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Fig3825
Senior Member
Posts: 286
Joined: Fri Jun 17, 2011 7:40 pm
Location: Alexandria, Virginia

Grow Light

Hi all,
I have two of these:
[img]https://ericson.thomasnet.com/Asset/1004-MHX-25.jpg[/img]

Here's a link to the [url=https://ericson.thomasnet.com/item/construction-lighting/lite-400-watt-metal-halide-temporary-light-fixture/1004-mhx-25ps]manufacturer's product page[/url] if you feel you need it.

They were given to me by an electrical subcontractor working on one of our projects. Most of the specs are irrelevant for my question, but I want to give as much info as I can before asking my questions. I truncated a lot, but here are the listed specs that I feel are relevant:


-EISA Compliant - Pulse Start
-High light output & long lamp life provide cost effective & low maintenance operation
-Open-air ballast for cooler operation
-Multi-Tap ballast:120V, 208V, 240V, 277V:Factory wired at 120V
-Clear 400 watt metal halide lamp included
-Metal halide lamp has a color temperature of 4000K
-Mogul-base porcelain Type O exclusion "pink" socket

I am currently only using one of the two I got. The light has a factory reflector available, which I bought and installed in lieu of the wire protective cage.

My questions are thus: S
Specifically, the color temperature... After doing some research, the 4000K temp doesn't do a lot for plant growth based on what I read. For growth, most HID MH bulbs are 5500K. Is this correct? I'm basing my information on this chart:

[img]https://futuregarden.com/lighting/PAR_chart.jpg[/img]

Secondly, the fixture has a Type O mogul base. Can I simply buy a MH bulb that fits the base and that is designed for growing (5500K) and pop it in this fixture since the ballast is designed for a 400W MH bulb?

Regarding my last question, does anyone know where I can get a 400w MH bulb, mogul base, with color spectrum of 5500k-6500K that isn't ridiculously expensive?

Should I be asking this in the hydroponics forum or the greenhouse forum? :) The vegetable forum gets WAY more hits than any other...

User avatar
Fig3825
Senior Member
Posts: 286
Joined: Fri Jun 17, 2011 7:40 pm
Location: Alexandria, Virginia

One more thing... The desired effect is maintaining growth on some japanese maples, crepe myrtles and a dwarf meyer lemon tree over the winter. I don't need any flowering or anything like that, although my meyer is currently growing lemons - but I only have one 'greenhouse' room and cannot run a HPS and MH at the same time in there, so I've decided to go with the MH. While I would like to have my lemons grow, It's not as important and maintaining good plant growth over the winter.

So, with that in mind, do I want 5500K or 6500K with regard to the bulb?

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