HPWC install: 90 degree bend in 6/3 THHN?

ElectricTundra · Mar 6, 2015

I have a couple of concerns with the way electrical guys are installing my HPWC.

- The 6/3 feeder (THHN?) is bent at a very sharp angle in the wall. When I was younger I was taught that a bend should generally be fairly wide and never less than 4 times the width of the cable and that really tight bends can result in a hotspot and potential fire. This is about 1 or 2 times the width of the cable. It's in a 2x4 wall so about 3.5" of space which is tight.

- None of the strain reliefs had enough thread depth to make it through the mounting panel and the charger itself so they just used a bushing. OK?

I don't want to make an issue out of something that isn't an issue.

Thanks,

wycolo · Mar 6, 2015

Photo or it didn't happen. :smile:
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ElectricTundra · Mar 6, 2015

wycolo said:
Photo or it didn't happen. :smile:
--

D***. Tough group. Had to drill a hole in a perfectly good wall, find some wire, bend it and stomp on it, drive to the hardware store to get a bushing since all I have on hand are clamps, get the entire rig to sit in the wall, get a pic, and post it. Sheesh

I was trying to add the pic while you were posting and somehow ended up creating a new thread and can't find the delete for the dupe thread anywhere. :cursing:

FlasherZ · Mar 6, 2015

NEC specs are no less than 5 times the diameter of the cable.

That appears to be NM-B cable, which means the entire cable assembly diameter must be considered instead of individual wires. That sharp 90" that I think I see is a no-no with NM-B cable. You can legally make a 90 degree turn work in a wall but you pretty much have to bring in the cable at the far back side of the stud and roll it in slowly. Of course, it's unclear how he's going to bring it in - if he uses an NM-to-rigid connector with some PVC to feed the HPWC, then he can consider the diameter of the wires instead of the cable unit.

It's going to depend upon how he plans to terminate it.

llavalle · Mar 6, 2015

It's the reason why I decided against running the wire behind the HWPC. I came in from the left side.. and even doing that was a bit a of a mess inside : the electrician had to loop the wires to make a large enough radius for the wires. Picture incoming...

edit : picture

I have 2/0 AWG Aluminium feeding my disconnect and 3 AWG Copper wire to the HPWC.

ElectricTundra · Mar 6, 2015

FlasherZ said:
It's going to depend upon how he plans to terminate it.

Thanks for the info. He's coming in the back of the HPWC via that non strain relief bushing. Should he be able to make this work in a 2x4 wall or does he need to come in the side?

FlasherZ · Mar 6, 2015

ElectricTundra said:
Thanks for the info. He's coming in the back of the HPWC via that non strain relief bushing. Should he be able to make this work in a 2x4 wall or does he need to come in the side?

In my opinion, it's not the best job in the world but I think he'll be able to make it work. First, whlie it works as a bushing, that's a PVC conduit connector for boxes; it's not really intended for that, but it'll work. The 6/3 I use is .65 in, so bend diameter is going to be 3.25" radius, which can fit within a 2x4 width just barely, if the cable is pushed up against the back side of the 2x4 wall. I think an inspector would frown at it, but may conclude it's legal. The cable doesn't appear to be attached to framing members - but that's legal in old-work as long as it's attached at the top of the wall. There's no support for that cable in that PVC connector (no clamp), so the entire cable's weight is only supported at the top of the wall.

It's the fastest / easiest way to do it without opening the wall a bit more (and subsequently patching it).

Cottonwood · Mar 6, 2015

llavalle said:
It's the reason why I decided against running the wire behind the HWPC. I came in from the left side.. and even doing that was a bit a of a mess inside : the electrician had to loop the wires to make a large enough radius for the wires. Picture incoming...

edit : picture

I have 2/0 AWG Aluminium feeding my disconnect and 3 AWG Copper wire to the HPWC.
View attachment 74188

Nice install.

I like the 270˚ turn inside the HPWC for a larger radius on the #3 wire, and great using the disconnect switch to transition from the 2/0 AL to the #3 CU.

I assume that the AL ground wire did get connected later.

llavalle · Mar 6, 2015

Cottonwood said:
I assume that the AL ground wire did get connected later.

Yep, I took that picture during the installation, the ground wire did get connected

The 2/0 AL wire was his idea (the electrician). I had about 65' to do, it was cheaper that way... and in any cases, here in Quebec, Canada, you're required to get a lockable disconnect switch in the same room. Most of the time, they pass inspection by putting a subpanel in the garage (which I did) but since a breaker is not lockable, it's not 100% safe.

Btw, I realize that 2/0 is overkill for 100amp (1AWG is fine) but we bought that for feeding my subpanel at 125A. It was easier to just buy 10' more to go from the subpanel to the disconnect switch.

There is close to 20KW passing in there, better be safe!

Now if that disconnect was smaller... At the Service Center, they have these cool rotating switch but they're rated "4X" (you can spray them with a hose) and are worth $500+ a piece (hubbell hblds10ac)

http://sigma.octopart.com/29790707/image/Hubbell-Wiring-Device-Kellems-HBLDS10AC.jpg

ElectricTundra · Mar 6, 2015

It is old work so you're right that nothing is supporting the cable in the wall. With that kink that he currently has in it, should I get him to pull a new one (I don't think he's got enough slack in the current cable to cut it off) or leave it as is? Dangerous as is?

wycolo · Mar 7, 2015

Having seen llavalle's, now I want one! - Lockable Disconnect Switch. KiloWatt thieves or no KiloWatt thieves, every HPWC deserves this treatment. Nice!!

