Conduit Embed Question

[John in OH]

I'm planning to run a 150 amp underground feed from a remote meter to my new detached garage and need advice on how to install the 2" PVC conduit through the building's footer and slab. I'll hire an electrician later to do the electrical work, but I was hoping to get a PVC conduit embed in place prior to pouring any concrete.

Structure will have a 2' wide footer 1' thick. Centered on top of the footer will be 5 courses of 8" block. 2x8 sill plate on block with 2x6 stud framing. Nothing is built yet.

My original thought was to place the horizontal PVC and long radius sweep in the bottom of the footer excavation and bring the vertical portion up just on the inside of the 8" block. But this leaves the conduit inside the building wall and I guess I'll have to use an LB elbow to take the cable back inside the stud wall and then up again into the breaker box. This doesn't sound like a very "clean" installation, but there is no way the 2" PVC can be fitted up through the inside of 5 courses of block ... at least without the block in place.

View attachment Embed.pdf

Any better ideas???

 

[John in OH]

Let me try attaching that sketch again as a .jpeg ....

 

[mrb]

whats going to be on the outside end of the conduit? Are you using direct burial cable, or conduit? If you can do it without exceeding 360deg of bends use a pair of 45s to kick the conduit back into the stud cavity right above the sill plate.

dont forget your ufer ground (required) before the pour and has to be inspected (if youre permitting this)

another tip is to rotate the sweep to point it toward where the power is coming from instead of having it come straight out of the building -this saves on bends if using conduit.

 

[LIVELY]

i don't understand why you can't fit the conduit thru the center of the block wall??

the blocks can be laid around the conduit.

we lay around posts and pipes alot.

i would wrap the conduit in insulation of some kind so it does not completely bond to the concrete footing or blocks--it will have a little slippage that way.

 

[John in OH]

mrb .... I was going to let the electrician decide on conduit vs. direct burial. Obviously, I'd rather go with which ever is less expensive ... assuming performance is the same. What are your thoughts? For the conductors, would you recommend copper or is aluminum satisfactory?

I like the double 45 suggestion ... that will make a much neater installation.

What is a "ufer" ground?? Not familiar with that term.

 

[Aceman]

I'd run it right up through the block. The masons can cut around the conduit if necessary.

 

[mrb]

mrb .... I was going to let the electrician decide on conduit vs. direct burial. Obviously, I'd rather go with which ever is less expensive ... assuming performance is the same. What are your thoughts? For the conductors, would you recommend copper or is aluminum satisfactory?

I like the double 45 suggestion ... that will make a much neater installation.

What is a "ufer" ground?? Not familiar with that term.

search it, but basically if you have a footing with rebar in it, you HAVE to bond the rebar and thats your grounding electrode.

 

[John in OH]

mrb .... ah, yes ... the rebar ground. Yes, that is in the plan. The concrete guy will install that as he places the rebar in the footer excavation.

Lively & Aceman ... in the interest of keeping my question simple I see I made an error by not providing the complete picture of the masonry. The first two or three courses will be 8" block, the last courses that are above finish grade will be 4" block with brick facing. Sorry for not giving you an accurate description of the actual wall construction.

 

[Aceman]

In that case, you'll need to ask your masons if they can fit a 2" conduit through their 4" block.

 

[Stuart in MN]

How deep are your footings? In Minnesota, they're usually deeper than underground conduits so we don't have to worry about trying to run conduits through them (the conduit would go through the foundation wall, above the footing) but I imagine the frost line isn't nearly as deep where you live.

I assume you're trying to make the installation as neat as possible by hiding the conduit inside the wall, but it would probably be a lot simpler and easier to bring the conduit up on the outside of the building and then go through the wall above grade with the LB fitting.

 

[fefarms]

You'll need some very heavy wire for 150 amps. Figure 1/0 copper or 3/0 aluminum. I don't believe it will be possible to bend the wires tightly enough to make the back-to-back 90 degree turns to get inside the wall and then into the bottom of the panel. Most of us don't work with wire this heavy very frequently, and tend to underestimate just how stiff and bulky it can get.

I'm with Stuart. Bring the conduit up outside the building, top it with an SLB, then come into the back of the panel, not the bottom.

 

[VHF]

The first two or three courses will be 8" block, the last courses that are above finish grade will be 4" block with brick facing.

I would probably center it in the 8" block and let the masons work around it as the lay the 4" block and brick on the upper layers.

If you have 6" wall framing lined up with the outside edge of the foundation, the conduit should still come up within the wall stud cavity.

 

[John in OH]

How deep are your footings? In Minnesota, they're usually deeper than underground conduits so we don't have to worry about trying to run conduits through them (the conduit would go through the foundation wall, above the footing) but I imagine the frost line isn't nearly as deep where you live.

I assume you're trying to make the installation as neat as possible by hiding the conduit inside the wall, but it would probably be a lot simpler and easier to bring the conduit up on the outside of the building and then go through the wall above grade with the LB fitting.

Stuart - Ahh ... life is easier in eastern VA than the frozen North! County requires bottom of footer to be minimum 18 in. below grade! Essentially, you have to run the electrical line under the footer just to get the minimum county-required 18 in. electrical depth.

You'll need some very heavy wire for 150 amps. Figure 1/0 copper or 3/0 aluminum. I don't believe it will be possible to bend the wires tightly enough to make the back-to-back 90 degree turns to get inside the wall and then into the bottom of the panel. Most of us don't work with wire this heavy very frequently, and tend to underestimate just how stiff and bulky it can get.

I'm with Stuart. Bring the conduit up outside the building, top it with an SLB, then come into the back of the panel, not the bottom.

Fearms - At the last minute, the contractor and I decided to increase the main conduit from 2" to 2-1/2" just to address the concern you expressed.

Decided to stay with the original plan to install the riser on the inner face of the block rather than up through the block webbing or from the outside. Time will determine the wisdom (or lack of) this decision. If the double 45 bend or the SLB elbow approach doesn't work, most probably, I'll end up building a bump-out/cable chase on the inside face of the wall and mount the breaker box directly above the riser.

 

[Charles (in GA)]

Surface mount the panelboard and build a chase with a removable front cover, below and above the panelboard. This will make it easier to add circuits in the future.

Charles

 

[Aceman]

Surface mount the panelboard and build a chase with a removable front cover, below and above the panelboard. This will make it easier to add circuits in the future.

Charles

If the masons won't let you go up through the block, I'd say do a bumpout for the panel like Charles mentioned.