What am I limited to for EV charging on this sub panel?

[Nick1994]

How far away is the clothes dryer from where you park? If it's close by you can get a splitter and plug both in, just only run one at a time. Can't run both at the same time.

https://www.amazon.com/Splitter-L-P...47&sprefix=nema+14-30+splitter,aps,136&sr=8-7

 

[The Critic]

I think @RhondaHonda needs to clarify - are you looking for a code-complaint solution, or just something that will "work?"

 

[JeffKeryk]

You should check into whether it is possible to set up your prospective EV to charge only during certain hours. I plug my Tesla in when it gets put in the garage and it stays plugged in until we use it.

I've never checked into whether I could restrict the charging hours. I keep things as simple as possible.

It is super simple. On Teslas, you don't schedule start time, you schedule the "Ready to depart time". It will take care of the start/stop based on state of charge.
This allows for off peak prices and balanced total usage.

 

[JeffKeryk]

I think @RhondaHonda needs to clarify - are you looking for a code-complaint solution, or just something that will "work?"

Spot on.
If anyone is considering an EV, please do not Mickey Mouse your charging solution. Do it right!

I was lucky as our house is older and had a small service panel. Years ago we upgraded the panel and most of the house wiring.
Of course, solar panels are the cherry on top.

 

[brianl703]

I believe current NEC for interconnected smoke detectors requires them to have their own dedicated circuit.

I cannot find anything which requires that.

Also, current NEC is not necessarily the adopted NEC for a given state or jurisdiction. Virginia, for example, is still on the 2017 NEC.

And some code requires them to be on a circuit shared with other loads:

If your jurisdiction has adopted Appendix K in the International Building Code (IBC), it is the Administrative Provisions for the NEC.
Section K111.6 states that smoke alarms shall not be connected as the only load on a branch circuit. They shall be supplied by circuits having lighting loads consisting of lighting outlets in habitable spaces.

https://forums.mikeholt.com/threads/smoke-detectors-afci-circuit.149974/#post-2348897

 

[dlundblad]

It looks like he has a 15 amp breaker just for the smoke detectors. I've never seen that done and it doesn't seem like a good idea (the breaker could trip or be turned off and you'd have no way of knowing till the smoke detectors started beeping for low battery).

Could remove that 15 amp breaker and connect the smoke detectors to a lighting/receptacle circuit like it's done everywhere else.

That frees up one space.

I’m not sure how the smokes being on a twin breaker will be a bad idea. They trip independently.

I wouldn’t have them with anything else in the circuit either. They would be more likely to trip that way.

 

[The Critic]

I cannot find anything which requires that.

Also, current NEC is not necessarily the adopted NEC for a given state or jurisdiction. Virginia, for example, is still on the 2017 NEC.

And some code requires them to be on a circuit shared with other loads:



https://forums.mikeholt.com/threads/smoke-detectors-afci-circuit.149974/#post-2348897

Also found this: https://forums.mikeholt.com/threads/dedicated-circuit-for-smoke-detectors.111016/

Perhaps it is a local issue, but all of the recent builds that I have seen have a dedicated circuit for the smoke detectors.

 

[brianl703]

I’m not sure how the smokes being on a twin breaker will be a bad idea. They trip independently.

I wouldn’t have them with anything else in the circuit either. They would be more likely to trip that way.

As noted above, IBC does not allow smoke detectors to be on their own circuit. I can only guess as to what the rationale for that is.

NEC does not address the issue.

 

[brianl703]

Also found this: https://forums.mikeholt.com/threads/dedicated-circuit-for-smoke-detectors.111016/

Perhaps it is a local issue, but all of the recent builds that I have seen have a dedicated circuit for the smoke detectors.

It is, IBC (which prohibits smoke detectors being on a dedicated circuit) is not applicable in all states. I have yet to find a code which requires them to be on a dedicated circuit.

 

[eljefino]

If someone's concerned about code, could they please quote what they think is applicable, as far as the challenge of having "many" "large-ish" loads on a subpanel fed like OPs.

If I add together all the breakers on my main panel, it will exceed the 200 Amp main, yet that is ok to do.

I myself am curious as well.

 

[UncleDave]

Garage Journal has a few electricians on the site that could be helpful.

Ive got an interesting pony panel setup in my garage as well.

 

[dlundblad]

As noted above, IBC does not allow smoke detectors to be on their own circuit. I can only guess as to what the rationale for that is.

NEC does not address the issue.

Honestly news to me. At my last job, we always did them on their own circuit. I’ve even done up my house this way.

I understand a lighting circuit should never trip, but you never know.

