[QUOTE=how many bars does your regulator go to? if it is 1 like mine then you will need more then 13 minutes because your room is much larger.[/QUOTE]

Not exactly sure how many bars it has just yet, I need to purchase it. What are bars... the amount of setting for flow intensity or something like that?

Do you notice a big increase in yield only running it once every three hours? I was told at the store I would want to put the c02 out pretty much every hour. I figured a simple twenty three to twenty four minutes of every hour the fans would be off, and I assumed emitting c02 for about 15 minutes would probably give me the desired PPM.

At the hydro store though I was told I would likely need more than twelve programs and I'm not sure why... I would assume once an hour would be plenty but I could be wrong?

Thanks for the info about c02 calculators online, I'll have to take a look. I also have a friend with a brain that measures PPM in the air, so he said he'd be willing to bring it over and I can monitor how quickly my room fills etc for a few hours and run my cycles accordingly - this combined with rough estimates from dimensions of the room should be enough huh?