400w MH to 250w MH - Big temperature difference?
 

So, I have been finding I don't really need to be running 400w MH over my tank, and since I got a call from the landlord curious about the high power usage, I figure now would be a good time to change to 250 w MH.

Part of my logic behind this is that the 250w bulbs should run cooler - is this correct? Having almost 1000w of light in my canopy over a 135g tank means that it is hot, particularly with this mini heat wave we have been having in Victoria. I find that the profilux turns the MH off really quickly as the tank heats up.

Will there be a significant difference in the bulb temperature between the 400w MH and 250w MH? I know I will see a difference on the ballast end (moving from an old magnetic ballast to digital).

Also does anyone have any feedback on the lumatek ballasts? I am thinking of getting two of those. I have 20 000 K XM SE bulbs right now, any recommendations for 250w bulbs?

there will be a little bit of difference in power consumption, more if you go with the lumitec ballast, but realy not that much. as for heat, a little bit lower but I doubt you would even notice it.

as for bulbs, if you like the look of 20K, go with the SE radium 20K 250 watt bulbs.

Steve

I have 2 tanks side by side of apx the same size. One is 400W and one is
250W. They both run about the same temp... which is like 82 today~

I think if you go from a 400W "HQI" down to a 250W electronic you will notice a difference in heat output because actual consumption will be halved from around 500W to 250W. However, if you're using, say, a 400W electronic ballast and go to a 250W HQI (M80) then you will hardly be using any less electricity and there will be no difference in heat.

When I went from magnetic 175W (M57) ballasts to 250W HQI (M80) my tank temps in the summer shot up quite a bit..

I can tell you I noticed a big difference in heat output from my old Iwasaki 400watt vs 250 watt XM's. Remember if using a magnetic ballast, extra heat as well.

I just upgraded from 250's to 400's and noticed quite an increase in the heat produced from the lights, doesn't affect the tank much as I have the fixture vented to the outdoors.

I'd be going from "hqi" which I understand to be a magnetic ballast (correct?) to a electronic (digital) ballast. It looks like everyone has a 50 / 50 opionion of if this will result in a change in temperature. What about electicity usage - Can I just simply figure out how many kWh this will result in saving and find out my power savings that way? Or is it not quite so simple.

I figured it would be this: [(800 w - 500 w) / 1000] x 6 hours per day x 7 days a week x 52 = 655.2 kWh

This would mean a 54$ savings in one year in electricity (based on BC hydros teir two rate). Unless there is a even larger difference in the electricity savings due the different ballasts being more efficient.

Any thoughts on this?