 

[brianl703]

Honestly news to me. At my last job, we always did them on their own circuit. I’ve even done up my house this way.

I understand a lighting circuit should never trip, but you never know.

My guess as to why the IBC does not want the smoke detectors on a circuit by themselves is that it could trip or fail (due to a bad connection or other problem) and nobody would know. Even if someone knew, hey, it's only smoke detectors, who cares?

If a lighting circuit trips/fails, the assumption is that will be noticed and dealt with much quicker. It's a lot more inconvenient for the lights to not work. So if the smoke detectors are on a lighting circuit....they are less likely to be without power due to someone's negligence.

 

[brianl703]

If someone's concerned about code, could they please quote what they think is applicable, as far as the challenge of having "many" "large-ish" loads on a subpanel fed like OPs.

If I add together all the breakers on my main panel, it will exceed the 200 Amp main, yet that is ok to do.

I myself am curious as well.

From what I've seen--you must add up all of the dedicated circuits (dryer, ac, well pump, range, etc) and then add 3 va (volt-amps) per square foot for general lighting circuits. This gives your max load, and you need to size the main breaker and it's service for that load.

In some cases you can apply load diversity to the calculation--for example, if you have a non-heat pump AC unit with an air handler that has electric heat strips (common in Florida from what I've heard), the heat strips and the AC unit would never run at the same time, so you would use the larger of the two circuits in your calculation and omit the smaller one.

 

[RhondaHonda]

The wire size should be printed on the insulation of the wire.

On the gray insulation or the individual colored wires within it? I can’t see more than what is visible in the picture of the gray insulation. Maybe if I pull the cover off the main panel in the basement garage I can see more but everything is drywalled.

 

[RhondaHonda]

OP has a 200amp main panel, the sub-panel is on a 100amp breaker, I don't think it's enough for a dedicated EV charger, which would need a 50-60amp breaker, doesn't matter if there is physical room for it, there isn't enough amps available, it would trip when another appliance, like a dryer is used.

The EV charger needs to be on the main panel.

Would using the 30 amp compressor circuit be ok in your opinion? I don’t need a 50-60 amp circuit in that garage for my use. I think I can get 50-60 amps in the main house as one of those panels looks to have quite a bit more room.

 

[dlundblad]

My guess as to why the IBC does not want the smoke detectors on a circuit by themselves is that it could trip or fail (due to a bad connection or other problem) and nobody would know. Even if someone knew, hey, it's only smoke detectors, who cares?

If a lighting circuit trips/fails, the assumption is that will be noticed and dealt with much quicker. It's a lot more inconvenient for the lights to not work. So if the smoke detectors are on a lighting circuit....they are less likely to be without power due to someone's negligence.

Smokes have battery backups. They’re pretty annoying if they are running low.

Very odd mindset.

 

[RhondaHonda]

How far away is the clothes dryer from where you park? If it's close by you can get a splitter and plug both in, just only run one at a time. Can't run both at the same time.

https://www.amazon.com/Splitter-L-P...47&sprefix=nema+14-30+splitter,aps,136&sr=8-7

Not far, about 8’ on the other side of the sub panel. This is a guest house that gets basically zero usage 90%+ of the year. The dryer definitely wouldn’t be running when I’d be charging. I’ll likely park in the garage attached to the main house most of the time, just like to have options and will probably have more than one EV at some point that we are in this house.

 

[RhondaHonda]

I think @RhondaHonda needs to clarify - are you looking for a code-complaint solution, or just something that will "work?"

I think code compliant would be nice. As mentioned above, overloading the panel is not going to be an issue as this sub panel is in a garage in the guesthouse that has almost no electrical load except a few weeks a year. If I can just make the 30 amp compressor circuit the EV circuit, that’s all I need.

 

[brianl703]

Smokes have battery backups. They’re pretty annoying if they are running low.

Yes, and if they're on a circuit breaker all by themselves, it's quite easy to yank the batteries out and turn that breaker off. Smoke detectors shut up, and the lights still work.

Very odd mindset.

I don't think so. There's a certain segment of society that does things like steal batteries out of smoke detectors. It's why some of them have anti-tamper features that make removing the battery (somewhat) harder.

This requirement is likely a product of experience with smoke detectors in rental housing, among other places.

EDIT: If you go back far enough, AC powered smoke detectors did not have a battery backup. Sometime around 1995/96 the code was changed to require a battery backup.

It seems that some codes prior to that time (maybe in Canada based on the site I read it on) required the smoke detector to be on it's dedicated circuit. According to what I read, the rationale for doing away with that and requiring them to be connected to lighting circuit: Someone would burn their toast and then shut off the dedicated smoke detector breaker and forget to turn it back on.