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apologies for another thread on ufers and feeders...

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billconner

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...but got frustrated trying to search for simple answers.

1. Rubble trench foundation (gravel from just below grade to 48" frost line with footing on top) - can I use the (20' steel) rebar in it for a ufer? The shallowness was what made me wonder.

2. 200 amp main panel is on opposite side of house from under construction detached garage, which is about 10' from house. Long run through house, short run to garage. I'm wanting a wiring method that doesn't require conduit through house but can be in conduit from house to garage. Picturing a pulling elbow coming out of house, down to underground, then 10' and stub up through new wall. Was thinking 60 amp but considering 100 - just storage, not designed to ever be heated, but suspect ev chargers some day.
 
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mike93lx

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Not sure on #1, but I think I would just drive 2 rods than add rebar solely for this purpose. Or is the rebar there anyway?

On #2, you will have to transition between wires. There isn't an option for wire of that size that can be outside of conduit plus be able to go underground. I think the best combo is aluminum SER in the house and either aluminum xhhw or mhf outside. I'd pick xhhw, personally.

How long is the total run? #2 is a sweet spot for wire size that can get you up to 90a (distance-limited) for not a lot of money. Getting to 100 is a size step in wire for little gain.
 
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billconner

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thank you. Less than 100' total panel to sub panel.

There will be rebar in concrete - 2 runs of 4 in 120' of footer - so that seemed easy.

Seriously considering 60 amp sub panel.
 
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mike93lx

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billconner said:
thank you. Less than 100' total panel to sub panel.

There will be rebar in concrete - 2 runs of 4 in 120' of footer - so that seemed easy.

Seriously considering 60 amp sub panel.
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Put in a bigger sub. At least 100a, if nothing more than for the spaces. Make sure you do a main breaker panel

I'd still run #2 and you can use a 60a breaker to feed it, if you want. You won't save a lot with downsizing the wire and that is the hard part of the work anyway.
 
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larry4406

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On the UFER, at least in my neck of the woods, rebar is 20’ max length.

So how does one embed 20’ continuous yet then turn up and connect (bond) while still continuous to the rebar making the bond (acorn nut) accessible? Answer can’t be continuous 20’ in the footer unless you weld the rebar or get bars longer than 20’.

One county I build in requires #4 copper 20’ continuous in the footing, forbids use of rebar for this reason, and then copper continues to either the panel or a junction location with mud ring for access.

Another county says that rebar’s overlapped 5 diameters and wire tied suffice as the splice. 🤷‍♂️ 😳
 
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wyliesdiesels

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pattenp said:
Actually PVC jacketed MC cable can be. The PVC jacketed MC cable can also be direct buried. It probably cost an arm and a leg.
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that has never been available anywhere out here and i have never heard of anyone being able to find it or use it in all of my contractor groups on facebook. plus the price is astronomical...
 
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mcbane

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larry4406 said:
On the UFER, at least in my neck of the woods, rebar is 20’ max length.

So how does one embed 20’ continuous yet then turn up and connect (bond) while still continuous to the rebar making the bond (acorn nut) accessible? Answer can’t be continuous 20’ in the footer unless you weld the rebar or get bars longer than 20’.

One county I build in requires #4 copper 20’ continuous in the footing, forbids use of rebar for this reason, and then copper continues to either the panel or a junction location with mud ring for access.

Another county says that rebar’s overlapped 5 diameters and wire tied suffice as the splice. 🤷‍♂️ 😳
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In my area the connection to the rebar doesn’t need to remain accessible. It just has to be made with a properly rated clamp and needs to be inspected before the concrete is placed.

I never understood the exposed connection requirement. Sure, you can verify that the copper cable goes to a rebar but once the concrete is poured how do you know that piece of rebar is longer than a few inches?
 
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mcbane said:
In my area the connection to the rebar doesn’t need to remain accessible. It just has to be made with a properly rated clamp and needs to be inspected before the concrete is placed.

I never understood the exposed connection requirement. Sure, you can verify that the copper cable goes to a rebar but once the concrete is poured how do you know that piece of rebar is longer than a few inches?
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I would expect the AHJ would inspect the bond before pouring. It's how the bond is being handled for my pool.
 
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larry4406

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Fairfax County VA considers the UFER bond a junction and it must remain accessible. So we use their 5 diameter splice rule and wire ties. Then a mud ring if the turned up bar is in a finished space.

Montgomery County MD requires the continuous #4 copper wire tied to the footing rebar for 20’ then turned up to the panel where the bond is made (no junction). I like this method and is what I did on my barn project.
 
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billconner

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I am confused that I saw the MC with PVC and it looked less than 4 pc of thhn and required nothing else. In the end I'll have to rely on inspector - who is a good guy - just wanted to mak a feasible proposal.

Since I'm trying to get out of this very inexpensively - in the $15,000 to 18,000 range for 28 x 32 - I may look at other options. I have an existing 50 amp sub panel and feed that will be abandoned - not 30' from planned new panel - so may try to reuse that feed, or at least the conduit. At the end of the day, I'd be fine with 2 or 3 - 20 amp circuits for lights and openers until we had an ev - not a certainty past 70.

