How many amps for new 240V install?

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EatsShootsandLeafs

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Aug 24, 2012
Messages
716
Walls are open so we're running a 240V circuit to the garage in anticipation of a future EV (I don't have one at this time). Going to do at least 50amps. 60 the electrician is going to use thicker wire so wants another $100-150. 80 amps he can do for another $100 again on top of that.

What's a heavy duty residential install look like these days? I assume when I put in an actual charge station later I can specify the circuit size and it will charge accordingly.

Thanks!
 
AFIK, as long as the wiring can carry the load, you can size the circuit breaker according to the device you use (80% continuous load). I.e., for a 40 amp EVSE, use a 50 amp breaker. You don't want to use an 80 amp breaker for a 40 amp EVSE. But having the wire be heavier than needed is fine. In fact you'll save a small amount of power due to the lower resistance.
 
There is no reason to install wire as thick as your arm...

What will you plan to do with that installation?

A home installation is a situation where there is one thing that you have.... Time.... No one will need to plug in, and have to run out again in 20 minutes.. Even with my 30 amp setup, I can charge 30 - 35 miles per hour. So in 2 hours, it can go from 30% charge to 90-100% charge.

Is that so bad? Even if you get a really big battery, like a Tesla, a 40 amp setup will be fine to charge because you will never drive that many miles during a day that you need FAST CHARGE!!!

I would say, get a 50 amp circuit, which will handle a future 40 amp charger.
 
Nubo said:
AFIK, as long as the wiring can carry the load, you can size the circuit breaker according to the device you use (80% continuous load). I.e., for a 40 amp EVSE, use a 50 amp breaker. You don't want to use an 80 amp breaker for a 40 amp EVSE. But having the wire be heavier than needed is fine. In fact you'll save a small amount of power due to the lower resistance.

This is my understanding as well. I don't generally suggest wiring that will handle 80 amps, but it won't hurt anything as long as the breaker is sized for the device.
 
Thanks, all.

Seems like more than 50 amp would be a waste of money. Guessing 14-50 is the best receptacle to get. Going full 60 amps now with 14-60 receptacle might be a pain, too.

I'm going to do 50 amps for convenience now and cost but if it's only a few bucks to go with a fatter gauge wire to handle future 60 I'll possibly have him run that. Then down the road I could put in a new breaker and receptacle without it impacting cost or compatibility now.
 
Awhile back, Tesla started including no >48 amp OBCs on the their US vehicles (https://www.tesla.com/support/home-charging-installation/onboard-charger). They used to have also have 40, 72 and 80 amp (via twin OBCs). And, 32 amp is new for the lowest end Model 3(s).

From looking at the specs for https://www.audiusa.com/models/audi-e-tron, they mention 9.6 kW AC charging, so I guess 40 amps. It seems like finally, non-Tesla powered US-market BEVs are finally getting over 32 amp OBCs. I wonder if the trend will continue and where the typical max will end up being? 40 amps? 48 amps? or still 32 amps?

Previously, you had to go with something Tesla powered to have 40+ amp OBCs.
 
Unless you are a super commuter 30 amp circuit and 24 amp EVSE is plenty 99% of the time.
Get 40 or 50 if you like but I would rather have 2x 30 amp for two vehicles.
If going 60+ then put it to a subpanel to split the power between multiple EVSE etc.
 
smkettner said:
Unless you are a super commuter 30 amp circuit and 24 amp EVSE is plenty 99% of the time.
Get 40 or 50 if you like but I would rather have 2x 30 amp for two vehicles.
If going 60+ then put it to a subpanel to split the power between multiple EVSE etc.
Numbers. 30 Amps 240V is 7.2kW With 12 hours of overnight charging, and 2.0 miles per kWh, commute out to 170 miles. Hard to find a super commuter doing more.
 
I'd ask the electrician about what it would cost to install a sub-panel in the garage. That's what I'm planning to do in my garage. I'll probably run 100A just to future-proof it although my OpenEVSE will be on a 35A circuit. Also ask about Al wire vs Cu. Al is much cheaper.
 
It's not cheaper if your house catches on fire.

Aluminum wire creeps under the pressure of the screw terminals, which results in looseness of the electrical connection, then arcing across the gap occurs and generates heat in the junction.

Special grease and fittings are used with aluminum wire in an attempt to mitigate this, but periodic inspection and re-tightening of the bolts and screws are needed. Aluminum may be used for the transformer pole-to-house wiring, but usually crimp lugs are used to make those junctions.

Use copper and sleep easy, just consider the cost difference as cheap fire insurance.
 
100A wow! Is that not the limit for a common home? I just installed 50A at my home with an openevse but I did see a coworker with a Tesla charger where the electrician installed a 60A which seems to be what Tesla wants if you see one of those Tesla home chargers in your future. I figure 40A is enough for home. I'll typically have enough to drive a family member to a nearby hospital if something crazy happened otherwise I am already maxing out the Leaf onboard charger. I do not see a sudden emergency long distance road trip as likely.
 
nlspace said:
Aluminum wire creeps under the pressure of the screw terminals, which results in looseness of the electrical connection
To my knowledge, this was a problem with the aluminum wire alloy used in the 60's and 70's, AA-1350, but is not a significant problem with the modern aluminum alloy AA-8000 when used with terminals rated for aluminum. So as long as the EVSE terminals are rated for aluminum, I wouldn't hesitate to use aluminum wire.

