Dendroboard banner
1 - 20 of 40 Posts

·
Registered
Joined
·
4,029 Posts
Discussion Starter · #1 ·
Just when I thought my tank was ready for my tinc to move in, I put my thermometer in. With 2 x 55 watt power compacts, my tank got up to 86 degrees!! :shock: What is the best way to vent the hood? I have plenty of ventilation holes, but touch the glass top, and it is warm!

I'm having trouble finding the right kind of muffin fan. I bought the 600ma 12 volt adapter that kyle recommended for ventilation, but I need something strong for the hood itself. I'm thinking about ordering from http://www.sciplus.com.

I don't understand if two fans equal 24 volts together, or if its the ma I cannot exceed.
 

·
Registered
Joined
·
707 Posts
Your voltage requirement shouldn't change. What you need to worry about is amps. The muffin fan I could find on that website draws 170mA. So with a 600mA powersupply you should be able to power 3 of these.
 

·
Registered
Joined
·
4,029 Posts
Discussion Starter · #4 ·
Cool. Isn't that the same technique by putting a halide inside a air cooled cylinder?

Good thing I've got some spare acrylic, I'm meaning to ask FCA to get me some new doors.
 

·
Registered
Joined
·
4,029 Posts
Discussion Starter · #5 ·
Brent, I'm going to try this heat shield thing. Now, do you have to unscrew the shield if you need to change the bulbs?

I'll call Paul and see if he can make one that will fit inside my fixture...

Do the fans run better if they suck air from the inside out, or blow into the hood? I would think it'd be better to have them blow into the hood personally and out through an exit hole.
 

·
Registered
Joined
·
1,373 Posts
So basically having a sheet of glass or acrylic between the tank and the lights will significantly reduce rising temps corrrect?

Luke
 

·
Registered
Joined
·
707 Posts
Darks!de said:
So basically having a sheet of glass or acrylic between the tank and the lights will significantly reduce rising temps corrrect?

Luke
It looks like 1-3 degrees F from what Brent wrote. I have a sheet of 1/4 acrylic between the tank and light. The temparature was rising about 2 degress. I added more air circulation and now it only adds about 1 degree. The acrylic probably is going to absorb some of the heat, but my guess is that since it passes so much light, most of your heat is from conduction rather than from absorbtion. Therefore, you will probably see greater heat reductions from moving the air around, creating a gap between the light source and materials that can absorb heat, and having a barrier that dissipates heat between the lights and the tank. Can't say you are going to get significant reductions, but probably a couple of degrees.

Marcos
 

·
Registered
Joined
·
4,029 Posts
Discussion Starter · #8 ·
That's what I would think too. The heat shield is elevated above the real glass top of the tank. It would be best to have two fans, one blowing through the lights, and another blowing between the lights and the glass top.
 

·
Registered
Joined
·
4,029 Posts
Discussion Starter · #9 ·
what is the best way to get high humidity without a misting system, but also have lots of air circulation with a fan?

I've wondered if piping my average humidifier (the kind that uses evaporation to add humidity) would help if it blows into the ventilation holes.

I have a water feature in the tank too.

What humidity is best anyway? Hans said his tank is only like 53% with the Netherlands paludarium style vent hood.

Brent, I have one question. I printed off your page, but I didn't know if you had an open hood design. Meaning, the lights came into contact with the vivarium air (or if they were sitting on glass).

My tank has a glass top and sliding doors.
 

·
Registered
Joined
·
1,926 Posts
Blort said:
It looks like 1-3 degrees F from what Brent wrote.
Actually the reduction was close to 10F moving from a bare bulb inside the viv to the finished product. Average daytime temp was around 88F with a bare bulb and now runs in the 77-80 range. Unfortunately I wasn't tracking min and max before the acrylic was added and I have no way of knowing the true mean so this is based on the most commonly observed temp during the day. But it's important to note it is not just the acrylic doing the work. Adding acrylic alone only dropped the temp 4-5 degrees F (which might be what your have cited). But designing the ventilation holes to produce a chimney effect provide the additional drop in temps

What this hood does is attempt to control for conductive and convective heat gain in the viv. It doesn't control radiant heat gain directly because the light energy at least into the near infrared (and probably into true thermal but when I tested solacryl, I couldn't measure above 850nm) goes through the acrylic into the vivarium. However, much radiant heat is absorbed by the hood and reflector and can be removed through convection through the vent openings.

