grounding in PS2DC

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rctcfamily
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grounding in PS2DC

Post by rctcfamily »

I've just finished installing a single FX2012E with PS2DC panel and home made AC panel to a wood backboard. Before I turn it on I want to make sure it is properly grounded. I'm in an Asian country where code is not an issue, just equipment and personal safety. The system will be used as a backup for computer servers and workstations. I'm a computer tech, not an electrician and there are not any qualified electricians available.

There is a 16mm2 cable from the ground bus in the AC panel back to ground in the main service panel for the building. The FX's AC out chassis ground is connected to this ground bus. Is it necessary or advisable to bond neutral to ground in this AC panel? I hope to eventually add a grid connection for possible bypass and/or possible charging through the FX.

On the DC side the battery bank positive is connected to the 250A breaker and also a 175A breaker for separate charging units. The battery bank negative is connected to the negative shunt. Positive cable from the FX is connected to the load side of the 250A breaker and the negative cable is connected to the negative shunt. Charger unit positive is connected to the load side of the 175A breaker and the negative to the negative/ground bus in the PS2DC. I have not connected anything to the external grounding lug on the FX. Do I need to connect the FX grounding lug to negative/ground or AC ground bus or nothing? Do I need to bond the negative/ground bus in the PS2DC to ground?

Thank you for your help
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mvrck
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Post by mvrck »

I would connect the FX grounding lug (or the interanl ground lug) to AC ground bus, that would normally be part of the PS2 wiring included in the PS2AC. See the PS2 wiring diagrams on this site for reference. (http://www.outbackpower.com/pdfs_wiring ... genbal.pdf)

As for the Neutral to Gound bonding, if the Inverter has ACIN from that sub panel, then you would not tie neutral to ground at the PS2DC or the inverter, since that should happen back at the main panel. There should only be one location where the bonding happens.
rctcfamily
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Post by rctcfamily »

Thanks for the helpful info. As you suggested our FX AC out chassis ground is connected to the ground bus in the AC panel. The inverter will not usually have AC in unless our separate charging unit fails.

Referencing the diagram you suggested, it shows a neutral to earth ground bond in the PS2DC. In our unit the neg/gnd bus is bolted directly to the metal case but we do not currently have the case grounded. It is mounted on a wood panel.

I believe we are fine on the AC side, but my concern is mostly that the DC side is properly grounded before I go turning the system on. If the neg/gnd bus does not need to be further connected to an earth ground then we are fine there too.

As I mentioned, I did not connect anything to the inverter's external grounding lug. The documentation said that this ground lug is common with the internal ground and it is not necessary to connect the external one to ground if the internal one has been connected to ground. However, the diagram you suggested shows both ground lugs connected to ground - the internal one to the AC panel and the external one to the DC panel. This is somewhat confusing. Can this be clarified for me?

Thank you.
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Post by Kent Osterberg »

The PS2DC case needs to be grounded for safety. Usually there is a bonding screw from the negative DC bus to the PS2DC that does that. A ground wire from the negative DC bus to the FX chassis or the AC ground bus will make sure that all the grounds are at the same potential.

One thing to watch out for is a possible ground connection at your separate charging unit. If there is a ground connection made there, you'll need to reconsider the DC grounding.
rctcfamily
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Post by rctcfamily »

Ok, so if I have a ground from the FX's AC out ground chassis to the AC ground bus, and then add a connection from the PS2DC negative/ground bus to the external ground lug on the FX everything should be properly grounded?

I'm using three Iota chargers in parallel and have connected the chassis ground of each to the ground bus in the AC panel. Does this interfere or change anything?

I appreciate all the help.
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mvrck
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560W (Kaneka 60W) on 1 Classic 150
1080W (Day4) on 1 Tristar MPPT 60
GVFX3524 + PS2AC/DC, MATE, HUB4, Charles 24V 30A Charger, Generac S4001, Trimetric 2020, WattPlot, greenMonitor Lite, 400AH Bank (4 ea Rolls Surrette S530 Batteries), and a lot of other solar refuse...
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Post by mvrck »

Since the ground is coming from the main ground buss to the FX and to the Iotas, that should be ok. Basically anything metal would be connected together to the ground buss. The PS2MP or PS4MP was made to make this a little easier. I wonder if those Iotas would have fit on one of those mounting plates??
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