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

[kingofbanff]

I fully understand there is a lot of energy stored in gas or natural gas which is way more efficient, however in my case for reasons I won't go into, in my situation a generator is not an option so I'm trying to do what I can with PV. thanks again for all the help.

[Sunking]

the Radian has a well-integrated generator input, so you can deal with longer blackouts pretty easily.

Thus is the foolishness of a Hybrid system for a grid tied system. For equal or less money, use a conventional grid tied system with a Generator and ATS sized to run everything in the house.

[jflorey2]

Well thanks for all the thoughts guys! I guess I'll keep a lot of long extension cords around the house! Then when I'm just running off solar I can plug into an outlet that is wired off my critical load panel and (assuming I'm not already using all my juice) run the cord to whatever I need to operate that isn't on the critical panel.

No need to do that; just choose what you want to run on your critical loads panel and wire accordingly. With a Radian 8kW inverter you'll be able to operate most basic appliances/critical loads (well pumps, sump pumps, furnace blowers, fans, lights, communications) without much fuss. In addition, the Radian has a well-integrated generator input, so you can deal with longer blackouts pretty easily.

[Sunking]

ButchDeal I understand there is no way I can run all my loads but I'd rather choose what I want to run at any particular time after the grid goes down rather than before I build out my critical load panel.

Will not work and does not comply with electrical codes. No inspector would pass it. With a 48 volt 350 AH battery, the largest load it can 2000 watts. That is not much power, just enough to run a refrigerator and a few lights. In terms of ac service that is just roughly 8 amps, and no code or inspector is going to allow you to connect to a 200 amp service.This is why the Inverter manufacture built a small Automatic Transfer switch with very limited power. It forces you to install an addition breaker panel (Emergency). and reroute your selected circuits from your main breaker panel to the Emergency Panel so you cannot over load your hybrid inverter. It there to protect your equipment and most importantly your life.

IMHO you really made a big mistake using a hybrid inverter with batteries. It would have been a lot less expensive for you to install conventional grid tied system, pad mounted generator with transfer switch, and 150 to 500 gallon LPG tank. You would have exactly what you wanted. When the power goes out, generator starts and you can run anything in your home including air conditioning.

Here is the kicker, a battery hybrid system requires a generator connected to AC2 port.

[ButchDeal]

Just pick your critical load circuits carefully. courtesy lighting, refrigerator, Gas appliances that require power, like oven and blower and or electro lighter for gas hot water heater and or well pump. a properly designed system will only cycle the battery bank during power fail. even if you have a full set of L-16's, it's not as much power as you think. it is only backup, If you want full house power you should consider a much larger 2 volt battery 24 of them and a "Outback flex power two" so you can maintain 240 volt appliances, but that's a lot for just backup power, you could just integrate a generator.

Good points on appliances but FlexPower 2 is a much smaller inverter system. With two radians OP is at 12kw inverter capacity, with FlexPower 2 would be limited to 7kw depending on inverters in flexpower2.

[Logan005]

Just pick your critical load circuits carefully. courtesy lighting, refrigerator, Gas appliances that require power, like oven and blower and or electro lighter for gas hot water heater and or well pump. a properly designed system will only cycle the battery bank during power fail. even if you have a full set of L-16's, it's not as much power as you think. it is only backup, If you want full house power you should consider a much larger 2 volt battery 24 of them and a "Outback flex power two" so you can maintain 240 volt appliances, but that's a lot for just backup power, you could just integrate a generator.

[kingofbanff]

You can't have it be a manual switch like you are thinking and to be honest you can move a lot of things to the critical load panel on your system. I would make sure you have LED bulbs in the fixtures on critical load

Well thanks for all the thoughts guys! I guess I'll keep a lot of long extension cords around the house! Then when I'm just running off solar I can plug into an outlet that is wired off my critical load panel and (assuming I'm not already using all my juice) run the cord to whatever I need to operate that isn't on the critical panel. Clearly not an elegant solution...
I'll let you know how it unfolds as we design it.

[inetdog]

H

This is because of the utility back feed/isolation/islanding requirements, correct?

Not entirely. The AC1 connection is configured for grid interaction so that the inverter can deliver power into the grid (either to your local loads or banking power back into the utility grid. But by design that connection can only deliver power when utility voltage is present already.
Only AC3 can deliver power when there is no grid input on AC1. That is why the connection is made from AC3 to the critical loads (needed when off grid) panel.
It is possible to run some unit in interactive mode when there is power present on AC2, but the inverter will monitor to make sure that it never tries to feed power back into the AC2 connection, since the generator could not deal with that.
When there is no power on AC1 the internal transfer switch opens isolating AC1 from AC3.

