GW2 "Panel Maximum Current" setting

[GWord]

Anyone know the importance of the " PANEL MAXIMUM CURRENT" setting in GW2? Not even sure what panel this is referring to (GW2, my home load panel etc...) or what limitations, if any, this setting imparts.

My physical setup is:

200A Grid -► 200A Breaker -► GW 2 -► 200A Breaker -► Home Load Panel
                 ▲
160A PW+Solar  ──────────┘

My Panel Maximum Current setting via GW2's portal page is 100A though. Others with 200A home service, what is your setting here?

 

[itsc]

Same with mine. Not sure if it matters. I’ve pulled more than 100A from the grid in at least one occasion.

 

[Vines]

It's a new feature of the Powerwall PCS. I wouldn't worry about it, as it is set to 100A by default.

 

[BGbreeder]

It's a new feature of the Powerwall PCS. I wouldn't worry about it, as it is set to 100A by default.

@Vines Do you know what happens if the load exceeds that number? Just curious as we would have to have an extreme event to pull that much power, though it has happened...

All the best,

BG

 

[Vines]

@Vines Do you know what happens if the load exceeds that number? Just curious as we would have to have an extreme event to pull that much power, though it has happened...

All the best,

BG

Like many things, it depends. This newly released setting is designed to prevent more than the given amperage from passing a given point. Hopefully, there is an upstream breaker that would trip if you pulled an unsafe amperage through it. If you exceed the setting this curtails the onsite generation sources, so that the conductors do not overload.

Say you had a PW+ and a PW and were still using the GW2 for whatever reason in your 200A service panel with just a 200A main breaker. All your PV and ESS sources are inside the GW2, for a total of 80A (50A+30A) of generation breakers. The code (2017 NEC 240.2`.B.2.2) says that wherever your essential loads subpanel occurs, that subpanel must have an OCPD protecting the panel. This is because the combination of your 80A of onsite generation and your assumed 200A grid connection adds up to more than the 200A rating of the essential loads panel and the GW2 and the wire. Therefore putting a 200A main breaker or "Panel Control=200A" on that essential loads panel prevents the addition of grid sources plus PV+PW sources from exceeding the 200A circuit rating. If you were to try to pull 240A from that backup system, the main 200A breaker in your 200A service panel would trip. If "Panel Control" wasn't set, then the PV and PW generation sources would happily supply the additional 40A that the main breaker could not supply. This may overload your 200A conductors or 200A distribution bus of the essential loads subpanel because of the nature of the load side tap within the GW2.

There are several ways to set up PCS settings, and this one is in addition to the other import/export controls. The typical use of this setting is to replace the need for a main breaker in an essential loads panel. Since PCS are already so edgy in NEC 2017, we have chosen to not really use this, and instead continue to use the main breaker in the essential loads subpanel. Import/export control is what we more often use for our systems, since preventing panel upgrades is a $4k win for the customer.

In those cases where we have no choice since a panel doesn't take a main breaker, we would consider using this setting. In that case it would satisfy the requirement shown in 2017 NEC 240.2`.B.2.2

The 2020 NEC will be code here in less than a year, and we can go PCS crazy then. In the meantime, I am satisfied not using this particular PCS setting.

 

[BGbreeder]

Thanks for the great explanation! It makes sense, and absent that control, those loads would be a problem for many installations that weren't as forward looking as yours. The NEC rules can be a real marvel.

All the best,

BG

 

[GWord]

Like many things, it depends. This newly released setting is designed to prevent more than the given amperage from passing a given point. Hopefully, there is an upstream breaker that would trip if you pulled an unsafe amperage through it. If you exceed the setting this curtails the onsite generation sources, so that the conductors do not overload.

Say you had a PW+ and a PW and were still using the GW2 for whatever reason in your 200A service panel with just a 200A main breaker. All your PV and ESS sources are inside the GW2, for a total of 80A (50A+30A) of generation breakers. The code (2017 NEC 240.2`.B.2.2) says that wherever your essential loads subpanel occurs, that subpanel must have an OCPD protecting the panel. This is because the combination of your 80A of onsite generation and your assumed 200A grid connection adds up to more than the 200A rating of the essential loads panel and the GW2 and the wire. Therefore putting a 200A main breaker or "Panel Control=200A" on that essential loads panel prevents the addition of grid sources plus PV+PW sources from exceeding the 200A circuit rating. If you were to try to pull 240A from that backup system, the main 200A breaker in your 200A service panel would trip. If "Panel Control" wasn't set, then the PV and PW generation sources would happily supply the additional 40A that the main breaker could not supply. This may overload your 200A conductors or 200A distribution bus of the essential loads subpanel because of the nature of the load side tap within the GW2.

There are several ways to set up PCS settings, and this one is in addition to the other import/export controls. The typical use of this setting is to replace the need for a main breaker in an essential loads panel. Since PCS are already so edgy in NEC 2017, we have chosen to not really use this, and instead continue to use the main breaker in the essential loads subpanel. Import/export control is what we more often use for our systems, since preventing panel upgrades is a $4k win for the customer.

In those cases where we have no choice since a panel doesn't take a main breaker, we would consider using this setting. In that case it would satisfy the requirement shown in 2017 NEC 240.2`.B.2.2

The 2020 NEC will be code here in less than a year, and we can go PCS crazy then. In the meantime, I am satisfied not using this particular PCS setting.

Thanks for the detail. I’ve got a 200A main breaker in my essential loads panel serving as the primary protection for the bus bar. Since my PW+PV comes in upstream at the gateway, this breaker catches net current, making PCS redundant I guess.

You mention this as a setting. Does it show up in the GW2 config wizard now?

