Measured Current Draw for various ODNO configurations

[GulfCoastAquarian]

Last night, I measured current draw for various ODNO configurations. I'm not sure they make sense, though. I measured current at the outlet with a Fluke 77 Series II Multimeter, so current readings would be avg and not RMS.

(A) With one F40T12 bulb hooked up to all four outputs of a 4-F32T8 ballast, I read 1.50 amps of current draw!

(B) With just two outputs of the same ballast connected to one bulb, I read 0.55A.

(C) With two F40T12 bulbs, each with two outputs connected, current was 0.72A.

Translating this to RMS (70.7%/63%) and taking into account the ballast factor (88%), I get 178 Watts being delivered to the first configuration (A), 65 watts for config (B) and 85 watts for config (C).

If these bulbs are efficient enough to provide 50 lumens per watt in standard configuration at 40 watts, then the one 4x OD F40T12 bulb was producing almost 9000 lumens! Assuming efficiency was much reduced, I'd estimate it to be closer to 5500-6500 lumens, since the light output seemed to be just slightly brighter than a 65w PC bulb I have. Is this possible? I only ran it for a minute or so and the bulb didn't get too warm to touch.

I don't understand why the output would increase so dramatically from 2x to 4x. One thing I am thinking is - for all these tests, I had only one yellow (common) wire connected to each bulb. I might retest tonight and see what happens when I connect both common wires to the single bulb combinations. I assumed they were truly common and it wouldn't matter, but perhaps I am mistaken.

[Flgatorguy]

Originally posted by GulfCoastAquarian

(C) With two F40T12 bulbs, each with two outputs connected, current was 0.72A.

Translating this to RMS (70.7%/63%) and taking into account the ballast factor (88%), I get 178 Watts being delivered to the first configuration (A), 65 watts for config (B) and 85 watts for config (C).

im tired so this question might sound quite dumb....but for figure (C) thats with 2bulbs and the one ballast correct?....my question is would double power to a 40w bulb be 80watts are am i missing something electrical here?.....because if its only 85w with 2 bulbs i need to go get another ballasts....or just use one bulb

[GulfCoastAquarian]

I'm really not sure of what's going on here, either. Some of these readings don't make sense.

But to clarify - yes, Config C is with one four bulb ballast hooked up to two bulbs (each 2x).

Double 40w should indeed be 85. But these ballasts are load sensing, and for some reason, output increases in ODNO configurations.

What is weird, is that the same ballast, driving only one bulb (with all four outputs), drew 178 watts! That's more than double the current for two bulbs. Electrical logic would seem to say the two bulbs, with their lower resistance, would have a higher current draw. But this is not so. I'm investigating why and I'll keep you guys posted as to what I find.