Can a VFX3648 be mated to a GVFX3648?

Discussion about OutBack Inverters in Off Grid Applications

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jcwells
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My RE system: VFX 3648, Mate 1, Mx- 60

Can a VFX3648 be mated to a GVFX3648?

Post by jcwells » Thu Aug 27, 2020 12:46 pm

Greetings,

I have an off-grid system whose current configuration dates to 2007. The MX60 has performed flawlessly now 7X24 for over 13 years in the -30 degree winters of northern Ontario to the 100 degree summer temps in my solar shed. The VFX3648 has also performed well over the same time with only summer time use. Needless to say, I've been impressed by the quality of these machines.

I now need to expand the system and would prefer to do that by adding another charge controller and another inverter. I would continue with the current equipment and just add another VFX3648 assuming my older equipment can be balanced together with a newer inverter to give me 7200 watts in a 2 phase operation. I have read of some issues with different firmware versions of Mates, Hubs and inverters and was looking for advice on what might work.

My Mate 1 and VFX are of similar 2007 vintage and the firmware has not been upgraded in either device. I do not have a Hub in the current configuration, and I realize I will need to add one to make this work.

The first question is; would a new VFXR3648 and a new Mate and Hub work with the older VFX3648? Would my older Mate work as well?
Secondly, there is a used GVFX3648 and Mate 2 of 2012 vintage for sale locally and I wondered if that might actually be a better option given the closer production dates, (but the models are not an exact match)?

I would prefer not to start from scratch with this expansion so any help would be appreciated.

Thanks,
John

raysun
Forum Emperor
Posts: 2951
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
SimpliPhi 48-3.8 (6 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: Can a VFX3648 be mated to a GVFX3648?

Post by raysun » Thu Aug 27, 2020 2:33 pm

jcwells wrote:
Thu Aug 27, 2020 12:46 pm
Greetings,

I have an off-grid system whose current configuration dates to 2007. The MX60 has performed flawlessly now 7X24 for over 13 years in the -30 degree winters of northern Ontario to the 100 degree summer temps in my solar shed. The VFX3648 has also performed well over the same time with only summer time use. Needless to say, I've been impressed by the quality of these machines.

I now need to expand the system and would prefer to do that by adding another charge controller and another inverter. I would continue with the current equipment and just add another VFX3648 assuming my older equipment can be balanced together with a newer inverter to give me 7200 watts in a 2 phase operation. I have read of some issues with different firmware versions of Mates, Hubs and inverters and was looking for advice on what might work.

My Mate 1 and VFX are of similar 2007 vintage and the firmware has not been upgraded in either device. I do not have a Hub in the current configuration, and I realize I will need to add one to make this work.

The first question is; would a new VFXR3648 and a new Mate and Hub work with the older VFX3648? Would my older Mate work as well?
Secondly, there is a used GVFX3648 and Mate 2 of 2012 vintage for sale locally and I wondered if that might actually be a better option given the closer production dates, (but the models are not an exact match)?

I would prefer not to start from scratch with this expansion so any help would be appreciated.

Thanks,
John
I'm an FX3048t user, so similar vintage inverter. The FX/VFX series have long been discontinued, if course. Their firmware cannot be upgraded in the field, if at all.

In order to stack the inverters, they need to be identical models and firmware levels.

The GVFX especially will not work. In fact, that was the first of the Grid Tied models, and is somewhat fussy even in its designed usage. IIRC, they don't work well, if at all, off-grid.

I, too am looking to upgrade my system, and came to the conclusion it will be more effective to sell my existing inverter/charge controller setup and replace them with new gear. I'm going to put in a Flexpower Two with FXR inverters (VFXR are available as well). New gear with a 5 year standard / 10 year optional warranty. Field upgradeable firmware. Advanced battery charging to support lithium out of the box, as well as other emerging battery technologies, in addition to traditional lead acid.

The new inverters' grid interactive modes don't relate to me, as I'm off-grid, but the Support mode might be useful to combine Inverter output to Generator output, should I ever need to fire up an electric arc-welder. ;)

My existing system (a Flexpower One panel, modified for a 2nd FM80 charge controller) sold to the first person to whom I mentioned its availability. He's happy to wait 90 days until my new kit is installed. The gear retains decent resale value.

