Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 69,886   Posts: 1,520,615   Online: 1043
      
Page 1 of 2 12 LastLast
Results 1 to 10 of 13
  1. #1

    Join Date
    Sep 2004
    Shooter
    8x10 Format
    Posts
    11

    UV Light box fan placement?

    I'm building a UV light box (tube type) using eight 24" BL tubes to make 8X10 pt/pd prints. I've gleened construction instructions from several sources, however, all directions and photos of the boxes are a little vague on fan placement. Some appear centered in a way that would cool both above and below the shelf supporting the ballasts. Others seem to be blowing across the tubes only. Can ya help a guy here? Thanks

  2. #2

    Join Date
    Dec 2002
    Shooter
    Large Format
    Posts
    6,242
    The greatest source of heat and the most prone to heat induced failure is the ballasts.
    Art is a step from what is obvious and well-known toward what is arcane and concealed.

    Visit my website at http://www.donaldmillerphotography.com

  3. #3

    Join Date
    Mar 2005
    Shooter
    ULarge Format
    Posts
    864
    Images
    24
    On my Edwards Engineering Light Box, the fan is centered to draw heat from the bulbs and the ballasts. When I build my own, larger light box, I also centered the fans. The one statement that you made which bothers me, however, is "Others seem to be blowing across the tubes only." My fans are set to draw the air out of the box, not to blow air across the tubes. If I place my hand next to the fan on the outside of the box, I can feel the air flowing out, not in.

  4. #4

    Join Date
    Mar 2003
    Location
    Greenville, SC
    Shooter
    Large Format
    Posts
    4,813
    Images
    5
    Quote Originally Posted by Allen Friday View Post
    On my Edwards Engineering Light Box, the fan is centered to draw heat from the bulbs and the ballasts. When I build my own, larger light box, I also centered the fans. The one statement that you made which bothers me, however, is "Others seem to be blowing across the tubes only." My fans are set to draw the air out of the box, not to blow air across the tubes. If I place my hand next to the fan on the outside of the box, I can feel the air flowing out, not in.
    I don't believe it matters whether the fan pulls the air out of the box or blows it in. Either way you will get the air exchange, because if you blow it in it has to come out.

    My unit of twelve 48" BL tubes has one 4" diameter fan on the side that blows air over the tubes. I know that this is efficient because I expose with a light integrator and the units of exposure remain constant in terms of one second = one unit, even with very long exposures of 15-30 minutes. If the system were not working the tubes would over-heat and the units would b longer.

    Sandy King

  5. #5
    bruce terry's Avatar
    Join Date
    May 2006
    Location
    Cape Fear NC
    Shooter
    35mm RF
    Posts
    190
    Quote Originally Posted by sanking View Post
    I don't believe it matters whether the fan pulls the air out of the box or blows it in. Either way you will get the air exchange, because if you blow it in it has to come out.
    Yeah, air is air I suspect. The fan mounted on the flank of my (homemade to Edwards specs) EELB w/12 24" tubes blows into the box and out the opposing vent cut-outs. Bottom quarter of the 4" blade-arc cools across the tubes, second quarter pretty-much wasted against the 3/4 plywood mounting platform, top 50% cooling the six hotter ballasts. Never a problem even running for hours. Superfluous info, just adding to what's been said.

    Bruce

  6. #6

    Join Date
    Mar 2005
    Shooter
    ULarge Format
    Posts
    864
    Images
    24
    Thanks for the info Sandy and Bruce. I didn't know if it would make a difference or not. I was wondering if a fan blowing directly on two or four of the tubes would cause some kind of temperature fluctuation that might lead to a difference in the output of the bulbs. Apparantly that is not the case.

    Allen

  7. #7
    donbga's Avatar
    Join Date
    Nov 2003
    Shooter
    Large Format Pan
    Posts
    2,056
    Quote Originally Posted by Allen Friday View Post
    Thanks for the info Sandy and Bruce. I didn't know if it would make a difference or not. I was wondering if a fan blowing directly on two or four of the tubes would cause some kind of temperature fluctuation that might lead to a difference in the output of the bulbs. Apparantly that is not the case.

    Allen
    [FONT=Arial][SIZE=2]I've made several 12 tube UV units and I've set the exhaust fan up so that it draws air across the tubes. The sides are ventilated to allow cool air to enter through the sides of the exposure unit.

    I also ventilate the top compartment that contains the ballasts, although the air vents there are passive but large.

    [/SIZE][/FONT]
    Don Bryant

  8. #8

    Join Date
    Jul 2003
    Location
    New Mexico
    Shooter
    Large Format
    Posts
    239
    UV light box

    I have not put fans in any of the ones I have built, but the top of the box is covered with peg board, so that the ballast area vents out the top.

    Part 2 is that my print drying screens sit on top of the box, starting at 4"s up prints dry in about 30min from the riseing heat of the box. Like AB says it a multi tasker.

