Do I have room in my electrical panel for 240 EV circuit?

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cwuwlaw

Member
Joined
Jul 9, 2014
Messages
12
Location
Mercer Island, WA
I am in the budgeting stage for purchasing a Leaf. I'm trying to figure out whether my old Murray panel is really full so that I'll have to add a subpanel. I've searched the forums and internet, but I think I'm just not getting it. I currently charge my C-Max Energi using a dedicated 120 volt 20 amp outlet that is on a dual breaker. The bottom spot on the dual/tandem breaker has an empty spot. See bottom right breaker in the below picture:

redir
http://1drv.ms/1nj4hXi" onclick="window.open(this.href);return false;



If I decide to add a 240 outlet, I'll be hiring an electrician to do so. But I'm hoping to have a better idea what I'm in for before calling out an electrician. When I first saw that the bottom space on the tandem breaker was unused, I thought I could just use that tandem space for a 240v. But then I researched a bit and it seams that tandem breakers are usually on a single pole, so that it can only output 120v. But based on the following wiring diagram on the panel door, I'm not sure whether some of my tandem breakers may actually be using both poles:

1muqNB9
http://1drv.ms/1muqNB9" onclick="window.open(this.href);return false;

What I don't understand is that there appears to be 7 spots for breakers on the right side of the lower (non-service) side of my panel (numbered 18-24). But I have only 5 breakers (4 tandem plus one single). Could that bottom tandem breaker be connected to 2 poles so that I can use that space for a 240v circuit?

Sorry if I've confused the issues using poor terminology. I promise I'm not planning to do the work myself. Just trying to get an idea of investment I'd need to make to upgrade to a 240v charger. If it looks like I'll need to add a subpanel at significant expense, I may just stick with trickle charging and top it off at public chargers when I'll be driving more than 35 or so miles a day.

Also, sorry if the pictures don't show up. I added the links, but they aren't showing when I preview this post.
 
DNAinaGoodWay said:
Yeah, can't see the pictures either.

Take a couple estimates from different electricians and see what they say.
Click to expand...


I added links to the pictures. I'll probably just go ahead and get estimates. Just don't want to waste their time coming out if the answer is obvious.
 
cwuwlaw said:
But based on the following wiring diagram on the panel door, I'm not sure whether some of my tandem breakers may actually be using both poles: [ . . .] What I don't understand is that there appears to be 7 spots for breakers on the right side of the lower (non-service) side of my panel (numbered 18-24). But I have only 5 breakers (4 tandem plus one single).
Click to expand...
I am not an expert on old panels but my reading of your panel photo and diagram is that your panel is already overloaded. If you look at the diagram, it shows 7 poles on either side in the bottom section, and the text below that talks about 7 poles maximum. In this context pole means breaker handle, so full width breakers count as one, and tandems count as 2. With that counting method, you already have 9 poles on each side in the bottom section.

So the upshot is you should have a subpanel installed and some of the circuits moved over to the subpanel to comply with the original panel's label and its limitations. Then you can add your new EVSE circuit to the subpanel.

As to your original question, a tandem breaker will have both poles on a single leg of the electrical service. If you look at the panel diagram, the poles are little squiggles, and the allowable locations for tandems are where the lines after the squiggles connect immediately before going to the dot representing the connection to a busbar (the vertical lines). That shows that the two tandem poles are on the same leg. [Lines crossing without a dot means no connection.]

Cheers,
Wayne
 
You have a 200 amp service, so if you have all the improper double pole breakers removed, and the 120 volt circuit replaced with a 240 volt in the same spot, you may be ok. Add all the loads and see how much is actually being drawn from the service.
 
johnrhansen said:
Whenever there is doubt, just replace the panel. It's kind of fun to do anyway, and they don't cost much. Another thing you can do if it's available is to convert to natural gas. You will save tons, and you can just use the water heater cb for your evse. That is if its the 20 amp evse
Click to expand...
 
Adding up the breakers in your panel to see if your panel can accept an EVSE is kinda like looking at your checkbook with some blank checks in it and thinking you have money in your bank account. :)

In order to pull a permit to put in a new circuit, your city/county, etc. will require some load calculations that are prescribed by the NEC to determine if your panel can accept additional load. These calculations are standardized and any good electrician should be able to figure out how much new load you can add...

The calcs involve the square footage of your house and an allocated load per square foot, among other things, so it isn't obvious just by looking at the panel...

