I have an existing 40-amp subpanel: a 125-amp main-lug load center, wired to a 40-amp breaker in the main panel with 8-3 NM-B.
The subpanel has one existing load – a minisplit heat pump. I wish to add a Level 2 EV charger to it. I'm unclear as to what size charger is acceptable.
Here is the technical manual for the existing load (minisplit), mine being the largest '15' size: https://portal.fujitsugeneral.com/files/catalog/files/%28D&T%29%20ASUG09-15LZAS.pdf
Page 2 of the manual (page 6 of the pdf) shows the "maximum operating current" as 13.4 amps, and the "rated" current as 5.2 amps. On page 68 (page 72 of the pdf) the "minimum circuit ampacity" is specfied as 16.5 amps.
The two EVSE under consideration are rated at 16amps and 20amps, respectively (calling for a circuit 125% as large).
Clearly the 16-amp model, protected by a 20amp breaker in the subpanel, is acceptable. But what about the 20amp model ? There seem to be two issues.
I know a branch circuit supplying a continuous load must be rated at 125% of the load. But I don't believe that's the case with a panel, that the panel's rating must be 125% the sum of all the loads of all the branch circuits served by the panel. So I don't believe I'm restricted to 32 amps (80% of 40-amps).
I'm also unsure which figure to use for the minisplit: 5.2 amps, 13.4 amps, or 16.5 amps.
Will the 20-amp EVSE fail to be code-compliant, or is the only issue nuisance tripping, which seems unlikely given the typical operating currents of the minisplit ?
For reference, here is the nameplate for the minispit (on the outdoor unit, which powers the indoor unit as usual with minisplit) …
Best Answer
The starting current isn't useful. It's an inverter drive/VFD, so starting current is a minimum case not a maximum. It's telling you essentially "don't worry about Locked Rotor Amperage (LRA) because this unit does not hard-start its motors".
I gather the indoor head takes power from the outdoor unit? The system has to figure for that voltage a sell. So per 440.6(B) it appears this unit gets 16.5 amps x 100% for breaker sizing.
Now, how it counts into the Load Calculation is a more complex matter. It appears to me based on 440.33 and .34, the figure used for the Load Calculation is the Rated-Load Current as defined at 440.2. This matches up to the 13.4A figure in my opinion.
That leaves 26.6 amps to allocate to all other loads.
EVSEs require a 125% derate off the actual charge rate so for example level 2 charging at 16A requires computing the breaker, wire and Load Calculation based on 20A. Don't accidentally apply this twice. Most EVSEs, when you commission them, will ask the circuit breaker size (that's not quite right, they mean the circuit size you want to use). If you say "20A" here, the EVSE will authorize the car's onboard charger to draw 16A actual. But don't add 25% more to that.
I think you can 25A from a panel that has 26.6A remaining, so it appears it can be a 25A breaker / 20A actual charge rate.
Speaking of that, you know about this thing, right? I know it can select 25A. Best bargain in town for the feature set, which includes firmware-configurable charge rate (so you don't need to buy a different EVSE if you upgrade ampacity), and Power Sharing across similar units (including the normal Tesla unit).