MH with 400-watt Lumatek Question

[TorturedSoul]

Anyone use a (400-watt) MH bulb with a 400-watt Lumatek ballast running on the 250-watt setting? I was asked about doing so. Specifically, the guy mentioned that he had read that dimming the 400-watt MH bulb with that ballast was not recommended and that he was concerned that doing so might either blow the bulb or shorten its useful life.

I don't have a clue. Anyone have experience with this bulb/ballast combination (and dimming it)?

 

[Hogdady]

Hello my friend,

Do NOT (according to Lumatek) run a 400w lamp on the 250w setting. The lamp must be changed to correspond with the wattage setting. The dimmable models have a selection switch for dimming each wattage lamp.

HD

 

[TorturedSoul]

Do NOT (according to Lumatek) run a 400w lamp on the 250w setting. The lamp must be changed to correspond with the wattage setting. The dimmable models have a selection switch for dimming each wattage lamp.

Do you have a link to the information on Lumatek's site or in one of their manuals/etc. that are posted around the Internet? I searched around, but the only such reference I could find was a statement in one of the manuals (not sure if it is current) that 400-watt MH bulbs should not be used in 600-watt ballasts. Couldn't find anything about not running a 250-watt MH in a 400-watt ballast (which seems to be an advertised feature) or dimming a 400-watt MH in one.

AfaIK the ballast in question is a dimmable one. Not sure there either. Will check sometime this weekend. I think it's new enough that it doesn't have SL, 100%, 75%, 50% - but I'm not positive.

I did read (one of Lumatek's .PDFs) a statement that dimming HPS bulbs would show a (slight) shift towards the red spectrum but that it was not enough to cause any problem for the grower.

I also read that the watts drawn on a 600-watt Lumatek ballast running @ 600 watt setting was 634 watts according to a UK site that tested it. Not sure what method they used to test. Assume it was a 240v ballast since UK mains supply is 240v nominal.

And that their 240v only models were somewhat more efficient than their 120v versions but that they were working on a new MOSFET which should help efficiency a lot on the 120v versions. (I suspect that the information was from older Lumatek documentation, because they've had models that work on either automatically with the switch of a cord for a few versions now.)

And that when running 240v, to make sure that the cord supplying the ballast carries two 120v lines and a ground - not a 240v line, a neutral, and a ground; and that when running a timer with a 240v ballast to make sure that the timer cuts both hots instead of just one.

And that when running a 600-watt ballast on the SL(?) setting, it runs the bulb at 662 watts - which might mean that a 400-watt Lumatek could run a 430-watt HPS bulb on the SL setting without any issues, assuming it fired properly. I'm not sure, since 430-watt bulbs called for different ballasts (differently rated components - maybe different firing voltage, I can't remember exactly) but a lot of C&C ballasts could fire/drive them.

When I visit this weekend, I'll probably either give him Lumatek's email address or just climb up his barn wall and yank the bulb from his old MH security light so he can try dimming it himself (depending on the weather and how my shoulder/etc. is functioning). If it pooches the bulb he'll only be out $15 or so for something that he only uses a couple times per year.

Will try to remember to post findings.

EDIT: One problem with information found on the Internet is that old information is often not pulled even when it is superseded or found to be incorrect.