Help needed on expanding existing outback system or change entirely?

System

I have an existing system (GTFX2524, MX60, Midnite ePanel, PSX240 for 240v output, Crown CR395x4, Sharp NT175x9). I am thinking about expanding the capacity.
The Sharp 175w 24v panels are wired 3 in each series, and 3 of them in parallel.
I am thinking about adding another 10 of 175w panels. Will need to add a Flex80 to handle these.
I am also thinking about buying another 4 batteries. The existing 4 were bought in 2008, they were mostly kept in float state until recently, in HBX mode for about a month. I hope I can still mix the batteries.

My choices
1) stay with current config, buy 1 GTFX2524, 1 Flex80, 1 e-Panel, 4xCR395 to parallel with the existing 4 (stay with 24v)
Pro, reuse, and lower cost. I can also separate the old and new bank, and let the slave inverter control this new bank entirely (slave will be on the 2nd phase of the 240v system).
Con: stuck with 24v system, only 5Kw from inverter, and no way to expand the capacity later on (as only 2 Grid-tie outback allowed per manual). The PSX240 becomes useless in this configuration. No redundancy, if any one phase is dead, lose half of the system, and the 240v circuit will go mad.

2) same as 1), except buy 1 GVFX3524. Put more load on the phase served by this inverter. total capacity will be 6kw, instead of 5kw. Is this possible?

3) ditch the existing GTFX2524, and get 2x GVFX3548, and everything else as 1).
con: the battery bank would have 4 old and 4 new for 48v. loss of 1000$ (assuming I can still get 1000$ back for the old GTFX2524)-- without considering fed rebate.

in this case, would I be better to go with the midnite NOTTAGUTTER and ultra-lite panels? Or, just to add another e-panel. The nottagutter does seem neater and can cover lots of wiring between the two panels, and be used to host other breakers and connectors that I put into another box.

4) shall I consider another system entirely? say Xantrex XW6048? It is cheaper than 2 GVFX3548, but would need to buy its monitor, learning curve again etc.


My goal: I have diverted 9 circuits (important load) to the transfer switch, and they are served by the outback system. If grid goes down, they are not affected. The panels will charge the batteries, and sell excessive back to the grid (not done yet).

My issue is: most of the time, these 9 circuits have little constant load (less than 300w) in the day time - sewer pumps, sump pump, important circuits and lights, and fridge. Other circuits (AV, furnace, range etc) are not tied into the outback system. How would sellback work? Would the excessive power go to my circuits first? (as those other heavy loads can consume a lot) -- which means both grid and inverter are serving the heavy loads, and only rollback the grid meter when the total load is less than the excessive power??

I would move more loads into the subpanel as the capacity grows (note that my subpanel currently is a gentran transfer switch - each circuit can be switched between the grid and outback system independently at any time).

Your opinions are greatly appreciated.

thank you

Cariboocoot

Re: Help needed on expanding existing outback system or change entirely?

Growing systems of any type is never easy, even if you planned for it in the beginning. Sometimes the components you expect to use disappear off the market!

Is your main interest grid-tie or having battery back-up for crucial systems? Frankly, the Outback systems aren't the most efficient grid-tie set-up available (and everybody knows I love OB equipment).

I wonder if the best choice here might be to leave the existing system alone, since it functions well for you, and add a separate grid-tie-only set up like a SunnyBoy or such. There would be some questions/issues with whether or not your existing service can take the addition - and of course you need the permits and co-operation of authorities & utility. But that would be the case with any modification.

Maybe you should switch the whole grid-tie system over, and re-wire the Outback to be emergency power only (since you've already got it). You'd add/reconfigure panels to feed a grid-tie inverter which would negate your usage and sell surplus to the utility, plus you'd have the OB in case the grid went down (it could be kept charged via the grid).

There's a lot of possibilities.

System2

Re: Help needed on expanding existing outback system or change entirely?

Thank you Marc.
I did wonder about the sunny boy approach, but still want to have the increased backup capability. I need to think harder and figure out what is the most important thing I need from the whole system.

Would mixing the batteries be a problem? Based on my current battery condition as described?

Any opinions on the MidNite NOTTAGUTTER system?

If I have a GTFX2524 and a GVFX3524, can I get 6K out of it? Or the 3524 will be limited to 2500 watts due to 2524?


any other suggestions folks?

thank you

Cariboocoot

Re: Help needed on expanding existing outback system or change entirely?

yoyo wrote: »

Thank you Marc.
I did wonder about the sunny boy approach, but still want to have the increased backup capability. I need to think harder and figure out what is the most important thing I need from the whole system.

Would mixing the batteries be a problem? Based on my current battery condition as described?

Mixing batteries is a problem if the existing set is "old", as in over one year and/or heavily cycled or showing signs of deterioration (lower full charge SG than when new). It's a bit of a judgment call. The new batteries get "dragged down" by the old ones as they will constantly try to even out charge between them.

Any opinions on the MidNite NOTTAGUTTER system?

Never seen or used one, but Midnite makes good stuff.

If I have a GTFX2524 and a GVFX3524, can I get 6K out of it? Or the 3524 will be limited to 2500 watts due to 2524?

If the 2.5 kW unit is back feeding one leg of the 240 VAC and the 3.5 kW on the other there should be no trouble; a 1 kW imbalance between legs is nothing to the power company. You'll have to go through the whole permit/install process again, of course. Ultimately they get to say yes or no to the plan. I'm not a "grid-tie guy" as a rule.


any other suggestions folks?

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