Like always, there's more than one way to solve a problem....
Please don't take me for the expert here - I'm not electrician - just a DIYer trying to set up something for 1st time.
Assuming you're new to this, I'll try to cover some details here, as I understand. Please feel free to anyone where I may be off.
While our idea isn't "totally" unique, I think it's a bit unusual: A backup system using DC/Inverter and not solar. Your Yeti reference is a whole new emerging market segment - and quite interesting.
Correct me if I'm wrong here, but I think this is how our two plans compare to each other:
What we have in common:
- Use generator during daytime power outage
- Utilize some type of essentials panel
- Night time back up power via Inverter / Battery bank
- Not have solar now, but maybe in future
What we don't have in common:
- I'd like 240v at both legs of primary panel
- You'd like 120v to 1 leg only (I'm not sure why?)
- I'd like auto transfer to my essentials (the switch in your link is manual type)
SIZING:
I think what you need is night time usage, not your total 8.8kw/day I think you referenced above. I checked my utility meter outside to confirm my overall overnight usage - easy.
Typical US home consumes roughly 30KWh's / day I believe, and about 1/3 of that at night. I confirmed with my heater running in Michigan in winter that 10Kwh was more than enough for an evening of energy - in my case.
Figuring 9KWh was my night usage, I ordered 16 each 280Ah LiFePO4 cells, yielding ~ (280ah x 48V = 13,440W), or at
60% DOD 8KWh, or 65% DOD for 9KWh.
For my inverter I wanted to consider a worst case over night + not worrying about someone getting up in A.M. and turning a microwave etc, hence my 4kw plan. Also keeping in mind while my evening low usage may be in the sub 1000W range, worst cases are motor start ups, like heater or fridge you mention on your essential list.. Key I think is double and round up. I suggest you consider more than 1,200W inverter.
The other thing to consider along with inverter size is inverter voltage, trying to keep well under 200A if possible, so my case is
4400w/48v=92A.
If I did 24v I'd be in the 200A plus club (not accounting surges). This means wires, switches BMS etc all need to be double duty... gets expensive and scary real fast IMHO.
For generator sizing I think it's
1.5 times Inverter sizing you should consider. I'm "trying" to get two 4.4kw Inverter Generators and connect in Parallel, and run off Natural Gas. At about 80% derating for natural gas I'm figuring 7.2kw peak power, or 1.6 times my 4.4kw inverter. Been on backorder though since Feb - quiet, small, parallel option, 240v so I could hook 1 or 2 - is what's checking my boxes.
You need the extra (1.5x) generator power since you want to be able to run things in power outage "plus" be charging battery bank for your next evening if that's your plan.
BTW, for the 120V you mention, I'm not sure why you're thinking 120v. Is your generator 120v or 240v? I'm guessing you know that 240v is just 2 legs at 120v. See below for more on why I want 240v.
SYSTEM PLAN:
If you're like me, this can be a bit confusing at the start trying to understand how things hook up and the options.
More importantly, if you're not knowledge about electricity, BE CAUTIOUS.
Basically there are a some basic options for alternate power to enter our existing system(s), including:
1 - Interlock system (what I'm planning)
Other MTS's, like example you ref'd above, can have alternate power "plugged" into box and switch devices individually:
Nature’s Generator Power Transfer Kit. This is pretty tradition way to hook up a generator, but didn't check all my boxes.
3 - ATS (Automatic Transfer Switch), basically what UPS system does, the moment grid power goes down.
In my application I'm thinking to use:
#1 option (Interlock) to "lock out" grid power into my panel and turn on alternate power into panel (which also leads to my sub panel with additional 25 breakers)
#2 option (MTS) to switch power from one of two sources. For my case I have MTS to Main and another MTS to Inverter (this is where it gets tricky). IOW, I can supply my Main "via my interlock" with either Generator or Inverter power for example. Manually.
#3 option (ATS) Isn't in my plan (more $$ and not as reliable IMO), but is a feature "in part" in most inverters (more on that next).
My plan will be traditional "in part" when it comes to the inverter feeding a small subpanel, or the essentials (sump pump).
This panel will feed my sump pump all the time, where the Inverter will power it with either grid-AC (what they call pass-through), or DC inverted to AC like a UPS (power outage / automatic back-up even if I'm out of town).
I'm adding the additional MTS to feed the inverter with either grid-AC, or Generator power if grid goes down.
When I switch my interlock, I'd incorporate secondary feature that forces off grid-switch to inverter - otherwise I'd be feeding inverter with it's AC.
The advantage of my plan is that I can distribute the 4.4kw backup power across both my Main Panel (25 breakers) and Subpanel (25 breakers) - why I want 240v or split phase.
A second option (more traditional) way is setting up Subpanel & selecting essentials. I see 2nd option as being a large rip-up for me and spending towards $10k + for something - I MAY NEVER USE? BTW, my subpanel is about 30 feet from main panel, why I say rip up.
Yes, I could exceed that 4.4Kw real fast with 50 breakers, but I'm willing to put the manual part in this process for backup only. I can live without things like 240v oven or Air Conditioner (live in Michigan and basement is always cool) - have ceiling fans everywhere. Tracking my usage with the SENSE system I can see that 4.4kw will go a LONG ways.
Yes, I could put a whole house backup generator in but I hear those can be a $$ pit. And, if I move I take my portable geny's and probably the inverter system.
I hope this helps you more than it confuses you. I've spent quite a while chewing on this and appreciate everyone's application is unique. It was cool to see you start this post as it's the closest I've seen to my case.
Attached is illustration of my plan, thus far... if this is how I go.