Oh and some more info, growing area should be 3' x 4' which works out as I think one 400w mh, or possibly one 250w hps.

RP1

And some supplemental northern light during winter from window.

RP1

I knew HPS were brighter for the same wattage but didn't think it was double as much. The MH spectrum is, however, much broader and it is a much more liveable with light, colorwise. HPS are almost always used when supplementing decent amounts of sunlight as efficiency and lumens outweigh issues of spectrum which are handled by the natural light. IMO a north window doesn't rate as much of a light source and the HID lamp is pretty much on its own. This would favor the MH lamp for that reason alone. But I have to wonder if the time for HID lamps is not pretty much at an end. The ballast and fixture of an HID system can last for a good many years and the bulbs should be good for at least a year per replacement. In much less time than it will take you to make use of your investment in the HID technology CFL and/or LED technology will be the light sources of choice for your application. I can't believe that a couple or three 125W CFL couldn't give you more than enough light for your winter garden. No ballast worries and brooder lamps (ceramic mogul sockets) are less than $20.00.

H

Unfortunately I can't use fluoros because of our cat, or at least, I don't think I can still.

Yeah the 400w hps sylvania gro lux is 58k lumens, similar metal halide is 35k.

It's £65 for the reflector, ballast and bulb. Fluoros would be more for the same amount of light.

Soo, metal halide then?

RP1

What is it about cats that makes them incompatible with CFL?? That one I've never heard. Mercury (in retrograde)? 60 cycle AC hum triggering latent homicidal instincts? Humans are simply highly evolved cats and HID is just jumped up fluorescent technology so, if CFL is bad for cats then its also bad for people and by extension (the distributive property) so is HID. But if you really are jonesin' for tens of thousands of lumens to whomp the species Cattleya with (whoa...) then MH I think would be the way to go OR a combo head like John (aerides) that combines a 250MH with a 250 HPS. Ah, yes, now that I think of it I recall discussions of the UV light from discharge lamps being harmful to pets. Actually it is harmful to people too (remember) but we don't usually crawl around on our hands and knees in the grow room. You should be happy to know that CFL are much less harmful a source of UV light than MH or HPS. Get sunglasses for you kitty(ies) or keep them out of the lighted area or just let them go for it. Years of evolution have no doubt taught their corneas (and ours) to deal with significant amounts of UV (a day at the beach is another thing entirely).

H

Naw it's the 60hz cycling which brings on epileptic fits in one of our cats and I don't think I want to risk bringing one on even when the drugs she's now on should prevent it.

Nothing to do with what they actually emit in terms of light.

Besides, why would I want to spend £60 + £60 on bulbs and a reflector when I can just spend £60, get more lumens and the bulbs are only £10 to replace?

RP1

Did I hear my names mentioned?

If you can't use Howard's suggestion of CFL, I'd sure try to go with 400-500 watts of MH if the fixture is going to be in a living space. HPS color is highly obnoxious. The loss in brightness from HPS to MH is immediately apparent, but if you are not trying to grow light grabbers (like standard cattleyas) and if you are only wintering over, it would be worth a try. How many months will the plants be indooors?

John

Hm, yeah there shouldn't be any plants which need hideous amounts of light. Plants should be indoors for 5 months, maybe less?

I am thinking of just partitioning it off with a dividing wall, in which case maybe I could get away with hps.

RP1

"Besides, why would I want to spend £60 + £60 on bulbs and a reflector when I can just spend £60, get more lumens and the bulbs are only £10 to replace?"

You definitely get more lumens from a 400W HID than a 125W CFL but you should! In the US HID systems cost well over $200 in the 400W range and the bulbs are in the $50+ range. That is a bit higher than your figures. Conversely I think one could get even a high wattage CFL for the same price as a HID lamp and it would not need a ballast, its already built in. Somewhere there are 200W CFL which give 200W HID systems a serious run for the money. I also am not certain that HID don't have some sort of 60 cycle flicker, I don't see why they shouldn't. There is considerable thermal lag in an incandescent filament which keeps its output constant despite the fluctuation of the current but discharge envelopes respond very quickly to the perturbations of the source current so you might want to check out their characteristics. Maybe you have already, just covering the bases.

H

Naw I think hids use high frequency ballasts which oscillate ~40khz.

Yeah over here a budget ballast + bulb + reflector = £65, the bulbs are around £10-20 (comes with one), whereas each 125w envirolite is £25, of course i'd need 3, then the reflector is another £60.

Metal halide then? I probably won't need the extra lumens from sodium, but I could always switch the bulbs.

RP1

RP1, just so you know, you can't change your mind about the bulb type after you buy the ballast, unless you get a special switchable ballast. Regular ballasts are specific to either HPS or MH.

J

Ah, I figured since it was the same ballast, must be a different variation. Looks like all the votes are for mh so I'll look into that.

RP1

Incidentally, see here under lights - hobby

http://www.3countieshydroponics.co.uk/system/index.htm

I wonder why MH is more expensive than HPS? I'm guessing the ones that say 'complete with MH and HPS bulbs' are dual systems like mine, with wattage divided equally.

