Why "critical load panel only" when grid is down?

[ButchDeal]

the connection from the CC / inverter/ battery is more of a T like this

inverter
|
|------------ Charge controller
|
Battery

If the sun is up you would have no problem running the washing machine
That is a very flexible configuration as well.

If you have the generator connected with auto start you likely could have quite a bit on the critical load panel without the need for the interlock and switchable loads unless you plan for it to be way over inverter breaker size. The outback will just start the generator to help it out, or to charge the batteries and help.
I wouldn't put things like electric water heater or electric dryer on the critical load but you could put them on your switchable load panel.

[kingofbanff]

Thanks to ButchDeal and gmanInPA for the time you are putting into this. I wish I had a level of expertise in any field so I could add value in a forum...
Using gmanInPA interlock I have adjusted my design. I originally got the interlock idea (not knowing what it was called) from here
So now I have three panels. The main panel will be fed by the grid. It will have circuits that will never be run off batteries or generator (fine I'll get a stinking generator you persistent b*******!)
The second panel will be the switchable loads. These are loads I may or may not want to run in a grid down situation. My washing machine for example. If the grid goes down mid cycle and I'm out of the house I don't want the machine to draw down my batteries. So by default when the grid goes down this panel goes down. I will manually need to switch the interlock at the critical load panel to get the inverter to feed this panel. Then I can shut down all loads on this panel until I want to use one if the sun is shining. The third panel will be the critical load panel.

[gmanInPA]

Make that "needing an external ATS" and I will agree. There is an ATS which is integral to the hybrid inverter.

Agreed/understood

[inetdog]

... and also freeing me of needing an ATS..

Make that "needing an external ATS" and I will agree. There is an ATS which is integral to the hybrid inverter.

[gmanInPA]

That is how you would deal with it using the non-radian inverters like mine if you wanted a generator. Connect it to AC1 with a disconnect on the Grid side.
The radian can deal with a generator on AC1 or AC2. AC2 just makes things simple as no other disconnect is needed.

Well my main reason for having it usually feed AC2 is so that it only feeds my critical loads typically and also freeing me of needing an ATS. It's main purpose is to recharge batteries based on SoC triggers - not to run the whole house. The Inverter and AGS turn on the generator. I suppose it could do that on either AC1 or AC2, but I want my grid and my generator to feed the inverter directly - though I know some people would rather have the genny feed the main. For my layout, that just didn't make sense. The other arrangement with the switches just gives me the freedom to run whatever I want off the generator(s) in un-forseen circumstances. Also, if I shut down my entire inverter system (using the DPDT bypass I have in place for such), I can still run the generator as a whole house-backup.

[ButchDeal]

I wasn't saying they were alike - only that I could imagine someone would argue that routing the generator back into the AC1 input on the inverter was some how anti-island - but indeed, it is NOT the same. There is no way I can back-feed the grid - period - not through a human decision. The only risk I incur is to my own equipment (and safety) as you speak of. In fairness, the moment you have any installed solar equipment, or electrical equipment installed, you're at equal risk - unless you are somehow prevented from changing any settings.

That is how you would deal with it using the non-radian inverters like mine if you wanted a generator. Connect it to AC1 with a disconnect on the Grid side.
The radian can deal with a generator on AC1 or AC2. AC2 just makes things simple as no other disconnect is needed.

[gmanInPA]

No, the two are nothing alike. If you rely on people making the right decisions to prevent power flow back to the grid, then you will put utility workers at risk, period.

That being said, in your case you are only putting yourself and your system at risk.

I wasn't saying they were alike - only that I could imagine someone would argue that routing the generator back into the AC1 input on the inverter was some how anti-island - but indeed, it is NOT the same. There is no way I can back-feed the grid - period - not through a human decision. The only risk I incur is to my own equipment (and safety) as you speak of. In fairness, the moment you have any installed solar equipment, or electrical equipment installed, you're at equal risk - unless you are somehow prevented from changing any settings.

[jflorey2]

[*]I'm sure some would argue that I'm relying on a setting in my inverter to prevent flow. The same could be said of trusting the islanding features of all hybrid inverters.

No, the two are nothing alike. If you rely on people making the right decisions to prevent power flow back to the grid, then you will put utility workers at risk, period.

That being said, in your case you are only putting yourself and your system at risk.

[jflorey2]

I might have found my solution. This guy has three panels. Main, critical and "switchable". . . . Thoughts?

How is that any better than having a main and a critical panel?