And every EVSE as well.
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FlasherZ · Mar 9, 2015

ElectricTundra said:
It is old work so you're right that nothing is supporting the cable in the wall. With that kink that he currently has in it, should I get him to pull a new one (I don't think he's got enough slack in the current cable to cut it off) or leave it as is? Dangerous as is?

It's hard to say. Give what I see of slack, I'm not sure how he's going to get it to connect into the HPWC's terminals with that short cable and leave anything to work with.

(That bend actually looks like the "end bend" in Romex spools...)

ElectricTundra · Mar 9, 2015

FlasherZ said:
It's hard to say. Give what I see of slack, I'm not sure how he's going to get it to connect into the HPWC's terminals with that short cable and leave anything to work with.

(That bend actually looks like the "end bend" in Romex spools...)

It does look like that and about as sharp of a bend. But it's off the middle of a spool. He did have it connected to the HPWC so it works mechanically.

DMC-Orangeville · Mar 9, 2015

Btw said:
Your watts loss and voltage drop will be much better using a larger cable. Aluminium (NUAL in your case, to be exact) is lighter and less expensive than copper. BUT - make sure that the switch is dual rated for either copper or aluminium. In Canada, you must also use antioxidant past on the aluminium connections (Not code in USA, but a good idea)....

PS: I have my charger set on 48 amps. The disconnect commonly used in Ontario is a "spa panel" 50 amp switch. Very inexpensive, and in stock at most wholesalers.

- - - Updated - - -

Noob

llavalle said:

Btw, I realize that 2/0 is overkill for 100amp (1AWG is fine) but we bought that for feeding my subpanel at 125A. It was easier to just buy 10' more to go from the subpanel to the disconnect switch.

Click to expand...

llavalle · Mar 10, 2015

DMC-Orangeville said:
BUT - make sure that the switch is dual rated for either copper or aluminium. In Canada, you must also use antioxidant past on the aluminium connections (Not code in USA, but a good idea)....

Yep, the breaker in the main panel, the lugs in the sub panel, the breaker in the subpanel and the disconnect are all rated CU/AL. As for the paste, I'm pretty sure the Canadian code only requires it if you join copper and aluminium or if using stranded aluminium wires - article 12-118(2)

wk057 · Mar 10, 2015

There are bend radius rules in the NEC, and as FlasherZ mentioned would be tight in a 2x4 studded wall and potentially unsafe (edge would be near the drywall on the opposite side and subject to potential penetration by a nail from the other side). I decided not to feed my HPWC from the back for many reasons, bend radius being a main one.

That said, the bend in your photo is definitely not large enough to possibly be the 3.25" radius required by the NEC, almost for sure. Whether that makes it unsafe or not, I generally side with the code on these things. However.... I've seen much worse and doubt you'll have a problem.

Also, I haven't seen it mentioned here, but keep in mind that with the 6/3 NM cable being used here you can only run the HPWC at 40A from a 50A breaker and *must* set the DIP switches inside accordingly to prevent over-current. I'm sure you're aware, but just in case your electrician has for some reason said otherwise I figure I'd mention.

DMC-Orangeville · Mar 10, 2015

llavalle said:
I'm pretty sure the Canadian code only requires it if you join copper and aluminium or if using stranded aluminium wires - article 12-118(2)

Yes, and the cable in the picture is stranded (I used to work for Alcan Cable, the manufacturer of that wire). Most cable larger than 10 AWG is stranded - to ease in bending, pulling and terminating. The paste just insures a clean connection, aluminium oxide is non-conductive. BTW, nice to see you looked up the CEC. I don't have my code book here, but that's basically what it says......

llavalle · Mar 10, 2015

DMC-Orangeville said:
Yes, and the cable in the picture is stranded.

Correct, I just looked at a left over cable. I'll check if the electrician installed the paste. Good catch.

Edit : and thanks!

brucet999 · Mar 26, 2015

ElectricTundra said:
I have a couple of concerns with the way electrical guys are installing my HPWC.

- The 6/3 feeder (THHN?) is bent at a very sharp angle in the wall. When I was younger I was taught that a bend should generally be fairly wide and never less than 4 times the width of the cable and that really tight bends can result in a hotspot and potential fire. This is about 1 or 2 times the width of the cable. It's in a 2x4 wall so about 3.5" of space which is tight.

- None of the strain reliefs had enough thread depth to make it through the mounting panel and the charger itself so they just used a bushing. OK?

I don't want to make an issue out of something that isn't an issue.

View attachment 74164
Thanks,

Did he cut off the ground wire?

llavalle · Mar 27, 2015

Cottonwood said:
I like the 270˚ turn inside the HPWC for a larger radius on the #3 wire, and great using the disconnect switch to transition from the 2/0 AL to the #3 CU.

Well well well... Turns out the 270 bend was not a gread idea. The red wire (mine) was pinching the small purple signal wire against the exposed part of the 240V cable that gets to the car.

The Self test ran fine but closing the cover pinched the wire. Plugging the car in (got my car a few days ago) resulted in a fault in the dashboard and red-right : "Cable Fault, check charger manual".

Now what I did after that is what you should not do : I decided to run a self-test on the HPWC. When the self-test closed the contactor, it shorted the circuit board and poof! Circuit board is burned and I needed a new HPWC.

This is clearly not Tesla's fault (my installer is responsible for that) but I do find the routing of the 2 small signal wires to be a bit "at risk". We re-used the loops in my new HPWC but we re-routed the signal wires AWAY from the exposed part of the 240V wires.

Any one needs a HPWC with a blown PCB ?

HPWC install: 90 degree bend in 6/3 THHN?

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