Sound right? Electrician recommended 40A with UF 8/3 outdoor wire to be buried under my concrete

[FlasherZ]

so what would be needed for an EVSE charger?

That UF-B cable will be fine for a hardwired EVSE with 40A charging or less.

For an EVSE with 48A charging load, #6 THWN in buried conduit is the best option.

For larger EVSE's (e.g., the Ford Charge Station Pro), it depends upon the amount of charging current you want it to offer. At that point, it's pretty much wire-in-conduit and you'll size the wires based on charging loads. For the most common beyond 48A charging (72A charging or 80A charging), you'll want #3 wire in conduit.

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[jefro]

If one wanted to set their EVSE at 48A.
May need to run 4 AWG. https://www.galvinpower.org/size-wire-for-a-60-amp-breaker/

An example on This Old House showed their local code install of underground. In the areas that one could get deep enough (and freeze may be part of this too) they could run conduit on a bed of sand. Cover with sand, Then add half dirt. They also then had to run a special yellow ribbon to warn diggers. On the areas they couldn't get to depth their inspector allowed them to concrete over to protect it from digging.
It usually never hurts to run pvc conduit usually your code has to be read. Good thing about direct burial is heat tends to get absorbed.

 

[bewbie]

thanks for all the info! i think i will go with the UF-B 6/3 and eventually go with the Juice Box 40. I unfortunately have to run the wire myself and am not efficient in running condiut.

 

[rdr854]

NEC/NFPA requires the circuit breaker be 25% greater than the evse output amperage. Wire should be sized for circuit breaker rating.
As the home owner you can do what you want and hope nothing happens. A licensed electrician must follow applicable codes.

I thought it was 20%, not 25%. The basis for this is that I needed a 100 amp circuit for an 80 amp charger.

 

[tls]

I thought it was 20%, not 25%. The basis for this is that I needed a 100 amp circuit for an 80 amp charger.

100 / 80 = 1.25

 

[tls]

UF-B Is direct burial (no conduit), so upgrading to 6-3 would not require larger conduit, or much more cost if distance is not too much. I would do 6-3, 70 amp breaker and 14-50 outlet.

You can't (legally or safely) protect a 50-amp outlet with a 70-amp breaker.

 

[PV2EV]

You may not use a 70A breaker on either a NEMA 14-50 receptacle (50A breaker max) or UF 6-3 conductors. When you use NM cable or UF cable, you must use the 60 degC column for ampacity, and for #6 cable that's only 55A. However, because a 14-50 receptacle is maximum 50A, you may not use more than a 50A breaker to protect it.

The way the NEC works is that it starts with the load. If the load is 55A (after figuring for continuous load requirements or if not required), you select the conductor for the load to be carried (in this case, UF 6/3 would be sufficient), then select the OCPD (breaker) to protect the circuit. Because there is no 55A breaker, a 60A breaker is sufficient.

Right, the 14-50 must have no more than a 50A breaker, and in many places requires a GFCI breaker. This may not work with many EVSE, so hard wiring is a better solution. That is were I was thinking 70A breaker, for a 50A EVSE. Or a 60A breaker for a 48A EVSE.

UF-B is rated for 90c, so should work @ 62.5amps (50amp x 1.25), correct?

 

[FlasherZ]

Right, the 14-50 must have no more than a 50A breaker, and in many places requires a GFCI breaker. This may not work with many EVSE, so hard wiring is a better solution. That is were I was thinking 70A breaker, for a 50A EVSE. Or a 60A breaker for a 48A EVSE.

UF-B is rated for 90c, so should work @ 62.5amps (50amp x 1.25), correct?

Unfortunately, no. UF cable may be identified at 90 degC, however like NM cable, NEC requires ampacity based on the 60 degC column. (NEC 2017 340.80) #6 UF is only rated to 55A, or a 44A EV charging load.

 

[FlasherZ]

If one wanted to set their EVSE at 48A.
May need to run 4 AWG. https://www.galvinpower.org/size-wire-for-a-60-amp-breaker/

If using UF cable, this is correct. However, #6 will work for wire in conduit.

 

[PV2EV]

Unfortunately, no. UF cable may be identified at 90 degC, however like NM cable, NEC requires ampacity based on the 60 degC column. (NEC 2017 340.80) #6 UF is only rated to 55A, or a 44A EV charging load.

So you get derated twice, once for the continuos load and again for the cable type, wow. So 4-3 UF for a 50A EVSE, or 6-3 THHN in a conduit. Glad my install is in conduit.

 

[bewbie]

So a run with 6/3 THHN in conduit will work for a 48A EVSE correct?

 

[RickLightning]

If the goal is to future proof, then you should run the largest wire that is feasible. I would never consider anything less than a 48amp EVSE, which requires a 60amp breaker, because that future proofs. I did this last summer.

 

[bewbie]

If the goal is to future proof, then you should run the largest wire that is feasible. I would never consider anything less than a 48amp EVSE, which requires a 60amp breaker, because that future proofs. I did this last summer.

So #6 in conduit should be ok?

 

[Maquis]

So a run with 6/3 THHN in conduit will work for a 48A EVSE correct?

Yes.

 

[RickLightning]

So #6 in conduit should be ok?

I am not knowledgeable in code.

If you are running conduit, and could easily swap wire out, then you can make a different decision than if you can't easily swap wire.

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