This hood doesn't use fans. Instead it relies on the heat rising from the bulb to create convective currents that draws in fresh cool air through the low end openings as the hot air rises out the top rear openings. I think the computer overclockers debate the benefits of blowing vs. exhausting fans and I'm not sure there is a consensus. In theory it shouldn't matter in a sealed case because the same volume of air that goes in must go out. It should matter whether you suck it or blow it, you are still moving the same amount of air.

And yes, I have to remove 6 screws to replace the bulb. I'm not sure that fitting the acrylic inside the fixture would help much because the back side of the reflector would still be exposed to vivarium air space and would radiate large amounts of heat into that space. My goal was to trap as much of the bulb, fixture, and hood heat as possible and reroute that heat outside the vivarium without using fans.
 

·
Registered
Joined
·
4,029 Posts
Discussion Starter · #11 ·
my tank design is the ventilation slot is in the back. Meaning, the back side of the tank is shorter than the front. Screening is placed. I like this design much better than holes ontop.

My vivarium is double the size of that tank Brent, but it has 2 x 55 watt power compacts. It is 20" tall.

Like you said, the chimney effect may work best. I bought from ACE hardware a big hole saw to make a nice cut to mount a fan. If I have the air blowing out through the top of the hood, convection would certainly work to my advantage.

How many fans, and how many ma would you recommend? Is it better to use multiple, smaller fans in different locations than one big one?
 

·
Registered
Joined
·
707 Posts
bbrock said:
Blort said:
It looks like 1-3 degrees F from what Brent wrote.
Actually the reduction was close to 10F moving from a bare bulb inside the viv to the finished product. Average daytime temp was around 88F with a bare bulb and now runs in the 77-80 range. Unfortunately I wasn't tracking min and max before the acrylic was added and I have no way of knowing the true mean so this is based on the most commonly observed temp during the day. But it's important to note it is not just the acrylic doing the work. Adding acrylic alone only dropped the temp 4-5 degrees F (which might be what your have cited). But designing the ventilation holes to produce a chimney effect provide the additional drop in temps
Thanks for the clarification, I re-read the article on your website. I was looking at the numbers in your min/max temps table and not the numbers in the text. It's too bad you don't have that other temperature data it would be interesting. So it looks like 4-5 degrees from the acrylic and another 4-5 from the vent holes? I wonder if you could get more temperature drops by doing a double pane acrylic with an air gap between the two sheets like in double pane glass house windows.

Good stuff thanks for sharing your page with us.
 

·
Premium Member
Joined
·
413 Posts
I have 4 x 55 CF bulbs on my 29 high. I keep a 4" 120v computer fan in the hood blowing in from one side. The back of the hood is 1/3 open space, and the fan is on a temp controler. My tank rarely gets above 75º. the tank has a glass top with one section of screening 1"x5". This ads ventelation and humidity is kept up by an ultrasonic humidifier on a timer going on for 5 mins once an hour during the light cycle. plus a water feature that runs almost the complete hight of the tank and is about 5" wide at the base tapering to about 2" at the top. heat is supplied by the lights and heat pads, one underneath and one against the back glass.

I like the idea above of seperating the light space with a devider but would worry about heat build up cutting the life of the bulbs short. Certainlly a fan in that section couldnt hurt. Also would you not lose light par from having the light travel through 2 pieces of glass or acrylic?

Bob
 

·
Registered
Joined
·
1,926 Posts
Blort said:
I wonder if you could get more temperature drops by doing a double pane acrylic with an air gap between the two sheets like in double pane glass house windows.
I'll bet you could. I've been thinking about trying it. I know Ben Eiben has used insulated glass on viv fronts and it seems like he may have used them on the tops. My only problem is that to do it right I would like to have the double pains pumped with argon and hermetically sealed by a professional glazier. The advantage is the surfaces between the panes stay clean and clear. It's not that expensive to do but I'm not sure if they can do it with acrylic and I'm sure they can only do flat panels.

I need to edit that web site. I haven't even read it myself. I just hammered it out in about 30 minutes and I think it is confusing.
 

·
Registered
Joined
·
4,029 Posts
Discussion Starter · #16 ·
How did you get 4 cfs over a 29 gallon?!?

I could just remove the back panel of my hood and just have one fan blow in, the other out.

I noticed that the majority of the heat is right under the bulb (obviously), and heats the glass before it can escape out through the back vent. I'm thinking about having each fan blow the length of each bulb, and with the back gone, it will have a place to exit.

