Complex install questions for 400A house

[Adrian Cockcroft]

I've got a "sprawling" single story house with a 400A feed and multiple sub-panels scattered around. We converted it to heat pumps for air and water a few years ago and have a large solar array connected to a 200A sub-panel on the far side of the house from the main feed. My main concern is that long power cuts tend to occur during winter storms, which is when I most want to keep the house warm and need a lot of heat pump power, and I have electric auxiliary heat, not gas, so it pulls a lot of power on very cold nights. The house is not easy to keep warm, high ceilings and solid concrete walls.

After well over a year, Tesla is finally starting to move on powerwall installation, but their inability to provide any transparency or discussion of what's going on or how they plan to install isn't inspiring confidence.

We've got 6 powerwalls in the order, we already have 30KW of solar, and eGauges on the main circuits and sub-panels so we can see where the power is going.
The powerwalls will tap into the 400A main panel, as we need to isolate and backup things on both of the 200A sides of the panel.

I have a bunch of questions that I'm hoping people here can help with.

I'm not sure how the gateway switching works for 400A? Are there two gateways working together?

How can I automatically switch off individual circuits during a power cut, to make the batteries last? I've seen some wifi enabled individual breakers that look promising, but I'm not sure how to tie them in to the gateway and automate turning off things like pool pump circuits.

Thanks for any ideas
Adrian

 

[ATPMSD]

Tesla is not the only game in town. Why not talk with other battery vendors? Just for example:

The 6 Best Home Battery Storage Systems

Home battery storage systems have skyrocketed in popularity during the past few years. We spoke to experts to find the best energy storage systems.

www.treehugger.com

 

[preilly44]

We have 800 amp service (we needed more than 400 amp service and our electric co doesn't offer 600 amp service) split up over 4 200 amp panels. We are backing up 3 of the 200 amp panels over 8 PW2s (3PW, 3PW, 2PW per 200 amp panel) and a 34KW solar system. I was hoping we could have all the PWs backup the entire house but Tesla said that wasn't possible because they only can backup 1 200 amp panel at a time.

I'm still waiting on installation so things may change. I'm curious to hear how yours turns out.

 

[Adrian Cockcroft]

Tesla is not the only game in town. Why not talk with other battery vendors? Just for example:

The 6 Best Home Battery Storage Systems

Home battery storage systems have skyrocketed in popularity during the past few years. We spoke to experts to find the best energy storage systems.

www.treehugger.com

I have looked at other suppliers, they either can't stack enough batteries together to build a large installation, or the batteries themselves are physically bigger and need to be racked indoors. I need to have them outside to be near the main feed, and I need 6 powerwalls to give me enough current feed. The install costs are also much higher. Tesla is charging a fixed $3K for the install for my system, which they are going to lose money on...

 

[Adrian Cockcroft]

We have 800 amp service (we needed more than 400 amp service and our electric co doesn't offer 600 amp service) split up over 4 200 amp panels. We are backing up 3 of the 200 amp panels over 8 PW2s (3PW, 3PW, 2PW per 200 amp panel) and a 34KW solar system. I was hoping we could have all the PWs backup the entire house but Tesla said that wasn't possible because they only can backup 1 200 amp panel at a time.

I'm still waiting on installation so things may change. I'm curious to hear how yours turns out.

Thanks, that helps, so we'll have a gateway on each side, and probably 3 PW on each. How does that work for power sharing during an outage? Does each gateway connected bank of PW drain separately? I will only have solar on one side, so they need to be linked to recharge while off grid.

 

[holeydonut]

IMO, the reason Tesla is so cheap is because they want low-hanging-fruit jobs that take the least amount of communication and brain (or AI) power.

Your project is the exact opposite of an easy cookie-cutter. And you personally are the exact opposite because you want transparency and involvement.

You can't have your cake for a massive discount and eat a delicious cake too. I think you should find a vendor that employs communicative and knowledgeable specialists like @Vines that cater to these bigger/complex installs.

Recall what you were feeling when you typed: "inability to provide any transparency or discussion of what's going on or how they plan to install isn't inspiring confidence"... and assume those feelings get 10x worse once you sign a contract with Tesla. Is that what you want?

 

[Vines]

IMO, the reason Tesla is so cheap is because they want low-hanging-fruit jobs that take the least amount of communication and brain (or AI) power.

Your project is the exact opposite of an easy cookie-cutter. And you personally are the exact opposite because you want transparency and involvement.

You can't have your cake for a massive discount and eat a delicious cake too. I think you should find a vendor that employs communicative and knowledgeable specialists like @Vines that cater to these bigger/complex installs.

