes, what kind of product would be an appropriate one to use? I guess if I had to I would install all the LBs.

Hi Jumper,

There will be a new load center within each unit. At the main 400 Amp there are 4 disconnect breakers (3 units and 1 house meter)

Any other info would be great!

Thanks
 
How is the existing feeder running? Conduit or cable? If conduit why you not using the existing conduit?
 
existing conduit is too small to accomodate feeders going from 50 Amp to 100 Amps... and rotted out. It runs up and down in between units via LBs.
 
tbakelis said:
Hi Dennis,

What's the footer? I've never actually drilled through foundation 18" below grade. Just trying to think if it would be an easier way of doing it than having to install all those LBs for 150' worth of wiring. If I had to seal the holes, what kind of product would be an appropriate one to use? I guess if I had to I would install all the LBs.

Hi Jumper,

There will be a new load center within each unit. At the main 400 Amp there are 4 disconnect breakers (3 units and 1 house meter)

Any other info would be great!

Thanks
Click to expand...

The footer is the concrete structure built underground below the frost line that carries the load of the house. All the structure parts are ontop of the footer and it is usually about 18" or so wide.
 
ah, I see. No footers here in the Bay Area, California. No snow! Foundations are just dug out, rebar and then poured.
 
Another way to do this is to run a 200 amp feeder to building 2 and install an exterior panel. From there just LB down to just below the joist and pipe thru the crawl space to the other side and lb down into the ground. This keeps all holes above ground and you only have 2 lb's.
 
tbakelis said:
ah, I see. No footers here in the Bay Area, California. No snow! Foundations are just dug out, rebar and then poured.
Click to expand...

That is the footer-- foundation is what sits on the footer-- the foundation is often cinder block or some similar material
 
shoot, am I having a blond moment right now. Let me think about this... I think you are right Dennis. It may be 18" wide down there... hmm.
 
It is sounding more and more like I am going to have to use the LBs unless I want to purchase a very long 1 1/2" hammer drill bit!
 
It's just so much easier without all those LBs!!! If I did attempt to drill and it actually worked out. What would you guys recommend I seal the holes with?
 
You need a disconnecting means outside or directly inside of each building. You can't come into the building and run across the joists without first hitting a service disconnect.

Why not mount a surface mount disconnect or loadcenter then drop out into the floor with the feeder or branch circuits?
 
tbakelis said:
Can the disconnecting means be within the actually load center servicing that unit?
Click to expand...

Yes, but the loadcenter needs to be on the exterior or immediately inside the building. You need to limit the length of conductors on the line side of the disconnect within the building. If you ask a combo inspector they probably will not evne know the requirements. You need to follow the NEC and CEC. See below.

225.31 Disconnecting Means. Means shall be provided
for disconnecting all ungrounded conductors that supply or
pass through the building or structure.

225.32 Location. The disconnecting means shall be installed
either inside or outside of the building or structure
served or where the conductors pass through the building or
structure. The disconnecting means shall be at a readily
accessible location nearest the point of entrance of the conductors.
For the purposes of this section, the requirements
in 230.6 shall be utilized.
 
curt swartz said:
Yes, but the loadcenter needs to be on the exterior or immediately inside the building. You need to limit the length of conductors on the line side of the disconnect within the building. If you ask a combo inspector they probably will not evne know the requirements. You need to follow the NEC and CEC.
Click to expand...

This is why I suggest running a 200 amp feeder to building 2 and then feed building one from that panel. I would think it is cheaper than running 2 conduits with 2 runs of wires and having to have 2 disconnects.
 
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