Dr. Watt tackles Double-Ended Metal Halide bulbs with a huge versus test - DE-MH/SE-MH/CMH (LEC)/DE-HPS. Best Lighting Products Provided Here: monstergardens...
Good video, well presented. If I may add one factor though: Light maintenance. We see that MH lamps hasve an extremely bad light maintenance over time. So even the Genesis, though a great output initially, will lose light pretty fast. Some HM lose up to 20% in less than 6 months. So in order to maintain light levels and yield. you would have to exchange these much more often. CMH on the other hand, but perticularly the Philips CDM 315 (Philips' name for CMH) has a far superior light maintenance: about 8% losses per year of use. What was not very clear to me though is the reflector used. Was it the same reflector for the DE and SE? That can make a huge difference to your measurements in the tent. We use an Ulbricht sphere for this, So indeed, the operating costs of MH are much higher than HPS. You were spot on identifying our worries as well, and we should add that single jacket MH ar NOT suitable or allowed in open fixtures, they do not have the /O (suitable for open fixtures) classification. This also has to do with the fact that MH arc tubes do emit vast quantities of UVC light. A broken out balloon does not cause the lamp to always switch off automatically, which can lead to extremely dangerous levels of UVC. Secondly, MH lamps operate under a much higher pressure than HPS. It is called HPS because the pressure in the arc tube is higher than a low pressure sodium lamp, which is more like a CFL or neon type of lamp. So when a Mh lamp fails, it fails explosive as you have demonstrated in your video. That is why /O lamps have a special protection against this, usually by an extra glass shield inside the lamp, or, indeed, a double jacket. Only these types of lamps are suitable for open fixtures. Last, but not least: Indeed, most HPS fixture manufacturers do not allow you to use MH lamps in their fixtures and it will void the warranty. This is for two reasons: 1. MH ballasts have a re-fire timer: they wait a couple of minutes for the lamp to cool down before re-igniting it. Immediate re-ignition can lead to explosion of a MH lamp, which we have actually been able to do in our test lab. I assure you, an exploding lamp is not pretty, blasting hot glass of over 1000C into your room (or ducting if it is an air cooled lamp). 2. A MH lamp can in some cases start acting as a rectifier. This is a technical phenomenon but suffice to say that a failing MH lamp can destroy your HPS ballast, which is not made to drive MH lamps. Other than that of course the fixtures were only approved by UL and CSA for very particular lamps, the DE HPS. Using other lamps that are not approved in your fixture is not in accordance with the NEC (National Electrical Code) and UL guidelines. It could even void your insurance in case of a calamity. Remember, UL was founded by insurance companies to increase safety. For the rest, I enjoyed this video. Well done!
Absolutely best RU-vid channel on growing lights. Very scientific, professional, to the point, high quality content and very useful data. Huge thank you guys! Are you planning to do similar test for Philips CMH vs LEP vs LED ?
Wow such great information in all the episodes. I am super impressed with the amount of facts, the well designed testing and the comical yet professional video editing! keep up the good work
Philips CMH, make sure you get that. Mixed with a diy or prebuilt Cree or Citizen COB LED (cob led > purple hue outdated LED tech), you will get high end resin and yield with a lowest watt per gram cost
There is, just be on the lookout to ensure the proper ballast is driving the bulb. DE CMH bulbs should NOT be placed into a fixture that also powers 1000w DE HIS lamps. The frequency used to push the DE HID is 100+kH and the frequency required to push the DE CMH is 100-200H, what happens when you over-power a CMH lamp? It runs the potential of exploding.
