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Flex One Backup Inverter suggestions

Posted: Sun Oct 27, 2019 11:43 am
by Clem Jonze
Aloha everyone,
I live in a remote area on the Big Island of Hawaii, running an off grid Flex 1 System utilizing a FX3048T inverter. After four years of trouble free operation, it appears the AC board on the inverter failed. Outback is sending another, but in the mean time I am operating on my Honda 3000 generator. Because of my remote location, I think it prudent to have backup equipment on hand, as my panels and charge controller, batteries, etc are still operational. Obviously I could have another Outback inverter, or a whole Flex 1 system as a backup, but I was wondering about having something a little less expensive. Has anyone used one of the many cheap Chinese inverters available on Amazon or locally as a backup while making repairs to your Outback equipment? If so, any connection issues to be aware of - if I was to connect it into the Flex 1 system? I know of course the Mate controller would not "see" or communicate with another brand of inverter.
Thanks in advance for any thoughts or advice.
BTW: The process of working with Outback to get warranty service is going on three weeks from initial contact. In the end, it will probably be a month waiting for parts. Yep, I could have gotten another board locally by paying out of pocket. Not really complaining about Outback, I am suddenly very aware I need a backup system ready to go when this happens again.

Re: Flex One Backup Inverter suggestions

Posted: Sun Oct 27, 2019 12:11 pm
by raysun
Aloha bruddah!

I'm a fellow Big Island (Ka'u) resident. I have essentially the same system, (FP1 w/FX3048T), and have thought often about the inverter being a single point of failure.

Our average consumption is fairly low, generally less than 400 watts. I bought a 700W @ 48V inverter of decent quality, and have run a trial using it, with an external transfer switch, to replace the FX3048T. It worked fine. The transfer switch is connected to the generator on the "grid" input and the 700W inverter on the "backup" input. If the load looks to be exceeding 700W then I manually start the generator which switches into the AC load circuit, taking over from the inverter (similar to what the FX3048T does with its internal transfer switch, but without the automatic switching logic.) I have an external charger that can be run from the generator if needed.

Doing a bit more research, I found another small, very capable 800W inverter/charger with internal transfer switch for about $550 that is a very close analog to the FX3048T functionality.

The backup inverter needs to be sized to run critical loads. I don't recommend a cheap 3kw inverter. A smaller inverter sized to handle critical loads, with generator backup to handle periodic large loads, is a good balance between quality, cost, and capability.

The 120VAC output from most all inexpensive inverters will be fed through a GFCI outlet. This is the type of outlet an appliance or extension cord is plugged into. Wiring the outlet to house wiring can be problematic at times, with nuisance tripping of output protection a frequent symptom. A small, stand-alone inverter best powers critical loads via direct connection or through a critical loads sub-panel.

Other small inverters have an AC OUT like the FX3048T and are best wired into a load panel.

Large inverters with similar capacity and quality of output as the 3048 will cost about the same as a 3048.

Properly wiring the backup inverter into the FP1 will require a sub-panel with an Inverter Disconnect (DC circuit breaker), mounting space for transfer switch, and generator 120 VAC input connector. The panel will accept heavy battery cables attached to the 48V primary battery and feed the inverter through the disconnect switch.

With the backup inverter battery feed wired into the shunt between battery and loads (the FX3048T being the primary load), the FNDC continues to track current flow out of the battery, maintaining accurate state of charge, though OpticsRE doesn't show the inverter power of course.

Re: Flex One Backup Inverter suggestions

Posted: Mon Oct 28, 2019 10:45 am
by Clem Jonze
Howzit Raysun!
We're down in the jungles of Upper Puna.
Mahalo for your recommendations. My "idle" load is around 200 watts. Triple that when the 1/2 HP catchment pump kicks in. My coffee roaster is the biggest power sucker, (1,200 W) but long as I use it only during full sun I'm good. Teaching the family not to run too many appliances at the same time is always a challenge. One reason why I'm looking at a backup 4000 watt inverter! The new AC board should be here today, but you never know. (life in Hawaii) My buddy is a PV tech and he says I can install the board without removing the inverter from the wall. We'll see about that. The inverter failure was a nice wake up call. All this time I thought we had backups and now I know we need backups for the backups! I'm looking at a couple different inverter options. My Outback system has been working well and trouble free for so long, I have become complacent and out of the loop with some of the updated technology available today. Even with the hassle, it is fun getting back into working on my system!