Heat Issues in a Television Cabinet

Cabinetmakers discuss how to keep a 50-inch plasma TV set cool in a tight cabinet. June 28, 2007

I am building an entertainment center for a client who has a 50" plasma, and all the related equipment to go along with it. The front of the plasma will not have doors, and will have a pullout. How much the pullout gets used is anyone's guess. The manufacturer calls for over 19" of clear space above the TV. I have 1-1/2", and this is due to space constraints, not me playing fast and loose with the specs. The folks at Pioneer told me that the pullout will allow the unit to cool properly, as now the TV has all the area in the world above it. Again, how much the pullout gets used is anyone's guess. So, I'm back to worrying about the temperature in the case. I have looked at a pile of different fans. Some 12 vdc, and some 110 vac. I would really like to have the fans powered all the time, but through a thermostat.

This also applies to the lower cabinet where the equipment is going to be housed. I know my client fairly well, and the less they have to think about, the safer the electronics are.

So, here are my questions:
1. Is there a way to use 12 vdc fans (they seem to be the most airflow for the least dB) on a stat?
2. If a fan is 22.8 dB, then are two fans 45.6 dB?
3. Can I run multiple fans on a wall wart?
4. Will the wall wart generate too much heat of its own?
5. Am I correct in thinking that the larger the vent that I make on the outside of the cabinet, the lower the noise of air blowing through will be?

My client has spent a substantial amount of money on the TV, and again on my cabinet (mahogany - natural), so I am trying to give them all of the joy, and no headaches. Also, if I've missed anything, please feel free to point it out.

Forum Responses
(Cabinetmaking Forum)
From contributor M:

I have never allowed more than an inch or two above the TV screen for ventilation when the screen is built into an entertainment cabinet. I have never had a problem or callback. The hot air will naturally vent out of the top space by convection.

For further proof of this, I offer the example of refrigerators - any cabinet guy who has dealt with counter depth refrigerator built-ins will know that one inch above for ventilation is enough. Refrigerators put out more heat than any TV.

As for venting any hot electronic components, I use thin speaker cloth in the cabinet doors in front of these units and usually have no problem with heat. The cloth is also transparent to infrared remote control signals.

If a customer wants a solid door in front of the components, I put in a 12v computer fan and just hook it up to a little low-amp 120v transformer. The fans runs all the time like they were designed to do in computers.

Remember that, like computers, electronic components, including TVs, have heat shut-off devices to keep them from getting too hot. So stop worrying about problems before they happen. They probably never will.

To answer your more esoteric questions: Doubling the fans will not double their sound. Any fan needs only a vent the size of its propeller to minimize its sound, and usually an even smaller vent hole will not increase sound from "whooshing". Don't bother to thermostat the fans - it isn't worth the money unless customer specifically wants it.

And one final fact: fans are always more efficient at sucking than pushing air. A four or five inch computer will provide a hell of a lot of ventilation if located at the exit vent hole.

From contributor C:
I ran into this same problem just in the last month. I built an entertainment center for a client 5 years ago when plasmas were the new thing. He paid $11,000 for just his screen alone. It lasted 5 years and went out. It stays on for 3 hours and then trips breaker. Sounds heat related. Just got done reworking his entertainment center for a new screen.

From contributor D:
If you want a thermostat to control the fans, you can purchase a line voltage thermostat. If you are using DC fans, connect the transformer/power supply input line to the output of the thermostat.

From contributor L:
Regarding the sound levels, the decibel scale is logarithmic and not linear. If it were linear, then the sound levels would simply add together. If you double the noise level, the decibels go up by 3 db. In other words, a 3 db increase in sound is a doubling of the volume (as perceived by the human ear).

From the original questioner:
I just found this NoiseMagic Thermocontrol for 12vdc fans. It looks like it would work very nicely in conjunction with the fans in my previous post. Anybody have experience with these, or something like it?

From contributor V:
I have no personal knowledge of that unit, but I would like to share with you what I have been told. I do a lot of work for a local appliance store and have become friends with the owner. He has always told me heat is the death of electronics and especially plasma. Which is why plasma has some longevity issues.

Whatever you do incorporate, heat dissipation as an integral part of the entertainment unit, not an afterthought. It's nice to see there are still some good guys out there looking out for their customers.

From contributor T:
You are on the right track. As a power source for your fans you could use a computer power supply. You can then use standard CPU fans to move your air out of the entertainment center. Most CPU power supplies can be used as DC supplies for 12 & 5 volts. You must simply connect two pins on the main power plug to turn it on. This can be done with a switch or it can be permanently wired together. There are some great low noise computer fans that move a lot of air on the same site you found that controller.