20 amp vs 40 amp

[VoltinME]

Greetings,
I am a proud owner of a 2 week old Chevy Volt. I decided to purchase the 240 Voltec charging station from SPX. I have received it with a thinking I would have someone install it. I got nervous. I figured will my electrician really know what they are doing, the permits, the guarantee...uggg...So I called SPX and I have decided to install through them. Good or bad the total will be around $1,700.... Now...I currently have a 20amp circuit in the garage ready to go but the electrician who did the site assessment recommended I upgrade to a 40 amp. More wiring is required. I was quoted 2 prices. One with the 20 amp and the other with the 40 amp. It is a difference of $300.

Is going to the 40 amp the better option? I don't know much about electricity but I get all charged up reading this website. (pun here. ) Any thoughts? Stick with 20 or go with the 40?

[PAredvolt]

20 amps @ 240v is all the Voltec needs. If you think you might buy a car in the future with a larger battery capacity, go for the 40 Amp service.

[solar_dave]

We went one step further and added a 60 amp sub panel in the garage, currently running 2 SPX 240 volt chargers off that.

[JMatt]

40 amp. The 2012 Ford Focus Electric already has a 6.6 kwh charger, which needs the 40 amp service. I'd expect most cars to need (or at least be able to enjoy) 40 amps in the near future.

[Lee Willis]

I'd go with 40 amp just for piece of mind. With a 20 amp, things should work, and they should be safe and durable, but you would be using most of the circuit capacity every day for a lengthy duty cycle period. High leve of loading means high stress = potential for problems.

With a 40 amp circuit, you will have equipment that will never be stressed beyond around half of its rated capacity. If it were mine I'd do the 40 amp circuit. And by the way, I am getting a 240 V charger but not from SPX, and I will have a 30 or 40 amp circuit, not just 20.

[dethier]

I bought the Voltec charger from SPX and had a local electrician install it. No problem. Any licensed electrician should be able to do it. And it only cost me $462 to have it installed. SPX would've charged a lot more.

[Neromanceres]

I'm an engineer who designs products that are wired by electricians.

The Volt SPX 240V charger is a 3.3KW unit and is only cETLus approved for use on a 20A circuit. A 40A circuit breaker is oversized and in a short circuit event the breaker may not be able to protect the charging unit. The relays may weld shut and prevent the ground fault protection from functioning properly. The electrician that told you that you could use a 40A circuit direct to the unit is misguided and possibly dangerous.

Now if you want to install 8AWG wire to handle a 40A circuit in the future that is fine. But the SPX charger needs to be on a 20A circuit breaker max.

There are other L2 EVSE's out there that are designed to be used on a 40A circuit to take advantage of the higher 6.6KW charging of some other vehicles (Ford Focus EV, Tesla, ... etc). But the Volt SPX charger is not one of them. The SPX Volt charger works to only 15A continuous.

https://www.homecharging.spx.com/volt/pdf/GM10-463A.pdf

[Noel Park]

Neromanceres #7

Good advice IMHO. My dryer service, which I took over for the Voltec charger, actually had a 40 amp breaker. My electrician told me the same thing and we switched it out for a 20 amp. I had a similar experience with the SPX installer, telling me that I needed a 40 amp circuit and trying to move me way up market. I gave up on them and had a local guy do it and it worked out fine.

[figaro]

Hey VoltinME, Neromanceres' assessment is completely correct. I went through exactly what you are going through. I went through a lengthy fact finding mission only to find out that GM had given me the wrong advice to go with the 40 amp breaker. My electrician and I had reservations so we dug deeper. Through my Volt advisor, we ended up consulting with a GM/SPX engineer...he said exactly what Neromanceres just explained.

Heed his advice, and go with the heavier gauge wire (be careful not to go too big or it won't fit into the Level 2 terminal sockets) and a 20 amp breaker.

Hope this helps. So far the charger has performed great...however, just yesterday I found that when preconditioning at the comfort setting (and high fan setting), the charger experiences a fault part way into the preconditioning session. When I do it in eco mode, the fault does not occur it.

Figaro

[VoltinME]

Thanks for all your advice!!