FP2 VFXR3648A Support mode questions

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skhurst
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FP2 VFXR3648A Support mode questions

Post by skhurst » Mon Jul 01, 2019 12:15 pm

Hi All,

Looking to install a FP2 VFXR3648A, hopefully with the input mode in "Support" and the inverters stacked. All loads are 120V on a single bus, input is 120/240. Questions I have are:

1. FP2 VFXR3648A spec sheet indicates it doesn't include the transformer, so I need to buy this separately, correct?

2. Would it be better to stack in series and use the step down to 120 after the inverters, or stack in parallel and step down before the inverters?

3. What is the difference between the PSX-240 and the FW-X240? Is it just the enclosure / fan / breakers?

4. The spec sheet for the psx-240 says 6kva, but also shows a 25A breaker on both 120 legs. Seems this would only allow 3kva on the 120V side in either step up or step down configurations? Do I need two transformers in parallel?

Thanks in advance!

Steve

Mike Curran
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Posts: 1111
Joined: Sat Aug 28, 2004 6:28 pm
My RE system: Outback:
- 8 (2x4) Evergreen 180's into one MX60 (2007)
- 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: (2012)
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied.

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

Re: FP2 VFXR3648A Support mode questions

Post by Mike Curran » Tue Jul 02, 2019 8:32 am

Hi Steve - I'm not sure I understand your setup.
All loads are 120V on a single bus, input is 120/240.
If there's just one 120V load bus, how is it the input is 120/240V?

If the input is truly split phase 240V (2 - 120V legs, 180┬░ out of phase for 240V across them), then I don't see why you couldn't just use the FP2's stacked in a classic master/slave configuration and not need a transformer. Each inverter will supply 120V but you'd get 240V measured across their 2 outputs. And you only need one FP2 unit, which includes 2 inverters, if I understand correctly.

Also, the 240V output across the 2 inverters is 6kva, but you're right, each inverter's 120V output would be limited to 3kva.

What am I missing?
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

skhurst
Forum Junior Member
Posts: 2
Joined: Mon Jul 01, 2019 11:12 am

Re: FP2 VFXR3648A Support mode questions

Post by skhurst » Tue Jul 02, 2019 9:49 am

Mike Curran wrote:Hi Steve - I'm not sure I understand your setup.
All loads are 120V on a single bus, input is 120/240.
If there's just one 120V load bus, how is it the input is 120/240V?

If the input is truly split phase 240V (2 - 120V legs, 180┬░ out of phase for 240V across them), then I don't see why you couldn't just use the FP2's stacked in a classic master/slave configuration and not need a transformer

What am I missing?
The cabin I purchased is only wired for 120 V, all on a single bus. It is not practical to change the breaker panel and the wiring that feeds it to 120/240. The power I have available to use is 5KW 120/240 split phase. My loads will typically be under 5KW, but will occasionally wander above that for short periods

If I understand the VFXR manual correctly, to do a parallel master/slave stacking, both inverters need to be on the same 120V leg. This would only let me use 2.5KW of my available power. So I either need to step down before the inverters or after the inverters.

Mike Curran
Forum Emperor
Posts: 1111
Joined: Sat Aug 28, 2004 6:28 pm
My RE system: Outback:
- 8 (2x4) Evergreen 180's into one MX60 (2007)
- 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: (2012)
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied.

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

Re: FP2 VFXR3648A Support mode questions

Post by Mike Curran » Tue Jul 02, 2019 12:58 pm

From looking at the manual, seems like parallel stacking of the 2 inverters you have would fit your needs:
Screenshot_20190702-155453.jpg
Screenshot_20190702-155427.jpg
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

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