Need some advice and resources that would be helpful in designing in Schneider's BCS (back up control switch) with my 48v offgrid solar build utilizing the XW Pro and eliminating the need of the PDP (power distribution panel). What I am trying to accomplish is how the AC power flows for the inverters, no longer requiring circuit breakers both "upstream" & "downstream" and no longer burdening the small relays in each inverter to transfer the loads. And how AC moves into and out of each inverter through only one AC breaker/one set of wires. I have looked at Schneider's install manual and it is pretty vague. Hoping someone has done something like this or has some knowledge on it. Thank you.
Schneider BCS Help
- Thread starter wyosolar
- Start date
400bird
Solar Wizard
Maybe it's simpler than you expect? Or more complicated than I do.
Current can flow either direction on the wires to/from the XW.
All the XWs produce power/charge from AC1.
The main inverter uses AC2 to sense voltage. I'm not quite sure why this is required as I'm pretty sure the BCS includes a WattNode that measures voltage and current.
I'm pretty sure you still need breakers on the XW AC inputs. The PDPs are mostly just nice metal boxes to hold breakers (AC and DC)
Current can flow either direction on the wires to/from the XW.
All the XWs produce power/charge from AC1.
The main inverter uses AC2 to sense voltage. I'm not quite sure why this is required as I'm pretty sure the BCS includes a WattNode that measures voltage and current.
I'm pretty sure you still need breakers on the XW AC inputs. The PDPs are mostly just nice metal boxes to hold breakers (AC and DC)
400bird
Solar Wizard
Functionally, nope. But the PDPs include breakers (depending on how many inverters, you may need to purchase more) and the bus bar/bypass that is used when the XW's internal transfer relays.
The BCS is AC side only. It's basically a remote transfer switch and power meter.
There are battery inputs on the bottom of the XW and breakers for both the battery and MPPT are normally mounted in the PDP.
Gotcha that makes sense, a Huge help! If I were to use the PDP and the BCS, I could send all DC power to the breakers in the PDP and then send all AC power to the BCS and not use the AC breakers in the PDP? Am I thinking about that correctly? And by doing so, I am protecting and controlling the DC side of things in the PDP and the AC in the BCS? If this is the case, would this also help protect the XWs internal relays from doing all of the work and shift the work to the BCS? Lastly, how would a remote start Generator tie into the system, via the BCS or the PDP?
400bird
Solar Wizard
How many XWs?
Which PDP?
Is grid present?
Are there AC breakers for individual inverters in the BCS? (I'm pretty sure the answer is no, based on the screenshot I took from the Schneider BCS manual)
Which PDP?
Is grid present?
Are there AC breakers for individual inverters in the BCS? (I'm pretty sure the answer is no, based on the screenshot I took from the Schneider BCS manual)
400bird
Solar Wizard
If you don't have the grid present to connect to, I don't see any purpose to the BCS. It's a transfer switch (for when the grid goes down) and energy meter (to facilitate zero export and other grid strategies)
I'd run the generator into the AC breakers on the full size PDP and skip the BCS entirely.
I'd run the generator into the AC breakers on the full size PDP and skip the BCS entirely.
I was thinking similar but was trying to see if I could use the BCS so if I wanted to add another XW in the future or tie in additional AC sources, the BCS would help reduce the headache of wiring it in. I also wanted to use the BCS so the XW's small relays are no longer being burden while transferring the loads. But maybe I am thinking about this wrong?
Gttnsun
Amps +-
Since the BCS is designed to work on AC1, you will have a hard time getting most generators to qualify power.
Ac2 is designed for generator power.
I heard Schneider is working on a firmware update to address this
Ac2 is designed for generator power.
I heard Schneider is working on a firmware update to address this
Gttnsun
Amps +-
Schneider has a recorded webinar on the BCS you might be able to get the information you need by watching it.
400bird
Solar Wizard
Good point, I hadn't thought about that.
400bird
Solar Wizard
The relays are on the AC inputs, the BCS (and all your loads/generator) is connected to AC input 1.
Using the PDP, your loads would be connected to the AC output (no relays) with only the generator connected to the input/AC2 where there are relays.