 

[Vines]

Thanks for the detail. I’ve got a 200A main breaker in my essential loads panel serving as the primary protection for the bus bar. Since my PW+PV comes in upstream at the gateway, this breaker catches net current, making PCS redundant I guess.

You mention this as a setting. Does it show up in the GW2 config wizard now?

I understand that it does but haven't personally seen it. My system should be live in another month or 2 and I can play with all the settings then.

 

[miimura]

I thought the last line on my Gateway Summary was kinda funny.

 

[wwhitney]

My question is, does seeing the "Panel Maximum Current" set to 100A automatically mean that the GW would do some PCS-stuff if some computation exceeds 100A, or does that only happen when PCS is further enabled through some other settings?

Cheers, Wayne

 

[Vines]

My question is, does seeing the "Panel Maximum Current" set to 100A automatically mean that the GW would do some PCS-stuff if some computation exceeds 100A, or does that only happen when PCS is further enabled through some other settings?

Cheers, Wayne

If panel maximum current is set, my understanding is that it works independently of other PCS settings.

 

[wwhitney]

If panel maximum current is set, my understanding is that it works independently of other PCS settings.

So what computation is it doing, and won't the OP be better off setting it to 200A, given the details of his configuration?

Cheers, Wayne

 

[Vines]

So what computation is it doing, and won't the OP be better off setting it to 200A, given the details of his configuration?

Cheers, Wayne

I would have to dig deeper but perhaps it's just left at the default setting. It might not be actually controlling anything.

OP how old was your installation?

Do you have a main breaker in your essential loads subpanel? What size?

If you do not have the main breaker in the essential loads subpanel then this should be set to the size that the main breaker would be.

To test if this is working, draw more than 90A, then 100A then 110A from the essential loads subpanel, and see if the Powerwalls deploy power at 90A of draw but stop powering the home when you try to pull 110A through the essential loads subpanel.

 

[itsc]

I checked the installer menu and it says leave blank for no limit. I think 100A is a bug in the report screen. It is probably a default value but it is not operative if not set. I have recently drawn more than 100A. In my case it is a whole house backup with three powerwalls and the main panel is full to the brim. I can hit 100A just charging the car at 48A and running two washers and dryers at the same time easily. Plus my kitchen stove can draw 50A by itself.

 

[Vines]

I checked the installer menu and it says leave blank for no limit. I think 100A is a bug in the report screen. It is probably a default value but it is not operative if not set. I have recently drawn more than 100A. In my case it is a whole house backup with three powerwalls and the main panel is full to the brim. I can hit 100A just charging the car at 48A and running two washers and dryers at the same time easily. Plus my kitchen stove can draw 50A by itself.

The question is not whether you can draw more than shown on the panel limit, the question is whether when you do draw more than the limit, do the Powerwalls continue to deploy power to offset the loads?

Since this is such a new setting, I would not expect many systems to have a valid entry here yet.

 

[GWord]

I would have to dig deeper but perhaps it's just left at the default setting. It might not be actually controlling anything.

OP how old was your installation?

Do you have a main breaker in your essential loads subpanel? What size?

If you do not have the main breaker in the essential loads subpanel then this should be set to the size that the main breaker would be.

To test if this is working, draw more than 90A, then 100A then 110A from the essential loads subpanel, and see if the Powerwalls deploy power at 90A of draw but stop powering the home when you try to pull 110A through the essential loads subpanel.

Dec 2021 install, and I do have a 200A main breaker at the essential loads panel. This was my original main for my service before the install and it was left in place. My new grid main is the 200A breaker in the GW2.

I‘ll do a bit of testing today. Was going to go in to the wizard and see if there was a new setting to adjust.

 

[GWord]

So quick update. No way to adjust in the wizard. There’s the site import limit variable that you can mess with but the 100A panel max seems hard coded somehow. I also put enough load on to crest over 100A while I was on self power but with the grid still available. All solar production plus power wall discharge went to zero and the system immediately switched to grid. With the solar generation at the time, plus 4 powerwalls, I think I should have been able to cover to load although maybe I don’t have a full understanding of how the PW+ units work with solar, on grid.

 

[Vines]

So quick update. No way to adjust in the wizard. There’s the site import limit variable that you can mess with but the 100A panel max seems hard coded somehow. I also put enough load on to crest over 100A while I was on self power but with the grid still available. All solar production plus power wall discharge went to zero and the system immediately switched to grid. With the solar generation at the time, plus 4 powerwalls, I think I should have been able to cover to load although maybe I don’t have a full understanding of how the PW+ units work with solar, on grid.

4 PW is about 83A continuous, plus whatever solar sounds like you probably have over 100A of onsite generation, maybe not much more but only you know that.

It does sound like your 100A panel limit is set, despite your having a 200A main breaker. Likely Tier 2 support or your installer can help you here, and increase that number to 160 or 200A.

EDIT: Still, without having installed it I cant be sure what exactly is going on with panel control.

 

[GWord]

4 PW is about 83A continuous, plus whatever solar sounds like you probably have over 100A of onsite generation, maybe not much more but only you know that.

It does sound like your 100A panel limit is set, despite your having a 200A main breaker. Likely Tier 2 support or your installer can help you here, and increase that number to 160 or 200A.

EDIT: Still, without having installed it I cant be sure what exactly is going on with panel control.

I’ll have to tighten up the test a bit. Might be worth a call to Tier 2 just to understand what this variable is. It will be interesting to see your experience with your install and if it defaults to 100 as well.

 

[dailo]

Today I saw what happens when you exceed this limit. I noticed that my solar production had gone to zero and when I when to look at the alerts it came back with max panel current error. I happen to be running a lot of loads with both AC units running, so I did exceed 100A for a bit. I have 200A service, but I assume because PW+Solar can send up to 60A back into the panel they set this limit as the max you can pull from the grid before shutting down the solar.