Measured actual electrical on my tank

[Delphinus]

Wow. I'm blown away by the 810w reading for 2-250W lights.

Everything else looks pretty good though! But yeah, ... wow. Paying 810w to get 500w of light? It sounds terrible.

[sphelps]

might be worth while switching your halide ballast to electronic. I would imagine the HQIs are running pretty hot and at very low efficiency at that wattage.

With pumps the rated wattage should actually aways be higher than the steady state. Reason being is the pump will use a more power during start up, using the proper rating allows you to plan your electrical configuration properly to avoid tripping breakers and overloading circuits. However many companies are now rating there pumps at steady state to give the appearance of higher efficiency, in fact I would bet you're actually getting higher peaks than you observed, the device you used simply isn't fast enough to pick them up.

[spreerider]

wow thats really bad efficiency on the lights, your only getting 61% efficiency, most MH ballasts are rated at 80%-97% efficient i would be concerned with this and proably retest the lights then try one at a time, seems like your ballast is not operating properly and could be headed for a burnout (definatly the extra heat would not be helping,
Also i would take my bulbs out and put them back in, check for corrosion on connections, and redo all electrical connections as they could be poor and forcing the ballast to pull more amps.

[fkshiu]

Yeah, it's an old "industrial" M80 ballast. I'll double-check everything, but it might be on its last legs. I wonder if it could be a capacitor issue?

[marie]

I have no idea exactly how bright your lights are but mine with the hqi ballasts and SE bulbs I am easily getting twice the light that I was getting with DE bulbs.
I expect there to be more watts used and the bulbs to be overdriven (no matter what stircrazy says)

[marie]

Info taken from sanjays site comparing a 250w SE xm bulb and a hqi ballast with a 400w SE bulb and an ordinary m59 ballast

ppfd of the 250w is 182 and the ppfd of the 400w is only 172. Your getting more light out of your 250w ballast then you would from a 400w ballast

[Delphinus]

I guess the real question is what are the real watts out of a 400W? It's like the 250W M80 is more like a "real" 400W. Looking at Sanjay's site ( http://www.manhattanreefs.com/lighting ) I note that switching to an electronic ballast for 250W the XM lamps drops to 115.

Assuming an electronic ballast really uses 250W (might be a stretch, I don't know), and we get 115 ppfd, that's like saying 0.46 ppfd per watt. If the HQI uses 405W but nets 182 ppfd, that's also 0.45 ppfd per watt, but we just "get more". So I guess it's not a real question of who's more efficient, but a question of how much PPFD do you want.

Wow, my head is swimming just trying to digest this. I knew that a 175W wasn't really 175 and 250W wasn't really 250 and 400W not 400W but I thought the "real versus rated" differences would be less than this.

Dang maybe T5's really are the way to go in the future.

[StirCrazy]

Originally Posted by marie

I have no idea exactly how bright your lights are but mine with the hqi ballasts and SE bulbs I am easily getting twice the light that I was getting with DE bulbs.
I expect there to be more watts used and the bulbs to be overdriven (no matter what stircrazy says)

now now, you can't hack on me when I am on the other side of the world and can't defend myself.

[marie]

Originally Posted by StirCrazy

now now, you can't hack on me when I am on the other side of the world and can't defend myself.

Well geez, if your on the other side of the world you shouldn't even notice you've been hacked