Recall what you were feeling when you typed: "inability to provide any transparency or discussion of what's going on or how they plan to install isn't inspiring confidence"... and assume those feelings get 10x worse once you sign a contract with Tesla. Is that what you want?

It will be interesting to see what Tesla does to solve this challenge, and whether their style will work for you with such large and complex job. It sounds like the OP likes the Tesla price but might prefer more communication from their design experts.

If you were to select a 3rd party their installation would be more expensive, but also would get the hands-on attention it deserves. Also 3rd party installers are not constrained by the Tesla machine, so can make smart and specific choices for you and your design. Also when you have questions and changes, you can just call your designer directly and change it.

With a 3rd party you could also get SGIP funds, which might get you back $2k ish for each of your 6 ESS. Tesla does not participate in SGIP for large installations to my knowledge. This will help reduce the delta between a 3rd party and Tesla pricing.

Finally, a 3rd party might be able to backup your whole home with just the single gateway depending on load calculations, instead of forcing you to split PV and ESS resources between 2 different systems. We just finished a whole home backup installation for a customer with a 12k sqft mansion with 600A switchgear.

 

[Vines]

I've got a "sprawling" single story house with a 400A feed and multiple sub-panels scattered around. We converted it to heat pumps for air and water a few years ago and have a large solar array connected to a 200A sub-panel on the far side of the house from the main feed. My main concern is that long power cuts tend to occur during winter storms, which is when I most want to keep the house warm and need a lot of heat pump power, and I have electric auxiliary heat, not gas, so it pulls a lot of power on very cold nights. The house is not easy to keep warm, high ceilings and solid concrete walls.

After well over a year, Tesla is finally starting to move on powerwall installation, but their inability to provide any transparency or discussion of what's going on or how they plan to install isn't inspiring confidence.

We've got 6 powerwalls in the order, we already have 30KW of solar, and eGauges on the main circuits and sub-panels so we can see where the power is going.
The powerwalls will tap into the 400A main panel, as we need to isolate and backup things on both of the 200A sides of the panel.

I have a bunch of questions that I'm hoping people here can help with.

I'm not sure how the gateway switching works for 400A? Are there two gateways working together?

How can I automatically switch off individual circuits during a power cut, to make the batteries last? I've seen some wifi enabled individual breakers that look promising, but I'm not sure how to tie them in to the gateway and automate turning off things like pool pump circuits.

Thanks for any ideas
Adrian

Tesla will be the one to design this, with 2 gateways likely. Each of your 2 systems will be independent when they design it. The PV will be divided, as will the powerwalls.

To automatically switch off circuits there are many different answers. The slickest answer is to use SPAN or something similar for the subpanels that contain breakers you want to turn off yourself. Other smart home solutions are possible, but I am not an expert. The Gateway does have the ability to shed one load when off grid through a dedicated 60v 1A DC contactor. This is usually an air-conditioner/heat pump through a dedicated thermostat control circuit. This circuit could be used to trigger other devices.

 

[arnolddeleon]

@Vines mentioned SPAN.io as option for smart switching. Another option, would be something like shelly.cloud switches/relays. Might be better than span if your loads are distributed or they're not on a dedicated circuit. There is whole rabbit hole around products that work with Home Assistant.

You mentioned backup heat which sounded like resistance heaters. Could upgrading/replacing the heat pumps be a cost effective option? It seems newer ones will rarely need backup heat in theory with most the climate in California

 

[jboy210]

@Vines mentioned SPAN.io as option for smart switching. Another option, would be something like shelly.cloud switches/relays. Might be better than span if your loads are distributed or they're not on a dedicated circuit. There is whole rabbit hole around products that work with Home Assistant.

You mentioned backup heat which sounded like resistance heaters. Could upgrading/replacing the heat pumps be a cost effective option? It seems newer ones will rarely need backup heat in theory with most the climate in California

I agree about the backup heat. We built a house in the 80s with a heat pump and it had resistance backup. But everyone I have talked to about current heatpumps say there was no need for this.

@h2ofun has a large home running on heat pumps, powerwalls, and solar and may have some insight on @Adrian Cockcroft's situation.

 

[h2ofun]

I agree about the backup heat. We built a house in the 80s with a heat pump and it had resistance backup. But everyone I have talked to about current heatpumps say there was no need for this.

@h2ofun has a large home running on heat pumps, powerwalls, and solar and may have some insight on @Adrian Cockcroft's situation.

I have a 400 amp service, 2 200 amp subpanels. So I split my 30K solar with 2 inverter, each drive a seperate GW2. Whole house. whole house 22K
backup generator. I see nothing wrong with using multiple GWs Makes it pretty easy. What was tricky was to balance the solar with the batteries for usage. Meaning, I needed to get my best 15K and 3 batteries with my heat pump heating/AC, since this is what takes the most power!!!!