Seems like clamping a bare #4 to rebar in footer below planned panel is a logical proposal.

I appreciate all the help!
 
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billconner said:
I am confused that I saw the MC with PVC and it looked less than 4 pc of thhn and required nothing else. In the end I'll have to rely on inspector - who is a good guy - just wanted to mak a feasible proposal.

Since I'm trying to get out of this very inexpensively - in the $15,000 to 18,000 range for 28 x 32 - I may look at other options. I have an existing 50 amp sub panel and feed that will be abandoned - not 30' from planned new panel - so may try to reuse that feed, or at least the conduit. At the end of the day, I'd be fine with 2 or 3 - 20 amp circuits for lights and openers until we had an ev - not a certainty past 70.

Seems like clamping a bare #4 to rebar in footer below planned panel is a logical proposal.

I appreciate all the help!
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The clamp needs to be listed for the purpose, which is why a upturned piece of rebar works as a connection point because not easy to find a listed clamp, and certainly not at a big box store.
 
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billconner

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Sorry to be dense but I don't see what turning rebar up does for me in terms of a clamp. I can get fast inspection and/or he'll say ok to a photo. I have a pretty good full service electrical supply down the block, so pretty sure they have or can get it.
 
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Norcal

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billconner said:
Sorry to be dense but I don't see what turning rebar up does for me in terms of a clamp. I can get fast inspection and/or he'll say ok to a photo. I have a pretty good full service electrical supply down the block, so pretty sure they have or can get it.
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It needs to be listed for use in poured concrete.
 
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mcbane

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Norcal said:
It needs to be listed for use in poured concrete.
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My inspector said that any "DB" stamped ground clamp is good for concrete encased, but I never saw any reference that said a listing for direct burial is directly transferable to concrete-encased applications. Is there in fact a separate listing requirement for buried in poured concrete?
 
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billconner

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For ufer here, inspector wants 2 acorn style clamps on rebar 10' apart with typical bare no. 4 stranded copper. Another local twist, but clear.

For sub panel feeder (60 amp) thinking SER from main panel - 6-6-6-6 aluminum - to a junction box on house wall nearest new garage. I thought about UF from there to panel in garage but instead I think I'll use 1" galvanized rigid and individual conductors - for shallower depth (6" vs 24") - and I've done that before, and haven't used direct burial cables before. Seems like if I stick to all stranded no. 6 I'll have no problems. Seem legal, near least material cost, and logical?

I'd like to mount the junction box (NEMA 3R ?) on exterior wall sheathing but not sure that keeps SER "interior". Just seemed neat to drop conduit vertically, 90, horizontal, 90 up, panel. And I'd rather not have a panel cover on interior wall there.
 
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mike93lx

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Ser doesn't need to be interior. It just can't be underground.

It's used in exterior applications all the time. Lots of houses in New England have it running down the exterior wall from utility connection into the meter box
 
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billconner

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So, for neatness, I can mount box on exterior just above sill plate and bring SER into it, before transitioning to some aluminum conductor in conduit? Anything less expensive than SER for 220 - 60 amp from panel across house? Seemed to be in the buck fifty range per foot.
 
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mike93lx

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billconner said:
So, for neatness, I can mount box on exterior just above sill plate and bring SER into it, before transitioning to some aluminum conductor in conduit? Anything less expensive than SER for 220 - 60 amp from panel across house? Seemed to be in the buck fifty range per foot.
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Yes on the first question.

On the second, I am not aware of any cheaper option. Either ser or conduit and xhhw
 
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billconner

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2 Related questions:

It seems stranded aluminum does not present any particular problem as long as the devices it connects to say ok for aluminum. Is that correct? Any special precautions? My first time with aluminum.

Second. I thought I would put a 60 amp breaker in existing panel and get a mains lug sub panel. I get no bond between ground and netural. But I was a little perplexed by existing main and sub panel - both 200 amp main breakers. I'll pull the cover off the main but looks like existing 200 amp sub must just be fed off main panel buss. Just different from what I'm use to. I haven't tripped main panel breaker - too much stuff to reset - but would guess - hope - it kills sub panel. Does that make sense?
 
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wyliesdiesels

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billconner said:
2 Related questions:

It seems stranded aluminum does not present any particular problem as long as the devices it connects to say ok for aluminum. Is that correct? Any special precautions? My first time with aluminum.

Second. I thought I would put a 60 amp breaker in existing panel and get a mains lug sub panel. I get no bond between ground and netural. But I was a little perplexed by existing main and sub panel - both 200 amp main breakers. I'll pull the cover off the main but looks like existing 200 amp sub must just be fed off main panel buss. Just different from what I'm use to. I haven't tripped main panel breaker - too much stuff to reset - but would guess - hope - it kills sub panel. Does that make sense?
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If this new subpanel is in a detached building and will have more than six breaker handles then you’ll need a main disconnect in it. I would not buy a main lig only subpanel in that case
 
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