Mike Curran
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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: Can a VFX3648 be mated to a GVFX3648?

Post by Mike Curran » Thu Aug 27, 2020 4:40 pm

The GVFX especially will not work. In fact, that was the first of the Grid Tied models, and is somewhat fussy even in its designed usage. IIRC, they don't work well, if at all, off-grid.
Ray, don't know why you're saying that. In my experience with 2 GVFXs, they work fine during a grid outage, and I have no reason to think they would underperform if left off grid. - Mike
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

raysun
Forum Emperor
Posts: 2951
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
SimpliPhi 48-3.8 (6 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: Can a VFX3648 be mated to a GVFX3648?

Post by raysun » Thu Aug 27, 2020 5:40 pm

Mike Curran wrote:
Thu Aug 27, 2020 4:40 pm
The GVFX especially will not work. In fact, that was the first of the Grid Tied models, and is somewhat fussy even in its designed usage. IIRC, they don't work well, if at all, off-grid.
Ray, don't know why you're saying that. In my experience with 2 GVFXs, they work fine during a grid outage, and I have no reason to think they would underperform if left off grid. - Mike
Yeah, I don't know why I'm saying it either. 🙃

jnh
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My RE system: GVFX-3524, FM-80+FM-60, ~4.9kW PV in mixed panels on movable platforms, 415 Ah AGMs @ 24V, 350Ah @ 12V, Hub4, Mate, FNDC, Brultech GEM 32-ch AC datalogger, Midnite E-Panel, homebrew DC-DC crossfeed to 12V system, Honda EU-1000i, Iota DLS-27-25
Location: St. Augustine, FL, US

Re: Can a VFX3648 be mated to a GVFX3648?

Post by jnh » Sat Aug 29, 2020 4:21 pm

The main problem using a GVFX/GTFX off-grid comes when you try to connect a generator to one (another, only relevant for larger systems, is that they have more limited options for stacking). These inverters are quite picky about the quality of any incoming AC power source, because they enforce grid-tie-appropriate constraints on voltage & frequency stability, waveform quality, etc. even when the AC source is set to Generator. (Newer FXR's and Radians have corrected this limitation).

An inverter-type generator, such as a Honda EU-series or Yamaha EF-series will work, as will most large industrial-sized gensets with good governors & AVRs, but small, inexpensive, home-sized generators are likely to be a headache, if you can get one to work at all. With a less-than-grid-quality source, the G*FX will see its power (AC-in LED blinking), but refuse to use it, or only connect for a short time.

One solution is to use a separate, dedicated battery charger of the appropriate output voltage & current capacity, connecting the generator only to this. AC-out loads would then never be powered directly from the generator. Power flow to loads when on generator would be AC -> DC -> AC, with two conversions - less efficient, but on the plus side there would be no switching transients, and any sensitive loads would remain isolated from "dirty" generator power.

One option would be to wire only the VFX you have now to the generator (and configure generator for full power at 120V, rather than 120/240, if it has a selector for this), in essence using the VFX as your dedicated charger, though any AC-out loads behind it would also be powered directly.

Even without stacking the mismatched inverters, both could still share a common DC bus & battery bank, each supporting its own, separate subset of 120V loads. You just wouldn't be able to get 240V out of this configuration since the two outputs wouldn't be phase-locked at 180-degrees apart.. voltage between AC-out-1 and AC-out-2 would gradually drift between 0 and 240... but this wouldn't matter if nothing's connected to both at once. There would then be not need for a Hub if you don't mind manually moving the Mate between devices to configure them.

With this setup, you could still connect a standard three-wire split-phase panel, with the two inverters' Neutral terminals bonded together, AC-Hot-Out 1 (from inverter 1) going to the black conductor and AC-Hot-Out 2 (inverter 2) to the red. It'd be safe so long as you had no 240V breakers installed, and no multi-wire branch circuits (MWBC's, typically kitchen duplex receptacles where the top outlet connects to black, bottom to red or vice-versa, white/neutral common to both... without a true 240V source these can overload the unfused neutral).