J

Yes, you would think with the fact that the MH is so much less efficient a source of lumens that it would be cheaper if anything but the fact is, the light is much nicer to live with and for this reason they probably sell more MH systems to the people that really don't use them for hardcore purposes for which aesthetics become secondary. What does a Capitalist do with a situation like that? Right you are.

H

I use HPS as my only source of lighting. I have two 430 HPS on light movers. I would NEVER EVER chnage them. They are the best bang for the buck; more lumens, more growth, better roots, etc. I use Sun Argo bulbs that have enhanced blue spectrums in them.

I have a separate grow room in the basement, I admit that. It would be very hard to use these lamps in a common household area because they give off a very unnatural, orange-hued light. But since they are in a specific area only used for growing, I have no problem. If this is your situation, get HPS over MH!

Christian

Christian, what orchids do you grow?

John

That's the key question... you have to know what you can grow well under any specific light system....

As for me, I mainly grow multifloral paph species and hybrids (they really do the best). I also have a large number of mini and compact catts. They grow and blomm without any problem. I also have some bulbos and aerangis/angrecums.

These lights put out a lot of heat and I use it to heat the grow room. I keep it constant at 83 degrees day and 60-63 degress at night. It took a lot of trial and error to learn how to maintain a constant environment.

Christian

According to my supplier, my system, which is 250 watts HPS plus 250 watts MH produces 49,500 lumens.

A system similar to Christian's (430 watts blue-enhanced HPS) produces 55,000 lumens.

This seems a significant difference. 5,500 lumen difference, for fewer watts. The decrease in watts is icing on the cake (cheaper and cooler). What I really want to know is whether the 5,500 increase in lumens would make a noticeable difference in growth.

I'm assuming if Christian was getting unnaturally elongated growth from blue spectrum deficiency he would have mentioned it. Personally I don't know whether a 25% boost in blue spectrum eliminates that problem or not.

Comments?

Thanks,

John

Plants (orchids) are used to a very balanced spectrum of light. There are going to be 'issues' when growing under artificial light especially HID sources which were not designed with plant growth in mind. Personally I don't think the 5,000 lumen difference will make a noticeable difference in growth being that it is concentrated in an area of spectrum that is fairly narrow and also falls right in the part of the photosynthetic response curve that is least efficient. I also wonder whether a 25% increase in what is almost nothing makes a significant difference. For now the smart money teams whatever light system happens to fit in your budget and energy plan with a decent amount of regular sunlight to fill the gaps. Failing that the combo head (MH + HPS). Every now and then I mention a low budget version of the combo head for those that must grow in basements and don't have the $$$ for HID. Besides the use of a strong CFL (85W range or multiple 42W range) which should be biased toward blue spectrum (6500K+) is the addition of 25% or so ordinary incandescent light. We keep getting told how inefficient incandescents are and we pony up $6.99 up to $15.00 and more for CFL that are supposed to last five years and they burn out in six months and you are burned because you don't have any documentation. You can run a 60W incandescent that cost 99c for quite a few months before you come anywhere near $15.00. No you cannot grow with it alone but the je ne sais croix that it adds to the CFL light is IMO what separates those struggling to grow under artificial light as a makeshift winter lifesaving stop-gap from those who embrace artificial light growing as a cultural method all its own with significant advantages.

H

John,

I honestly have had no odd or elongated growths on my plants. I was worried about that when I invested in HPS two years ago but it never ocurred. Thank goodness.

About your other question.... I have no idea. All I know is the 430 HPS with the argo sun bulbs (enhanced blue) really works well for me and blooms what I want to bloom. Thus, I can't complain. I do put my plants outside for 4 months during the summer and I am sure this helps a lot.

I remember being overwhelmed when I had to make a decision on what kind of light system to buy. Been there, done that. I am sure your decision will result in happy plants though.

Christian

Thanks for your response Howard. I'm sure you are right. But just for my own info, I wasn't clear on your assertion that the additional lumens fall in a fairly narrow and useless part of the spectrum. Is it a foregone conclusion that whatever engineering was involved in producing the enhanced lumen count would only affect yellow light as opposed to positively affecting the red and blue parts of the spectrum as well?

There is also a Hortilux 430 watt blue enhanced HID bulb now that offers in excess of 58,000 lumens (in a given reflector) as opposed to the Son Agro that offers 55,500 - both of which exceed mine at 49,500. I tried to find a spectrum analysis of it, but the best I could do was a potgrowers chatlist. But they seem to like it, report cooler growing, whiter light and bushier growth. That's getting really tempting now, especially with Christian swearing by his Son Agro.

J

Oh, that explains it. Your plants are getting "real light" during prime growing season. Oh yeah, this was RP1's thread originally. What am I doing in this stupid city!!!!!

Back to Plan A. Ditch the orchids, remodel the kithen.

J

Doh, for pitys sake. Changed my mind yet again. Going for the hps 400w, it is a switchable ballast so if need be I can always buy a metal halide bulb.

RP1