Cheers, Wayne
 
salyavin said:
100A wow! Is that not the limit for a common home?

Most modern homes use 200A service I believe. I just installed a new 200A service at my house although I probably rarely use more than 40A at any one time. The main reason I did that upgrade is so that my (yet to be installed) solar system won't be limited by the service entry equipment.

The wire is the biggest cost difference since a 100A sub-panel will cost about the same as a 50A sub-panel, ditto for the breakers. Opening the walls and running the wires is the same. I could probably save $50 by using a smaller gauge cable but since the EVSE will already need a 35A circuit I thought I'd just give myself some headroom for the future and spend the extra $ now.
 
I ran a 50A circuit to the garage to use my 40A Tesla UMC1 with a 14-50 plug. That's good enough for charging our 2 cars even though the cars could take more (my S has the 48A OBC, while our X has a 72A OBC).

Of course, I got a free Tesla HPWC from a referral last year, and that deliver up to 80A (on a 100A circuit). If I had better planned ahead, I probably would have run at least a 60A circuit to the garage to allow me to charge at 48A.
 
nlspace said:
It's not cheaper if your house catches on fire.

Aluminum wire creeps under the pressure of the screw terminals, which results in looseness of the electrical connection, then arcing across the gap occurs and generates heat in the junction.

Special grease and fittings are used with aluminum wire in an attempt to mitigate this, but periodic inspection and re-tightening of the bolts and screws are needed. Aluminum may be used for the transformer pole-to-house wiring, but usually crimp lugs are used to make those junctions.

Use copper and sleep easy, just consider the cost difference as cheap fire insurance.

I didn't know they did aluminum still for residential...

The new house is on a 200A breaker. That's the standard on homes around here. My current one was made mid 2000's and is on 200a also.

Kind of leaning to 50 amp breaker, 60 amp capable wire, and 14-50, so that I don't need to worry about adapters, then the wire is there if I ever need it with a new breaker.
 
What is the max amps for a LEAF these days? I still think 24 amps charging on a 30 amp circuit is way plenty even for a Tesla/Rivian with max battery.
 
smkettner said:
What is the max amps for a LEAF these days? I still think 24 amps charging on a 30 amp circuit is way plenty even for a Tesla/Rivian with max battery.

AFAIK still 27.5 amps. I hear 7.7kw mentioned occasionally, but again, AFAIK, it hasn't been implemented. They are still relying on DCFC speeds, ironically.
 
Kind of leaning to 50 amp breaker, 60 amp capable wire, and 14-50, so that I don't need to worry about adapters, then the wire is there if I ever need it with a new breaker.

Smart move.

I have an older Schneider Eaton hard wired EVSE at my house since 2015. Its wired with #6 THHN which is good to 65 amps, but it’s protected with a 40 amp breaker since the ESEV draws max 30 amps. It’s served me very well for about 4 years now charging my 2015, then 2018 leafs, and now my 2019 Leaf plus. It puts in 25 miles of range each hour the car is being charged.

At the barn/shed at our country vacation house I also ran #6 in flex conduit to a 14-50R receptacle. That is protected with a 40 amp breaker. I bought a spare Nissan 120/240 ESEV plugged on eBay for about $250 and leave it there all the time. I turn that breaker on only when charging. I may be using that receptacle for my RV at times.

There’s another one listed right now on eBay https://www.ebay.com/itm/2019-Nissan-Leaf-Charger-OEM-NEW-240v-120v/264602333350

Picture of the Hard wired Eaton in garage at house. It’s right below the CB panel.

hg6HdSGl.jpg



Here’s the one in the barn at country vacation house as I was wiring it. If you look closely it’s connected to a 40 amp breaker in the barn 60 amp sub-panel.

llaxMJPl.jpg
 
Flyct said:
Kind of leaning to 50 amp breaker, 60 amp capable wire, and 14-50, so that I don't need to worry about adapters, then the wire is there if I ever need it with a new breaker.

Smart move.

I have an older Schneider Eaton hard wired EVSE at my house since 2015. Its wired with #6 THHN which is good to 65 amps, but it’s protected with a 40 amp breaker since the ESEV draws max 30 amps. It’s served me very well for about 4 years now charging my 2015, then 2018 leafs, and now my 2019 Leaf plus. It puts in 25 miles of range each hour the car is being charged.

At the barn/shed at our country vacation house I also ran #6 in flex conduit to a 14-50R receptacle. That is protected with a 40 amp breaker. I bought a spare Nissan 120/240 ESEV plugged on eBay for about $250 and leave it there all the time. I turn that breaker on only when charging. I may be using that receptacle for my RV at times.

There’s another one listed right now on eBay https://www.ebay.com/itm/2019-Nissan-Leaf-Charger-OEM-NEW-240v-120v/264602333350

Picture of the Hard wired Eaton in garage at house. It’s right below the CB panel.

hg6HdSGl.jpg



Here’s the one in the barn at country vacation house as I was wiring it. If you look closely it’s connected to a 40 amp breaker in the barn 60 amp sub-panel.

llaxMJPl.jpg

That's a lot of wall switches :)
 
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