Skybox: battery breaker specs and grounding

True Hybrid Energy System
Post Reply
DrewS
Forum Junior Member
Posts: 3
Joined: Mon Dec 09, 2019 9:09 pm
My RE system: System at issue: Stacked Skyboxes with SimpliPhi batteries and a hybrid DC and Emphase IQ7 panels

Skybox: battery breaker specs and grounding

Post by DrewS » Mon Dec 09, 2019 9:25 pm

First, Skybox specs for connecting a battery bank calls for overcurrent protection using a 175A 48V DC, 10 kAIC breaker. The AIC value seems to pose a problem. We find disconnects like Mechanical Products, but the IC is 1.5 kA, which is typical of several other DC breakers. I have spoken to an engineer at Mechanical Products; he said that with 48V DC, the lower AIC value was fully acceptable. Please advise. If a 10 kAIC rating is in fact essential for a DC breaker, does anyone have specifics on a suitable breaker and a source.

Second, we understand that we need to bond the negative battery terminal in the BOS to ground for each Skybox. The ground buss in the BOS is already grounded to the main meter panel. Does it need to be more complicated than connecting the negative battery terminal to the ground buss in the BOS.

Many thanks,

User avatar
IanMcCluskey
OutBack Product Management
Posts: 154
Joined: Tue Aug 28, 2018 1:16 pm

Re: Skybox: battery breaker specs and grounding

Post by IanMcCluskey » Tue Dec 10, 2019 7:58 am

Thank you for posting, I have moved your topic from the Webinar forum to the SkyBox Inverter forum.
Ian McCluskey
Product Manager


Alpha Technologies Inc. / OutBack Power Technologies
3767 Alpha Way Bellingham WA 98226 USA
http://www.alpha.com

Mike Curran
Forum Emperor
Posts: 1788
Joined: Sat Aug 28, 2004 6:28 pm
My RE system: Outback - Garage roof:
- 8 (2x4) Evergreen 180's into one FM80 (2007/2020 - replaced MX60)
- 6 (2×3) ALEO S79-300's into one FM80 (2017)
- 2 grid-tied GVFX3524's classic stacked for 120/240VAC (2007)
- 12 Surrette/Rolls 2V x 1766Ah (2007)
- Hub10.3, Mate3s, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

Westinghouse Solar - Barn roof: (2012)
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied

Outback Skybox - Barn roof: (2019)
- 14 Talesun 275W in series (DC array input to SB charger)
- 3 SimpliPhi 3.8 batteries, 48V, 225Ah total
- AC coupled input (manual switch during grid outage only) from 14 Talesun 275W,
Enphase M215 microinverters, normally direct grid tied

All self-designed and self-installed
Location: Chagrin Falls, Ohio

Re: Skybox: battery breaker specs and grounding

Post by Mike Curran » Tue Dec 10, 2019 8:38 am

As far as interrupting capability, I would think that the breaker that's supplied with the Skybox BOS enclosure should meet whatever is required.
Second, we understand that we need to bond the negative battery terminal in the BOS to ground for each Skybox
Looking at the Skybox quick start guide http://outbackpower.com/downloads/docum ... ox_qsg.pdf for wiring I don't see where it says to connect the battery negative to ground. In fact, I would think that doing this would defeat any ground fault protection that you might have. Where did this idea come from?
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

DrewS
Forum Junior Member
Posts: 3
Joined: Mon Dec 09, 2019 9:09 pm
My RE system: System at issue: Stacked Skyboxes with SimpliPhi batteries and a hybrid DC and Emphase IQ7 panels

Re: Skybox: battery breaker specs and grounding

Post by DrewS » Wed Dec 11, 2019 5:16 pm

Mike,

Both came from the last page of the Quickstart Guide.

"THe battery connection is not bonded to ground. Make sure to establish a negative-ground bond for each battery system."

"Overcurrent protection: The battery disconnect device in the BOS does not provide overcurrent protection. THe installer must provide protection for the battery circuit according to the following parameters:
* Max 175 Adc
* Minimum 10 kA AIC"

Mike Curran
Forum Emperor
Posts: 1788
Joined: Sat Aug 28, 2004 6:28 pm
My RE system: Outback - Garage roof:
- 8 (2x4) Evergreen 180's into one FM80 (2007/2020 - replaced MX60)
- 6 (2×3) ALEO S79-300's into one FM80 (2017)
- 2 grid-tied GVFX3524's classic stacked for 120/240VAC (2007)
- 12 Surrette/Rolls 2V x 1766Ah (2007)
- Hub10.3, Mate3s, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

Westinghouse Solar - Barn roof: (2012)
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied

Outback Skybox - Barn roof: (2019)
- 14 Talesun 275W in series (DC array input to SB charger)
- 3 SimpliPhi 3.8 batteries, 48V, 225Ah total
- AC coupled input (manual switch during grid outage only) from 14 Talesun 275W,
Enphase M215 microinverters, normally direct grid tied

All self-designed and self-installed
Location: Chagrin Falls, Ohio

Re: Skybox: battery breaker specs and grounding

Post by Mike Curran » Thu Dec 12, 2019 9:51 am

Thanks, Drew. Those are good questions then.

With these requirements, I'm surprised that neither the BOS nor the qsg (either) has a neutral to negative ground connection or indicates in the wiring instructions to make this connection, and where.