About heat shields, how close can they be to the bulbs? And what kind of acrylic is safe without warping? I'd like to try the double pane idea, but now I'd worry about the concentrated heat between the glass and the acrylic, as well as shortening the life of the bulb.
 

·
Registered
Joined
·
707 Posts
bobzarry said:
I have 4 x 55 CF bulbs on my 29 high. I keep a 4" 120v computer fan in the hood blowing in from one side. The back of the hood is 1/3 open space, and the fan is on a temp controler. My tank rarely gets above 75º. the tank has a glass top with one section of screening 1"x5". This ads ventelation and humidity is kept up by an ultrasonic humidifier on a timer going on for 5 mins once an hour during the light cycle. plus a water feature that runs almost the complete hight of the tank and is about 5" wide at the base tapering to about 2" at the top. heat is supplied by the lights and heat pads, one underneath and one against the back glass.

I like the idea above of seperating the light space with a devider but would worry about heat build up cutting the life of the bulbs short. Certainlly a fan in that section couldnt hurt. Also would you not lose light par from having the light travel through 2 pieces of glass or acrylic?

Bob
Bob,

Do you have any pictures of your setup? It sounds interesting. Also, how is the temp controller on your fan wired? Finally, you mentioned a light cyle in coordination with your humidifier, can you explain that in more detail.

This talks pretty in depth about the visible light losses:
The visible light band ranges from 400 – 700 nanometers. Within this band, colors occur in the sequence observed in the rainbow, ranging from violet, to blue, green, yellow, orange and red. Each wavelength in the visible light band causes a particular sensation of color. As shown in Figure 1 and Graph 1, solar radiation is most intense in the visible light band. This band is also the area where the human eye is most sensitive to radiation. However, the eye is not equally sensitive to light emitted at all wavelengths; it is most sensitive to the light in the yellow and green areas of the spectrum.

When a light beam strikes a material, some light is transmitted, some reflected, and the rest is absorbed. Light transmission depends on the reflectance at both surfaces of the material and the absorption of light into the material. Colorless ACRYLITE sheets typically absorb less than 0.5% of visible light per inch of thickness. However, some light is reflected at both surfaces. A beam of light striking a smooth ACRYLITE sheet perpendicular to the surface (at 0º angle of incidence) will lose approximately 4% of its light at each surface due to reflection, resulting in a total loss of 8%. Therefore, the overall light transmission will be approximately 92%. If light rays strike the sheet at angles greater than 30 degrees from the vertical, the surface reflectance will be greater than 4% and, thus, the overall transmission will be smaller. For example, when light falls on colorless ACRYLITE GP or ACRYLITE FF sheet from all angles, as from a sky of uniform brightness, the transmission factor will be approximately 85%.
Where you would probably take the losses is in the UVA/UVB bands since those curves are more adversely affected by increased thickness. For example using OP4 acrylic at 280nm you get about 70% transmission at .125 inches, about 5% at .5 inches, and 0 at 1 inch.

Marcos
 

·
Registered
Joined
·
1,926 Posts
bobzarry said:
I have 4 x 55 CF bulbs on my 29 high. I keep a 4" 120v computer fan in the hood blowing in from one side. The back of the hood is 1/3 open space, and the fan is on a temp controler. My tank rarely gets above 75º. the tank has a glass top with one section of screening 1"x5". This ads ventelation and humidity is kept up by an ultrasonic humidifier on a timer going on for 5 mins once an hour during the light cycle. plus a water feature that runs almost the complete hight of the tank and is about 5" wide at the base tapering to about 2" at the top. heat is supplied by the lights and heat pads, one underneath and one against the back glass.

I like the idea above of seperating the light space with a devider but would worry about heat build up cutting the life of the bulbs short. Certainlly a fan in that section couldnt hurt. Also would you not lose light par from having the light travel through 2 pieces of glass or acrylic?

Bob
Bob,
Have you measured temps with the fans off to see how much of a difference the fans vs. passive cooling makes? That's something I've thought about doing and could easily do it on my test hood. But I've gotten really cranky about the noise of fans and ballasts as they interfere with my being able to listen to the frogs. My goal is to have the mechanics dead silent so I'm trying to redesign to get rid of the cooling fans that I have if possible.