Schneider offers a kit with the breakers and bus bars needed to add a 3rd XW to the full size PDP. I'm not sure the BCS would be easier, but I haven't seen pictures inside one.
How large is your generator? Is it going to max out the transfer relays? Shouldn't matter as the XW will adjust current to respect the relays' limits.
I am looking at least a 13kw diesel generator. I was able to find this brief schematic of how the BCS would work in an off grid/generator setup. I found this on the webinar that Mtnsun sent. They have a firmware update that allows this situation. I am still trying to figure out in the diagram if they are using a PDP and how it all ties together. Seems like a pretty new idea.
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Gttnsun
Amps +-
The way understand it is, each XW has a 60 amp relay, there is no guarantee that all the relays will close at the same time, so all the power could be momentarily passed through 1 relay before the others close. The more XW's the bigger the chance of it happening. This is why the BCS is recommended for multiple XW installation.
A 13 kw should not exceed 60 amps so overloading the relays is probably not going to happen. But I understand you want options in the future so a BCS could be a good choice.
That is correct. So according to their diagram do you think they are using a PDP with the BCS? PDP for all DC components and the BCS for all AC components? If so, which AC components from the XW (AC1, AC2, L1, L2, etc) are going to/from the BCS, Generator, and main panel? Thanks!
That is correct. So according to their diagram do you think they are using a PDP with the BCS? PDP for all DC components and the BCS for all AC components? If so, which AC components from the XW (AC1, AC2, L1, L2, etc) are going to/from the BCS, Generator, and main panel? Thanks!
Gttnsun
Amps +-
In the webinar it shows a few different configurations, one shows using 2 PDP's and 4 XWs. I think the max number of XW per PDP is 3, so if you go to four XW it gets more complicated.
The screenshot you are showing looks like no PDP and a battery combiner with DC breakers installed in the combiner box, and it must have the DC busbars inside,
But I am not sure. It also shows 4 XW Pros which exceeds a single PDP.
If you stick to 3 XW pro you might be able to use a single PDP and a BCS together. The PDP is UL listed so it makes permitting easier, if that is important to you.
I have dual XW Pros with a PDP, but no BCS so my knowledge is limited.
The screenshot you are showing looks like no PDP and a battery combiner with DC breakers installed in the combiner box, and it must have the DC busbars inside,
But I am not sure. It also shows 4 XW Pros which exceeds a single PDP.
If you stick to 3 XW pro you might be able to use a single PDP and a BCS together. The PDP is UL listed so it makes permitting easier, if that is important to you.
I have dual XW Pros with a PDP, but no BCS so my knowledge is limited.
I noticed that too. I did some further reading and reasoning and this is where I am at:
The struggle is finding specifics/clarity on where the AC1, AC2, AC INV OUT, MPPTs, and DC lines tie into the BCS and whether or not a PDP is useful or required. My tentative plan is to have both XW's AC1 lines to land inside of my main 200A load panel with each tie-ing into a 60A breaker. The AC1s would supply power from the PV/batteries to the Main 200A panel and then to the home loads. When my battery bank is low and I don't have enough solar to keep up, I would have my generator tied into the main AC feed on the BCS and when the ATS senses (via AC2) the need to switch power, the generator feed would then flow down into the main 200A panel and supply the power for the home loads and also back feed the AC1s to the 2-XWs and then onto charge the batteries. The AC2 line from the main XW would be used as the sense lines between the inverters and the BCS. Once the batteries are fully charged, the ATS in the BCS will switch and cutoff power from the generator and the AC1 lines would resume as power feed to the main 200a panel and home loads. AC INV OUT would no longer be used. AC1 would be used both directions supplying power to the panel and recieving power from the panel via the BCS/Generator. I hope this makes sense and that I have thought about this correctly as the wiring manuals are pretty vague on this. Should I be using a PDP for my AC1 breakers from the XWs instead of 2-60A breakers in the main 200a panel for the AC1s? Should I be using a PDP for the DC breakers coming from the MPPTs and the batteries? Or can I get rid of the PDP and just use a battery/MPPT combiner with my own breaker setup? Please let me know if I am missing anything. Any help would be greatly appreciated.