Also, it's funny that the W/D in the qsg doesn't at least show a separate, external DC breaker between the Skybox BOS disconnect switch (which I mistook for a breaker) and the battery. :-k

Edit : I just ordered an Outback DC breaker for this application, their part # PNL-175-DC
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

Mike Curran
Forum Emperor
Posts: 1788
Joined: Sat Aug 28, 2004 6:28 pm
My RE system: Outback - Garage roof:
- 8 (2x4) Evergreen 180's into one FM80 (2007/2020 - replaced MX60)
- 6 (2×3) ALEO S79-300's into one FM80 (2017)
- 2 grid-tied GVFX3524's classic stacked for 120/240VAC (2007)
- 12 Surrette/Rolls 2V x 1766Ah (2007)
- Hub10.3, Mate3s, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

Westinghouse Solar - Barn roof: (2012)
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied

Outback Skybox - Barn roof: (2019)
- 14 Talesun 275W in series (DC array input to SB charger)
- 3 SimpliPhi 3.8 batteries, 48V, 225Ah total
- AC coupled input (manual switch during grid outage only) from 14 Talesun 275W,
Enphase M215 microinverters, normally direct grid tied

All self-designed and self-installed
Location: Chagrin Falls, Ohio

Re: Skybox: battery breaker specs and grounding

Post by Mike Curran » Thu Dec 12, 2019 12:21 pm

Sure looks like a 175A DC breaker inside the BOS. Why else would it have "175" printed on it?
Skybox disconnect switch v1.jpg
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

Mike Curran
Forum Emperor
Posts: 1788
Joined: Sat Aug 28, 2004 6:28 pm
My RE system: Outback - Garage roof:
- 8 (2x4) Evergreen 180's into one FM80 (2007/2020 - replaced MX60)
- 6 (2×3) ALEO S79-300's into one FM80 (2017)
- 2 grid-tied GVFX3524's classic stacked for 120/240VAC (2007)
- 12 Surrette/Rolls 2V x 1766Ah (2007)
- Hub10.3, Mate3s, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

Westinghouse Solar - Barn roof: (2012)
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied

Outback Skybox - Barn roof: (2019)
- 14 Talesun 275W in series (DC array input to SB charger)
- 3 SimpliPhi 3.8 batteries, 48V, 225Ah total
- AC coupled input (manual switch during grid outage only) from 14 Talesun 275W,
Enphase M215 microinverters, normally direct grid tied

All self-designed and self-installed
Location: Chagrin Falls, Ohio

Re: Skybox: battery breaker specs and grounding

Post by Mike Curran » Thu Dec 26, 2019 6:45 pm

@DrewS: I added an Outback 175A battery breaker to my system today.
Barn battery brkr (2).jpg
Also, the short green cable (either #6 or #8) supplied with Skybox was designed to make the battery negative to ground bus connection.
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

User avatar
BoMagluyan
OutBack Product Management
Posts: 31
Joined: Mon Mar 19, 2018 12:29 pm
My RE system: SkyBox
12x EnergyCell PLR batteries in an IBR3
no PV

Re: Skybox: battery breaker specs and grounding

Post by BoMagluyan » Wed Jan 08, 2020 11:13 am

Mike Curran wrote:
Thu Dec 26, 2019 6:45 pm
@DrewS: I added an Outback 175A battery breaker to my system today.Barn battery brkr (2).jpgAlso, the short green cable (either #6 or #8) supplied with Skybox was designed to make the battery negative to ground bus connection.
@DrewS, Looks like that is a good addition for you. We're sure any AHJ would agree your install complies with the NEC.
We sell Integrated Battery Racks (IBR2 and IBR3) which include this breaker. This breaker is UL-listed, compliant to UL498, and provides bi-directional over-current protection.
Our IBR2 and IBR3 are UL9540 compliant, when paired with SimpliPhi batteries. We're working on the same certification with two of our lead acid batteries.
We have seen many installers and AHJ's agree that this breaker is not required.
Because SkyBox is fully compliant with UL1741 and the NEC, we are able and required to state that the 175A-rated switch inside the SkyBox BOS is neither an external disconnecting means nor a breaker in this application. This switch is UL listed, but not to UL498. It is not bi-directional. It protects the batteries. I'll close my paragraph about this 175A device with a delicately worded sentence: there are many components inside the SkyBox that ensure the battery never sees 175A.

You're correct, almost entirely, about the short green cable. It's a #4. It's 10.5" long, and comes in the sundries kit. I had to ask our compliance engineer to do a little research on this cable. It is best referred to as a “Direct-Current System Bonding Jumper” as that is what NEC calls it . We wouldn't want it to be confused with the AC Neutral connection grounding. The DC System Bonding Jumper goes between the equipment grounding conductor (ground wire system for dead metal) and the grounded circuit conductor (negative in our common applications). In some cases, the NEC requires this for DC systems with battery operating voltage between 60 and 300 volts [250.162 (A)]. So we included the wire in case it was needed. Our thinking is: if the AHJ requires you to install the wire, you have it. But you don’t need us to tell you if it is allowed or not allowed under the NEC. In the lab, for some of our testing, we put this cable on the top of the two battery cables on the negative connection of the SkyBox BOS. We did not find anything that would not allow this.
Attachments
cable IMG_20191212_120622 resized.jpg
Bo Magluyan
OutBack Product Management

OutBack Power Technologies, Inc.
An Enersys Company
1628 W Williams Drive, Phoenix AZ 85027 USA
www.outbackpower.com

Post Reply