View Full Version : HID bulb life

08-20-2009, 03:11 PM
I know how the bulbs will burn for 24000 hours and all, what I am really interested in is how long they really produce good growing light brightness and spectrum and how their life is affected by ballast type and burn duration times.
So, specifically, I am using the Lumatek 400 & 600 watt digital ballasts.
The 600 watt is used 12/12 and I currently use a Solarmax HPS bulb.
The 400 watt is used 18/6 and I currently use the MH "Chrome dome" reflectorized lights.

I am most interested in how often I should replace the 600 for flowering.


08-20-2009, 07:13 PM
I do know 1 thing. HPS bulbs generally have a longer life than MH.
Lumatek rocks.
As the Lumatek tech rep said, " the lumatek is the caddilac of ballasts"
I was also recently looking into this issue and was trying to do some math based on 18 hour days.
I came to my own conclusion that changing bulbs every 2-3 grows was a waste of money.
I was wrong.
I just put new bulbs in and really noticed a difference.
Definately change them every 2-3 harvests or once a year at the minimum.
If your spending your hard earned $$ on power you want your lights running as close to optimum as possible.
Don't try to save a few $$ and put this off.
It is worth it.

08-21-2009, 10:55 PM
i would say every 6 months, but it might depend on light manufacturer.

some people might chime in and say longer but i would change at this time before it burns out and the light quality diminishes, if you dont certainly know theres always experimenting.

take pictures of the first crop from when the bulb was new to the second crop then the third crop and see if theres any quality lost in the plant. if not then you would obviously figure out that you would only need to worry about when the light would burn out and change it before it did to avoid complications.

08-22-2009, 04:26 PM
Read lamp manufacturer's data on lamp life.

I use hid, both hps and mh on 16 hr/day cycle and the lumen falls below 85% in about 17,000 hrs or 3 years.

08-25-2009, 05:48 PM
Here is the interesting thing... I just put a new 600 HPS Solarmax in, but first I used a light meter, a real quality handheld photographic light meter, to measure the brightness of the old Solarmax. I saw that the old bulb had the same reading as the new one, so brightness or lumens have not degraded.
Now this old bulb was started around Jan 1, 2008 and has been burning 12 hours per day ever since. About a year and 3/4. That is only about 7250 hours, far short of the advertised 24000 life.
Now, why did I bother to change the bulb? Well, my yields have been decreasing and I am not sure why. Maybe it is the heat of summer in the room although I got real good yields last summer under the same basic conditions, maybe it is the quality of the light... I am not sure so I am trying everything. I believe my feeding is OK because I have gotten great yields on the same basic regimen, the schedule Fox Farm publishes.
I grow in FoxFarm Ocean Forest and use their nutes as well. I use molasses near the end of flowering too. I was getting great results but lately things aren't so good. I got lax and fell into a routine for a while and overwatered by not being careful and ruined a whole crop :( so I started chrecking the soil and moisture and cut way back but I seem to be getting stunted plants and paltry yields. I am obviously doing something wrong... or the quality of Fox Farm has gone to hell, which is most doubtful.
It isn't the strains - I am growing from the same clones and/or seed batches as I have before.
That 's why I am interested in learning if I really should be replacing the bulb yet or when... I know brightness is the same, but I have no means of measuring the color and quality of the light. It looks the same to my eyeballs. It will, of course, take a long time to see if the bulb change has a dramatic effect. All I know is I need to get back on track and not get over-confident again... :cool:
Any solid info on light quality degradation would be most welcome.

Sunlight Supply
08-26-2009, 09:55 AM
There's a thing called "lamp maintenance curve" you can read about it on I believe Philips website. Basically even though the lamps say they have 24,000 that's the average life until the lamp goes completely dead. The hours in between that time the lamp slowly decrease the output and color spectrum. First, the naked eye will not be able to see true color spectrum or output (sure you will be able to if there is a dramatic change in output). Gasses and salts found in lamps burn out as the lamps are fired. The salts that create the bluer spectrum tends to burn out quicker. So if you notice lower yields with a lamp that has been burned over 5000 hours it's due to this and a lower intensity. Brand new lamps usually take about 100 hours of burn time to hit the peak of the initial lumen output. So your test may have reflected this. Try again after 100 hours with the meter on the floor, same reflector, same ballasts, same hanging height, and without plants or anything around that might cause shadowing. Usually, what we have seen is a drop in about 10-15% lumen output after about 5000 hrs, but what you can't messure is the colors that fade after this time. It pays for itself by replacing lamps at least once a year (between 4000-5000 hrs), MH you should replace after 6-8 months they tend to burn out quicker.