If you do just look at the panel, the connected load, and the open spaces available to make a decision about adding load, that may work if you have plenty of capacity left but it is not really the recommended method to use as your panel gets closer to electrical capacity...

You could probably add a circuit to charge your car if it were to only be used at midnight since the load is minimal in most homes at that time. But what will happen when you or someone in your household plugs in your car to charge on that new circuit at the peak time of the day when loads in the house are at maximum? Will it overload or trip your main breaker? That's when the NEC load calcs will come in handy...
 
Randy said:
In order to pull a permit to put in a new circuit, your city/county, etc. will require some load calculations that are prescribed by the NEC to determine if your panel can accept additional load. These calculations are standardized and any good electrician should be able to figure out how much new load you can add...

The calcs involve the square footage of your house and an allocated load per square foot, among other things, so it isn't obvious just by looking at the panel...
Click to expand...
In one of the photos, this looks like a 200 amp service panel on the sticker. So unless they are using mega electricity in a huge house, adding a 30 amp EVSE load should not be a problem.
 
Hey, don't harsh his buzz with facts - he was really on a roll, there!

When I suggested the loads be added, I was talking about the maximum load per breaker. That is nothing at all like the lame checkbook analogy.
 
Not a huge house (1930 sq ft) and we have ample capacity. We have gas heat, so our biggest power draws are water, stove, A/C and oven. We may just convert the water to gas and use that breaker for the EV charging. The power company will kick in $950 towards the conversion cost.
 
in my town, gas is $1.10 per therm and electricity is $0.11 per KWH. 1 therm is 29.3 KWH. Let's say you use 250 therms a year to heat your hot water, that's 7325 kwh. So electric usage is $805 per year and gas usage is $392 ((250 X 1.1)/.7) Gas heaters are 70 percent efficient. you will make 400 bucks a year just in energy savings converting to a gas water tank. If you wash a lot of clothes, a gas dryer is a good deal too.
 
cwuwlaw said:
I am in the budgeting stage for purchasing a Leaf. I'm trying to figure out whether my old Murray panel is really full so that I'll have to add a subpanel. I've searched the forums and internet, but I think I'm just not getting it. I currently charge my C-Max Energi using a dedicated 120 volt 20 amp outlet that is on a dual breaker. The bottom spot on the dual/tandem breaker has an empty spot. See bottom right breaker in the below picture:

redir
http://1drv.ms/1nj4hXi" onclick="window.open(this.href);return false;



If I decide to add a 240 outlet, I'll be hiring an electrician to do so. But I'm hoping to have a better idea what I'm in for before calling out an electrician. When I first saw that the bottom space on the tandem breaker was unused, I thought I could just use that tandem space for a 240v. But then I researched a bit and it seams that tandem breakers are usually on a single pole, so that it can only output 120v. But based on the following wiring diagram on the panel door, I'm not sure whether some of my tandem breakers may actually be using both poles:

1muqNB9
http://1drv.ms/1muqNB9" onclick="window.open(this.href);return false;

What I don't understand is that there appears to be 7 spots for breakers on the right side of the lower (non-service) side of my panel (numbered 18-24). But I have only 5 breakers (4 tandem plus one single). Could that bottom tandem breaker be connected to 2 poles so that I can use that space for a 240v circuit?

Sorry if I've confused the issues using poor terminology. I promise I'm not planning to do the work myself. Just trying to get an idea of investment I'd need to make to upgrade to a 240v charger. If it looks like I'll need to add a subpanel at significant expense, I may just stick with trickle charging and top it off at public chargers when I'll be driving more than 35 or so miles a day.

Also, sorry if the pictures don't show up. I added the links, but they aren't showing when I preview this post.
Click to expand...

OK I looked at your pictures and recently I did this at my own home so I did research Circuit Breaker panel and how to wire 240V.

Essentially every house gets 2 Phases of 120V each and one Neutral and a Ground is created in the panel. The way you get 240V is when you send the two passes tot he Car and if you have a multimeter you measure a voltage between the two phases you will see 240V.

