EV Charging station off subpanel in garage remodel

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I am be a bit out of my league here. I was a new construction plumber for many years but never had any electrical experience until I decided to replace the original service panel on my 1950s home last year.

I'm posting here because I have read enough and done enough that I feel comfotable asking questions which, I think, are approproate to this board. If not, could someone please help me out by pointing me to some site where I can ask questions of this nature without offending anyone. ;-)

I've read a lot of the archived treads and many have provided some insite into my plans but I am still not clear on several things. I have hired a liscensed electrician to help me with everything, I'm discussing, but since he is able to simply do the math in his head and since I hired him to do the job without a permit/inspection I have to question a few things and I have to be sure that a few things, I know are safety hazards, are "to code" even without a permit or an inspection.

With that said here is my senario and my questions.
Senario:
Single Family residence with Murray 200 amp service. We plan to run a 125 amp rated sub panel off this main service panel to supply the power for my garage remodel project. This sub panel will have an 80 amp breaker at the main service panel and will be run 60-70 ft. away using 4/3 WG romex through the attic. and down the inside of the wall to the attached garage. Amongst one 20 amp. lighting and three 20 amp. outlet circuits I will be adding a 220/240 circuit off the subpanel to power a compressor I aready own. That compressor draws 16 amps so I planned for a 20 amp double pull breaker for it. The 220 run will be approx. 35 - 42 ft., depending on how I run it, of 8/3 WG to get to the other side of my garage.

1. Does anyone here have any experience with installing an EV charging station? If so, can they give me some idea what kind of load to expect from such a device? I'd like to install the 220/240 (Compressor) circuit, described above, so that someday when I buy my first electric hybrid car I already have a line on the correct side of my garage to supply it. The specs. for the only one that I could find on the internet said Input: 180-240 VAC, 30 Amps, Output: 6kW 40-430V but the documentation for installation says... This charger requires a dedicated branch circuit. The branch circuit must be a single phase 208 - 240Vac rated circuit equipped with over-current protection of 40amperes.

Assuming this means the circuit should have a 40 amp. breaker even though the charger is only capable of drawing 30 amps. I think my 80 amp. subpanel will be to low amps. to handle this type of charger with all the other devices I'm planning on running on my subpanel. Any advice/comments on this would be appreciated. I hadn't thought of the AV charging system until recently and, so, I already purchased all the supplies mentioned above, based on the original plan to just run the compressor off of the 220 line. I could return the 80 amp. breaker and get a 100 or 125 amp breaker but then I'm pretty sure I'd have to replace the wire, which I cannot return.

2. What does the code say about 220 romex without conduit? I'm a bit concerned about having a 220 line running across my ceiling (through my attic and down my wall) without being encased in a conduit but if code allows for it then it would certainly be the most cost effective and easiest way to go for the run from the main to the sub. I'll probably do the same for the 220 line to the compressor, if code allows. There it would run through the 2x6 attic floor joists/garage ceiling beams to get to the other side of the garage.

3. I keep seeing references to sections of the code as numbers such as 210.52. I've looked at all the links I could find that take me to the NEC code but none of those pages have numbers such as those referenced in the forums. Where can I find the documentation/code that those number are referencing?

4. I have quite a bit of computer equipment I'm planning on running off of one of the 110 circuits which will be off the subpanel and it was recommended to me, by another electrician, to run an isolated circuit for this purpose. Can someone tell me exactally what an isolated circuit is and what advantage it might have for running computer equipment? Also, do you think it is worth the extra time and cost to make a circuit isolated under my circumstances?

Thanks in advance ~Garth
 
First problem. Romex (a.k.a. NM cable) can only be used at its 60C ampacity rating even though it can be used at 90C for thermal derating. A 4-3 NM cable is limited to 70 amps, so you can't use an 80A breaker on that wire.

You don't need to grossly oversize your compressor circuit. If its nameplate is 16 amps, because its a motor it needs to be increased by 25% so the ampacity must be 20A minimum. #12 wire is actually rated at 25A, so you could use #12 wire. For a 240V motor running less than 50 feet, I wouldn't oversize, but you are right on the edge of where I'd oversize. At most, 10-2 would be all you need. (and the compressor won't need a neutral, so 10-3 is not required).

A vehicle charger is probably considered to be a "continuous load". That requires that the amp rating be increased by 25%. So a 30A load would have to actually be considered a 37.5 amp load. Therefore, you need #8 wire and a 40A breaker.

Romex can be run exposed, but it can't be exposed to physical damage. The inspector is the judge of what exposed to physical damage is. Typically, you run guard boards (like 2x2's) on both sides of the wire if it is low enough that things could knock, pull, or abrade it. If you run it concealed, you have to make sure nails won't penetrate it so it must be 1.25" back from the face of a stud or joist. If its not, you must put metal nail guards on the stud/joist to prevent that from happening.

