Shared Breaker - Timer to Avoid Conflict

[alansmallen]

Long time reader, first time poster. Eagerly awaiting our M3 and getting the garage hooked up with a HPWC. It'll be run to a 30 amp breaker that is shared with an oven that is used about 10 times per year. I'd love to find a way to make sure the car only pulls power at night (when the oven is definitely not being used). Should we run a dedicated timer between the breaker and the HPWC, or will the scheduled charing in the car be enough to make sure no power is being pulled?

Thanks!

 

[brucet999]

Long time reader, first time poster. Eagerly awaiting our M3 and getting the garage hooked up with a HPWC. It'll be run to a 30 amp breaker that is shared with an oven that is used about 10 times per year. I'd love to find a way to make sure the car only pulls power at night (when the oven is definitely not being used). Should we run a dedicated timer between the breaker and the HPWC, or will the scheduled charing in the car be enough to make sure no power is being pulled?

Thanks!

The car has a timer already. Just set time for charging to start and, forever more, whenever you plug in at that location, the car will set up to start charging at the pre-ordained hour. It won't shut off at some set time, however, so if charging would go on past the early morning time when your PoCo rates go up, you will have to remember to unplug.

 

[alansmallen]

The car has a timer already. Just set time for charging to start and, forever more, whenever you plug in at that location, the car will set up to start charging at the pre-ordained hour. It won't shut off at some set time, however, so if charging would go on past the early morning time when your PoCo rates go up, you will have to remember to unplug.

Thanks! Does the HPWC pull any significant type of power if the car is plugged in but not set to charge yet?

 

[brucet999]

Thanks! Does the HPWC pull any significant type of power if the car is plugged in but not set to charge yet?

Nope. Probably about like what your TV uses for standby when turned off.

 

[alansmallen]

Nope. Probably about like what your TV uses for standby when turned off.

Perfect. Shouldn't be enough to trip the breaker if the oven is not in use.

 

[tga]

At least on the S and X, delayed charging only effects the start of a charge cycle. If cabin overheat protection or preconditioning kicks in while the car is plugged in, it will pull a few amps (7? 8? I forget the exact number) from the wall for cooling. Heat is even more (cabin and battery heat are 6kw each).

NEC also requires that car charging outlets be on dedicated circuits, so this install is iffy from a code standpoint.

 

[MorrisonHiker]

You could consider the Dryer Buddy. There are versions which prevent both outlets from working at the same time.
Dryer Buddy™

As others have mentioned, the car would only charge at night when scheduled...but such a device would make it easier for others to use the oven or charge the car without having to worry about tripping the breaker.

 

[alansmallen]

You could consider the Dryer Buddy. There are versions which prevent both outlets from working at the same time.
Dryer Buddy™

As others have mentioned, the car would only charge at night when scheduled...but such a device would make it easier for others to use the oven or charge the car without having to worry about tripping the breaker.

My oven is built into the wall so I don't know if I'd be able to get it in between there and the breaker.

At least on the S and X, delayed charging only effects the start of a charge cycle. If cabin overheat protection or preconditioning kicks in while the car is plugged in, it will pull a few amps (7? 8? I forget the exact number) from the wall for cooling. Heat is even more (cabin and battery heat are 6kw each).

NEC also requires that car charging outlets be on dedicated circuits, so this install is iffy from a code standpoint.

Didn't know it had to be on a dedicated circuit. Might have to piggyback the oven to a different breaker and leave the 30a open for the car.

 

[eprosenx]

This would definitely not be code compliant. As mentioned, EVSE's must be on a dedicated circuit. Moving the oven to share with something else would also not be allowed I don't think (there may be conditions where like an oven and a range can share one circuit I think, but an oven I don't think can share with anything else).

Why not just add a new breaker for the car charging? Do you not think you have enough overall capacity in the main panel (is it like a 200a panel/service?)

Very often, lack of physical space in the panel can be rectified by installing "tandem" breakers which basically doubles your breaker capacity by putting two breakers in one position.

Can you post pictures of your panel? (and the sticker on the door with all the tech specs)

 

[alansmallen]

This would definitely not be code compliant. As mentioned, EVSE's must be on a dedicated circuit. Moving the oven to share with something else would also not be allowed I don't think (there may be conditions where like an oven and a range can share one circuit I think, but an oven I don't think can share with anything else).

Why not just add a new breaker for the car charging? Do you not think you have enough overall capacity in the main panel (is it like a 200a panel/service?)

