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I live in a condo. The main breaker is only 70A. Now what? [Resolved]

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Since I started this I discovered a document on my city’s website for the planning of residential installations of L2 EV chargers. A main breaker of at least 100A is required for them to approve anything.

The manufacturer of the DCC energy management box suggests a 30A maximum EV charging circuit when used on a 70A main.

Hrm, one would think the city should actually follow the NEC load calculation process rather than set arbitrary limits. I think the reality is that nobody really has a clue how to do the NEC load calculations properly. I have tried a number of online calculators and they all result in different numbers. There is also disagreement on what things to include and what not to include (like is the refrigerator part of the two small appliance circuits for the kitchen? or is it separate)?

I did some math based on your 70a feed and for instance if you did not have that AC unit I suspect you could fit a 30a car charging circuit into your load calculations and still stay under 70a. So if that was the case, the cities arbitrary 100a requirement would be too restrictive. (how many sq feet is your home btw as that is a major factor? - also is the "GDO" circuit just the garage door opener - odd to have it on a dedicated circuit)

On this load shedding box: It is a novel idea and I think it is where the future is headed, though I am not a massive fan of how they implemented it, nor am I a fan of the cost.

I believe the future will be a device that clamps on your mains with CT's and then sends a signal to the EVSE (wall connector for instance) to get it to ramp down load or completely stop charging. It would make use of the existing ability of the Wall Connector to cut off the car from charging or to pare back load. All that would be required would be the CT's and a control board.

This load shedding device wants you to route all the power to your panel through the device. I am sure they do it since that is the easiest way for them to get CT's over that main feed, but it could be done simpler. It could simply have current CT's that you put over your mains in your existing panel (or at any point along the feeder) and then have a contactor for the EV circuit to take care of the load shedding. There is no really good reason to run all the current of your panel through that box (which may be a higher install cost).

But with that being said, I don't know of any other product being sold that solves this kind of issue, so unless you can convince someone to sign off on just installing a 30a, 20a, or 15a 240v breaker without some kind of interlocking system like this, then this might be the only obvious option.

I suspect if you put a Sense on your panel and ran it for a while you would come to find out that you don't use that much power. I wonder if providing that evidence to the city would be sufficient to let you do something without a load shedding device. Though you don't have enough time to gather a year of data (or even at least a months worth as NEC allows for in some cases).

FWIW, I might consider wiring up a Wall Connector on a 50a circuit (tandem breaker with that 30a AC one) and then just set it to the 15a (12a continuous) setting to make the city happy. That would get you started and then as you got more proof of your usage levels you could crank it up later using the rotary dial once you determined that you actually had headroom.
 
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You should never put a NEMA 14-50 on a 20A or a 30A circuit.
For a 20A circuit, the appropriate socket is NEMA 6-20.
For 30A it is either NEMA 14-30, NEMA 10-30 (obsolete) or NEMA 6-30 (no native adapter).
Tesla UMC adapters are available for NEMA 6-20, NEMA 10-30 and NEMA 14-30.
To be pedantic here, I think putting a single 14-50 receptacle on a 20 A circuit is technically allowed
as long as your intended load does not exceed the ampacity of that circuit, but regardless, it is a bad idea.
I only would ever recommend putting a 40 or 50a circuit on a 14-50 (and the 40a only in very limited situations).

As stated above, the right thing is to put a 6-15, a 6-20, or a 14-30 on those lower amperage circuits
so the receptacle and the circuit are directly matched.

You are right, if I plan to use 20 A, I should install a NEMA 6-20.

I was mentioning the NEMA 14-50 since this is what I have for my kitchen oven range.
The oven is connected to a dual 50 A breaker inside my home.
And the main breaker next to the meter in the garage is a dual 60 A,

Oven 50 Amp cord.jpg

I will need to make an assessment of my home usage, but honestly I never use the oven.
I only use the range for cooking once a day around 7 pm.

Otherwise I only use a microwave and a small mini oven-toaster.
The microwave and the mini oven are connected to a single 20 A breaker on the first 120 V phase.
I have a fridge connected to a single 20 A breaker on the second 120 V phase.

I plan to use the PG&E EV rate from 11 pm until 7 am, and my commute is around 45 miles one way.
Using Tesla chart for the Model 3, a 20 A (max) / 16 A (nominal) 240 V 15 Kwh provides 15 miles / hour.
So for 8 hours, I will get 120 miles.

