Sizing new power feed to small garage

[mike93lx]

I do mean SER. Lowes calls it "2-2-2-4 Aluminum SER Service Entrance Cable (By-the-Foot)" but maybe you know it as #2 SER or something else?

You're right, I was mistaken on the labeling, I'll correct my post.

 

[wyliesdiesels]

important correction here to make sure you don't get the wrong wire.

SER isn't labeled like that, so I think you mean MHF. They are different and the distinction is important since SER has specific limitations (like it can't be underground)

I do mean SER. Lowes calls it "2-2-2-4 Aluminum SER Service Entrance Cable (By-the-Foot)" but maybe you know it as #2 SER or something else?

EDIT: Can't staple MHF to the joists. I'm crossing the basement so underground really isn't an issue. Current sub uses the same SER I call out.

SEU and SER is typically labeled "AL(or CU) type SE cable style U (or R)"

 

[AntonLargiader]

I see where you got mixed up. In order to simplify the run to the garage, I decided I should essentially rewire the whole basement. Yes it's scope creep but in this case I embrace it; the basement is a wiring disaster and it's not very big. Once I have relocated the panel I can make the run to the garage and that is where we were talking about MHF. However, with the panel on the outside wall facing the garage I think I can just run the #6 TW that I already have, plus a ground, in conduit.

 

[wyliesdiesels]

I do mean SER. Lowes calls it "2-2-2-4 Aluminum SER Service Entrance Cable (By-the-Foot)" but maybe you know it as #2 SER or something else?

EDIT: Can't staple MHF to the joists. I'm crossing the basement so underground really isn't an issue. Current sub uses the same SER I call out.

And MHF must be in conduit when inside buildings...

 

[AntonLargiader]

SEU and SER is typically labeled "AL(or CU) type SE cable style U (or R)"

Yeah, but that's a mouthful. What do you call it in fewer than ten syllables?

 

[wyliesdiesels]

Yeah, but that's a mouthful. What do you call it in fewer than ten syllables?

yes it is

So i just say SER OR SEU...

 

[MikeF2316]

I'm back to planning the basement subpanel move as the first step. It looks like 2-2-2-4 AL SER (which is what serves the current sub) is still allowed to go to 90A if uninsulated, so I would do that. The SER would run across the unfinished basement between or under the joists (the 'under' part is running behind a wooden crossbeam to it's actually pretty well protected). Total length would be just under 40'. As for establishing that 90A is sufficient, I couldn't find a lot about sizing subpanels so I applied a few of the regular load calc techniques and came up with 62A:
- 8100 VA for garage. That's 6600W for an EVSE and 1500W for a block heater. That's worst case. Lights and outlets aren't going to be in use during the moments that the EVSE and block heater are drawing max current.
- 4050 VA for four 15A branch circuits. 3000 VA plus 35% of the other 3000.
- 2025 for the 15A 240V well pump circuit at 75%
- 675 for the other 25% of the well pump because it's the largest motor
- total 14,850 VA divided by 240 = 62 A.

So it looks like even at 90A I have some cushion even if my garage load calc is off. In reality the four branch circuits are very lightly loaded; they're just separated because they are diverse in nature.

Everything look good on the SER and the load?

What if you strike it rich and buy a Tesla? They have optional chargers that need a 90 amp circuit all to themselves!

Sorry, couldn't resist.

 

[AntonLargiader]

What if you strike it rich and buy a Tesla? They have optional chargers that need a 90 amp circuit all to themselves!

Sorry, couldn't resist.

In-laws have one (a few years old now) and the 50A circuit has been fine. I picked the 6600 number because that's what the Leaf draws and we may end up with one. Really I have no idea what we may end up with but I'm pretty sure it won't be a Tesla. . And if it is I will just wave the checkbook and tell someone to make a 90A circuit appear!

We spent a weekend in an i3 last summer, and have the use of a Volt half the time. We definitely like the EV thing.

 

[sberry]

You will need to add a main if this is going to 8 space panel.

 

[AntonLargiader]

You will need to add a main if this is going to 8 space panel.

At the garage, yes. I want that regardless, as a means of disconnecting, but my recent questions were about the sub in the house.

Still gathering info prior to pulling a permit for the work. But it looks like:

- 90A breaker in main panel to exposed 2-2-2-4 AL SER under joists to 100A MB panel across basement.

