400W Mh vs 400W HPS - will they cover the same area?

Discussion in 'Grow Room Design/Setup' started by HaHend, Jan 29, 2014.

  1. Hi,

    I read that 3'x3' (9 sq ft) is the ideal size for a 400W HPS bulb (~45-50W/sqft).

    However a 400W HPS bulb has around 60.000 lumens whereas a 400W MH bulb has around ~35.000-40.000, so roughly 33% less lumens.

    Therefore I asked myself if the coverage area for a 400W MH woud drop by 33% compared to a 400W HPS bulb?

    If that would be the case the light coverage would only be ~ 2.5'x2.5' (6.25 sq ft)?e

    What are your experiences? How much area can your 400W MH cover?
  2. #2 GOLDENBOY, Jan 29, 2014
    Last edited by a moderator: Jan 29, 2014
    Do you only have the mh bulb? Lots of people use the hps light from start to finish with no problem. If your using your mh bulb just for veg and then switching to a hps I wouldn't worry about it to much. Youll still have good coverage. When your plants are small they dont need as much light as when they are budding. Sent from my SGH-I747M using Grasscity Forum mobile app
  3. #3 snoopdog6502, Jan 29, 2014
    Last edited by a moderator: Jan 29, 2014
    The MH bulb will work just fine. They even do a fine job of flowering.
    I like to grow with mh, I believe the UVA rays from MH make for better quality.
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  4. #4 Tunga, Jan 30, 2014
    Last edited by a moderator: Jan 30, 2014
    Yes as snoopdog said a 400w MH will work just fine a 3x3 tent.
    Remember that as seedlings the plants don't necessarily want to be blasted with insane amounts of light, so the little less light a MH puts out compared to HPS is not so bad. In fact I usually keep my 400w MH a little higher than I would normally during the first week or so to keep it from burning them. Then by the time they're a good size and ready to flower, the HPS goes in. :)

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