I could may be use a separate meter to put a NEMA 14-50 plug, but I want to limit the installation cost,
and I also need to install a 30 to 50 feet line connection.
 
Nobody's confirmed yet. The problem is that I'm on an airplane tomorrow morning and I won't be back in town until literally the night before I was scheduled to take delivery of the car. I don't have the ability to deal with this right now.

I really hope I didn't just eat $2,500 but it's starting to look like I did...
If they want refund the $2,500 you could delay delivery for a few months.
There may well be a cheap solution (eg. 100A breaker and confirm wire has sufficient gauge).

BTW, here in the good old USA (United States of Australia) we are blessed with 240V at every outlet, so this sort of problem isn't so severe. If you can find a wall plug you'll get 2.4kW charging.
 
I believe the future will be a device that clamps on your mains with CT's and then sends a signal to the EVSE (wall connector for instance) to get it to ramp down load or completely stop charging. It would make use of the existing ability of the Wall Connector to cut off the car from charging or to pare back load. All that would be required would be the CT's and a control board.

In theory, Tesla could easily offer this feature. Or, they could make the communication protocol public (or shared with partner) and have another company provide this product. No contractors, etc. Should be much lower cost.


The DC-9 product routes all power through the box and splits off the EVSE with a breaker. It would work if there are no breakers in the main box.

However, the DC-10 product does have external CT and requires a breaker in the main panel.
 
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You are right, if I plan to use 20 A, I should install a NEMA 6-20.

I was mentioning the NEMA 14-50 since this is what I have for my kitchen oven range.
The oven is connected to a dual 50 A breaker inside my home.
And the main breaker next to the meter in the garage is a dual 60 A,

View attachment 344578

I will need to make an assessment of my home usage, but honestly I never use the oven.
I only use the range for cooking once a day around 7 pm.

Otherwise I only use a microwave and a small mini oven-toaster.
The microwave and the mini oven are connected to a single 20 A breaker on the first 120 V phase.
I have a fridge connected to a single 20 A breaker on the second 120 V phase.

I plan to use the PG&E EV rate from 11 pm until 7 am, and my commute is around 45 miles one way.
Using Tesla chart for the Model 3, a 20 A (max) / 16 A (nominal) 240 V 15 Kwh provides 15 miles / hour.
So for 8 hours, I will get 120 miles.

I could may be use a separate meter to put a NEMA 14-50 plug, but I want to limit the installation cost,
and I also need to install a 30 to 50 feet line connection.

Can you post a picture of your main panel?

I am shocked that you would have a 50a oven on what is only a 60a main feed. That is a crazy tiny amount of available power.

A 90 mile round trip commute is nothing to sneeze at. You are going to need to be nearly maxing your electrical feed all night in order to regenerate enough range.

I wonder if you could upgrade your main breaker in the garage and run larger gauge wires from there to a subpanel in the garage where you then had a 60a breaker to go towards upstairs and a decent size breaker to go to the car.

Or maybe pursue getting a dedicated meter just for the car in the garage.
 
In theory, Tesla could easily offer this feature. Or, they could make the communication protocol public (or shared with partner) and have another company provide this product. No contractors, etc. Should be much lower cost.


The DC-9 product routes all power through the box and splits off the EVSE with a breaker. It would work if there are no breakers in the main box.

However, the DC-10 product does have external CT and requires a breaker in the main panel.

Ah yes! For this use case I think the DCC-10 is a better option. Assuming that challenger panel is of the safe variety and that he can get a tandem breaker to share with the AC breaker pole (otherwise replacing that panel is easy), then I would just do the DCC-10.

I probably would do it on a full 50a circuit and do a wall connector. Then you could dial in either on the rotary dial (OR actually on the car since you no longer have the code calculation worry) the number of amps you wanted to charge at each night. If you selected too many amps the load shed device would activate and cut you off.
 
OP here. I heard back from the city regarding the proposed installation of the DCC box. They're open to it; I just have to submit plans that show load calculations and provide a "narrative", then have it installed by a licensed electrician. Bottom line is they didn't say "no" so it looks like I've got a realistic pathway to get 240V/30A. Thinking about calling up Tesla and saying "We are go for launch...".
 
A less expensive option might be to run both the HVAC and EVSE off the same 30a circuit with a transfer switch, since you rarely use the HVAC.