- 60A breaker in sub to #6 TW and #8 ground wires in 1" schedule 80 PVC conduit through house and garage walls, buried minimum 18" deep with LBs on outside walls, to 60~100A breaker (screwed down) in 8-stab Eaton panel in garage.

- two 8' ground rods at garage connected to breaker box and ground bar with ... ?

- re-distribute circuits in basement between panels as outlined. Run outlets and lights in garage to sub with protection below ceiling level. Exterior light over door. No breaker for the EVSE as we don't know what we will end up with.

- Subs have separate ground and neutral bars with unbonded enclosures.

 

[mike93lx]

- two 8' ground rods at garage connected to breaker box and ground bar with ... ?

From my research and feedback here, 6AWG bare, solid. use 5/8" rods and spread them at least 6' apart.

 

[AntonLargiader]

Got the permit yesterday. Sent an email to the inspectors asking confirmation on a few details and they confirmed that I do not need any additional protection on the SER for my situation, my panel location sounds OK and I should leave the trench ends and middle open for the inspection but complete everything else.

So, time to buy some stuff I guess. 100A MB panel, 40' SER, some conduit/elbows/LBs/*******, some breakers, #8 ground wire, another rod, exterior light for doorway, etc. And do some more digging.

 

[pattenp]

Got the permit yesterday. Sent an email to the inspectors asking confirmation on a few details and they confirmed that I do not need any additional protection on the SER for my situation, my panel location sounds OK and I should leave the trench ends and middle open for the inspection but complete everything else.

So, time to buy some stuff I guess. 100A MB panel, 40' SER, some conduit/elbows/LBs/*******, some breakers, #8 ground wire, another rod, exterior light for doorway, etc. And do some more digging.

If using #8 for the grounding electrode(rod) conductor it needs to be protected in conduit. #6 and larger if not exposed to physical damage does not need to be in conduit.

 

[AntonLargiader]

Getting the first round of supplies today. Going to place the panel. Is there any regulation on the height above grade where a conduit enters the house? I want the conduit to end in an LB that goes straight through the exterior masonry wall into the back of the panel. Right now that would be roughly 24~36" above grade.

 

[AntonLargiader]

Got the panel and SER, painted the wall, hung the panel, pulled the wire and connected it at the new panel with paste.



Now I need to work my way back to the main with cable clamps. Then I will probably feed the old sub with a 60A breaker while I connect the new sub to the 90A breaker. Then I'll migrate the circuits one by one as time permits.

When I install the service out to the garage, it will probably go out of the upper right knockout in the back of the panel.

 

[pattenp]

You should have used a NM clamp in the knockout for the SER. How close to the panel do you have the wire supported/secured?

 

[AntonLargiader]

The plastic bushing you see is threaded onto the bottom of an NM clamp. It's exactly the same as what I have on the existing subpanel.

The cable will be first secured about 6" above the panel, where it hits a joist. Then it will cross to the other side of that joist bay and head toward the main.

 

[wyliesdiesels]

did u remove the bonding screw on the neutral bar?

 

[AntonLargiader]

The bonding screw was never installed. The empty hole for it is immediately to the left of the neutral lug in the photo.

I do want to get another ground bar, and I need another retention screw for the first ground bar. FWIW a ground bar did not come with this kit but my work panel (Homeline, like this one) had an extra one lying in the bottom.

 

[AntonLargiader]

And Wylie thanks for pointing out in the other thread that I can't tape the black #6 I have for neutral. Small bummer that I can't re-use what I have but it'll only be 50' or so.

 

[AntonLargiader]

OK, borrowed a monster hammer drill and punched through the foundation for the 3/4" conduit. Also re-routed the SER in the basement to keep more of it in the crawl space rather than in the full-height part because I had an extra 8' or so. Next is to hook the 90A panel up to the main, and start migrating circuits.

Since the inspector will want to see the trench open, and it rains in the spring, laying in the conduit will be the last thing I do before calling in the inspection.

That conduit enters the 100A panel at the bottom. I plan on using the nearest breaker slot (bottom right) for it to reduce clutter. As far as I can tell there's a lot of personal preference, a tiny bit of theory regarding large breakers being closer to the feed, but nothing that actually says that I can't have that 50A breaker at the bottom and the others at the top.