 

[Vines]

I have a 400 amp service, 2 200 amp subpanels. So I split my 30K solar with 2 inverter, each drive a seperate GW2. Whole house. whole house 22K
backup generator. I see nothing wrong with using multiple GWs Makes it pretty easy. What was tricky was to balance the solar with the batteries for usage. Meaning, I needed to get my best 15K and 3 batteries with my heat pump heating/AC, since this is what takes the most power!!!!

The only thing wrong with multiple GW is that the PV and ESS must be divided somewhat permanently. Your use of the house will determine which system will run out of power first.

If there is just one GW, then no matter what you do under backup situations, all your PV and ESS comes from the same bucket of resources, so you can always maximize it.

 

[h2ofun]

The only thing wrong with multiple GW is that the PV and ESS must be divided somewhat permanently. Your use of the house will determine which system will run out of power first.

If there is just one GW, then no matter what you do under backup situations, all your PV and ESS comes from the same bucket of resources, so you can always maximize it.

Yep, which is great until you have multiple 200 amp subpanels, one has to compromise. Or, does someone have a 400 amp GW yet?

 

[Vines]

Yep, which is great until you have multiple 200 amp subpanels, one has to compromise. Or, does someone have a 400 amp GW yet?

There are other solutions possible, that keep the 400A from the service while on grid.

 

[h2ofun]

There are other solutions possible, that keep the 400A from the service while on grid.

So, if one already has the 200 subpanels wired, and one wants whole backup, what would you recommend to a customer? Is there a better way than what I did?

 

[Vines]

So, if one already has the 200 subpanels wired, and one wants whole backup, what would you recommend to a customer? Is there a better way than what I did?

As time goes on, we get smarter and problems have slicker solutions.

Someone today has additional options with our installation company compared to when your system was installed.

 

[BGbreeder]

In order of simplicity;
Given everything that you are trying to keep powered, you might consider further upgrading the solar, as you want to have heat during the worst case scenarios of winter, and clouds. Most of Salinas isn't exactly sunny all day in the wintertime...

Bite the bullet and put in a large ICE backup generator for the fringe days.

I am not sure what you mean by backup resistance heating. If it is space heaters, your heat pumps will give you much better bang for your buck.

While it is less sexy or flexible, but I would also consider solar heating as an option, especially with in floor heating that can soak up low grade heat, or as preheat for your heat pumps.

Cost probably is close to running the opposite of simplicity...

All the best,

BG

 

[Adrian Cockcroft]

In order of simplicity;
Given everything that you are trying to keep powered, you might consider further upgrading the solar, as you want to have heat during the worst case scenarios of winter, and clouds. Most of Salinas isn't exactly sunny all day in the wintertime...

We're at 600ft in the hills near Salinas, get plenty of sun, and I upgraded from 20KW to 30KW last year.

Bite the bullet and put in a large ICE backup generator for the fringe days.

Been there and done that and not doing it again.

I am not sure what you mean by backup resistance heating. If it is space heaters, your heat pumps will give you much better bang for your buck.

I have new heat pumps, and when its freezing outside they need help as my house is hard to heat. I have 4.5ton Mitsubishi and they have resistive backup heat for the coldest days.

While it is less sexy or flexible, but I would also consider solar heating as an option, especially with in floor heating that can soak up low grade heat, or as preheat for your heat pumps.

I'm not digging up the floor... I have under-floor heating in the more recently built guest house and solar heating for the pool. Doesn't help keep the main bedroom warm at night.

Cost probably is close to running the opposite of simplicity...

All the best,

BG

 

[Adrian Cockcroft]

The only thing wrong with multiple GW is that the PV and ESS must be divided somewhat permanently. Your use of the house will determine which system will run out of power first.

If there is just one GW, then no matter what you do under backup situations, all your PV and ESS comes from the same bucket of resources, so you can always maximize it.

OK, so the problem is that the solar is all on the other side of the property, on a 200A sub panel, and there's no easy way to run conduit to that side (no attic or subfloor and it's a long way). The main bedroom that I want to heat is on the side that doesn't have solar... thanks for clarifying that.

 

[Vines]

OK, so the problem is that the solar is all on the other side of the property, on a 200A sub panel, and there's no easy way to run conduit to that side (no attic or subfloor and it's a long way). The main bedroom that I want to heat is on the side that doesn't have solar... thanks for clarifying that.

Are there any other loads in the subpanel with the PV solar system?