Critical Loads Panel question

[Ejimenez]

Still learning the basics lol

Critical loads panels are to just power those X amount of items when the grid goes down with PV and batteries correct?

When setting up an a solar system, the main house panel is powered by solar+batteries (if you go SBU instead of SUB) right? So its like Panels->inverter->main house breaker panel-> critical loads panel

When grid is down then its Panels->inverter->critical loads panel



Sooooo if im generating enough solar or have enough solar+batteries I can run a dryer BUT when the grid goes off then I cannot if its not in the critical loads panel correct? What happens if my solar+battery aint enough to power my main house panel? I assume inverter switches to grid power to supplement the rest? (if Solar+batteries=6kw and I need 2kw more then the inverter uses those 2kw from the grid for a total of 8kw (if the inverter can handle such power of course)

 

[Hedges]

You may want batteries to power datacom, alarm, etc. That would be "critical loads".
In my case, because I use AC coupled PV, my GT PV inverters are also critical loads.

You can have additional important battery-backed loads such as refrigerators & lights, but need a way to shed them so critical loads don't get shut off.

And then you have loads you'd like to power from PV if possible, such as A/C.

If you wire your inverter downstream of main panel, you can put "critical" and/or "important" loads panel downstream of inverter.
By putting an interlocked "generator" breaker in your main panel, you can manually select other loads to operate from inverter as well.

My system has one power relay to connect/disconnect important loads. The inverter switches two signaling relays at different battery SoC. It can switch a relay when there is excess production.
HVAC thermostat could also be controlled - it is low current.

 

[Ejimenez]

Trying to grasp all you said

I plan on powering on batteries the whole house except electric oven, electric dryer, electric water heater and central 36000BTU AC

I do plan on putting on batteries 2 ACs (12000BTU and a 18000BTU with a 22 and 19 SEER rating) and everything thing else at home (PCs, fridge, computers, TVs, etc)

I guess I would pretty much put my whole house as a critical load panel? lol except those few items, Also by NOT adding them to run on batteries I can still run them on solar IF production is high enough right? or would it be grid only energy?

This is a autoconsumption system so its not sending back to the grid to lower my grid bill by credits

 

[Hedges]

You need enough batteries to power loads until the sun returns the next morning (or the next week.)

If your truly critical loads happen to run on 12V, you could given them their own AGM battery, so when everything else shuts off they continue.

If you have enough PV and battery you can run AC in the day, refrigerators and electronics evening/night.
But you need to determine how much power - consumer energy labels, Kill-a-Watt, etc. (It won't be what shows on appliance label continuously, in most cases.)

I think things like refrigerators could be shut off at night. My old ones are power hogs, but some are quite low power, so that wouldn't be needed.

Shutting off some loads when the sun goes down will let you get by on much less battery. PV panels cost a fraction of what batteries do, so laundry, water heater, A/C, cooking are all possibilities during the day. Depends on how much you want to spend. That means these go on a separate panel, not "critical load". Unless you have some other form of switching (home automation, etc.)

Central A/C may or may not work with your inverter size and amount of panels. Mine is small, so I power it.

Not sending back to grid means you want to enable additional load (e.g. water heater) when there is surplus from PV.

 

[hwy17]

I guess I would pretty much put my whole house as a critical load panel?

It's a viable strategy but comes with hurdles about amperage and wire size. If you're not careful you can end up with a solark.

 

[Ejimenez]

I will be getting 20kw in batteries and planned on 6.4kw PV system but planning on upping that to 8.2kw with a 8.2kw inverter (talking to the guys to see how much $$$ would it be over). I'm new to all this stuff and the more I read the more I learn and more I get confused LOL

 

[Hedges]

8kW load on 20kWh of battery will last like 2.5 hours.
In the winter, you'll spend the remaining 10 hours of night in darkness.
Or, you can power about 1600W all night.

You'd be surprised how much a few lights, computers, TV, etc. add up to.
It can work, but you should determine what your power draw is.
That's why I suggest separating critical from important loads, and automatically shutting some down when necessary.

 

[Ejimenez]

8kW load on 20kWh of battery will last like 2.5 hours.
In the winter, you'll spend the remaining 10 hours of night in darkness.
Or, you can power about 1600W all night.

You'd be surprised how much a few lights, computers, TV, etc. add up to.
It can work, but you should determine what your power draw is.
That's why I suggest separating critical from important loads, and automatically shutting some down when necessary.

Yea, when the power does go out we plan to treat the system as a backup so even if we could power up a lot of things we would go with the basics lights, fans, TV, PC) and not big big loads like AC, stoves, etc (we got small gas tanks with a gas stove for when power goes out.)

When the grid is on then we plan on running everything like normal but using as much PV and Battery as possible to limit grid use (I prob plan on using 50% battery during the day if needed since at night according to some calculations we can power the fridge, 1 18000btu AC and a 12000btu AC for a max of like 8-9kw per night.

Not trying to have multiple days of backup batteries since were I live its pretty much constant summer all year around, we can limit day use to charge batteries for the night if we are going to have multiple days blackouts or such (I guess that makes sense?)

 

[Tulex]

You'd be surprised how much a few lights, computers, TV, etc. add up to.

I can say I was amazed. We hum along at around .6-.8kW when nothing major is running, I had no idea it would be that high. But then I went around the house and looked at all the things plugged in. It really does add up.

 

[Ejimenez]

I can say I was amazed. We hum along at around .6-.8kW when nothing major is running, I had no idea it would be that high. But then I went around the house and looked at all the things plugged in. It really does add up.

Indeed, I always try and unplug things like phone chargers and not leave my PC on sleep either. Almost everything plugged in draws a little bit of charge and the average house has a LOT of things plugged in lol