I think the person was telling you to run "isolated ground" circuits for your computers. For a home, this is worthless, as most of your grounds are already isolated unless you're using metal conduits everywhere. Perhaps he meant to run a dedicated circuit for your computer which would be a good thing (a circuit with only one receptacle and used just by your computer equipment). This will reduce the effects of something noisy (like a vacuum cleaner) plugged in some other place from affecting your computer.
Learn about NEC 220 (or have your electrician help you through it) to calculate the load on the panel. A 70A panel may be enough to cover your loads, but it may be close. The calculation is not just adding up everything. A demand factor is applied which allows you to run more than you'd think. You need to know what loads are continuous, which ones are motors, the nameplate amps and volts for the connected equipment, and if living space is connected, you need to know the square footage and whether there is a laundry or kitchen in that space.

To see the NEC by number, go to the library or bookstore and look at the book. There is also a lame online viewer which you can get to here:
http://www.nfpa.org/aboutthecodes/list_of_codes_and_standards.asp
Select NFPA 70
Select Preview this Document
Agree to the terms
Click Open the National Electric Code
Click the numbered text icon in the lower right corner to get a table of contents.
Click on the major section you want (e.g. 220)
When the document opens, you'll see all the subparts to 220 like 220.1 or 220.3, etc.
If you want to look up a specific reference, like 310.16, click on the major number in the table of contents (310 for this example).
 
Follow up

Follow up

Mark,

Thanks for answering all my questions with such detail. It sounds as if we may have undersized the 4/3 WG cable for all the devices I want on the sub-panel. We went with 4/3 primarily because it just barely fit through the 3/4" flex conduit I already have in place from the attic, as a future, to my service panel. I'll try to run everything through NEC 220 to figure this out. Since I paid about $350 for that cable I, really, don't want to recycle it and buy a thicker gauge.

It does sound like we have the ideal size 8/3 WG for the, future, EV Charging unit. For the compressor this cable is oversized but over-sizing should not present a problem as long as the breaker is the correct amp. rating. You, sort of, made it sound like over-sizing can be a problem. Other than being more costly is there something I'm unaware of that makes over-sizing a bad idea, even when you are trying to plan for a circuit which will need to handle a much greater load on it in the future?

I'll keep all your tips in mind for the routing of the cables. The one cable, to the sub-panel from the service panel, will run on top of the ceiling beams, in the attic and then down the wall so that one should be fine. Just to be safe I'll put it in flex conduit when it runs inside the wall just before the sub-panel box.

The other cable I'm still debating how to run. I can drill holes through the middle of the 2x6 floor joists/ceiling beams, which will keep it out of harms way and beyond the 1.25" back you say is necessary. Unfortunately, I'd be running about 18' of it through those joists which will weaken the floor of my loft a bit. I would be saving about 6 to 8' of cable by routing it this way and I already need to drill holes to run 110 romex for lighting through those same joists/beams.

Alternately, I can go into the new storage space/loft I've created, and send it parallel along the roof ridge beam. This route will require an extra 6 to 8' of cable and leaves the cable exposed to the storage area. There is a 1" copper, cold water, pipe that runs along one side of the ridge beam; so, the 240 cable would run parallel and very close, within a couple inches, to that pipe.

This is probably one of those things you would have to see to decide which route is optimal but what do you think based on the information I've provided?

I know there is code on when romex/cable needs to be inside conduit and when it does not. It seems obvious that it can run through the attic without being in conduit but what about through a loft area where we will be storing boxes and such. Would the 240 cable need to be in conduit to run it overhead through this loft area and meet code?

As for the computers ?isolated circuit?, I think you were correct that he was telling me to run an isolated ground circuit since he mentioned a grounding rod in the same conversation.

When you mentioned the metal conduit, it made me realize that maybe he was suggesting this because most of the outlets in our house are not grounded or are grounded only by the box. Recall that this house was built in the 50s; so, there is no ground wire in the original romex used to build the house. The boxes have a ground wire which runs from one box to the next and then I think it went to a cold water pipe somewhere but when I re-piped the house, I did away with that. Eventually, I'll ground each outlet but that will take some time and a lot of crawling around under the house. The most critical outlets are grounded or have GFIs. For example, the Washer and Dryer outlet already has a ground. I?ll be replacing that outlet with a GFI during my remodel since I?m moving the washer and dryer into the garage. All the new circuits will be grounded which reminds me of one last thing I wanted to ask about.

I read in the archive forums some posts that made it sound like a sub-panel must be connected to both the neutral and ground of the service panel. Is this correct? I planned to have a separate ground for the sub-panel so I'm wondering what would be the optimal configuration?

Thanks again for all your input. ~Garth
 
I am locking this thread.

Garth we can not answer how to questions here.

If I am mistaken and you are in the electrical trade send me a PM.
 
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