FWIW the drill punched through the foundation like it was made of dirt. From the looks of the brown dust coming out, the 85 year old concrete wasn't a whole lot different than dirt.

 

[AntonLargiader]

Still chugging along. Only one circuit left in the old subpanel. Pulled 14-2 from the new sub to the box where that circuit spread out (it's for the basement lights and a few other things) and noticed that the other wires were 12-2. OK, pulled 12-2 to the box. Looking closer, the older stuff is 12g but the electricians a few years ago used 14-3 for the three-way switches and for the receps that split off. Arrgh. I'll probably replace all of the 12 with 14 to make the 3-way connections easier. The other stuff on that circuit is being split off anyway.

The old circuit is one of two remaining bits of BX in the basement. The other one goes to my computer's receptacle. Once I deal with those, I think everything will have modern grounding. Ummm... except maybe some wiring to the front door that is buried in stucco. Not going to dig that out yet, if that's the case.

EDIT: so is it legal to mix 12g and 14g wiring in one circuit?

 

[wyliesdiesels]

Yes but not a great idea. breaker must be 15a.

 

[Abeo]

Seems like you have things figured out...
my 2 cents: I oversized my conduit when running my 60 amp service so that I could easily pull 90 amp capable wires if I outgrew it (or if an EV appeared). Very little additional cost, and I do not want to dig that trench again.

 

[AntonLargiader]

The old sub is gone and the circuits are nearly all sorted out. I'm cleaning up some stapling and then will move on to phase 2, the feed to the garage. I'm comfortable with the 3/4" conduit and #6 wire; that will give me enough for any EVSE that I might reasonably use. It's a short distance and if I need to upgrade that there will be other work involved anyway (like building a new garage).

So, two questions:

1) When did code prohibit phase-taping #6 and smaller? THWN is expensive right now and I'd rather use the TW that I have. We are on the 2011 NEC.

2) What is the minimum circuitry that I need in the garage? One car, open in front (no garage door), one man door. I will have two receptacle outlets (one under the panel and one in front of the car) and lights on the ceiling and over the man door. Is that enough to meet code? It has exposed studs and I am thinking of using MC.

 

[AntonLargiader]

Talked to the inspector today to clarify the AFCI issue, just to make sure I didn't get blindsided during the inspection. He considers any circuit I have moved to a different panel location to be "modified/extended" and therefore subject to being brought up to code. However, while Virginia is on the 2011 code which requires AFCI in most living spaces, it has modified the code to restrict AFCI requirements to bedrooms only, like (I think) 2008 and earlier had. Not a big deal; I will be adding AFCI over time anyway but it sounds like I am already nearly compliant. I should add one more DF breaker to the upstairs lights circuit that has one or two receptacles on it.

As for my earlier questions: 1) I think it was 2008 that restricted taping, but THWN isn't as expensive as I thought so it's not a big deal. And 2) I don't really care as I am installing lights and outlets regardless.

 

[AntonLargiader]

This project isn't dead. Reading through it I realize I've not been very clear about what subpanel is what.

In my basement, I removed the old 90A subpanel and installed a new one at the other end of the basement, pulling a lot of circuits over to it. That I think was covered in a different thread.

Last weekend I realized I needed to finish the trench to the garage. I had dug it - mostly - a year or two ago and never got it fully dug out, and had cried uncle and left some UF in it to power the new garage panel with one leg. So over the weekend I pulled out the UF, dug the trench to full depth, and installed the 3/4" PVC conduit. I had bought new white #6 and green #8, and planned to use the old black #6 TW I had for the hots, However, that old TW insulation is much thicker than the newer stuff, and the cable is stiffer. It slid OK down a straight section of conduit but I didn't want to risk it with the curves, so I bought new black THWN (thinner than the new white THWN for some reason) and pulled that through pretty easily. Hooked it all up and we're good, except I need to:

1. install a tie-down for the backfed breaker in the garage
2. drive the ground rods and connect the GEC.
3. pull a few inches of extra wire through in the basement and install a conduit bushing.

The required lights and recep are in and functioning. When the porch construction is complete, I will get the garage inspected at the same time. The center of the trench has been filled in but I need to leave the ends open.

The garage sub. Yeah, dark I know.


Conduit at the garage


Conduit at the house Needed a dogleg to go around the footer.


In the basement sub. Lower right. Will get a bushing when I find it.