So ...
In the Vero datasheet ....
0.946 of 25C 'Typical' Flux .
'Typical' Flux at 25 C is 9900 lm .
Flux is measured from a pulsed Vero 29 ,in order to keep Tc =25 C .
(Not to heat up ) .
So 0.946 * 9900 =
9365.4 lm
Vero 29 has a typical Vf 0f -16 mV / C ..
so ...
55-25 = 30 C
30 * 0.016 =0.48 V
From typical 25C Vf of 38 VDC ,subtracting 0.48 VDC =
> Vf= 37.52 V ...
LER= 321
Io=2100 mA
Tc=55 C
so ....
37% radiant efficiency ...
At 2100 mA and with aTc=55 C .
Bye-bye HPS ...
No matter the type or wattage ..
The 600W of HPSs have highest efficiency figures ,close to 33-35% ,
only when brand new and for a short while after,~1500-2000 hours .
For the 400 & 250 watt HPS ,better assume a rad.efficiency of ~30%..At best case ...
And this dual COB fixture is a direct high-tech substitute or 'competitor' of the latter HPS power class ...
( Most of growers will be getting about 200 gr from every grow cycle with a 400 W HPS .
Same most growers will be getting about the same yield ,with half the wattage ,using two Vero29 at 2100 mA ..Around 0.8 - 1gpw ..Maybe a 'better' spectum accounts for that constant difference between the two techs used ..Light power distribution is pretty similar at both cases,I would hardly guess ...Nothing else is left to be accounted for ..Radiated heat from HPS ?
It's bull that forces plants to assimilate more nutes ..Bull ..They take up more water...
That's why the HPS buds lose much weight / size when drying - 75% w/w ,while the SSL COB buds lose pretty much less weight / size when drying ...55-65 % w/w
They 'hold' less water-load ,first -place ...)
At a Ta =35 C (...hot summer days ) ,junction temperature will be around 70-75 C ..
Even then ,the service life of the fixture ,it extends more than 50.000 hours .
4x7x18=504
10x7x12=840
Average grow cycle = 1344 hours .Say 1400 h.
Minimum number of full grow cycles ,per COB arrays' service life (LM 80 ):
36 .
For every 3-6 grow cycles one new HPS is needed ..
for 36 grow cycles a min. of 6x HPS lamps will be needed .
6 x $50 = $300 ..
Thats about half of the (...'retail' let us just say ) price of the COB fixture ...\
Add a crappy ballast of $50 ,a $10 reflector ,wiring and electricity cost difference for 36x grows (that's gonna be plenty ),
to the HID option ...
And that is your best-best -best ,as cheapest of cheapest -@$$€$ , case / option with HPS..
Spending ~$400 one can DIY make a dual-COB fixture exactly like that ...
(I need kinda more ,in order to make it for him/her ,instead ...
..But not much ..)
Cheers.