Now in the Circuit breaker panel I see you many half inch breakers, see the one you have marked for EVSE and the empty.. those are both sitting on the same phase and hence if you put a wire in the empty one you will get the same phase as output and not of any use to you. So in order to tap into the OTHER phase you need to get a line out of the breaker immediately on top of the current EVSE breaker, move whatever is already wired up there can be moved to the empty breaker. Of course you need to make sure the AMPs etc match. Here is a 30AMP Quad Circuit breaker I used.. If you can plug this in your panel you will get your 2 phases from the inner 2 points as they are in tandem or the outer 2 points...
http://www.lowes.com/pd_116637-82364-BQC230230_0__?productId=3009434&Ntt=circuit+breaker&pl=1&currentURL=%3FNtt%3Dcircuit%2Bbreaker%26page%3D2&facetInfo=" onclick="window.open(this.href);return false;

Hope this clarifies... Essentially with some clever moving about of circuits you can get two phases as needed.
Let me know if you have any questions.. it is easy and I installed this myself.
 
I don't like those panels with multiple service disconnects. There is no main breaker in this panel. If the fire dept needs to turn off power in an emergency they have to flip all the upper ones, it will take them that much longer, or in the dark they might miss one. I don't think they can even make them that way anymore. I would definitely replace it at a convenient time for you with a more modern panel. Doesn't have to be right away. Basically... don't go the sub panel route. If you touch any wire in there, replace the entire panel.
 
There is no main breaker in this panel.
Click to expand...

Damn. If John is correct (the top of the panel is missing from the photo, and I assumed that since this one looks like mine it also had a Main), then either replace the panel or maybe add a small sub-panel above it with just a main shutoff, clearly labelled.
 
cwuwlaw: Since many people getting a Leaf are finding it necessary (or desirable) to upgrade their service panel, perhaps it would be useful to discuss panel features that most people should consider. I'll lay out a few of my own thoughts that are intended for people who have moderate size homes.

1) The first is capacity -- 200 amp panels provide enough even for multiple EV families (especially if they realize that 16a EVSEs are sufficient for overnight charging).
2) Number of slots -- 30 to 42.
3) Width of breaker slots -- 3/4 inch rather than 1 inch may be necessary in order to get panel to fit in space available.
4) Number of circuits -- best to match number of slots as tandem breakers have a lot of shortcomings (as already noticed in this post).
5) "Plug on Neutral" capability (New!) -- reduces wiring clutter in box due to AFIC/GFIC "pigtail" wires. (This will become more of an issue as AFIC breakers become much more prevalent. They are still pretty expensive now at $30-$40 or so).
6) Breakers widely available.

One example of a box to consider (because I have some familiarity with it) is the Square-D QO QO142M200PC panel, currently available at Home Depot (but not yet at Lowes), which meets all of the above.

I don't expect everyone to agree with me, but I welcome any conversation on the matter...
 
johnrhansen said:
I don't think they can even make them that way anymore.
Click to expand...
I don't know if anyone is making split bus panels anymore, but the NEC allows up to six breakers to make up the building disconnect. So the existing panel is still NEC compliant, if not quite as simple as a panel with a main disconnect. I don't see any problem with that aspect of things.

Cheers, Wayne
 
johnrhansen said:
There is no main breaker in this panel. Basically... don't go the subpanel route. If you touch any wire in there, replace the entire panel.
Click to expand...

LeftieBiker said:
Damn. If John is correct (the top of the panel is missing from the photo, and I assumed that since this one looks like mine it also had a Main), then either replace the panel or maybe add a small sub-panel above it with just a main shutoff, clearly labelled.
Click to expand...

Definitely ignore LeftieBiker's advice. They just are not familiar with split bus panels and the NEC which results in many uninformed responses in threads they should be leaving alone.

I definitely wouldn't consider adding a sub panel as a solution. When you get an electrician out I suspect they may be will be willing to add an 240 volt circuit for your EVSE by doing a bit of rearranging or recommending replacing your water heater with minimal cost but in the event that they would prefer to replace the panel I think that's a good long term solution. Definitely refer to a trusted electrician but I doubt there is anything particularly unsafe about your current setup even if it's not following the panel instructions to the T. If you can't budget for a panel upgrade at this time it's more than likely that your electrician will not feel compelled to scare you into it.

Have you looked at adding solar PV? If you add that you can get your panel replaced as part of that install and get the 30% federal credit to cover it :)


Randy said:
In order to pull a permit to put in a new circuit, your city/county, etc. will require some load calculations that are prescribed by the NEC to determine if your panel can accept additional load.
Click to expand...
More accurately they MAY require it but I'm willing to bet more times than not load calcs are not being required.
 

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