Powerwall Automated Load Shedding?

[jimmyz80]

Has anyone seen or invented any good ways to shed large electrical loads during a grid failure? Our Powerwall design is going to end up backing up the whole house, since it'd be a huge job to separate our pool and spa equipment onto a separate sub panel.

It would be nice to just have some automation in place to disconnect the pool and spa equipment (50A each) from the household wiring, whenever a grid failure is detected. This seems to be a common thing offered by generator manufacturers. I've seen inexpensive modules from both Generac and Kohler, which open a 50A contactor when the grid goes down. These both rely on a signal from the generator transfer switch though. The Generac solution seems pretty slick, I believe the generator slightly lowers the line frequency and then the downstream load control modules detect this and open their circuits.

I also tried searching for any sort of 50A wireless load control devices that I could integrate with my SmartThings hub, but commercial options only seem to go up to 40A. All of the 50A Z-Wave switches look like science fair projects, with a bunch of components cobbled together in a generic weather-tight box.

It would be cool if Tesla offered some hardware to do this, since it looks like the gateway already has a load shedding signal output. Just need the downstream hardware to ingest that signal and operate some relays/contactors (preferably wirelessly).

 

[jjrandorin]

If you dont want those operating during an outage, just tell tesla to leave those circuits in the main panel. They are likely going to install a backup loads panel anyway, they usually do even for whole home backup.

Thats the simplest solution (not putting items that you dont want or need to run in the backup loads panel). I have (1) circuit left in my main panel, which my 60amp wall connector. So, My entire house except for that one connection is backed up with the 2 powerwalls, including my AC. They had no issues leaving that in the main panel.

Failing that, I dont know... I have read some users here trying to work on various ways but have not followed up on it at all since its not something I need.

 

[wwhitney]

With a low amperage wireless relay solution, and a large load to shed, the simplest way to use it is to find the appropriate internal control wire, and use the relay to open it when desired. E.g. for an air conditioning unit, you can interrupt the thermostat wire that calls for cooling.

An alternative is to use the small wireless relay to drive a larger relay that will kill power to the entire load.

Cheers, Wayne

 

[bob_p]

If we have a power outage while away from home, we have apps that provide access to our thermostats and pool equipment - so we can turn those heavy power users off remotely.

For short outages, we want to keep everything running. It's only if there's going to be an extended outage that we'd be concerned - and in that case (hurricane), we'd likely be home to manually throw the breakers.

 

[RKCRLR]

I have a situation where it would be very expensive to install a critical loads sub-panel and was wondering the same thing.

Can Gateways communicate with each other?

If a 2nd Gateway could be installed and commanded to stop transferring power when the grid goes down (like a transfer switch) then non-critical loads could be put on that branch.
Not cheap but still cheaper than what I'd have to go through to install a critical loads sub-panel the standard way.

 

[gpez]

The 50 amp requirement seems to be a killer. I have my Powerwall integrated with my home automation system so it can do exactly this when we're away if the power goes out - all of the lights will automatically shut off, the "someone's home" simulation (which randomly turns lights on and off) will stop, my desktop PC will shut down, etc. Nothing there though is high amps and you're right that it looks like the highest rated z-wave switches are only 40 amps.

There are lots of contact relays that are available which if you're able to wire it up to your spa and pool on/off switch that would work well. Doesn't actually physically disconnect them but would work. Pretty much what @wwhitney said. I have a couple FortrezZ MIMO switches (FortrezZ) to control my garage door and low voltage holiday decorations which would work as a contact switch. They support both NO and NC which makes them flexible.

 

[dortor4ev]

Leviton load center panel w/breakers you can remotely control via various integrations - all you need is the Powerwall to be a "sensor" in google/home or homekit - and then you could setup up automations to toggle the correct breakers when running on battery power!

The Leviton Smart Load Center

 

[chrisbailey13]

When they set up the load panel, they can exclude the equipment you don't want to be backed up, but when the grid is up, that equipment will take advantage of the Solar/powerwall configuration.

That is the simplest configuration.

 

[SoundDaTrumpet]

@jimmyz80 Not really touched upon yet from others, the installer can add current sensors to the equipment not backed up. My A/C subpanel is not backed up BUT "monitored" by the Powerwall System. When the grid is up, the Powerwalls sees the A/C and offsets/powers the A/C. Great way to reduce peak usage. Grid down, the A/C doe not operate. This works well, during winter and fire season (Oct/Nov), the furnace still runs. The only downside, grid down, hot in house, the furnace fan kicks on providing some air circulation, and runs continuously as like if the A/C busted.

 

[GenSao]

Tesla's Powerwall Gateway does support a hard wired load shedding. Inquire with your installer.

