Bypass circuits

[ASword]

In planning an inverter-based system with a generator and AC coupled PV, it’s pretty clear that having a quick and easy (ie spouse compatible) means to disable the fancy stuff and fall back on the existing grid/ATS/generator system will be essential. Ideally one big “pull this” lever.

I think this means switch primary panel to inverter line to primary to ATS, inverter to secondary panel line to ATS to secondary, and generator to inverter line to generator to ATS. So that 3 big 240v circuits that need to be cut over, preferably in an interlocked fashion. Plus the generator control lines, although that might be done just by hitting the rapid shutdown on the inverter. There are undoubtedly details around things like shared grounds/neutrals that need to be taken into account.

I haven’t yet found any switch that can do this. Any pointers?

 

[SunDave]

Hi, I have a Sol-Ark 15k, which has a generator input. I run the generator inlet to that. For the spouse compatible bypass, you could do similar to what I have as well. The outdoor meter goes straight to a "farm panel", which is a 200 amp panel that has 200 amp pass-through lugs. In that panel there is a 100 amp breaker, that goes to my main panel. On my main panel there is a manual interlock so that I can use that 100 amps straight from the grid if the inverter fails somehow.

Meter to farm panel. There it "forks" to allow straight to main panel, or to inverter. Does that make sense? Not perfect, but satisfied my requirements. The only downfall is that I would have to shut off power to everything for a few seconds to pull the grid wires from the inverter when it comes time to replace it, but you are talking seconds.

It is definitely easy to switch to straight grid. Just two breakers. The generator is taken care of by the inverter itself.

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The big difference is that I use DC coupled solar. I could run AC coupled solar into the inverter, but then I lose using that input for the generator and I have to re-think the whole setup. Making sure the AC coupled solar and generator don't interact adversely will be key in your setup. Sounds like you have multiple panels, so that could help if the ATS is put in the right spot. Some inverters remove the need for an ATS.

What equipment are you planning on using?

 

[ASword]

I have an existing standby generator, ATS, and AC coupled panels. The AC coupling feeds the main panel, the generator feeds the secondary panel when the grid goes down. My current thinking is to install an inverter (probably Midnite AIO) so that the main panel, generator and AC coupling feed the inverter when it is not bypassed, and it feeds the secondary panel. In bypass mode, however, we would want to revert to the secondary panel being fed from the ATS which is fed either from main panel or generator. Don't care about losing AC coupling when the grid is down, but need the generator.

 

[Brucey]

For simple inverter bypass of 60A something like this would probably work:

MidNite Solar MNTRANSFER Dual Transfer Switch 240VAC

Shop now for MidNite Solar MNTRANSFER Dual Transfer Switch 240VAC.

www.stellavolta.com

 

[rogerheflin]

Or something like this if you can survive with 100amp

https://www.reliancecontrols.com/products/reliance-controls-tca-series-manual-transfer-panel-metal-indoor-tca1010d

I have my critical load panels connected to a 60a one. One input is the inverter and the other is a 60a breaker on my main panel.

 

[LakeHouse]

it’s pretty clear that having a quick and easy (ie spouse compatible) means to disable the fancy stuff and fall back on the existing grid/ATS/generator system

You'll get lots of suggestions on how to do what you're trying to do, and I'll stay out of that.
But I would suggest that you (and everyone else) consider something else: write an Operator's Manual for your system.
I've done this for my off-grid cabin mainly for two reasons: Sometimes there are people there when I'm not there, and they need to be able to operate the system, AND, someday I'll die (hopefully not soon) and my family will continue to use the property after that.
With this is mind I have of course tried to design everything to operate mostly without intervention, but there are times when it's unavoidable, such as commissioning in the spring and decommissioning in the fall (the cabin is inaccessible in the winter).
I have sections on commissioning, decommissioning, troubleshooting, etc.
The additional upside is that writing the manual also prompted me to adequately label everything in the system... I didn't want the procedure to say things like 'turn on the big breaker on the left by the inverter', so I named and labeled that breaker.

 

[Lavarock7]

Simple system here (6000XP) with a very old utility Service Panel (200 amp split phase). Using solar and batteries for power as default and using grid in battery low conditions, etc.

Because breaker box will be updated/replaced at some point, I just use a 10 circuit transfer switch. No expensive rewiring of the breaker box and all someone would have to do is throw 10 switches from solar to grid and then if desired, hit the big red button to shut down all solar (and it turns the battery breakers off too on the EG4-LL's). In fact, since the 6000XP is one one side of a wall and the service panel is on the other side of the wall, I am going to parallel the big red buttons (emergency shut down) so either button will shut'er down!

 

[ASword]

write an Operator's Manual for your system.

This is beyond excellent advice. I still have a todo list for this, and really ought to get serious about it. Certainly for things like primary power it is essential from day one. On top of that, for critical systems like primary power there needs to be big obvious simple instructions for things like bypass and emergency shutdown.

 

[SunDave]

That's a lot of branching going on. When you want to use the generator, and grid connections for two different purposes. You may want to make a line drawing and find the simplest solution. It will be tricky to have it both complex, and simple to operate for your spouse.

Parallel systems are another option. If X is down use Y would be the only instructions. Some outlets would still be powered. That's how I run heating. Just 3 separate systems, that don't rely on each other.

 

[ASword]

I’ve got a line diagram. A question that I think I have an answer to is whether all the neutrals should be tied together (i.e. not switched). Another thread here says neutrals should be bonded to ground, and the whole building should have a unified ground. If that’s the case there there are 6 lines to switch, otherwise there are 9. I’ve actually found a changeover switch that’ll handle 6 lines, at 100A 240v.

I don’t see how a fully parallel system is possible in the same house.

 

[fastbike]

I’ve got a line diagram. A question that I think I have an answer to is whether all the neutrals should be tied together (i.e. not switched). Another thread here says neutrals should be bonded to ground, and the whole building should have a unified ground. If that’s the case there there are 6 lines to switch, otherwise there are 9. I’ve actually found a changeover switch that’ll handle 6 lines, at 100A 240v.

I don’t see how a fully parallel system is possible in the same house.

That depends on the grounding system in use. We use MEN, where protective earth (PE) is bonded to the Neutral wire at the main switchboard and at subsequent distribution boards. It would make no sense to be interrupting the Neutral, in fact in a multi phase system you could be providing a pathway for current to flow from one phase to another if the active conductors switch off after the neutral (or conversely switched on before neutral).
Consult a trained electrician.