question

Here is a link to an article describing the Power Limits, including a table which details the lower limit for each model.

https://www.victronenergy.com/blog/2018/04/20/multiplus-quattro-inverter-chargers-improved-current-limits/

I don't know exactly which model your customer has, but the lower limits for firmware 2733431 and 2748431 is 13A (26A for the pair). Firmware 2758431 has a lower limit of 13.4A (26.8A for the pair).

The GX is certainly convenient to do this with via lan/laptop, etc., but I doubt it will give more 'granularity'.

Perhaps just disconnect/switch the AC IN away from one of your units, so halving the shore load?

abrahamsolar says: Thanks @JohnC & @WKirby for chiming in. Firmware version on these Quattro units is 431, for the record. I removed the Digital Multi Control GX from the system & we're now using the CCGX to adjust the AC In amps but our available choices are still no smaller than 27 amps AC @ 120 volts. This matches the chart to which WKirby linked: for these product ID 2753 Quattros, the chart shows no less than 13.4 AC amps "In" for each of the pair. 27A is still too high because many of the shore power locations where my client needs to connect are only 20 amp capable or even as low as 15 amp capable. My next efforts were attempts to get only one of the two Quattros to draw AC IN. If I merely unbolt the "Hot 1 IN" cable from the slave Quattro as suggested by JohnC, both units crash when grid is connected & the CCGX throws an error since the second Quattro is not seeing AC IN. In some cases, this type of response would be appropriate but in this case I want the slave to "only invert" & to never use the energy that's available on AC IN. Using the latest VEconfigure software, Virtual Switch on the Slave was set to "Ignore AC Input" whenever VS = ON. Tab A in VEconfig was set to make VS = On whenever the battery voltage is 60vDC or lower for one second--which will always be true with the Tesla auto style lithium batteries we're using. Tab B is all grayed out with all fields at the -1 second factory default. If I've interpreted the grayed out Tab B fields correctly, no condition is able to set VS = Off. That all looks good on paper, but it didn't work in reality. Using my clamp style AC ammeter, I could tell the slave was still transferring AC load & therefore the 13.4 amps IN limit was still in play for each Quattro. I think the slave is not charging but my goal of getting 13.4 A as the limit for the pair is still wanting. I also tried to uncheck the "Enable Charger" box in VEconfig on the slave only...same problem as described above. I'm aware that by dialing the DC charge amps maximum quite low, that indirectly reduces the amount of AC power draw...but the PowerAssist is much less beneficial to my client if I use this approach as a workaround. The client specifically chose Victron because of PowerAssist & specifically wanted much more "assist capability"...& more inverting capability...compared to the limited DC charge power available if he's plugged into only 15 amps or 30 amps of 120v AC shore power. That's why we've got two Quattros instead of only one...not for more DC charge capability but for more inverting/more PowerAssist. In a stacked pair such as this, am I unable to fully change the slave behavior without also changing the master behavior...or what else am I missing? I'm running out of ideas so I've asked the Victron techs to read this thread & chime in with their suggestions. Thanks & Jolliness, Community folk.

I thought there was a mode where two parallel units could be driven from 1 input, but that might have been with the old HUB systems. (same as 3 phase from 1 phase supply)

It might sound strange...and might cause problems, but you could try putting the Quattro's in series instead of parallel.

series in this case means putting AC -out of the first unit into AC-in of second unit, AC-out of second unit supplies loads.

To prevent unwanted DC currents when on a 15A/30A shore supply, I'd disable charging from one of the units in this situation (might do something smart with AC in 1/2 inputs).

When (without shore supply) not more than 5kVA of power is needed, you can turn off the first unit to safe on standby energy use.

In a similar situation with 1x 8kVA unit I've used one of the aux to connect a switch where the owner can select 'small shore supply' where the unit reduces charge current, and when drawing more than x power, shore supply is ignored and all power comes from the batteries until drawing less than the shore supply can handle.