VHO technically refers to the .. um .. I'm sure to get this wrong but I'm going to make a stab at it anyhow... the amperage pushed through the bulbs. NO lamps (whether 20W, 40W or whatever, depending on the length), use one amperage (plus whatever voltage to make it 20W or 40W), then HO uses an amperage higher than that, and then VHO uses an amperage even higher than that. 48" VHO lamps are 110W, 24" VHO's are 75W.
So anyhow, there's no such thing as a "40W VHO". More likely he means he's running 40W lamps overdriven using a 110W ballast. Which you can do (assuming an electronic ballast is used), you will get some increased lumen output of the fluorescent, at the cost of (presumably) shortened useful lamp life.
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-- Tony
My next hobby will be flooding my basement while repeatedly banging my head against a brick wall and tearing up $100 bills. Whee!
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