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QUESTION: How big of a Charging circuit can I get installed?

Jlindo

Member
Mar 4, 2018
75
61
94404
Guys, need your input! I am getting info on adding a Tesla Wall Charger which I've already bought for my incoming Model X 100D.

Here is my panel, and main circuit. I would love your input. Some notes:

- The sub-panel shows Jacuzzi, but we removed it, there is no Jacuzzi.
- Also shows 'Heat (H)' where there was Radiant Heating, we now have central Gas.
- We do have AC but never use it.
- Our dryer is electric, regular 110V.
- I have a Tesla Wall Charger

Based on the photos here, how many Amps can I reach for my Wall Charger?

View media item 118429View media item 118431View media item 118430View media item 118428
 

Rocky_H

Well-Known Member
Feb 19, 2015
6,407
7,568
Boise, ID
Get a load calculation. That stuff depends on how many square feet your house has and other stuff. There should be forms online for a load calculation; go ahead and Google for them.
 

davewill

Active Member
Feb 5, 2014
1,828
1,979
San Diego, CA, US
Use 90 amp circuit breaker with 72 amp (dip switched). You'll be fine. And, if there is amperage irregularity because of load issue, the Tesla and HPWC can work together to lower the current input to the car.
What an irresponsible post!

The car will lower the current if it thinks there is something REALLY wrong with the circuit. It is NOT a replacement for doing a proper job of figuring out what size circuit you can have and will not stop you from popping the main service breaker or overloading a feeder or panel.
 

Jlindo

Member
Mar 4, 2018
75
61
94404
It appears my main feed is 125 Amps, as the wire appears to be 1/0 gauge (125A max) going into the main from the ground. Even though they appear to have installed a 200A breaker for some reason.

Anyone have any reason to believe otherwise? :)
 

miimura

Well-Known Member
Aug 21, 2013
6,350
6,044
Los Altos, CA
How many amps are the unused Heat, Jacuzzi and Spare breakers? You could probably replace those with one breaker equal to their sum. However, you should get a licensed electrician to do a complete assessment including load calcs appropriate for your jurisdiction.
 
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miimura

Well-Known Member
Aug 21, 2013
6,350
6,044
Los Altos, CA
It appears my main feed is 125 Amps, as the wire appears to be 1/0 gauge (125A max) going into the main from the ground. Even though they appear to have installed a 200A breaker for some reason.

Anyone have any reason to believe otherwise? :)
The utility does not have to follow NEC ampacity tables for their feed lines on their side of the meter. If they placed a 200A meter, then they are responsible to provide you a voltage within tolerance. In return, you have to notify them if you connect any significant additional load. The best way to address this issue is to pull a permit for your HPWC installation and notify PG&E how much additional load you have added.
 
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Rocky_H

Well-Known Member
Feb 19, 2015
6,407
7,568
Boise, ID
It appears my main feed is 125 Amps, as the wire appears to be 1/0 gauge (125A max) going into the main from the ground. Even though they appear to have installed a 200A breaker for some reason.

Anyone have any reason to believe otherwise? :)
@miimura answered this one, but I also have a friend who is an electrician who explained my confusion on that a couple of years ago. Electric code for that uses an assumption that not all of the circuits are going to be active at one time, so there is a different table of what external feeder line can supply the main breaker for a building that is different from the table you are probably looking at for a strictly 1:1 thing of the current a single wire in a branch circuit is allowed to carry.

In return, you have to notify them if you connect any significant additional load. The best way to address this issue is to pull a permit for your HPWC installation and notify PG&E how much additional load you have added.
I think I disagree with this one. I haven't really heard about needing to notify the utility, unless that's just part of what the permit accomplishes. I thought that is the point of doing a load calculation and following code, so you stay properly within the operating limits of your breaker in your own house's panel. Then there shouldn't be any need to notify anyone beyond your own meter.
 