Very often, lack of physical space in the panel can be rectified by installing "tandem" breakers which basically doubles your breaker capacity by putting two breakers in one position.

Can you post pictures of your panel? (and the sticker on the door with all the tech specs)

We're totally maxed out and can't add another breaker without replacing the panel with a newer, larger unit. It's a 60 year old house that we did an addition to a few years ago and added a subpanel for the new section.

 

[alansmallen]

This would definitely not be code compliant. As mentioned, EVSE's must be on a dedicated circuit. Moving the oven to share with something else would also not be allowed I don't think (there may be conditions where like an oven and a range can share one circuit I think, but an oven I don't think can share with anything else).

Why not just add a new breaker for the car charging? Do you not think you have enough overall capacity in the main panel (is it like a 200a panel/service?)

Very often, lack of physical space in the panel can be rectified by installing "tandem" breakers which basically doubles your breaker capacity by putting two breakers in one position.

Can you post pictures of your panel? (and the sticker on the door with all the tech specs)

Attaching photos of the main panel and the subpanel if have any ideas.

 

[smatthew]

Do you have 3 ovens? I see Oven on both panels, and "steam oven" on the second.

Tandem 220 breakers are also an option.

 

[alansmallen]

Do you have 3 ovens? I see Oven on both panels, and "steam oven" on the second.

Tandem 220 breakers are also an option.

I don't believe the one line from the first panel is still in use. We replaced it when we did the addition. That being said, using anything from that first panel for the car would require ripping up the ceiling and running a pretty long new line of wire. The second (nicely labeled) panel is next to the garage.

 

[eprosenx]

View attachment 324706 View attachment 324707

Attaching photos of the main panel and the subpanel if have any ideas.

More on this later, but first thoughts:

You can use tandem breakers on some of the existing circuits. Most of your breaker positions allow for tandem installations.

But then I am concerned since I see at least one tandem in a position it is not supposed to be allowed, and I think there may be multiple brands of breaker used which may or may not be rated for use in that panel (it is complicated since some breakers are cross rated into other panels).

Beyond the mechanical “can you add a breaker”, the bigger question is the load calculation of the house. Would you be allowed to add another load?

You have a TON of circuits in the house for only a 200a service, but I suspect many are lightly loaded.

 

[eprosenx]

I don't believe the one line from the first panel is still in use. We replaced it when we did the addition. That being said, using anything from that first panel for the car would require ripping up the ceiling and running a pretty long new line of wire. The second (nicely labeled) panel is next to the garage.

I can’t see well enough. Can you post more detailed pictures that for instance show the ampacity of the breaker feeding the sub panel? Also, pictures with the panel covers removed would be useful. One thing I am wondering about is what the wire gauge and type is feeding the sub panel.

As you already know, you are probably really pushing the 200a feed limits by the calculations at least.

I have a “Sense” unit for monitoring my power which is cool. Might be interesting to get a practical picture of what your actual power draw is.

 

[alansmallen]

I can’t see well enough. Can you post more detailed pictures that for instance show the ampacity of the breaker feeding the sub panel? Also, pictures with the panel covers removed would be useful. One thing I am wondering about is what the wire gauge and type is feeding the sub panel.

As you already know, you are probably really pushing the 200a feed limits by the calculations at least.

I have a “Sense” unit for monitoring my power which is cool. Might be interesting to get a practical picture of what your actual power draw is.

I can snap more photos soon. The breaker feeding the subpanel is 100 amps.

 

[eprosenx]

I don't believe the one line from the first panel is still in use. We replaced it when we did the addition. That being said, using anything from that first panel for the car would require ripping up the ceiling and running a pretty long new line of wire. The second (nicely labeled) panel is next to the garage.

What is up with all the unlabeled breakers in the subpanel? Are those just spare? Or are they all used but unlabeled?

Now back on my computer, it looks like there are tandem breakers in your main panel in places that there should not be. And probably wrong brands of breakers as well.

I think the reason for allowing or not allowing tandem breakers was because there was a rule saying panelboards could not have more than like 40 breakers in them, but it may not have been a technical reason (with that being said, the old panelboards must comply with the rules from when they were manufactured and certified). Also, I think from a practical standpoint mixing breakers of certain types between manufacturers is super common, but technically not allowed. Nobody wants to be responsible for a fire when two things that were not certified or tested together cause an issue.

 

[alansmallen]

In popping open the sub panel, we are able to find some unused space. Thanks for everyone's help on this!