I'm not open to this idea. The AC always takes priority; it needs to "just work" for my SO who isn't going to mess with any complicated, "dangerous" switches by the circuit breakers in the garage.
 
I'm not open to this idea. The AC always takes priority; it needs to "just work" for my SO who isn't going to mess with any complicated, "dangerous" switches by the circuit breakers in the garage.
A transfer switch is not dangerous. You could switch to the car when you plug in, and switch to HVAC when you unplug - it would always be on HVAC when you are not home.

The point is you have lots of options for home charging - from an automatic load transfer switch, adding a 240v circuit, charging on 120v, or a manual transfer switch. If you don't want the car, cancel the order - but home charging is not an issue.

Have you had any other electricians (other than the one that said you could put a 240v/30a charging circuit on your existing panel) come out to look?
 
Can you post a picture of your main panel?
Main dual breakers 60 A 240 V near the electric meter in the garage.
20181014_221037.jpg

Top two single breakers: 20 A 120 V (Left: phase 1 - Fridge) (Right: phase 2 - Microwave)
Center dual breakers: 50 A 240 V (2 phases - Electric range and oven)
Bottom Left and Right breakers: 15 A 120 V (Living room) (Bedrooms)
20181014_084826.jpg
I am shocked that you would have a 50a oven on what is only a 60a main feed.
That is a crazy tiny amount of available power.
Well, I think it's more simple for the appliance maker to put the same plug to all the devices regarding of the exact power needed.
So you can have a range using natural gas and an electric oven, and an electric range and oven using the same plug.

I don't think also that an oven need that much continuous power, after 10 minutes an oven reach the expected temperature
and only additional energy is needed to keep it warm because of convection loss.
A 90 mile round trip commute is nothing to sneeze at.
You are going to need to be nearly maxing your electrical feed all night in order to regenerate enough range.
20 A (max) / 16 A (nominal) 240 V 15 Kwh provides 15 miles / hour. So for 8 hours, I will get 120 miles.
I wonder if you could upgrade your main breaker in the garage and run larger gauge wires from there to a subpanel
in the garage where you then had a 60a breaker to go towards upstairs and a decent size breaker to go to the car.
Or maybe pursue getting a dedicated meter just for the car in the garage.
Well, last month I used 400 kwh for 30 days period, It's about 13 kwh / day, if you consider 8 hours of been sleeping,
It's just less than 1 kwh every hour (less than 10 A 120 V). Only the fridge run all the day long for few minutes.

Since I don't really use the oven, only a microwave most of the time,
charging a car battery in middle of the night at 20 A 240 V seems not an issue.

If my daily mileage incrase, I will get a separate meter to install a 40/32 A 240 V plug, but if all the tenants
do the same in the future, the building will be overcapacity, and a new line to the street transformer will be needed.
 
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Main dual breakers 60 A 240 V near the electric meter in the garage.
View attachment 344904

Top two single breakers: 20 A 120 V (Left: phase 1 - Fridge) (Right: phase 2 - Microwave)
Center dual breakers: 50 A 240 V (2 phases - Electric range and oven)
Bottom Left and Right breakers: 15 A 120 V (Living room) (Bedrooms)
View attachment 344902

Well, I think it's more simple for the appliance maker to put the same plug to all the devices regarding of the exact power needed.
So you can have a range using natural gas and an electric oven, and an electric range and oven using the same plug.

I don't think also that an oven need that much continuous power, after 10 minutes an oven reach the expected temperature
and only additional energy is needed to keep it warm because of convection loss.

20 A (max) / 16 A (nominal) 240 V 15 Kwh provides 15 miles / hour. So for 8 hours, I will get 120 miles.

Well, last month I used 400 kwh for 30 days period, It's about 13 kwh / day, if you consider 8 hours of been sleeping,
It's just less than 1 kwh every hour (less than 10 A 120 V). Only the fridge run all the day long for few minutes.

Since I don't really use the oven, only a microwave most of the time,
charging a car battery in middle of the night at 20 A 240 V seems not an issue.

If my daily mileage incrase, I will get a separate meter to install a 40/32 A 240 V plug, but if all the tenants
do the same in the future, the building will be overcapacity, and a new line to the street transformer will be needed.

Wow, I have never seen that small a service panel (with so few circuits) even in a condo. What year is that from?

So I think there is basically zero chance that your local electrical authorities (AHJ) will let you add anything additional to that 60a service feed load calculation wise. 60a is just an extremely tiny service. Even though as you state, say 20a at 240v but only run overnight (while you are not cooking) is likely to be fine. The issue is that they do this all of calculated load and they have to assume a future tenant might run the oven all the time, etc...