brucet999

Active Member
Mar 12, 2015
2,690
1,497
Huntington Beach, CA
The utility does not have to follow NEC ampacity tables for their feed lines on their side of the meter. If they placed a 200A meter, then they are responsible to provide you a voltage within tolerance. In return, you have to notify them if you connect any significant additional load. The best way to address this issue is to pull a permit for your HPWC installation and notify PG&E how much additional load you have added.
The PoCo does not supply your panel, the homeowner does, Meters are capable of much higher amperage than 200 even if the supply cables cannot. You could place any sized panel, but it is unlikely that the PoCo would be supplying 200A on wire that cannot support it. More likely is that the installer of the panel failed to down-size the main breaker and that they did so without PoCo involvement.
 

brucet999

Active Member
Mar 12, 2015
2,690
1,497
Huntington Beach, CA
Guys, need your input! I am getting info on adding a Tesla Wall Charger which I've already bought for my incoming Model X 100D.

Here is my panel, and main circuit. I would love your input. Some notes:

- The sub-panel shows Jacuzzi, but we removed it, there is no Jacuzzi.
- Also shows 'Heat (H)' where there was Radiant Heating, we now have central Gas.
- We do have AC but never use it.
- Our dryer is electric, regular 110V.
- I have a Tesla Wall Charger

Based on the photos here, how many Amps can I reach for my Wall Charger?

View media item 118429View media item 118431View media item 118430View media item 118428
The Jacuzzi breaker can be removed and replaced with one for your wall charger, as long as the wires for it have been removed or at least safely capped off.
Your dryer is operating on 240V 30A circuit, not 110V.
Has radiant heating been removed? If so, that breaker (probably 240V 20A) should be removed and could be replaced with a breaker for your wall charger.
The fact that you don't use AC would be irrelevant to any inspector.

Since that is a smart meter, PoCo can tell you what your highest usage at any one time has been during the past year. With my old 100A meter, the incoming underground wires were rated by SCE at 150A, but the highest usage in the previous year was 24A (when Blue Max was charging on a dryer outlet). They can also tell you how much amperage they are able to supply you on those feed lines.
 
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miimura

Well-Known Member
Aug 21, 2013
6,350
6,044
Los Altos, CA
@miimura answered this one, but I also have a friend who is an electrician who explained my confusion on that a couple of years ago. Electric code for that uses an assumption that not all of the circuits are going to be active at one time, so there is a different table of what external feeder line can supply the main breaker for a building that is different from the table you are probably looking at for a strictly 1:1 thing of the current a single wire in a branch circuit is allowed to carry.


I think I disagree with this one. I haven't really heard about needing to notify the utility, unless that's just part of what the permit accomplishes. I thought that is the point of doing a load calculation and following code, so you stay properly within the operating limits of your breaker in your own house's panel. Then there shouldn't be any need to notify anyone beyond your own meter.
I should go back to the PG&E field office and take a picture of the sign they had at the service window. They clearly said they should be notified of new loads. I believe the building department does notify PG&E when permits include significant new loads.

I have also heard several horror stories of people burning up their feed line while drawing a load well within their main breaker.
 

cmaster

Member
Dec 4, 2014
240
76
United States
Wow. You are great at snapping with "irresponsible".

He has 200 amps. There is nothing wrong. It's not overloading. I saw his pictures of the box, there is nothing in there that is overloading btw.

What an irresponsible post!

The car will lower the current if it thinks there is something REALLY wrong with the circuit. It is NOT a replacement for doing a proper job of figuring out what size circuit you can have and will not stop you from popping the main service breaker or overloading a feeder or panel.
 
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bob_p

Active Member
Apr 5, 2012
3,705
2,815
Before spending a lot of $$$ trying to squeeze as much power as possible for Tesla charging, you should also consider what you really need.

We have an HPWC on a 100A circuit (capable of charging at 80A) and a 14-50 (able to charge at 40A). Our 2012 S P85 has dual chargers, and can support up to 80A charging. Our 2017 S 100D has a 48A charger (the 72A chargers were made standard after our car was delivered).

Assuming that you keep the charge of a 100 battery pack between 10-90%, at most you'll be charging 80KWhr overnight.

If you are able to support 72A charging, that's about 15.5KWhr of recharge per hour, or to go from 10% to 90%, that would take a little more than 5 hours.

If you used a 14-50 outlet, getting 40A charging, that's about 8.5KWhr of recharge per hour. For 10% to 90%, it would take about 9.5 hours.

