Cool! Two mini-Suns. I am wondering why they draw 85w each? The Vero 18 needs 28.4v @700ma or 19.9w for each emitter. Power supply loss?
Not only ....
3x 19.9 = 59.7 Watts the 3x Veros power
85-59.7 = 25.3 Watts the 2x Fans & the PSU 3x Bucks losses ..
Now when it's a single Panel it draws 5 Watt more ( 90 Watts ) instead of 85 per panel when two of them ...
That's is absolutely normal ...
The more the PSU / bucks are operating close to their 100% load ,
the more efficient they become ...
Adding the third panel ,then at 700mA ,probably each panel will draw ~ 80Watts
(~240 Watt Full system's power ,at max driving )...
So ,here you see another "compromise" between If of dies/ arrays versus Io of PSU(s) ..
The higher the If of the dies/ arrays,the lower their efficiency ...
The higher the Io of the PSU(s),the higher it's/ their efficiency ....
And because If=Io ....
So ,in a 'dimmable' unit/fixture /system ,the two efficiencies should add up and divided by two ,to get the system's overall efficiency ..
The most efficient method ,is the 'non-dimmable' drivers/ PSUs ,that will drive the leds/arrays at a low current figure ,
so their efficiency remains at high levels ,while the drivers/PSUs will operate at their full load or as close as possible to it .
To drive a CXA/Vero efficiently at 350 mA ,the driver should also operate as close as possible ,to
the If & Vf of the CXA/Vero (i.e 350mA ,Vf =32.5 Volts for driving the cxa ..
But then driver ,especially if of low quality,will eventually degrade in efficiency ,due to high temps ....
The other options is the way I like to follow ...
Wide range dimmable drivers of high quality ..
At high If / Io the loss of efficiency from leds/arrays is "counteracted" by the increased efficiency of the drivers ...
Plus ,the fixture has an adjustable power ,'following ' the needs or restrictions of number,species of plants ,
grow methods ,available room/space and more ...
Driving many leds/arrays at low currents ,has quite a 'few' strict rules ,
in order for high efficiencies to be achieved ...
But spreading out the light ,is a great advantage for plants ...
The disadvantages of this way are more technical ..
(high cost of multiple drivers/leds-arrays-heatsink units,increased weight ,
hanging /height adjusting issues ,are few to name ..)
Cheers.