Electrician wants to put in a Disconnect for the FCSP

[Maquis]

You can't really give that answer as it will depend on how long his run is. You have to account for voltage drop over the run which could require he upsize his wiring, the rule of thumb is 3% for a branch circuit.

He specified the length in the very first post.

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[Traconesu]

I have a 125ft run of copper for the FCSP being ran. There is about 90ft to get to the attached garage and the rest to where the charger is being placed. Electrician says it’s a national electrical code to put in a disconnect on the entry into the garage because it’s going to be rated at 100amps. He said he could do that or a panel. Other electricians I have talked too said to go straight from the main panel to the charger, nothing in between. I told them I don’t need something in between that could fail but they are not budging. They said they will make sure it is pulling 80amps at the charger even with the disconnect there. Any opinions on what I should do? They have done this before and been successful.

I'm retired now but have been an electrician all my life. So naturally I installed my 80 amp charger myself. Very short run to my 200 amp service breaker panel maybe 3 feet. Connected directly to a 100 amp 2 pole breaker. A 100 amp 2 pole breaker located inside your main service panel should suffice as a disconnect but the NEC changes every year so it's possible they want an available disconnect in the garage that will be more readily accessible in an emergency. It may have something to do the distance from the main service panel.

 

[Traconesu]

So the electrician wanted to run aluminum from the main panel to the disconnect to help with the cost. What gauge wire should it be? Am I going to lose any charging capacity at the FCSP or have my house burn down from using aluminum on that long of a run with continuous amperage load to the disconnect? Will the the aluminum or disconnect slow down my charging?

I personally don't like using aluminum wire even though it's cheaper you are required to use a larger size cable for aluminum wire.
The charger requires copper wire so it sounds like he's using the disconnect to transition from aluminum to copper wire. With a 90 foot run to the garage it wouldn't be a bad idea to have a disconnect located in your garage. It can be a non-fusable which will be a lower cost. There's no fear of fire as long as proper sizes breaker & wire are used for 100 amp circuit.

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