Since daily driving typically uses far less than 80KWhr in a single day, your overnight charging will likely be much less than the above numbers.

We've been able to charge our S P85 at 80A for 5 years. In that time, we've only needed the faster 80A charging a few times - and that was back in 2013, before the supercharger network. We needed to charge quickly after doing our daily driving for work, doing a quick recharge at home to 100%, and then taking a road trip. Without the superchargers, we had to have the max charge on the battery pack to reach our destination (with a 30A public charger).

Once the supercharger network was deployed, we haven't used the faster charging at home.

Even with the 100 battery packs, you should be able to charge fine with only a 14-50 outlet or an HPWC on a 50A circuit.

Anything above that, you probably will never use, and not get any value out of spending the extra $$$ to support a higher amp circuit.
 

Lasttoy

Active Member
Mar 24, 2017
1,604
850
St Augustine, Fl
You are screwed by pictures. Need double blank to install circuit breaker . I dont see any blanks?...
I upgraded entire panel to 40 cb . So i had a double to install 50 amp breaker. My house only has 100 amp service. If house hass 200 amp you can install a 100 amp breaker.
Good luck.
 

davewill

Active Member
Feb 5, 2014
1,828
1,979
San Diego, CA, US
Wow. You are great at snapping with "irresponsible".

He has 200 amps. There is nothing wrong. It's not overloading. I saw his pictures of the box, there is nothing in there that is overloading btw.
That's not what you said. You said to put in a 90a circuit and not to worry because the car would save him if there wasn't enough capacity. That's 100% wrong and irresponsible to post.
 
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Jlindo

Member
Mar 4, 2018
75
61
94404
Before spending a lot of $$$ trying to squeeze as much power as possible for Tesla charging, you should also consider what you really need.

We have an HPWC on a 100A circuit (capable of charging at 80A) and a 14-50 (able to charge at 40A). Our 2012 S P85 has dual chargers, and can support up to 80A charging. Our 2017 S 100D has a 48A charger (the 72A chargers were made standard after our car was delivered).

Assuming that you keep the charge of a 100 battery pack between 10-90%, at most you'll be charging 80KWhr overnight.

If you are able to support 72A charging, that's about 15.5KWhr of recharge per hour, or to go from 10% to 90%, that would take a little more than 5 hours.

If you used a 14-50 outlet, getting 40A charging, that's about 8.5KWhr of recharge per hour. For 10% to 90%, it would take about 9.5 hours.

Since daily driving typically uses far less than 80KWhr in a single day, your overnight charging will likely be much less than the above numbers.

We've been able to charge our S P85 at 80A for 5 years. In that time, we've only needed the faster 80A charging a few times - and that was back in 2013, before the supercharger network. We needed to charge quickly after doing our daily driving for work, doing a quick recharge at home to 100%, and then taking a road trip. Without the superchargers, we had to have the max charge on the battery pack to reach our destination (with a 30A public charger).

Once the supercharger network was deployed, we haven't used the faster charging at home.

Even with the 100 battery packs, you should be able to charge fine with only a 14-50 outlet or an HPWC on a 50A circuit.

Anything above that, you probably will never use, and not get any value out of spending the extra $$$ to support a higher amp circuit.

Thanks, that's super helpful and practical advice. Much appreciated.
 

Jlindo

Member
Mar 4, 2018
75
61
94404
That's not what you said. You said to put in a 90a circuit and not to worry because the car would save him if there wasn't enough capacity. That's 100% wrong and irresponsible to post.

Thanks guys, as it happens, it would appear that although I have a 200A breaker on the main panel, the input from the PoCo to my home may be 125A. There is a 1/0 gauge wire coming in which apparently carries a max of 125A. Not sure why there's a 200A breaker!
 

cmaster

Member
Dec 4, 2014
240
76
United States
How is that wrong? 90 amp is in the context to his posts. Is it used elsewhere? What do you mean it's wrong btw? I like to know.

That's not what you said. You said to put in a 90a circuit and not to worry because the car would save him if there wasn't enough capacity. That's 100% wrong and irresponsible to post.
 

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