Can a 200amp load panel be added next to my meter box and then feed my main 100amp panel?

Question

I currently live in a 4 units condos building. On my side of the building we got a double meter box. Here’s the exact model

The ground floor condo has a 200amp main panel and mine is a 100amp.

First question: the double meter box is graded for 2X 200amp can I conclude that I can have access to 200amp instead of 100amp? Is it already available or my service company needs to upgrade the link to the main grid ? My building was constructed in 2016

In my unit my load is well balanced with my 100amp. I have an electric oven, electric dryer, an air conditioning unit and about 6000 watt of electric heating.

I just bought an PHEV car and would like to install a level 2 charger. My car can manage up to 38amp of load for charging.

So here’s my second question: Assuming that 200amp is available, could I install an outside 200amp load panel next to the double meter box with 4 breaker space, add a 40amp breaker for my Level 2 charger and a 100amp breaker for my main panel inside.

Could a panel like that do the job ?

I will of course hire an electrician do to the job but I need to know first if it can be done.

Thanks.

Answer 1

Basically that should work. But a few things to consider:

• Only the utility knows what feed wires you have to the meter, and only the utility can change those wires. For a 2016 build it is likely that you already have 200A-rated feed wires, and the fact that your neighbor already has 200A service is a good indication, but not a guarantee.
• Small panel at the meter, feeding the existing main panel as a subpanel is a good idea. That small panel will become your new main panel.
• Since this will be a main panel, you will most likely need to move your ground rod (or Ufer ground) connection from the existing main panel to the new panel.
• The new main panel will have neutral bonded to ground. Neutral must be unbonded in the old main (now sub) panel. Which means you may have a lot of moving of ground wires off of the neutral bar in the old main panel.
• The new main panel should have a 200A main breaker as well as a breaker for each load - 40A and 100A. If someday you upgrade the other panel to 200A, you will need to replace the feed from the main to the sub.
• You may have a problem with the existing feed. This is a biggie. The existing feed only needs to be rated for 83A. With your service changed to 200A, it needs to be rated for the full 100A of the panel. Depending on existing wire size, this may be a real issue. If it is an issue and therefore needs to be replaced, replacing it with larger wire (166A will do for 200A service) may be worthwhile, even if you are not replacing the 100A panel at this time.
• While I am reasonably certain you won't have an issue, technically you should do an NEC Load Calculation to make sure everything is OK. But going from 100A to 200A, even if you were a little bit over before you should have plenty of room to add 40A EV.

Answer 2

I really want to pull you back from what looks like a costly path here. You are thinking of the load as a traditional "dumb" load, which necessitates giving it a fixed amount of power. Modern EV charging standards are much smarter than that.

This allows you to sidestep the 100A/200A question entirely, a question that I think will go badly. The only evidence I see is the metering equipment being rated for 200A, but that doesn't mean much - all metering equipment on the market today is rated 200A. Anyway, let's get back to the good stuff.

From your loads which you described, your panel is fully subscribed, with no room at all. So we go directly to EVEMS aka Load Management. This ignores traditional provisioning rules; that is, we're no longer treating the EV station as an entirely stupid load. For about $300 extra over the cost of a normal wall unit station, it adds a power monitor which dynamically adjusts EV charge rate so the house cannot be overloaded (at least, not by the EV).

It will slow EV charging if you heavily use all your electric large appliances at once; so don't do that if you really need peak charging in a narrow time window.

Suitable models on the market today include the Wallbox Pulsar Plus w/ separate power meter, or the Emporia Load Management bundle with special firmware specifically to do this, or Tesla's J1772 Universal Wall Connector with Neurio power meter.

Any of these companies can refer you to electricians who have been through their training course and are familiar with the equipment; most random electricians have never heard of it, and/or hate it because it threatens sales of VERY profitable service upgrades.

As far as building this, the EV needs a breaker protecting the 40A circuit, and it needs an enclosure in which to put the power monitor. That Siemens panel you were looking at would be just fine, honestly. Since the 40A circuit is under active load management, it's not 140A of load to the meter, only 100A. The 200A main breaker can be disregarded.

The only change I would make is, you have chosen the 4-space version of that panel to scrimp a couple of bucks. I would go with the 8-space version, because there are many marvelous things that are well suited for the other 6 spaces, including a generator interlock, a surge suppressor, and solar. None of those things add draw to the panel, so the 200A main breaker can continue to be disregarded.