Author Topic: Need Help w/a Subpanel Install  (Read 1084 times)

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Offline flybynite

  • Posts: 12
Need Help w/a Subpanel Install
« on: April 09, 2019, 11:04 PM »
I am in the process of installing a 125A sub panel in my garage to run a jointer/TS/planer and charge an EV and was hoping some experts could help me iron out the nuts and bolts!

The distance from the main panel (200A) to the garage is roughly 70 feet with half of it in a basement, part of it in a crawl space, and the rest in in a subterranean conduit to the garage. 

My plan is to use (per NEC):

2/0 AWG XHHW for the 2 hot lines and neutral and then 6 AWG.  The subpanel itself will be earth grounded via rods.

The car and tools are obviously power hungry, but my house loads are not high (natural gas furnace/dryer/stove/hot water heater).  Besides, I would never be charging the car, and jointing/ripping/planing at the same time!

Anyone have any recommendations/advice to offer?  Thanks!

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Offline jonnyrocket

  • Posts: 24
Re: Need Help w/a Subpanel Install
« Reply #1 on: April 10, 2019, 12:57 PM »
You didn’t mention, but I assume that your 2/0 wire is aluminum? And I think you were typing this out but had a typo so I will just state that you need 4 conductors.  One for each of the legs, one for neutral and one for ground. Typically designated  as SER type cable if you are buying this in cable type, or you can use individual conductors, but those will require conduit the entire distance, whereas the cable will only require conduit underground as long as the other parts are covered by wallboard.

Again, i think you already know this, but i will say it. You need both the Ground conductor from the main panel, and local ground rods (usually just one ground rod is required at a separate building).

I’m not an expert but I have a few years experience wiring houses and small commercial spaces. So don’t take my advice as final. I always recommend that you pull a local permit and talk to your inspector before you do the work. He will help point out any local codes and requirements that may be specific to your county/city. It’s always better to make them a partner in your project instead of someone that could ruin your project.

If you have any other specific questions, post them here.

« Last Edit: April 10, 2019, 01:17 PM by jonnyrocket »

Offline flybynite

  • Posts: 12
Re: Need Help w/a Subpanel Install
« Reply #2 on: April 10, 2019, 04:27 PM »
You didn’t mention, but I assume that your 2/0 wire is aluminum? And I think you were typing this out but had a typo so I will just state that you need 4 conductors.  One for each of the legs, one for neutral and one for ground. Typically designated as SER type cable if you are buying this in cable type, or you can use individual conductors, but those will require conduit the entire distance, whereas the cable will only require conduit underground as long as the other parts are covered by wallboard.

Again, i think you already know this, but i will say it. You need both the Ground conductor from the main panel, and local ground rods (usually just one ground rod is required at a separate building).

I’m not an expert but I have a few years experience wiring houses and small commercial spaces. So don’t take my advice as final. I always recommend that you pull a local permit and talk to your inspector before you do the work. He will help point out any local codes and requirements that may be specific to your county/city. It’s always better to make them a partner in your project instead of someone that could ruin your project.

If you have any other specific questions, post them here.

Apologies, but you are correct: I plan to use 2/0 aluminum for the 2 hot and 1 neutral because of the lower cost, increased flexibility of the cable, and the resistance to moisture of the cross-linked polyethylene XHHW cable sheathing compared to THHN.  I plan to use 6 AWG for the ground, and plan to run a ground from the main panel to the sub panel in addition to the two earth ground rods.  I had planned on using individual conductors to make routing/pulling easier in confined spaces, and had planned on using conduit the full length of the run in the crawl space/underground.  Would I need conduit for individual conductors that are routed through floor joists?  It might be difficult to get conduit in there...

Will it be difficult to fit 2/0 leads into a 125 amp breaker?

Thanks!  [big grin] 8)

Offline rvieceli

  • Posts: 983
Re: Need Help w/a Subpanel Install
« Reply #3 on: April 10, 2019, 04:47 PM »
@flybynite yes individual conductors are required to be in conduit all the way.

Ron

Offline jonnyrocket

  • Posts: 24
Re: Need Help w/a Subpanel Install
« Reply #4 on: April 10, 2019, 09:09 PM »
A heads up, imif you were using #6 for the GND conductor to the GND rod, that’s fine.  But the GND wire between the sub panel and main panel needs to be sized for a 125A circuit. So it will need to be larger than #6. I.e for Aluminum it would need to be a number 1/0 and for copper, a #2.  This is where using the SER cable for the run between the two makes it easy. Note that SER has four conductora while SE only has 3. If you can’t find SER at the local Home Depot etc, the local electrical supply house will have it.

As to the question about getting the wire in the breaker, 2/0 is big wire and will likely fit, but always check first. Some are easier than others.  What brand is your main panel?

Offline DeformedTree

  • Posts: 467
Re: Need Help w/a Subpanel Install
« Reply #5 on: April 10, 2019, 10:17 PM »
I'm curious on your panel in your house to feed this.  I'm not aware of any brand that has anything more than a 100A breaker to feed a panel, thus why sub-panels tend to be 100A.