    Jan Pietrzak


    Quote Originally Posted by donbga View Post
    [FONT=Arial][SIZE=2]I've made several 12 tube UV units and I've set the exhaust fan up so that it draws air across the tubes. The sides are ventilated to allow cool air to enter through the sides of the exposure unit.

    I also ventilate the top compartment that contains the ballasts, although the air vents there are passive but large.

    [/SIZE][/FONT]

  9. #9

    Join Date
    Apr 2006
    Location
    Aurora, OH
    Shooter
    ULarge Format
    Posts
    76

    Fan Cooling of Fluorescent Tube Light Sources

    OK, the engineering side of me can't pass up this one up. Take a look at Jon Edwards light source plans on his web site for an excellent deisgn example - www.eepjon.com. I've been using his units in workshops and classes at local universities for 5 years. The single box fan in the 11x14 unit draws air over both the tubes and ballasts through holes cut in the opposite side. The internal shelf to which both the ballasts and the lamps are fastened creates a baffle separating the two chambers on three sides. The fourth side is open from top to bottom which is where the box fan resides thereby allowing air draw through both top and bottom chambers. The top chamber has three holes and the lamp chamber has 5 holes giving a ratioed air flow between them. For this design to provide proper ventilation across both tubes and ballasts, you do need the hinged flip down door at the front where you insert the contact printing frame. By closing the door, the chambers are sealed and air flows across the box from side to side cooling all of the components. If no door is used or it is left open, the open door becomes the primary inflow bypassing the tubes and ballasts.

    The ballasts should be ventilated in addition to the tubes. Sandy is correct that by giving good ventilation across the tubes, variation in light output is reduced by keeping the tubes cooled. But a ballast will fail prematurely if it is not also cooled. The operating life of the ballast will be extended if it is also ventilated. I built a large light source years ago for the University of Akron. Ventilation was by convection only through holes drilled in the plywood top. One of ther ballasts failed 3 weeks into the class due to excessive heat build-up over the day.

    As far as push vs pull, drawing air into the box through vent holes is a better design than pushing air into the box. I learned this from engineers who design industrial control equipment for 0-60 drgree C environments. Virtually all industrial control cabinets draw air into them and exhaust the warm air. With properly placed inlet holes, this design provides better air flow and fewer eddy currents inside the box. As an aside, ever heard of blowing air into a darkroom for ventilation rather than drawing it out? Use Jon's design as a guideline in your construction.

    Bob
    Last edited by bobherbst; 01-07-2007 at 10:11 PM. Click to view previous post history. Reason: Additional comments

  10. #10

    Join Date
    Sep 2005
    Shooter
    ULarge Format
    Posts
    86
    I have an Edwards print drying box that pushes air into the box rather than pulls it. It seems to work pretty well. Also, having built five darkrooms, each with a different ventilation system, I have found that pushing air into the room and adjusting the passive exit vents maintains a positive pressure in the room and prevents dust from entering - by far the best plan I've been able to come up with.



    Quote Originally Posted by bobherbst View Post
    OK, the engineering side of me can't pass up this one up. Take a look at Jon Edwards light source plans on his web site for an excellent deisgn example - www.eepjon.com. I've been using his units in workshops and classes at local universities for 5 years. The single box fan in the 11x14 unit draws air over both the tubes and ballasts through holes cut in the opposite side. The internal shelf to which both the ballasts and the lamps are fastened creates a baffle separating the two chambers on three sides. The fourth side is open from top to bottom which is where the box fan resides thereby allowing air draw through both top and bottom chambers. The top chamber has three holes and the lamp chamber has 5 holes giving a ratioed air flow between them. For this design to provide proper ventilation across both tubes and ballasts, you do need the hinged flip down door at the front where you insert the contact printing frame. By closing the door, the chambers are sealed and air flows across the box from side to side cooling all of the components. If no door is used or it is left open, the open door becomes the primary inflow bypassing the tubes and ballasts.

    The ballasts should be ventilated in addition to the tubes. Sandy is correct that by giving good ventilation across the tubes, variation in light output is reduced by keeping the tubes cooled. But a ballast will fail prematurely if it is not also cooled. The operating life of the ballast will be extended if it is also ventilated. I built a large light source years ago for the University of Akron. Ventilation was by convection only through holes drilled in the plywood top. One of ther ballasts failed 3 weeks into the class due to excessive heat build-up over the day.

    As far as push vs pull, drawing air into the box through vent holes is a better design than pushing air into the box. I learned this from engineers who design industrial control equipment for 0-60 drgree C environments. Virtually all industrial control cabinets draw air into them and exhaust the warm air. With properly placed inlet holes, this design provides better air flow and fewer eddy currents inside the box. As an aside, ever heard of blowing air into a darkroom for ventilation rather than drawing it out? Use Jon's design as a guideline in your construction.

    Bob

Page 1 of 2 12 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin