Sharing AC circuit with wall charger

[njmurvin]

I have purchased a wall charger for my new-to-me 2019 MX. My service panel on my house is on the opposite side of the house from the garage. While possible, it will be complicated and expensive to run a new circuit to the garage for the wall charger. There is no dryer circuit to commandeer- so that’s out.

However, I do have a 50 amp circuit just outside the garage powering my AC condenser unit. It sits idle probably 9-10 months out of the year and even when we do use it, we never run it past 11pm. I plan to charge the car between midnight and 8am. At 40 amps charging this should handle topping off the car nightly with no issues. Because these devices don’t routinely overlap, I am considering sharing this circuit between the AC and the charger.

Just because I don’t usually do something doesn’t mean it can’t happen that the charger and AC might find themselves on at the same time. So I’d like some protection against that aside from relying on the 50 amp breaker in the main panel. I have read about DPDT switches and using a small panel with a breaker interlock to assure both devices can’t run simultaneously. But those are manual switches and would be cumbersome to use on a daily basis.

Is there some kind of auto transfer device I can buy or build that would allow both devices to remain connected to power but, if the AC is running, would cut off power to the charger?

 

[Genie]

Evannex sells a smart splitter that says it does that. I haven’t tried it but they send endless email offers about it.

 

[ATPMSD]

The 50-amp AC circuit is probably a hardwire solution. They do not make a spliter that supports a 50-amp circuit with a hardwire input and two hardwire outputs (the Wall Connector also requires a hardwaire connection.) And of course the Wall Connector requires a dedicated connection.

So what can you do?

Install a sub-panel and terminate the 50-amp circuit at the sub-panel. Run one circuit to the AC unit and a second to the Wall Connector, each with its own 50-amp breaker. Then enable only one of the two circuit at a time. When you do not need AC you can leave the wall connector enabled and when you do need AC you will just have to flip both breakers.

Be adviced that breakers are not designed to be used as “switches” so the right answer it to run a separate circuit.

 

[njmurvin]

Definitely a hardwire circuit. There are a number of manual switchover solutions. I was hoping someone has done something like this and found or made a clever solution for automating the process. I would even be willing to use a timer based solution where at, say midnight, the power source would disconnect from the AC circuit and connect to the charger circuit and vice versa at 8:00 am. It seems to me that something like this could be accomplished with a timer and some relays. I’m just not exactly sure how to put something like this together.

 

[RayK]

I don't know of an automatic transfer switch, though somebody probably makes one, but a manual transfer switch might do. I had a thought that whenever I get around to installing my Wall Connector, I also put in a 14-50 outlet and have a manual transfer switch select between the two. In one position of the switch, power would be applied to the WC and the other position, the NEMA 14-50 outlet. It would run off a single 240V (two phase) 50A breaker. Something like this:

https://smile.amazon.com/Baomain-Universal-Changeover-SZW26-63-Position/dp/B01IZ5ZFYC/

You mention that a manual switch would not work in a day-to-day application. But how many times to you run the A/C during the day, and then charge the car at night? Are you charging every night?

 

[njmurvin]

You mention that a manual switch would not work in a day-to-day application. But how many times to you run the A/C during the day, and then charge the car at night? Are you charging every night?

The car is new to me. I haven’t really formed charging habits yet. I was planning on just making it routine to plug in every night.

For 9-10 months out of the year, it wouldn’t be an issue as we seldom if ever run the AC outside of summer. But on those hot days, it would mean a trip to the garage at about 11:30pm to throw a switch - not the end of the world but far from ideal.

It’s becoming clearer that I need to bite the bullet (or should I say break out the wallet?) and install a separate, dedicated circuit for the charger.

 

[RayK]

So a little poking around I find this:

Upgrade pak for 50amp Electric Range Buddy, RV Buddy and Welder Buddy on order waiting for build to external whip for Hardwire EVSE Charging Station

This is an Order Upgrade Pak for pending 50amp Electric Range Buddy's, Welder Buddy's and RV Buddy orders of any number. It upgrades the order with an external whip so that in addition to the front facing two outlets there is a 50amp whip exiting the bottom of the unit to be hardwired directly...

www.bsaelectronics.com

A companion upgrade to an Electric Range Buddy (50A) that seems to support a hardwired Wall Connector.

edit: Hmm... not sure that this would be viable. It looks like the A/C compressor would need to be plugged into the Buddy (14-50 outlet). I imagine that the A/C unit is (required to be?) hardwired. I'm sure that somebody more familiar with the electrical code can verify this.

 

[njmurvin]

I was thinking something like this (utilizing a timer, transformer and relay). The 12v transformer output assumes that's the voltage required to energize the relay coil. If I have this right, normally closed on the relay (no power to the transformer) would energize the AC Condenser. At midnight until 8:00am the transformer would be ON and the relay would switch power to the Wall Charger. This is based on some very simplistic knowledge on my part. Please feel free to comment - especially those who know this stuff.

 

[Genie]

That looks ideal. Continous duty relay.