Charging cord size for EVSE

[AntonLargiader]

I recently bought an Emporia Smart Home EVSE. 14-50 plug (40A actual) or hardwire (48A actual). It had a problem so they sent me a new one.

The old one, which was a refurb, has a 3/4" diameter 9-9-10-18 S-cord to the charging gun, while the newer one has a 7/8" 8-8-10-16. Both have the same 15/16" cord to the plug, but I can't see any ID on it.

The smaller cord is WAY more flexible, but I'm wondering if it was undersized for the maximum throughput that the EVSE has. It's not really an issue for me - our car only draws 32A - but a table I see on line indicates that the ampacity of 8 cord with two current-carrying conductors is somewhat less than the output of this EVSE.

Thoughts?

 

[75gmck25]

If you use a 40 amp breaker with 8 gauge copper wire and reduce its rating to 32 amps because it's a continuous load, I think you are within the right specs.

I have a Chargepoint Flex EVSE, and IIRC when I hard-wired I found that the conductors in the charge cord looked like they were only about 8 gauge, unless it was a really flexible 6 gauge wire. Followed the documentation for hard-wire and I used 6/3 copper and a 60 amp breaker (found out later that it only needed 6/2) . This covers EV's that draw up to 48 amps maximum.

Also, don't forget that the actual charger is in your car, and the EVSE you purchased has a handshake/management function that works with the car. I don't know how closely the EVSE monitors heat and amp draw, but it may be able to reduce amperage if there are problems.

 

[AntonLargiader]

I'm mostly talking about the cord to the gun (which carries the same current as the appliance cord) being 9 AWG for a device potentially passing 48A.

I don't think the EVSE has any control over amperage other than connecting or not connecting. My understanding is the EVSE broadcasts the max current available, the car requests connection, the EVSE connects, and then it's up to the car to draw an appropriate level (no greater than what the EVSE initially offered).

 

[dscheidt]

The NEC rules on wire ampacity are very conservative. They assume that wires are going to be buried in insulation, and other pessimistic assumptions. The manufacturer of the device isn't bound by them, and because they know things about their product and how it is used, can specify wires that are smaller. That cord connecting the car is in free air, so it can shed heat pretty effectively. They also can be sure they're using components that can run at high temperature. That they increased the size of the cable suggests they had a problem with the old one.

 

[75gmck25]

I agree that the EVSE has minimal control over amperage.

However, when I installed mine there was a menu where you picked the vehicle and then picked the amperage choice from a list. In my case the list was incorrect (it maxed at 16 amps), and I had to go through tech support to get it to show the correct max of 32 amps.

I don't know how it would've worked if I had configured the EVSE for a Ford Lightning or a Tesla, which would have a much higher max amperage, but didn't really have one of those vehicles. My current EVSE would still only ask for 32 amps, so maybe it doesn't really matter.

 

[PCustoms]

The NEC rules on wire ampacity are very conservative.

And NEC doesn't apply past the building (which you sort of mentioned).

The evse would have been built and tested by an NRTL (i.e. UL). If it wasn't, then you probably shouldn't be using it.

9awg isn't common in the USA either, so I assume it's metric that someone labeled for the US.

 

[AntonLargiader]

Emporia is a Canadian company. Might explain the 9 AWG. The label says UL Certified with a number.

I'd way rather have the thinner cable that came with the first unit. Dealing with the thicker one isn't awful but it's just a lot less flexible. I'll figure out a good way to use it so that it doesn't have to bend much.

 

[gtae07]

However, when I installed mine there was a menu where you picked the vehicle and then picked the amperage choice from a list.

That's odd. I'd have expected that you set the max ampsrage on the EVSE based on the wire and breaker feeding it. The vehicle should be smart enough to know what its maximum amperage is, and when you connect them they'll figure out the max based on whichever is lower.

At least, that's how my Tesla wall charger is...

 

[johnre]

I'd have expected that you set the max amps [range] on the EVSE based on the wire and breaker feeding it. The vehicle should be smart enough to know what its maximum amperage is, and when you connect them they'll figure out the max based on whichever is lower.

True, it's entirely in the handshake between EVSE and vehicle - you plug it in, the EVSE tells the vehicle the maximum current that it can deliver, and the vehicle is supposed to limit its current draw to that maximum capacity.

But my older Clipper Creek HCS-50 has no such means to set that parameter that it communicates to the vehicle - it's hardwired into its embedded control system. That means in my case I need to size the breaker and wire gauge to the EVSE appropriately for worst case.

 

[75gmck25]

I have seen other complaints about the Chargepoint installation and setup for the max amperage. They provide directions for wiring a circuit for 60 amps (or 48 amps continuous), but then you use the installation app and configure it to the vehicle and its max amperage.

The Chargepoint Flex EVSE has smart app features that I can access, and to get a POCO rebate I also allowed the power company to access the EVSE. Every so often I see an app message in the morning that says the power company has limited the charging rate for my EVSE because of high power load in the area. However, its always a very short time period, and always at night.

 

[AntonLargiader]

Yeah, those sound like confusing instructions. Many charge stations serve more than one vehicle. It's not like the station can force the current out or anything like that.

Are you on Dominion Power? We are. They have that program and I might just sign up for it; the Emporia can do what they need it to do.

 

[75gmck25]

I have Dominion Power. With the Chargepoint Flex EVSE I got a $120 initial rebate, and with the power monitoring I get $40 back each year for 3 years.

Home Depot has the Chargepoint EVSEs online with free shipping, and I was able to get a 10% discount for Military/Home Depot Pro. Still pretty expensive overall, but they are well supported.