Wiring to the output panel may need to be one size larger than usual, say #4 AWG rather than #6, because that common neutral could potentially carry the sum of both inverters' output currents, not just the difference.

Maybe put all the 120V loads you need to keep running 24/7 on one inverter's output (say, odd breaker positions), and less important or more intermittent loads on the other, so that inverter #2 can be shut down when not needed and save you ~20-25W of standby power.

jcwells
Forum Junior Member
Posts: 3
Joined: Thu Aug 27, 2020 11:15 am
My RE system: VFX 3648, Mate 1, Mx- 60

Re: Can a VFX3648 be mated to a GVFX3648?

Post by jcwells » Mon Aug 31, 2020 11:12 am

Thank you for the thoughtful responses. So the equipment is too old to consider stacking and thus I have the option of a 2nd unit that would remain electrically isolated so as not to produce 240 volts, or start fresh with new equipment.

This installation is on an island in northern Ontario and is only used during the summer months. If it were used full time I would have no hesitation in moving to all new equipment where I would enjoy a return year round. Having said that, the pending upgrade is significant as I have built a second cottage on the island, which, given the reducing costs of off-grid power, will have much higher loads. Whereas the initial build was minimalist, with propane stove, fridge and water heater and only the basic electrical necessities, the new cottage will have electric hot water, refrigeration, a dishwasher and only rely on propane for the stove. I will be adding approximately 3KW of solar to the almost 2KW I have now, and changing out the AGM battery bank to lithium from one or 2 EV cars (I have contacts in the car wrecking world).

Since the existing cottage will only receive occasional use once the new building is complete it looks like it will make sense to leave the current inverter connected to that building and only turn it on when guests are using it. That would leave me free to size a new 240 volt system for the new building. I don't really need 240 volts right now, but will need at least 6000 watts or so available for the new building. So keeping in the Outback family is 2 VFXR3648A's the way to go? I really don't need the extras that come with the FLexpower 2 packages unless the bundle prices are a bargain. I have had great luck with Outback, but if the forum rules allow it, is there another option I should consider for new charge controller, inverter and monitoring?

Thanks,
John

raysun
Forum Emperor
Posts: 2951
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
SimpliPhi 48-3.8 (6 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: Can a VFX3648 be mated to a GVFX3648?

Post by raysun » Mon Aug 31, 2020 12:14 pm

jcwells wrote:
Mon Aug 31, 2020 11:12 am
Thank you for the thoughtful responses. So the equipment is too old to consider stacking and thus I have the option of a 2nd unit that would remain electrically isolated so as not to produce 240 volts, or start fresh with new equipment.

This installation is on an island in northern Ontario and is only used during the summer months. If it were used full time I would have no hesitation in moving to all new equipment where I would enjoy a return year round. Having said that, the pending upgrade is significant as I have built a second cottage on the island, which, given the reducing costs of off-grid power, will have much higher loads. Whereas the initial build was minimalist, with propane stove, fridge and water heater and only the basic electrical necessities, the new cottage will have electric hot water, refrigeration, a dishwasher and only rely on propane for the stove. I will be adding approximately 3KW of solar to the almost 2KW I have now, and changing out the AGM battery bank to lithium from one or 2 EV cars (I have contacts in the car wrecking world).

Since the existing cottage will only receive occasional use once the new building is complete it looks like it will make sense to leave the current inverter connected to that building and only turn it on when guests are using it. That would leave me free to size a new 240 volt system for the new building. I don't really need 240 volts right now, but will need at least 6000 watts or so available for the new building. So keeping in the Outback family is 2 VFXR3648A's the way to go? I really don't need the extras that come with the FLexpower 2 packages unless the bundle prices are a bargain. I have had great luck with Outback, but if the forum rules allow it, is there another option I should consider for new charge controller, inverter and monitoring?

Thanks,
John
If vented inverters have worked for your environment, then VFXR3648 is a good choice, otherwise the FXR3048 is the lower power, lower maintenance, sealed unit.