[cebury]

H

You can't have it be a manual switch like you are thinking

This is because of the utility back feed/isolation/islanding requirements, correct?

[ButchDeal]

Guest I've sketched out what I think you are saying in the diagram attached. When the grid goes down there is a switch at the "2" in the circle.
I would like the main switch at the "1" in the circle. I would also like a switch at "2" which also opens (disconnects) when the grid goes down for the following reason:

I understand there is no way I can run all my loads but I'd rather choose what I want to run at any particular time after the grid goes down rather than before I build out my critical load panel. So for example I envision marking all my non critical loads at the breakers in the main panel and when the grid goes down flip them all off. After they are off I close the switch at "2" so the main panel is now live (but "1" is open so no power is going back to the grid to zap workers). I can then selectively turn breakers on if I need power at a certain place for some amount of time.

The switch at 2 is built into the radian.
The connection between the charge controller, battery and inverter is a "T" or buss connection
As many have stated your inverter is not large enough to have the disconnect at "1" but you can move a lot of loads like lights, well pump, fridge, garage door opener, tv, satellite, Internet to the critical load panel. Just not your electric range, electric water heater, heatpump, etc.

You can't have it be a manual switch like you are thinking and to be honest you can move a lot of things to the critical load panel on your system. I would make sure you have LED bulbs in the fixtures on critical load

[jflorey2]

I understand there is no way I can run all my loads but I'd rather choose what I want to run at any particular time after the grid goes down rather than before I build out my critical load panel. So for example I envision marking all my non critical loads at the breakers in the main panel and when the grid goes down flip them all off. After they are off I close the switch at "2" so the main panel is now live (but "1" is open so no power is going back to the grid to zap workers). I can then selectively turn breakers on if I need power at a certain place for some amount of time.

Nope, won't work. Several problems:

1) Under no circumstances will your inverter "backfeed" a dead main panel. It is designed expressly to never do that no matter what switches you throw.

2) If you just move all your loads to the critical panel here's what will happen:
-It will get very hot one day and demand will peak. Your A/C will be running full blast.
-Outage will occur due to system stress from demand peak.
-Your inverter will switch over automatically.
-Your central A/C will attempt to start its compressor. The (relatively small) battery pack will not be able to source that much current, the battery voltage will sag and the inverter will shut down. All your loads will go off.

3) Your DC wiring is wrong. You will have + and - going to the battery, the charge controller and the inverter.

[kingofbanff]

ButchDeal I've sketched out what I think you are saying in the diagram attached. When the grid goes down there is a switch at the "2" in the circle.
I would like the main switch at the "1" in the circle. I would also like a switch at "2" which also opens (disconnects) when the grid goes down for the following reason:

I understand there is no way I can run all my loads but I'd rather choose what I want to run at any particular time after the grid goes down rather than before I build out my critical load panel. So for example I envision marking all my non critical loads at the breakers in the main panel and when the grid goes down flip them all off. After they are off I close the switch at "2" so the main panel is now live (but "1" is open so no power is going back to the grid to zap workers). I can then selectively turn breakers on if I need power at a certain place for some amount of time.

[kingofbanff]

ButchDeal I've sketched out what I think you are saying in the diagram attached. When the grid goes down there is a switch at the "2" in the circle.
I would like the main switch at the "1" in the circle. I would also like a switch at "2" which also opens (disconnects) when the grid goes down for the following reason:

I understand there is no way I can run all my loads but I'd rather choose what I want to run at any particular time after the grid goes down rather than before I build out my critical load panel. So for example I envision marking all my non critical loads at the breakers in the main panel and when the grid goes down flip them all off. After they are off I close the switch at "2" so the main panel is now live (but "1" is open so no power is going back to the grid to zap workers). I can then selectively turn breakers on if I need power at a certain place for some amount of time. Solar schem1.pdf

[gmanInPA]

...If you are going to run central A/C, for example, you are going to need an enormous battery - both for energy storage and for power delivery during start transients...

Trying to run central A/C off of solar is just plain nuts. If A/C is that important, get a generator for those loads. It's cheaper and quite simple to setup. Critical Loads should be just that - Critical. Granted, if you live in Death Valley or the Sahara - maybe A/C is critical - but a battery-based system is not a good way to go about that.

[jflorey2]

Thanks for the quick reply. If my inverters (Radian 8048 and 4048 probably) are large enough why can't I power both panels with my PV when the grid is down?

You can. But you need enough storage to make that practical. If you are going to run central A/C, for example, you are going to need an enormous battery - both for energy storage and for power delivery during start transients. By using a smaller battery you still get backup at a lower cost/weight/size. (Note that the 8048 requires at least 350 amp-hours of battery at 48 volts, which means 17kwhr of storage anyway - which is a pretty large battery.)