The heat build-up inside the hood around the lights does not seem to be an issue. First, I'm using UVB bulbs that need to be replaced every 6 months to a year anyway and they easily last that long. But I've had regular CF bulbs last for years in these hoods. Second, I'm not sure if you can see it well from the images on my page but there are a LOT of vent holes above the lights so heat does not build up inside the hood. Heat rises so it goes out the top and is replaced by cool air at the sides. Finally, those bulbs are much hotter than the air that surrounds them so they are obviously built to tolerate heat.

I should also point out that the hood on my page is a small viv with a CF which is the worst case scenario for heat buildup. I have a much larger viv with 2 96w CF that stays right at room temp without any fan or lots of ventilation in the hood.

Edit: Marcos beat me to it in the above post so the following is basically a repeat of what he posted much better above.

You would lose a little light going through two panels. The solacryl I tested passed a little over 93% of visible light so through two panels you would get 93% of 93% or 86% of the visible light passing through.
 

·
Registered
Joined
·
1,926 Posts
Rain_Frog said:
How did you get 4 cfs over a 29 gallon?!?

I could just remove the back panel of my hood and just have one fan blow in, the other out.

I noticed that the majority of the heat is right under the bulb (obviously), and heats the glass before it can escape out through the back vent. I'm thinking about having each fan blow the length of each bulb, and with the back gone, it will have a place to exit.
It helps to think about the different ways that heat is transfered: radiation, convection, and conduction. Radiation is when energy is emmited from a source and then strikes an object. That object absorbs some of the energy and warms up. That's largely what is happening to the glass near the bulb. The light from the bulb passes through the glass but some of it is absorbed so it heats up the glass (or acrylic). No matter what you do, that light needs to go through the glass so it is going to heat up. Other radiation hits the reflector and hood where, again, some of it is absorbed and heats up the reflector and hood. Those warmed surfaces can reradiate heat or have heat carried away by convection or conduction. Convection is when air passing over a warm object heats up. The air molecules themselves get warm and then can carry the heat to other places. So the air passing over the hot bulb and other surfaces can get warm and then either mix with the vivarium air or get vented off. A chimney effect or blowing a fan across the hot bulb, reflector and hood speeds the convective heat loss and carries the heat away from those objects faster so they cool down. I don't think conduction plays a big role here. That is when heat is transfered through a conductor like when the handle of an iron skillet gets hot. Glass is a good insulator and poor conductor so I doubt much heat is conducted from a light to the viv space.

So, what cooling systems attempt to do is to convect heat away from those warm surfaces before they can be reradiated into the vivarium space. Obviously the more air you blow across the hot surfaces, the faster they will cool and the closer they will stay to the temperature of the fresh air being blown in. However, at some point adding more air movement will not add to the cooling effect of the vivarium because the point of the lights in the first place is to put radiation inside the vivarium and onto the plants. You can't radiate the plants and viv without warming it up at least a little. I use to think that fans were necessary to adequately cool these CF lamps but as I've experimented, I'm discovering that I can get adequate cooling in most cases without fans. However, if you really pack on the lights over a relatively small space, I'm guessing that fans would be a must.

About heat shields, how close can they be to the bulbs? And what kind of acrylic is safe without warping? I'd like to try the double pane idea, but now I'd worry about the concentrated heat between the glass and the acrylic, as well as shortening the life of the bulb.[/quote]
 

·
Premium Member
Joined
·
413 Posts
lots of questions...hope I dont leave anything or anyone out...if I do its not intentional.

I have a 29 high. thats a 24"x12" foot print. the hood I custom made and is 11"OD high with a front opening pannel. this gives me enough room to fit the 4x55w cf's comfortably and still have plenty of room to open and do maintenance. Sorry I dont have any pics.... my digital camera craped out about a year ago and I never replaced it.

the 4" fan is surprisingly quiet. and I use electronic ballast also very quiet. originaly I had a 3 inch fan and it did not do a very good job and was much noisier. As far as the controller: I used a heat controller with probe commonly sold by most of the reptile supply houses, and they are fairly inexpensive. in order to control cooling I used a relay wired to the power=off post. (the controller sends current to the relay as it normaly would to power a heater. the fan is pluged onto the power=off side of the relay so when the controller sends power the fan turns off...when the controller shuts down the fan comes on) doing this reverses the use of the heat controller and lets you use it for cooling.

what I meant about the humidifier and light cycle is this: my lights are on a timer set for 14 hours. I purchased a digital timer from radio shack that lets you set multiple times on and off. so during the same 14 hours that the lights are on I have the timer on the humidifier set to come on once an hour for a 5 min duration.


Bob
 
1 - 20 of 40 Posts
Top