The Flexpower Two is no significamt cost savings, but is "plug and play" with pre-wired components.

Can both locations be fed from a common system?

For lithium batteries, it may require a newer Inverter for the advanced charging functions. Lots of lithium packs require voltages outside the normal lead acid battery range, particularly for battery protection (Low Battery Cut Off and High Battery Cut Off especially). Alternately, an external battery monitor can be used with relay control to shut the inverter down.

The full Outback ecosystem has benefits for remote monitoring, advanced battery charging and system-wide control functions - like Global Charge Control. However, its not the only way to put up a usable system.

Midnite Classic charge controllers are also well regarded, though more expensive. A fully programmable controller will be necessary for most all lithium, especially DIY.

If not using the FNDC for monitoring, the Victron BMS7xx series are useful, and under US$300.

I am going through a similar conversion. After considering the options, my choice is to replace my FX3048T inverter (on a Flexpower One panel) with dual FXR3848A-01 inverters (on a Flexpower Two panel.)

My FP One setup sold in about 30 seconds to the first person I mentioned it to. He is waiting delivery when the new system is commissioned. The OB gear has good resale value.

My system is 120V single phase, and the FP Two is easily wired for that with parallel inverters, the secondary in power save mode until loads demand more than the primary can deliver. Also, Support mode seemlessly blends inverter power with generator power in case I need to support loads over 6kW.

Switching the system to 240V split phase in the future would be a trivial exercise. Everything needed for BoS components are already there.

Support for two charge controllers is included as well. If electric hot water is planned, two charge controllers are going to be an imminent need, IMHO.

jcwells
Forum Junior Member
Posts: 3
Joined: Thu Aug 27, 2020 11:15 am
My RE system: VFX 3648, Mate 1, Mx- 60

Re: Can a VFX3648 be mated to a GVFX3648?

Post by jcwells » Thu Sep 03, 2020 9:59 am

In answer to your question, both buildings have their power supplied from the same solar shed. Further, your comments have lead me to consider simply replacing the existing inverter with a new larger unit that could supply both buildings when needed. The Radian GS 8048A would seem to be a viable option, delivering the power I need, including 240 Volts, in a single box. The grid tie features would be wasted, but the power output is attractive. Any comments on this configuration particularly since you have not gone this route in your upgrade?
Thanks,
John

raysun
Forum Emperor
Posts: 2951
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
SimpliPhi 48-3.8 (6 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: Can a VFX3648 be mated to a GVFX3648?

Post by raysun » Thu Sep 03, 2020 10:36 am

jcwells wrote:
Thu Sep 03, 2020 9:59 am
In answer to your question, both buildings have their power supplied from the same solar shed. Further, your comments have lead me to consider simply replacing the existing inverter with a new larger unit that could supply both buildings when needed. The Radian GS 8048A would seem to be a viable option, delivering the power I need, including 240 Volts, in a single box. The grid tie features would be wasted, but the power output is attractive. Any comments on this configuration particularly since you have not gone this route in your upgrade?
Thanks,
John
If 240V split phase works to supply the loads, then the Radians work well. Note that an 8kW Radian consists of two independent 4kW modules that work in tandem. The 4kW Radian consists if a single 4kW module (I was corrected on this). I've not really studied the architecture in detail, but assume there is some manner of "power save" mode on the 8k unit when the total load is less than a single module can deliver.

I'll be using FXR inverters because the house wiring is 120V single phase, and we don't use 240V loads.

The grid-interactive features are not generally useful in an off-grid setting, but there is one of the seven modes worth exploring - Support - which takes effect when on backup generator. Should loads exceed the generator's capacity, Support mode will enable inverting, seemlessly blending inverter current with generator current. This would permit the use of a slightly undersized generator in the system. It would also permit powering loads in excess of inverter capacity by combining maximum generator output with maximum inverter output. Less need to oversize the system to occasionally run that arc welder.

I plan on using Support with the dual FXR setup, as my Honda EU7000is is rated at 5.5kW continuous.

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