eprosenx
Active Member
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.