Any breaker rated for the amperage will accept cable size you need (wouldn't make sense otherwise).

Offline flybynite

  • Posts: 12
Re: Need Help w/a Subpanel Install
« Reply #6 on: April 10, 2019, 11:42 PM »
A heads up, imif you were using #6 for the GND conductor to the GND rod, that’s fine.  But the GND wire between the sub panel and main panel needs to be sized for a 125A circuit. So it will need to be larger than #6. I.e for Aluminum it would need to be a number 1/0 and for copper, a #2.  This is where using the SER cable for the run between the two makes it easy. Note that SER has four conductora while SE only has 3. If you can’t find SER at the local Home Depot etc, the local electrical supply house will have it.

As to the question about getting the wire in the breaker, 2/0 is big wire and will likely fit, but always check first. Some are easier than others.  What brand is your main panel?

Perfect, I found this SER cable that is 2/0-2/0-2/0 1AWG which should do nicely and is reasonably priced    8)

I'm curious on your panel in your house to feed this.  I'm not aware of any brand that has anything more than a 100A breaker to feed a panel, thus why sub-panels tend to be 100A.

Any breaker rated for the amperage will accept cable size you need (wouldn't make sense otherwise).

My main panel is a 200 amp square-d 2813 box by Schneider Electric.  I had planned on using this square d 125 amp breaker to feed the sub-panel.

I could do a 100 amp subpanel which would simplify things but the EV will pull 80 amps.  That doesnt leave me much to keep lights on in the garage/operate the garage door/etc.  The thought was that I would push the subpanel to 125 amps to give me a little flexibility.

Am I trying to build the impossible?  [scared]

Offline DeformedTree

  • Posts: 467
Re: Need Help w/a Subpanel Install
« Reply #7 on: April 10, 2019, 11:59 PM »
I'm curious on your panel in your house to feed this.  I'm not aware of any brand that has anything more than a 100A breaker to feed a panel, thus why sub-panels tend to be 100A.

Any breaker rated for the amperage will accept cable size you need (wouldn't make sense otherwise).

My main panel is a 200 amp square-d 2813 box by Schneider Electric.  I had planned on using this square d 125 amp breaker to feed the sub-panel.

I could do a 100 amp subpanel which would simplify things but the EV will pull 80 amps.  That doesnt leave me much to keep lights on in the garage/operate the garage door/etc.  The thought was that I would push the subpanel to 125 amps to give me a little flexibility.

Am I trying to build the impossible?  [scared]

Ok, nice to see such a thing is out there for some brands.

Most the EV chargers I have seen only go to 60, I know the spec can even get to 100A, but I don't think any brand is using them.  There isn't a huge need since you have all night, so until you have 500-600mile EVs and you only have a few hours and you drive all of that every day, you probably won't come up short.   Remember your house is still there running, so you won't be able to pull more than what your house typically has available to spare. I get your thinking, but it very well is overkill.  But since you can do 125A with that breaker, I would probably do as you are, even if you never can leverage it.

Offline jonnyrocket

  • Posts: 24
Re: Need Help w/a Subpanel Install
« Reply #8 on: April 11, 2019, 12:18 AM »
Sounds like you’re well on your way with the SER cable.
What size conduit do you plan to run? 2” PVC?  Be sure to use the larger radius “sweep” 90 degree pieces for any 90s.


On breaker sizing, keep in mind that a load can’t be higher than 80% of a given breaker. So for an EV Charger that requires an 80A breaker, the real draw will only be 80% of that breaker. And in fact any load between 57A and 64A require an 80A breaker. 
Same goes for power tools. So it’s best to add up the loads based on tool nameplates, not by the breaker size (and also be ware that nameplate ratibgs are also higher than the actual load of the tool.

Based on what I have seen and what I know about battery charging, your EV charger would only ever reach that max load rating (between 57A and 64A) when the batteries are cold, and if the batteries are completely drained. Even then it would slowly ramp the charge rate so it would happen once the batteries reach about 25% charge.


 

Offline tjbnwi

  • Posts: 5947
  • Cedar Tucky Indiana
Re: Need Help w/a Subpanel Install
« Reply #9 on: April 11, 2019, 12:48 AM »
You're on the right track.

The conduit will need at least 2 expansion joints.

Tom

Offline rvieceli

  • Posts: 983
Re: Need Help w/a Subpanel Install
« Reply #10 on: April 11, 2019, 07:16 AM »
@flybynite You should be able to use a 100 amp feed for your sub-panel. As Mentioned most EV don't really need more than a 60 amp breaker and even a 50 would be ok.

Tesla's charts even out from 60 amps up in breaker size. The car doesn't charge any faster on a larger breaker in other words even though the wall connector is rated for 80 amps. A 50 amp breaker shows only a slight decrease in charge speed.

https://www.tesla.com/support/home-charging-installation/wall-connector

drop down to 100 amps and you should be able to use either 1-1-1-3 SER or 1/0-1/0-1/0-2 SER

I'm currently running my shop on a 60 amp breaker and that includes a 50 amp welder circuit. Although the conductors are rated for 90 amps so I can pop up if needed.

Ron