Charging Install Second Home (Electrical Advice Needed)

[andisimose]

Soliciting the hive mind as Ive been given a few options.

Our secondary home was built in the 60s and been modified a few times, while pulling a new wire from the panel is absolutely possible it wont be easy or cheap. So we have been given a few options using some existing wiring and not entirely sure where to go.

Situation:
In one of the remodels of this house the dryer was moved and added into a new breaker, but the wiring from the old breaker was left in the crawl space very close to where we would need to plug in our car. Its 8-8-8 Copper SEU cable

Option 1: ($$$) Run a whole new length of cable and install a EVSE or 14-50 outlet

Option 2: ($$) we would install a junction box and "splice" (or use a disconnect**) a extension of 8 ga cable to go approximately 15 feet further on the house to get to the driveway side of the home and install a full fledged EVSE, I'm told we could do a 50 amp circuit as copper SEU is rated to 50a on the 75 degree column?

Option 3: ($) we would install a junction box and "splice" (or use a disconnect**) a extension of 8 ga cable to go approximately 15 feet further on the house to get to the driveway side of the home and install a 6-50R in a outdoor box and buy a amazon adapter and use our travel chargers for charging. Its only 3 wires so a 14-50 is really out if we want to be in code compliance.

** I say disconnect as where the junction would be is right at the crawl space door and would provide a good place to put a within sight disconnect for service/etc.

What would y'all do? Its a second home were at on weekends in the summer and it would be my R1S whenever it comes and occasionally my wife's PHEV (albeit not necessary for her to ever HAVE to charge)

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[SANZC02]

Depends on how old that old wire is.

If it were me, I would run new 6 gauge thhn from the panel using the slot that old 8 gauge is consuming. Might cost a few hundred more but worth the piece of mind to me.

 

[Hoo D. Hoo]

I'm with @SANZC02 . The house is 60 years old, has been through modifications -- who knows what shape that old wiring is in or what flaws are buried somewhere you can't see between the box and your new location?

Safety and peace of mind are paramount. Take Sanz's suggestion. If there's existing conduit, using that where you can may save a little. But run brand new wire with brand new insulation.

 

[golden_frog]

I also vote for new 6 gauge wire. Just ran 75 foot of it for mine.

Option 3- portable charger? If it's only seasonal and on weekends, can't you get like 200 miles in 72 hours?

 

[Moon]

Depends on how old that old wire is.

If it were me, I would run new 6 gauge thhn from the panel using the slot that old 8 gauge is consuming. Might cost a few hundred more but worth the piece of mind to me.

One more vote.

I have experience installing a Tesla WC myself in a modern house. I did a lot of research at the time, and many people on different forums, recommend 6 gauge wire, it is a bit hard to pass them through conduits, but worth it, peace of mind.

 

[jeeden]

One more vote.

I have experience installing a Tesla WC myself in a modern house. I did a lot of research at the time, and many people on different forums, recommend 6 gauge wire, it is a bit hard to pass them through conduits, but worth it, peace of mind.

Did you use non metallic conduit or metallic? I read somewhere that using non metallic would drop the temp rating again similar to using romex?

 

[Moon]

Did you use non metallic conduit or metallic? I read somewhere that using non metallic would drop the temp rating again similar to using romex?

Someone in Teslamotorsclub had done tests using heat gun, max temperature reported was within 120°F charging at 40 AMPs.

I used non-metallic PVC, Sch 40, 3/4" conduits which are rated for 90° C and for the L1, L2, I used Southwire SIMpull #6 THHN and #6 bare copper for ground. I could have used #8 for the ground, running #6 bare copper through 3/4" conduits was hard.

Many people have also used Romex 6/3 concealed using 3/4" or 1" conduits, I found it to be a bit expensive.

About heat, just remembered reading comments from others mentioning why we must hang the charging cord relatively loose when full length is not used - it won't trap the heat, minor, but in case someone plans to charge at max amps all the time must pay attention to all these facts. In our case cord is always in tight loops, about 2ft(one loop) is all we use as the car sits very close.

It's been almost an year with Model Y, we hardly charge at max current, mostly we charge at 16 or 24 amps overnight, just one or two times we might have charged at 48 amps.

 

[jeeden]

Someone in Teslamotorsclub had done tests using heat gun, max temperature reported was within 120°F charging at 40 AMPs.

I used non-metallic PVC, Sch 40, 3/4" conduits which are rated for 90° C and for the L1, L2, I used Southwire SIMpull #6 THHN and #6 bare copper for ground. I could have used #8 for the ground, running #6 bare copper through 3/4" conduits was hard.

Many people have also used Romex 6/3 concealed using 3/4" or 1" conduits, I found it to be a bit expensive.

About heat, just remembered reading comments from others mentioning why we must hang the charging cord relatively loose when full length is not used - it won't trap the heat, minor, but in case someone plans to charge at max amps all the time must pay attention to all these facts. In our case cord is always in tight loops, about 2ft(one loop) is all we use as the car sits very close.

It's been almost an year with Model Y, we hardly charge at max current, mostly we charge at 16 or 24 amps overnight, just one or two times we might have charged at 48 amps.

Thanks for the information, I appreciate the details. When I said heat I meant the electrical code heat rating of the wire in the conduit, not the charger cable. Technically 6/3 romex is not rated for 48 amps continuous at max temperature. That would be the major reason to go to 6 gauge THHN. When you put the THHN in conduit, you are again subject to a heat rating though depending on the type.

 

[Moon]

Technically 6/3 romex is not rated for 48 amps continuous at max temperature. That would be the major reason to go to 6 gauge THHN. When you put the THHN in conduit, you are again subject to a heat rating though depending on the type.

Good to know, yes agree, there were mixed opinions, like here for e.g: https://teslamotorsclub.com/tmc/threads/anyone-use-this-romex-6-3-cable-during-install.199177/

Yes, #6 THHN are better.

 

[SANZC02]

Good to know, yes agree, there were mixed opinions, like here for e.g: https://teslamotorsclub.com/tmc/threads/anyone-use-this-romex-6-3-cable-during-install.199177/

Yes, #6 THHN are better.

That thread is not accurate, will it work sure but, it does not meet code. 6/3 Romex is rated at max 55 amps so based on the 80% continuous use parameter the max you should use it for is a 44 amp continuous load. Romex is usually put on a 50 amp breaker for a 40 amp continuous draw.

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