Emergency Power Backup design review

[crzykidd]

Looking for feedback on this design. We live in an area where we can lose power for 2-3 days from time to time. So the main design of this is to provide backup of critical loads, a few light circuits, fridge, freezer, gas furnace fan etc. Batteries will last about 24 hours on the load, solar will augment some, and if needed will run generator a few hours a day to charge batteries. Not a lot of room for solar, nor do we have great producing days in the winter in the PacNW. Main panel is on the grid, and using a generator interlock in the panel for when needed.

First time designing something like this so just looking for feedback, thoughts etc.

 

[Shimmy]

What you are proposing looks like overkill for your stated needs. Is your furnace fan 120V or 240V? Fridge and freezer are likely under 4kWh/day, more commonly under 3kWh/day.

You should only need to plug the Chargeverter into your generator directly, and a backup inverter is likely unnecessary; the money is likely better spent on a bypass for the critical loads panel (maybe even a 14-50 inlet connector for the generator).

 

[crzykidd]

I will be adding additional circuits, but really care about the critical. Will have Internet on it, plus some home automation items and my computer etc. TV etc. Last year we lost power for 12 days. When you work from home and have $1000s of food in your freezers/fridge better to go a little overkill than not enough. Also will be adding 6 more panels down the road, just not immediately. If needed will charge the EV etc. 100% agree on the extra inverter, but had it and just wanted it in the mix in case it was needed..

 

[Shimmy]

I get it, and am in a similar situation. For me (in a climate that doesn't require heat or air conditioning for survival), my base critical loads are 15kWh/day and ~2,000W peak demand. I have 2 refrigerators and a chest freezer that need backup, along with a fairly substantial IT system that includes several network switches, 8 access points, and a 16-camera DVR system.

The issue with your concept (in my opinion at least) is that the PV is unlikely to be able to really add value in reducing generator needs. For a Critical Loads Panel system, you really need to minimize what is on it to the bare essentials. Very quickly you start hitting a point where a whole-house system is simply more practical.

For me I evaluated an EG4-3000W 120V AIO with 15kWh battery, a Schneider 6800W with a 30kWh battery, and an EG4 or SolArk 12000W AIO and a 40kWh battery. The first would be critical loads only, the second would handle 90% of my needs, and the last one 120% of my needs. With the other work that needed to be done, just shelling out for the bigger system and simplifying the installation was a clear winner.

I'd suggest trying to pencil out a few options for yourself in a similar fashion and look at the bill of materials and complexity of operating the system. Without the benefit of year-round solar covering loads you are likely to find that a utility-out scenario requires running on generator at least 8 hours a day.

 

[crzykidd]

Thank you for the feedback, lots to think about there... With that in mind am I thinking through the wiring sizing, breaker sizes, fuse sizes, etc. correctly?

I am doing some usage charting on circuits over the last couple weeks and will use that data as well to determine what is critical, vs nice to have and then spend some time thinking through the process you outlined above.

Thanks

 

[Shimmy]

With that in mind am I thinking through the wiring sizing, breaker sizes, fuse sizes, etc. correctly?

Yes and no; breaker and wire sizing are really the last step, so you have a few minor things that will shake out as you validate your equipment needs and selection.

 

[Rednecktek]

So a couple thoughts...

It looks like you've got about 2300w of array there? For most of our year that's going to get about 10% performance or so so you're going to need to seriously curb your inverter choices there. That 6Kw unit is going to need a significant chunk of your battery capacity to exist and your panels are going to have a hard time refilling that between Oct and April at the very least depending on where exactly you live. Re-crunch your numbers and see what's actually critical (fridges, lights, etc) and re-size for that. The smaller the inverter, the less standby draw it has.

Backup inverter? Why? If you want a spare then size your system and just buy and program a cold spare you can install in a pinch.

That LVX6048, is that the low frequency split phase version? Do you need 240v on your critical loads panel? If that's the unit I think it is that thing is like 130w/hr just to exist!

Is that the actual picture of your generator? Your inverter might not charge from it as most AIO's have a real hard time with non-inverter type generators.

Just my thoughts. I had a place in Monroe and 300w of panel couldn't keep up with a 200wh/day load for weeks at a time.

 

[Rednecktek]

Another thing that comes to mind, but if you actually need 240v split phase but don't want to feed a LVX at 130+w/hr, RZLB makes a 3Kw and 4Kw split phase inverter that only draws about 25w in standby.

 

[chilly2]

Another thing that comes to mind, but if you actually need 240v split phase but don't want to feed a LVX at 130+w/hr, RZLB makes a 3Kw and 4Kw split phase inverter that only draws about 25w in standby.

Have you tried any of those RZLBs out? I just got one and hope to hook it to the house panel (for grid down situations) but am hesitating over a couple of points in the manual. Have opened another thread so as not to hijack this one.