How is your unit heated/cooled btw? I assume some central heating source like radiators?

With all that being said, you might be a prime candidate for the load shedding ability that has been discussed in this thread. In this case the model of unit that can go "inline" on the feed from that main breaker in the garage up to your unit. You could tap say 30a off of that and have it load shed the car when necessary (like if you ran the oven and all burners on the stove at once). This should not impact load calculations as it is a "scavenger" class of energy use. It will only let the car charge when it is otherwise not in use.

Another solution as mentioned might be to investigate the main meter base and switchgear. If it is rated for say 100a then you might be able to swap the 60a breaker with a 100a breaker and run new 100a capable wire to a sub panel in the garage and then pull a 40a circuit off of that for the car (good for 32a of charging), and then have a 60a breaker to continue on using the existing wiring to feed your unit upstairs. This would be a very robust solution. The trick is that you would need to ensure the building main electrical service is not near capacity (the power company might be able to help with this since if they have upgraded their smart meters they may have historical 15 minute readings on everything for the past year or more. I am sure this would not allow more than one or a handful of EV's due to the main panel load considerations, but you might be able to squeak in before others ask to do the same...
 
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I just had a DCC put in as part of my charger installation. Definitely pricey but was the only way to get the installation approved in my condo and better than worrying about what happens when you're charging the car while the dryer, heater, etc. are all running.

Nice first post. Out of curiosity, how did you find out about the DCC? From your electrician?
 
I just had a DCC put in as part of my charger installation. Definitely pricey but was the only way to get the installation approved in my condo and better than worrying about what happens when you're charging the car while the dryer, heater, etc. are all running.

Was the DCC installation signed off by a city inspector? Did they ask any questions or request any additional information when the permit was requested? Or was it installed without a permit? :)
 
I did some math based on your 70a feed and for instance if you did not have that AC unit I suspect you could fit a 30a car charging circuit into your load calculations and still stay under 70a. So if that was the case, the cities arbitrary 100a requirement would be too restrictive. (how many sq feet is your home btw as that is a major factor? - also is the "GDO" circuit just the garage door opener - odd to have it on a dedicated circuit)

Yep, GDO stands for Garage Door Opener. Maybe back in 1989 they had extra high power electric motors in them...

But with that being said, I don't know of any other product being sold that solves this kind of issue, so unless you can convince someone to sign off on just installing a 30a, 20a, or 15a 240v breaker without some kind of interlocking system like this, then this might be the only obvious option.

I got in touch with the manufacturer of the DCC. They're quite responsive and they referred me to an electrician in my area who I've been in contact with. Although I'm out of town at the moment, the electrician did a drive-by of my property and inspected the shared panel on the building exterior. It's a 400A panel with four 70A breakers on it (each leading to separate condos, one of which is mine). He also said the panel feeds each unit via some fairly large conduits, which he felt we could route higher capacity wire through if necessary allowing us to change the main breaker from 70A to 100A. If I could swap the main breaker to 100A and then replace the Challenger sub panel in my garage with something newer, I could probably get a 30A circuit installed without having to deal with the DCC box at all. Of course, if none of that's possible then the DCC is probably my last hope.

I'll know more this coming week when I return and I can meet the electrician in person.

Based on some comments here it sounds like the 70A main breaker to my unit is just barely adequate as it is even without adding an extra circuit for charging an EV. IANAE but does anyone know if electrical load calculations changed during the past 30 years?
 
Yep, GDO stands for Garage Door Opener. Maybe back in 1989 they had extra high power electric motors in them...



I got in touch with the manufacturer of the DCC. They're quite responsive and they referred me to an electrician in my area who I've been in contact with. Although I'm out of town at the moment, the electrician did a drive-by of my property and inspected the shared panel on the building exterior. It's a 400A panel with four 70A breakers on it (each leading to separate condos, one of which is mine). He also said the panel feeds each unit via some fairly large conduits, which he felt we could route higher capacity wire through if necessary allowing us to change the main breaker from 70A to 100A. If I could swap the main breaker to 100A and then replace the Challenger sub panel in my garage with something newer, I could probably get a 30A circuit installed without having to deal with the DCC box at all. Of course, if none of that's possible then the DCC is probably my last hope.

