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Generator specs?

Posted: Tue Oct 15, 2019 5:22 pm
by mhspohr
I don't think I'll be installing a generator but if I did, what are the specs for the generator?
- Generator voltage? 120/240?
- Generator frequency? 50/60 hz?
- Generator power? min/max?
- Does the Skybox just pass the raw generator input through to the loads or does it invert it to charge batteries and run the loads at regulated voltage and frequency?

Re: Generator specs?

Posted: Sat Nov 02, 2019 6:45 am
by mhspohr
Got my Skybox installed. Found a sticker on the side which states generator input 170-285 volts 48 amp max.
Doesn't seem to require a neutral wire.
I think I'll set up the generator input as a backup at least until AC coupling is available.

Re: Generator specs?

Posted: Sat Nov 02, 2019 7:01 am
by Mike Curran
Doesn't seem to require a neutral wire
The Skybox wiring diagram shows both a neutral and a ground connection to the generator. I strongly recommend you connect them.

Re: Generator specs?

Posted: Sat Nov 02, 2019 7:44 am
by mhspohr
There is a neutral bus which I could connect to a generator neutral wire. However, the generator input to the Skybox doesn't use a neutral wire. Unlike the Grid and Load connectors which both connect the neutral to the upper unit, the Generator input connects the center neutral connector to ground.
Also, given the large voltage input range, I'm thinking that the generator input is not fed directly to the loads in its raw state but goes through voltage regulation/transformation of some kind before feeding into the output.
Would be useful to have some clarification on this from Outback.

Re: Generator specs?

Posted: Sat Nov 02, 2019 8:07 am
by Mike Curran
Here's a screenshot of the Skybox W/D:
Screenshot_20191102-105916.jpg
It doesn't show a neutral connection between the Skybox and the BOS, nor does it show a ground to neutral connection anywhere. In fact, the commissioning instructions specifically call for checking continuity between the ground and neutral busses since this connection should be made at your main service panel, not inside the Skybox equipment.
Screenshot_20191102-110621.jpg
Edit: The commissioning instructions refer to continuity between "6" and "10". These are the neutral and ground busses within the BOS.

Re: Generator specs?

Posted: Sat Nov 02, 2019 8:23 am
by mhspohr
Yes, I am clear that there is a connection between the Neutral and Ground buses at the service entrance (per NEC) and that is how my system is wired.
However, the issue I am trying to sort out is whether or not the Neutral wire from the generator is used/necessary. The generator connection between the BOS and the upper unit does not pass the neutral wire, just a ground wire. That is why I think the neutral wire from the generator is not used. (This would be similar to the newer Enphase inverters which do not have a neutral wire, just L1, L2 and ground.)

Re: Generator specs?

Posted: Sat Nov 02, 2019 8:46 am
by Mike Curran
You're right that there's no neutral into the Skybox proper, but if you have 110 volt AC loads in your house then I believe you'll need the generator neutral connection to run them off the generator. The generator neutral will connect to your loads neutral through the BOS neutral bus. Without it, when running your 110V loads from the generator (through the BOS) you could very well be feeding them 240 volts instead of 120!

Trust me, I once disconnected the neutral while doing some rewiring on my system while in "backup" operating mode, thinking the inverters would do their normal split phase 110V output. I ended up frying a couple of computer surge suppressors, a computer power supply, and a microwave oven :oops: I was lucky I didn't have more stuff on my backed up load panel operating at the time.

Re: Generator specs?

Posted: Sat Nov 02, 2019 9:04 am
by mhspohr
Ouch!
That's a bad experience.
That is why I would like some clarification from Outback on the generator input. It doesn't appear to me that the generator input uses the neutral wire and I infer that it must process the generator input somehow (such as running it through a separate inverter with a proper split phase voltage regulated output).
Again, this is just speculation and your experience running in backup mode (I assume from battery) without a neutral wire is a cautionary tale.

Re: Generator specs?

Posted: Sun Nov 03, 2019 10:09 am
by raysun
The Skybox Quick Start Guide clearly shows generator wiring using 4 leads: L1, L2, Neutral, and Ground.
Screenshot_20191103-080652_Adobe Acrobat.jpg

Re: Generator specs?

Posted: Sun Nov 03, 2019 10:20 am
by mhspohr
The generator neutral wire is connected to the neutral bus with the grid and load circuits and does not go up to the inverter.
I took the top cover off yesterday and attempted to trace the generator path. It's very busy up there but it looks to me that the generator input L1-L2 goes to the inverter where it is combined with PV and battery input ending up as split phase output.
I'll have to test the generator input without a neutral wire.

Re: Generator specs?

Posted: Sun Nov 03, 2019 11:15 am
by raysun
Good luck with pulling the neutral from a split-phase circuit.

Re: Generator specs?

Posted: Fri Nov 08, 2019 12:00 pm
by mhspohr
I've been digging more into the documentation. In particular the Programming Manual has a lot more information on the generator.
I've been assuming that you could run the generator, battery and solar all at the same time to meet the load. In order to do this you would have to run the generator input through the inverter. However, it looks like you can't run all of them together.
Here's an interesting bit of information:
"While PV power charges the batteries (see page 20), the generator cannot be used
to charge, but can be used to run loads. The generator can charge batteries when the
PV input is inactive."

So, when the grid is disconnected and the generator is running, the output of the generator goes to the Loads without any conversion so you get the voltage and frequency of the generator direct. The generator can run loads and charge the battery (if PV is not active) but cannot be combined with PV.
So... it does look like you'll need a neutral wire connection from the generator since the generator is connected directly to the loads.

Re: Generator specs?

Posted: Mon Jan 13, 2020 1:47 pm
by mhspohr
I have two potential sources of generator input. One is an actual small 120v generator (2500 W) and the other is my SMA inverter which during a power failure can provide up to 2000 W of 120v AC.
I purchased a 110/220 volt transformer. This is a single wire wrapped around a circular core with a center tap. You can put in 110v from center to one end or 220v across the entire coil. You then get 220v with a center "neutral" wire which I feed into the Skybox generator input.

Re: Generator specs?

Posted: Mon Jan 13, 2020 2:21 pm
by Mike Curran
I may be overstating the obvious, but make sure to set the Skybox Generator Max Input Current Limit according to your source's capability.

Re: Generator specs?

Posted: Mon Jan 13, 2020 2:41 pm
by mhspohr
Mike Curran wrote:
Mon Jan 13, 2020 2:21 pm
I may be overstating the obvious, but make sure to set the Skybox Generator Max Input Current Limit according to your source's capability.
Yes, thanks, I've got that set.