1 hour ago, JoanTheSpark said:

Any brand out there that shares the 'internal' DC bus between the units (400VDC) to reduce conversion losses?

SolarEdge. The "internal" DC bus is on the roof :-)

I've thought about the following idea a while ago - not to parallel the outputs of the 3KW infinis, but rather to cascade them.  Since the infini can easily handle twice its rated capacity (and more) while grid power is available I think you might be able to cascade 2 (or more) infinis.

First infini: GRID connection either connected to grid or not, depending on grid availability, may be configured to "feedback to grid" or not, PV array connected, battery bank connected.

Second infini: GRID connection connected to first infini's LOAD connectors, "feedback to grid" must be DISABLED, load connected to LOAD connectors, PV array connected, battery bank connected.

Note: PV arrays and battery banks of 2 infinis NOT IN ANY WAY SHARED or electrically connected.

First infini will be able to supply up to 3KW, depending on PV, battery and configuration.  Second infini will also be able to supply up to 3KW (again depending on PV, battery and configuration), but furthermore it will also "see" the first infini as the "grid" and add the 3KW from the first infini and be able to supply a load of up to 6KW.

Technically you should be able to cascade more infinis in the same way, without having any electrical connection between any battery bank or PV array and with having the "feedback to grid" option DISABLED on all downstream infinis.

5 minutes ago, superdiy said:

cascade them

The first time your kettle turns off and the second infini (which is set not to feed back) adjusts its feed-in too slowly it could potentially blow the first one.

I could see this working with devices that are designed to have another generator connected on their output, like when you have a GTI connected to the output of a Multiplus, but I don't know if you can do that with an Infini.

2 minutes ago, plonkster said:

The first time your kettle turns off and the second infini (which is set not to feed back) adjusts its feed-in too slowly it could potentially blow the first one.

I hear you, it all depends exactly how they do the "backing off". Since the grid and load waveforms are synced, it might work, even if the "backing off" is slow.

1 minute ago, TinkerBoy said:

Superdiy, this is an interesting idea, why not just put the load in the grid feed side and then you can have as many as you want without anything blowing up.

I think we are talking about the same thing here.

1^st infini's load connection connected to 2^nd infini's grid connection - 2^nd infini's load connection connected to the load. Or do you have another idea?

I'm referring to the 3KW infinis which only have GRID and LOAD connectors, I'm not sure if you are perhaps referring to the 5KW infinis and if they maybe have more connectors?

Something else to consider, story below.

Over the weekend I was playing with the Ziehl UFR1001e anti-islanding device. I have a sparky coming in some time in the next week to install a new DB and all the goodies, so I wanted to be sure that everything works and is set up for a single-phase installation (they always ship configured for three phase by default).

When I had the device plugged into the grid and set to the UK program, it works beautifully (somehow I cannot get the German one going with just one phase). When you turn it on, it counts down from 20 (spec likely says wait 20 seconds before you engage) and then the two relays click in. Perfect.

When I put that same device on the output of my Multiplus it never gets to zero. It counts down, stops halfway, then restarts. Basically, some of the parameters (dV/dt, dF/dt and d^2F/dt) are exceeded, that is, the Ziehl doesn't consider the waveform stable enough to qualify as a grid that you can tie with.

Now the Infini has NRS097 certification, probably because it's at least as good as th UK and/or German specifications, which means it will likely refuse to tie with the first one unless it is in bypass... which defeats the purpose.

Edit: Then again, a GTI will tie with a multiplus on the output... so maybe I just have this device set up incorrectly.

2 minutes ago, TinkerBoy said:

You dont put anything on the load side of the inverter, You put the load on the grid side. So you draw your power from what would have been exported. I have my setup like that now and use a modbus meter to see how much I am exporting or using. Only thing is if the grid fails you also have no power until you switch the load back to the load side of the inverter. But I have not had to do that up to now.

OK, yes, I'm with you.  But as you've said, you need the grid and therefor your solution will not work in off grid installations.

4 minutes ago, plonkster said:

Now the Infini has NRS097 certification, probably because it's at least as good as th UK and/or German specifications, which means it will likely refuse to tie with the first one unless it is in bypass... which defeats the purpose.

Spanner in the works. 

So, did anyone try and do a parallel connection on the 3KW models?