[gmanInPA]

kingofbanff - I am providing this to demonstrate how you can have your cake and eat it too - albeit expensive cake. All of the negatives about cost and maintenance aside (as Sunking has often mentioned), if you are dead-set on a battery-backup system, and want to be able to run anything, here is one way to do it. It's important though that you understand a few important details:

Okay, firstly... please pardon the very poor symbology in this diagram - the tools I had at the time had very little to offer and I was trying to convey to an electrician what I needed setting up. Secondly, I have a lot of extras in this setup that many would not incur the cost of doing and aren't required, but I wanted them: A DPDT that allows me to bypass the entire inverter system and runs everything directly off the main; a generator selector that allows me to optionally run my interlock from either my backup (diesel) or portable (tri-fuel) generator. It is a belt and suspenders approach. I'm sure Sunking will have a hay day with me for this setup

1. Without a very expensive system, you likely won't be able to run your whole house on battery backup. That is why the critical loads are isolated.
2. You can however run your entire home on a generator.
3. Because generator is usually feeding only the inverter (via the inverter's AC2 input), this would normally rule out using that generator for the whole house.
4. The diagram above shows what I did to work around this. My backup generator can alternatively feed either the inverter or the main panel which blocks it from feeding the inverter's AC2 input and routes it ultimately to the AC1 input. You need an interlock for the generator feed into the main panel (what is in the photo you attached). You also need some sort of switching to manually direct the generator to the main panel vs the inverter. I accomplished this with an interlock between two breakers in my power distribution panel (see photo 2 for mine).
5. If for some reason I want to run a circuit on the main panel in a grid-down situation, I must flip the two switches above
   1. One to direct power away from my inverter
   2. The interlock in my main panel to prevent the generator from back-feeding into the grid.
6. Supposing I have my generator directed toward my main panel instead of the inverter, the inverter would still receive power (via the AC1 input) because it is a branch circuit off the main panel. Important: If enabled, I also have to turn off "Sell Mode" (where the inverter "sells" power back to the grid) because you DO NOT want to try to send surplus power back into a generator-based utility. I'm not entirely sure how the inverter would handle that situation, but I'd rather not find out.
7. I'm sure some would argue that I'm relying on a setting in my inverter to prevent flow. The same could be said of trusting the islanding features of all hybrid inverters.
8. Because I have the main panel interlock. There is no way for the above system to backfeed the grid. It passed all local electrical inspections with flying colors.
9. This does require that you have some means of determining when grid power is restored so you can reverse the above steps at that time.

*The above is ONLY for the case where I want/need something from the non-critical loads to be powered during a grid-down event.

[ButchDeal]

I might have found my solution. This guy has three panels. Main, critical and "switchable". See photo. When the grid is Up this panel is fed from the grid. When the grid goes down he has the option to manually switch it over so it is now fed by the inverter. The gate on it prevents both the inverter and the grid being able to feed at the same time. Thoughts?

This makes no since if you are using the outback inverters just put this panel on the critical load side, and done.

[gmanInPA]

If you're inverter is not on a branch circuit off your main panel, then I could understand this approach. I'm not sure why that would be either necessary or desired for a hybrid setup tho. Just bear in mind you can't load an inverter more than its AC output breaker size.

[gmanInPA]

If your inverter is on a branch circuit, any of the loads on the inverter are grid supported with grid power and supported by pv/generator/battery when grid down. It sounds like you're viewing your loads as either/or. If you're planning on a hybrid inverter, that's just not the case.

Where this could be helpful is where I mentioned it earlier - to switch where the output of your generator goes. That device is an interlock.

When th grid is down, it can't feed a panel. When it's up and powering an inverter, it powers the inverter and the inverter determines how to use / combine the grid, pv, generator, battery to support the loads. You don't need to manually work that out if you're considering a hybrid setup.

[kingofbanff]

I might have found my solution. This guy has three panels. Main, critical and "switchable". See photo. When the grid is Up this panel is fed from the grid. When the grid goes down he has the option to manually switch it over so it is now fed by the inverter. The gate on it prevents both the inverter and the grid being able to feed at the same time. Thoughts?

[gmanInPA]

I too could go a pretty decent amount of time for the investment. And to the point that batteries sit there not getting used.. we intentionally shut our power down at the main ~ 1/month. We could (and may start to) do weekly. Some would scoff at such, but it is good for our industrial battery to do so, and saves us approximately 15% of our electric cost for that week. Further, we are able to get a realistic test of the equipment, et al. Without much conservation, my battery would go ~24h with no additional charging. That is to a 50% DoD. I could certainly go lower - and the battery manufacturer recommends such at least a handful of times per year.

To me the redundancy and just good old-fashioned options are worth the investment.