Juicebox 48 Load Sharing Setup

[astonius]

@timesinks thanks for the detailed write-up! I have a follow-up question from my other thread about your setup. This shared-circuit arrangement sounds really clean and efficient, and it also sounds like it’s in line with NEC so long as they are setup to load-share. I’m curious if the Juicebox installation guidance explicitly outlines the 3-port splice you made, or if it specifies a sub panel with a dedicated breaker for each unit (or both). I’d really like to use the Tesla Gen 3 connectors, but the manual only mentions the latter option which adds a fair amount of cost. Do you see a reason why this setup wouldn’t work with those units or would not be within code?

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[timesinks]

@timesinks thanks for the detailed write-up! I have a follow-up question from my other thread about your setup. This shared-circuit arrangement sounds really clean and efficient, and it also sounds like it’s in line with NEC so long as they are setup to load-share. I’m curious if the Juicebox installation guidance explicitly outlines the 3-port splice you made, or if it specifies a sub panel with a dedicated breaker for each unit (or both). I’d really like to use the Tesla Gen 3 connectors, but the manual only mentions the latter option which adds a fair amount of cost. Do you see a reason why this setup wouldn’t work with those units or would not be within code?

Honestly, I think the most literal reading of the 2020 code requires a dedicated branch circuit (breaker) per EVSE (because "outlet" is broader than receptacle and includes hardwire outlets). But the feeder to the subpanel can be sized using the load sharing limits, which means you still have shared 6AWG wire feeding two 48A EVSEs at the same time and protected by the single upstream 60A breaker. I guess the main difference is you can turn only one off without the other if you need to service them.

625.40 Electric Vehicle Branch Circuit. Each outlet installed for the purpose of charging electric vehicles shall be supplied by an individual branch circuit. Each circuit shall have no other outlets.

625.42 Rating. The power transfer equipment shall have sufficient rating to supply the load served. Electric vehicle charging loads shall be considered to be continuous loads for the purposes of this article. Service and feeder shall be sized in accordance with the product ratings. Where an automatic load management system is used, the maximum equipment load on a service and feeder shall be the maximum load permitted by the automatic load management system.

That said, the juicebox install manual is pretty clear that they want to be on the same "circuit" and that multiple outlets can be installed "per circuit".

I think there's a little bit of inconsistency between the code and the install manual. But code also requires that listed equipment be installed according to the included instructions, and I know that at least here in WA, that's the most commonly written correction on electrical permits. The inspectors here put a lot of emphasis on following the manufacturer's instructions.

My inspector had never seen a load-shared EVSE installation before and asked me a ton of questions about how it worked, genuinely curious about it because he fully expected to be seeing more of it down the line. We talked through it all, he was convinced the setup was safe and reasonable, and he asked for a copy of the install manual just so he could learn more. Since there is some ambiguity and some conflicting provisions, there's a lot to be said for figuring out the local consensus before committing too firmly to any particular design.

And while regular 60A breakers are probably a lot cheaper than those 3-tap polaris connectors, a suitable enclosure for the subpanel will probably eat into those savings.

 

[lefkonj]

Just wanted to clarify, you basically wire each 14-50 outlet to the same breaker and use the software to control the load. I saw some posts with a middle man box connected to the breaker and the chargers connected to the middle man.

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