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Self ballastered MVBs ok to be set on dimmer switc

Discussion in 'Habitat Lighting' started by replover, Mar 7, 2006.

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  1. replover

    replover Elite Member


    Is it ok to control temperature emitted by the Mercury vapor bulb by using a dimmer switch? I know people use dimmer switches to control the amount of heat radiated from a regular light bulb/basking bulb, but I am asking about MVBs, specifically, Rep-Pro's Self Ballastered MVB.
    Does it affect UV output? Wear out the bulb somehow?

    The climate's starting to warm up a bit and this is stumping me. I can't adjust the distance of the bulb constantly, not can I change to a new MVB everytime the weather changes.

    I currently have two bulbs. One MVB 160 Watt and one regular basking bulb 150 watt. The MVB shines on its favo basking spot, but the other light keeps the other end of the platform warm. Don't know if I should turn off the basking bulb, or dim it. Would that correct the temperatures overall?Because the heat from the basking spot would radiate elsewhere? Or will the MVB basking spot still be too hot?

    While I'm at it. Do lower Wattage MVBs emmit less UVB? Or just less heat and light and use less electricity?
  2. jmherp

    jmherp Elite Member

    Nope, im pretty sure they wont work like that, i will keep tripping itself off...

    You can try to dim the normal basking spot to see if that helps, but you wont be able to use a dimmer on a MVB...
  3. replover

    replover Elite Member

    Ok I understand. Would like to know the exact mechanism of how that works though. Perhaps Dominick would be able to explain that as he works with these bulbs?
  4. Dominick

    Dominick Founding Member

    Jayr is correct, you cannot dim MV lamps.

    Mechanics behind it: Mercury vapor lamps use an arc tube in place of the filament in standard lamps. Arc tubes are rated at a specific wattage, which makes them fire and ignite the Mercury, creating the vapor which emits the light. When the wattage drops below the arc tube rating, as would be the case when you try to dim them, the arc tube would simply shut down and go into a reset cycle. After the 10-15 minute cool down, the arc tube would try to re-fire, but not having enough wattage, would once again shut down. This cycle would continuously occur until the arc tube failed altogether.

    Jayr made a good suggestion to dimmer the other lamp instead.

    Lower wattage bulbs emit less heat, the UVB is generally the same. ;-)
  5. zaroba

    zaroba Elite Member

    maybe you could work out another solution to limiting its heat output.

    most barbacue grills have the holes with the sliding metal over them to open and close the holes.
    maybe a similer, but larger, mechanism made out of sheet metal would work to limit some heat. the metal itself would absorb heat, but overall, it might keep the heat at the top of the tank preventing it from radiating down to the bottum of the tank. once the metal gets really hot though it might not help much

    another solution is to use fans on a thermostat.
    if the viv has a vent on each side of it, you could rig up 2 small fans to run on a thermostat.
    one on one side to blow the hot air out, and another on the opposite side to suck cooler air in from the room.

    yet another and probably more effective solution would be both of the above.
    in the first idea, the metal after a while would get hot and be of less use. however, if the fans in the second idea are creating a cross breeze accross the metal sheet, they will keep it cooler and allow it to absorb more heat from the light then is going to the bottem of the tank. if the fans are on a thermostat keeping the temp withen a few degeress of what its sert, it'll turn on and off the fans as needed, and small fans don't use much power. it might act like a heatsync and fan on a pc cpu but on a larger scale.
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