This is wrong.Your power usage quotes are flawed, it largely depends on the quality of the ballast, as this could flucuate ALOT.
Also your coverage is flawed too.
You’ll get better light coverage with 2-400’s. better yet, 2-600’s. The great thing about the 600’s are they put out the same amount of light as a 750 watt HID would if you based it on the efficiency of a 1,000 watt HID. In other words, you'll get 75% of the amount of light from a 600 as you’d get from a 1,000 at 60% of the energy cost.

A 250 watt HID will illuminate a 2' x 2' garden.
A 400 watt HID will illuminate a 3' x 3' garden.
A 600 watt HID will illuminate a 3.5' x 3.5' garden.
A 1000 watt HID will illuminate a 4' x 4' garden.
You can see from this how 2 400's or 600's would be better than a 1000 watt light.

Quote:

Originally Posted by Al B. Fuct You'll put less heat into the area using a single lamp than with multiple lamps of lower power output. There's a certain inefficiency in all HID lighting- some power is wasted as heat. That efficiency factor is poorer per lamp watt in 400s and 600s than in 1000s. You can remotely locate the ballast, outside the grow room airspace, to mitigate that effect somewhat as the waste heat from that inefficiency comes mainly from the ballast. You have the aircooled hood happening already taking care of the rest.

Oh, of course, you're right, silly me. I must have been relying on the pot gnomes to light two of my 4x4 tables.

Get out of your growbooks and run an op for a while (like about 10 years)- you'll find out what works and what is just a booklearned wank.

Simple as this- 50W per sqft of HPS for a flowering area is ideal, 40w/sqft will do fine.

Just to be clear, my op has four 4'x4' trays in the flowering area. Each pair of trays is lighted by a single 1000. Works fine.

Absolutely false that a pair of 400s will work better than a single 1000. Due to ballast wastage as heat, you use almost the same amount of power from the mains- for 200w less light. A 1000 makes ~150,000 lumens, a 400 makes ~50,000. It'll take about 1100-1200W to run either a 1000 or a pair of 400s. Why would you willingly settle for 50,000 less lumens for THE SAME power input to the ballast(s)?

Silly, silly, silly.

This little twist in the thread brings to mind a problem I've always had with cannabis growing forums. Because there's few really definitive cannabis grow guides- even Ed Rosenthal's older stuff is now largely disproven- everyone THINKS they know best.

I'm not going to get into wankfests over 'plant available watts' or other such nonsense. When you go out to buy HPS lighting, you get one useful figure you can use for broad comparision- and that's the lumens number.

I'm going to claim I know better than MOST of the growbooks, for one simple reason. I've been running a highly productive grow op since about 1997 (with pix posted in my gallery)- as well as a few really ordinary ones for a couple of years before I got it really nailed down.

There's only one growbook I trust- 'Indoor marijuana Horticulture' by Jorge Cervantes, Robert Connell Clarke and Ed Rosenthal (ISBN 1-878823-17-5) though my copy, dated 1993 (and autographed by my pal Jorge, can you believe it?) is starting to show its age.

agreed 1k is superior to 2 400w it would take 1200 watts to equal the output. and a 1k foot print is 5x5 easy

Well, SHIT. My entire photo gallery has been deleted except for ONE pic of my mums!

WTF?!

I delete pics from my local HDD after posting for security reasons. I can take more pix, but what a pain in the ass.

Hey Admin, what's going on?

well I went ahead and shoe-horned ths 1000 watter in my space, and it just raised the temps maybe 3 or 4 degrees no big deal, I've also got clones just about ready so I had to redo my old veg space with a 400 sodium just to get started whilst my other grow still going. when thats over i'll just move everything to it new home with the bigger light, never thought the 1000 wold be so much brighter than 800 but man it is. Cant wait to get this other grow started, as ive really been wanting to do this kind of grow, thanks for all the info, youve helped out alot!!!!

Thanks for your comment abs.

While the 50W/sqft rule of thumb is the ideal, anything over about 35-40W/sqft of HPS lighting will give good results in a SoG op.

The SoG technique, where lower branching is pruned off early in the flowering cycle, greatly increases the airflow around the plants and also reduces shading of the parts of the plants (that are not pruned off). You can get away with somewhat less than the ideal 50w/sqft figure because of the removal of excess foliage.

The main part of the plant grown in SoG- the big fat colas on the top of the mainstems- will be getting plenty of light at 35-40W HPS per sqft.

That 3-4 degrees can be a problem... like I said before, keep an eye on your air temps. Use a digital thermometer which has a peak memory feature. Increase your ventilation capacity if you can't keep air temps under 28C.

Those 1000s are EFFING bright, aren't they? Seriously, don't look at a burning 1000w lamp if you can avoid it. Wear a cap with a visor in your op to protect your eyes.

The 400 will raise mother plants just fine for you. A 400 HPS has worked for my mums for a lot of years, but one could probably get away with a 250 MH or HPS.

Happy to share any info with you that I can!

*sigh*

Here's what happened...

grrr...grumble... growl...