rmay635703
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Joined: Wed Jan 19, 2011 7:43 pm

Re: Should I install a 20 amp 110 circuit along with my new 240??

Thu Jan 04, 2018 12:32 pm

MikeD wrote:wwhitney (or anyone else): Assuming one has 200a service, I would be interested in knowing (say, according to a recent NEC) how one could ballpark estimate if it were safe to add two new 40a 240v EVSE circuits at one's residence so that two 6a Leafs could be charged at the same time.


Look at your panel, add the amps up of populated breakers.

If you have 120 amps or less of installed load in the panel

good to go.

wwhitney
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Re: Should I install a 20 amp 110 circuit along with my new 240??

Thu Jan 04, 2018 12:55 pm

rmay635703 wrote:Look at your panel, add the amps up of populated breakers.

If you have 120 amps or less of installed load in the panel

good to go.

It's not anywhere near that simple. The following might be typical: the above procedure gives you 400 amps. The NEC load calculation gives you 200 amps. And actually measuring the current on your service conductors gives you under 100 amps.

To answer the question properly you need to do an NEC load calculation. The EVSEs will show up in the calculation as 125% of the EVSE's pilot signal with no demand factors. So if the existing load calculation is under 125A, then you could add two 30A EVSEs to get a total under 200A. I don't have any rules of thumb for doing an NEC load calculation.

Now as a practical matter, even if the NEC load calculation before EVSEs is 200A, the actual peak current on the service conductors might be only 100A. The EVSEs are basically the only household load that will actually add their rated current to that figure on a continuous basis. So you could add two 30A EVSEs to the service while keeping the service conductor current under 160A continuous (the maximum allowed for a 200A service).

Also, it is important to notify your power company that you're getting an electric vehicle. That 200A service might have service conductors on the power company side that are really only good for 100A continuous, likewise for the transformer feeding your service. If you are regularly adding a full 60A continuous load to your service, the power company may need to upgrade their equipment.

Cheers, Wayne

jake14mw
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Re: Should I install a 20 amp 110 circuit along with my new 240??

Thu Jan 04, 2018 1:00 pm

rmay635703 wrote:
MikeD wrote:wwhitney (or anyone else): Assuming one has 200a service, I would be interested in knowing (say, according to a recent NEC) how one could ballpark estimate if it were safe to add two new 40a 240v EVSE circuits at one's residence so that two 6a Leafs could be charged at the same time.


Look at your panel, add the amps up of populated breakers.

If you have 120 amps or less of installed load in the panel

good to go.



? I have 400 total. 14 Fifteen Amps, 6 Twenty Amps, 1 Thirty Amp, 1 Forty Amp

MikeD
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Re: Should I install a 20 amp 110 circuit along with my new 240??

Thu Jan 04, 2018 4:32 pm

jake14mw: A 200a residential service usually means 200a at 240v, so when adding up breaker amps, divide the amp rating of 120v breakers by 2. So, for example, a 15a 120v breaker should be added up as though it were 7.5a. As wwhitney wrote, the NEC is somewhat complex in evaluating a more precise load calculation in trying to determine when one's service is inadequate for adding additional loads (like EVSEs).

I guess it goes without saying if your main breaker starts tripping, your service is probably overloaded! The question is how to avoid getting into that situation...

Without getting into complexities that the NEC does:
A 200a service is roughly 240v x 200a = 48,000W. If you add up all the power of all your lights, appliances, EVSEs, etc and the sum < 48,000W then I think you may be OK (unless I need some simplifying factor that wwhitney may be so kind to mention). This assumes everything is on at the same time. If you are over this figure (especially by a lot), then you need to do more thinking/more calculations concerning the possibility for overloading your service...

smkettner
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Re: Should I install a 20 amp 110 circuit along with my new 240??

Thu Jan 04, 2018 8:38 pm

200 amp panel? That is 48 kW. If you have space just pop them in and let it rip.
Run everything and you would be lucky to use half the rating.
You can add breaker ratings all day and the loads are much less.
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Tsiah
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Re: Should I install a 20 amp 110 circuit along with my new 240??

Sat Jan 13, 2018 3:36 pm

wwhitney wrote:
Tsiah wrote: If you're installing an outlet, code requires the neutral to be at the outlet even if it's unused.

If you're installing a receptacle that provides a neutral (14-50) rather than one that doesn't provide a neutral (6-50).

Cheers, Wayne

That's what I mean, but I've never seen a 6-50 on an EVSE...they all seem to be 14-50 or hardwired.

wwhitney
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Re: Should I install a 20 amp 110 circuit along with my new 240??

Sat Jan 13, 2018 4:07 pm

Tsiah wrote:I've never seen a 6-50 on an EVSE...they all seem to be 14-50 or hardwired.

I've never seen one either, but they do exist, eg:

https://store.clippercreek.com/index.ph ... duct_id=70

Cheers, Wayne

wmcbrine
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Location: Maryland

Re: Should I install a 20 amp 110 circuit along with my new 240??

Sat Jan 13, 2018 5:21 pm

Tsiah wrote:That's what I mean, but I've never seen a 6-50 on an EVSE...they all seem to be 14-50 or hardwired.

I think it's actually the most common EVSE plug, by number of models; it's just that the very most popular EVSEs seem to lean 14-50.

MikeD
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Re: Should I install a 20 amp 110 circuit along with my new 240??

Sun Jan 14, 2018 1:03 pm

There are reasonable expectations that in 2019 Nissan will increase the on-board charger's power by a factor of nearly 2 (or possibly even 3) times to go along with a larger battery option which they plan to have then in order to be more competitive with the Tesla Model 3. The AC Level 2 (J1772) charging specifications currently provide for up to 19.2 kW (240v at 80a, for example), although most public Level 2 EVSEs currently max out at around 7kW. Most Leaf owners are probably satisfied if their home's EVSE is capable of completely charging their Leaf overnight, so being able to charge at 30a (or perhaps 40a) will do that, at least for Leafs bought before 2025, I would guess. Also most people don't even need a completely charged car in the morning if they are confident that they don't need more range that day.

One factor I haven't seen mentioned much is that when eventually it will be possible for one's Leaf to power a house (Leaf-to-home or V2H), the circuit to do that will, I believe, need to have a neutral. CHAdeMO 1.0 (the current specification) is capable of doing V2H with the right hardware, so It (or something like it -- not the AC J1772, I don't believe) could eventually be useful not just for fast charging.

GlennD
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Re: Should I install a 20 amp 110 circuit along with my new 240??

Thu Jan 18, 2018 10:58 am

wmcbrine wrote:
Tsiah wrote:That's what I mean, but I've never seen a 6-50 on an EVSE...they all seem to be 14-50 or hardwired.

I think it's actually the most common EVSE plug, by number of models; it's just that the very most popular EVSEs seem to lean 14-50.


Tesla popularized the 14-50 connector. That is what the 40A supplied EVSE's use. Given the number of Tesla's out there it has become a semi standard. If you are building an EVSE range plugs with that connector are CHEAP. They are really a comity. Both 40 and 50A cables are under $20 shipped from eBay.
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