Powerwall Installer Manual - April 20, 2020

 

[dortor4ev]

ok internet do your job…I'm asking for the greater power of the internet to identify for me an existing solution to the following problem…

• Problem to be solved: Use a low volage control circuit to interrupt 120 volt AC "feed" in my circuit panel.
• Reason: I have floor heaters that are 120v 20 amp loads - I want these floor heaters to be "turned" "off" when the powerwall is "off grid"
• Details: it is impractical to run a control circuit all the way to the thermostats (the wire run is hideioius) - but the panel that powers the floor heaters is reasonably close to the powerwall gateway
• Idea: buy an off the shelf part relay that I splice into the "HOT" wire that powers the floor heater - this relay will either be on/off base on low-voltage control circuit - and will either let power flow or not-flow based on low-voltage feed status from powerwall gateway

• Powerwall "on-grid" - relay is closed and allows power to flow - result = floor heaters have power
• Powerwall "off-grid" - relay is open and interrupts power - no powerflow - result = floor heaters have NO power

this seems to me it's got to be an already solved problem - can anyone help me with this?

the twist in my request seems to be I'm taking the approach of interrupting the actual power-circuit - so it's "high-volage" at 120 volts that I'm messing with - rather than the lower voltage thermostat

the thermostat is itself powered by the 120 volt circuit and the heated flow is wired to the thermostat - so there is _NO_ low voltage control circuit to interrupt to turn the floor heater on or off…

this is the thermostat I'm using

https://smile.amazon.com/nVent-NUHEAT-Programmable-Dual-Voltage-Touchscreen/dp/B0832BZTPJ/ref=sr_1_6?crid=229MB1VXOLH91&dchild=1&keywords=nuheat+wifi+thermostat&qid=1588993887&sprefix=nuheat+wifi+,aps,207&sr=8-6

thanks in advance if anyone can help me - I'll be happy to post photos and videos of the setup.

 

[dortor4ev]

anyone know if this would do the trick?

https://www.newark.com/idec/rssdn-2...6137?MER=sy-me-pd-mi-alte#anchorTechnicalDOCS

RSSDN-25A - IDEC SOLID STATE RELAY 4-32VDC/48-660VAC 25A PANEL MOUNT

 

[power.saver]

Yes, that would work, a bit pricy though. The "D" model you linked had 32v DC control, so you would have to find a DC source to drive it (transformer + rectifier) but you could run that through the PW Aux contacts. The "A" model has AC control, which might be simpler if you have access to a circuit on the grid side of the PW. Connect it to that and skip the PW Aux contacts. When the grid goes down, the SSR will open.

 

[wwhitney]

Relay in a box, this model should do it:

https://www.amazon.com/Functional-Devices-RIB2401B-Enclosed-Relay/dp/B000LEUJU6

That was my first thought for the OP, too, but they only go up to 30 amps.

Cheers, Wayne

 

[dortor4ev]

all I need is 20 amps ;-)

 

[chrisbailey13]

I think you guys are thinking about this WAY too hard. If @jimmyz80 does not what a WHOLE HOUSE backup, Tesla can design the system to only backup the circuits he wants. The other circuits will still take advantage of the Solar/Powerwall when the grid is up and he will still be able to offset his grid usage. But when the power goes out, only the circuits in the backup load panel will be powered.

 

[RKCRLR]

^^^^
It isn't always that simple. In my case the Gateway will be 250' from my house. Installing a critical loads sub-panel the conventional way would require trenching through landscaping, etc.
And there is no way to run the non-critical loads if desired. My power was out for nearly 2 weeks last year. The spa water got a little nasty. I'd like to be able to manage which things run depending on priority.

 

[chrisbailey13]

^^^^
It isn't always that simple. In my case the Gateway will be 250' from my house. Installing a critical loads sub-panel the conventional way would require trenching through landscaping, etc.
And there is no way to run the non-critical loads if desired. My power was out for nearly 2 weeks last year. The spa water got a little nasty. I'd like to be able to manage which things run depending on priority.

In your case you are right....I was speaking to the OP's question.

 

[Bryantclan]

I have basically the same problem with an added twist. I already have a generac generator with its transfer switch after the gateway. Whole house is covered and just like the OP there is no way to separate my loads due to the level of complexity of my setup.

One note on the generac load shed boxes they work by looking for a variance in the freq up or down. This has the interesting effect of causing the loads to be shed when the batteries are full while the power walls are curtailing the solar. So when the batteries are the most full the biggest loads shut off.

 

[CrazyRabbit]

i believe there is a configurable output from the gateway (generator) which you might be able to use.