I'll know more this coming week when I return and I can meet the electrician in person.

Based on some comments here it sounds like the 70A main breaker to my unit is just barely adequate as it is even without adding an extra circuit for charging an EV. IANAE but does anyone know if electrical load calculations changed during the past 30 years?

That electrician sounds right! I really like the idea of pulling new wire through the existing conduit. Most cost effective will be aluminum wire, but if you are limited on conduit space and want more capacity then copper will give you a lot more capacity for the same sized wire (though it is quite expensive right now - still way less than a DCC box). Keeping things simple is worth a lot to me. The DCC box is just complexity asking for failure (though if there are no other options, it very much serves a need).

I might pull the largest wire allowable in that conduit - if indeed that panel you come off is a 400a panel and it only feeds four units, then that won't be your limit. If you can get a breaker for that main panel that is 125a and can fit wire in that conduit rated for 125a, then I might take it all the way up to a 125a subpanel in my unit. Heck, at that point you could probably install a 60a breaker to a Wall Connector and charge your Model 3 at maximum amps (48a continuous). Pretty much any subpanel you purchase these days will be rated for 125a.

Note that once you get up to a 100a service (or above - up to 400a) for whatever whacky NEC reason, 310.15(B)(7) allows you to only size the conductors to 83% of the service rating. So a 100a service only needs 83 amp capable conductors. Don't ask me why (I am sure it was because builders were pointing out that nobody was really using the full service capacity - so rather than change the load calculation formula, they modified this?). I am not convinced this "hack" in the code is a good idea as we head into the EV world, but it exists and is totally allowable to make use of. My house (and nearly every home I run across) takes advantage of this. It uses 4/0 aluminum wire for a 200a service which is only rated to 180 amps, but 310.15(B)(7) says you only need to plan for 166 amps.

What’s Happening to Table 310.15(B)(7)?

So to recap:

Best available option is to replace your existing panel with a new one rated up to 125 amps and that has more breaker spots.
Re-conductor through that conduit with new wire - either aluminum or copper depending on conduit size availability
Install a 14-30r, or a 14-50r, or a Wall Connector on a 50a or 60a breaker (if you do a Wall Connector you can crank it down to fit in any load profile you need it to fit in)
Replace main breaker in Condo panel with appropriate size for new wire gauge - optimally 125a! Otherwise, whatever the next size down that can be used in that main panel and with appropriate ampacity wire.

Wire options:
125a breaker
1 AWG Copper (2 AWG Copper allowed if factoring in 310.15(B)(7))
2/0 AWG Aluminum (1/0 AWG Aluminum allowed if factoring in 310.15(B)(7))

100a breaker
3 AWG Copper (4 AWG Copper allowed if factoring in 310.15(B)(7))
1 AWG Aluminum (2 AWG Aluminum allowed if factoring in 310.15(B)(7))
 
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You are really overthinking this. One electrician already said you could add a 30a charging circuit.

Quick back-of-the-napkin load calc: 24A HVAC and another 20A for applicances (microwave, dishwasher, refrigerator, washer, dryer) brings you to 44A. Another 6A for lighting and other miscellaneous and you are at 50A - if everything is running at the same time. I think you would have a hard time generating a 50A load in your house if you tried.

Another way to look at it is your highest electric bill during the year - my guess is maybe 36kWh average per day. That would be a 15a average load.

Get an electrician to do real load calculation, and I'll bet you'll find you can add a 20A charging circuit to the existing panel without any issue.

If you want to upgrade your electric service and replace the panel that is fine - but why not use the money to upgrade your M3 instead?
 
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I got in touch with the manufacturer of the DCC. They're quite responsive and they referred me to an electrician in my area who I've been in contact with. Although I'm out of town at the moment, the electrician did a drive-by of my property and inspected the shared panel on the building exterior. It's a 400A panel with four 70A breakers on it (each leading to separate condos, one of which is mine). He also said the panel feeds each unit via some fairly large conduits, which he felt we could route higher capacity wire through if necessary allowing us to change the main breaker from 70A to 100A. If I could swap the main breaker to 100A and then replace the Challenger sub panel in my garage with something newer, I could probably get a 30A circuit installed without having to deal with the DCC box at all. Of course, if none of that's possible then the DCC is probably my last hope.
Sounds like an excellent plan.

I would be very nervous about adding anything to a panel as small as what you have now. Then when you consider how old it is, much better to go with new components.
 
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