Waste Heat and Enclosure Cooling

[mph]

Hi,

I'm brand new here and did try to search for what I needed first little or no luck, so here goes.

I'm putting together a new home theater system. I was looking at a Denon 3808 for the receiver. Since this is going in an enclosure, I'm concerned about the heat generated within. I've read several articles on enclosure cooling and the all say to "get the published waste heat BTU's/per hour" from the manufacturer, and recommended no more than 85F temperature within the enclosure.

So, I posed the question to Denon. Their reply was:
"I passed your question on to the product developer and this is his response."
" We don’t have that information. I would suggest about 72 degrees."

Now I'm a bit green at this... but I would think that first off 72 degrees would be a bit unattainable, without an expensive refrigeration system, and moreover, that the developers don't know how much heat a given unit generates.

I almost felt like writing them back and asking them what happens when the temp. hits 80? My house doesn't have air conditioning(it really does)... Does this mean I can't use your products in the summer?

To make a short story long... Does anyone have an idea of how much waste heat there'll be? Even a ballpark guess would be a start. Using the formulas found on the net, I get around 2500, which I don't think is even close. All my other equipment is very low wattage so a ballpark plus a few should be fin.

Thanks,

 

[mph]

enjoythemusic,

Thanks for the reply, The formula that I found in a couple of places, including my brother, who was an ETN3 (Electronics Technition) in the navy. is (total watts x 0.8) x 3.412 = btu's/hr. Now this would work out to just under 2,500 btu's/hr. Figuring on 130w x 7 channels, which is whats advertised. According to, that is, where I could find CFM calculators, would require over 400 CFM of cooling. That's using the calculator at Middle Atlantic designed for audio equipment racks. I can't post the link due to forum rules... less than 5 posts. This seems quite a large amount of air. I've seen 1,200 watt 8 channel amplifiers with a rating of 850btu's/hr. Hence my confusion.

My guess here is that the formulas that I've found may be a bit outdated due to more efficient technology. I guess I'll shoot for the middle of the road and monitor the temperature in the cabinet for the first couple of months. Thermometers are cheap enough.

The bottom line is that this system is a very large expense for me. I just want to make sure my investment is properly cooled and lasts as long as it should.

BTW. I'm looking at a thermoelectric peltier cooling system. I've gotten quotes from $325.00 to $835.00, but can build one for under $120.00 including controller.

I'll post results in a few weeks when I get all the supplies.

 

[jrgreene1968]

I just use a fan i got from Lowes in the back of my cabinet, setup to suck the hot air out. The fan cost me 14 bucks and works great. Im running an onkyo 805(which run way hot) and a lpa-1 7 channel amp..everything stays cool. Without the fan, it gets pretty hot in there though

 

[TLS Guy]

enjoythemusic,

Thanks for the reply, The formula that I found in a couple of places, including my brother, who was an ETN3 (Electronics Technition) in the navy. is (total watts x 0.8) x 3.412 = btu's/hr. Now this would work out to just under 2,500 btu's/hr. Figuring on 130w x 7 channels, which is whats advertised. According to, that is, where I could find CFM calculators, would require over 400 CFM of cooling. That's using the calculator at Middle Atlantic designed for audio equipment racks. I can't post the link due to forum rules... less than 5 posts. This seems quite a large amount of air. I've seen 1,200 watt 8 channel amplifiers with a rating of 850btu's/hr. Hence my confusion.



My guess here is that the formulas that I've found may be a bit outdated due to more efficient technology. I guess I'll shoot for the middle of the road and monitor the temperature in the cabinet for the first couple of months. Thermometers are cheap enough.

The bottom line is that this system is a very large expense for me. I just want to make sure my investment is properly cooled and lasts as long as it should.

BTW. I'm looking at a thermoelectric peltier cooling system. I've gotten quotes from $325.00 to $835.00, but can build one for under $120.00 including controller.

I'll post results in a few weeks when I get all the supplies.

You have used power going to the speakers for calculation, this is not correct. Look on the tag on the unit, it will state its power consumption, it should also be under specifications. Most of the time the unit will only deliver a watt or two average to the speakers. But there will be peaks, and if you play music with no dynamic range at high power it will heat up in a hurry. The power going to the speakers will be about 40% or so of the draw and will not make heat, the other 60% will be heat, plus the quiescent power draw of the unit.

I would cool it with fans as suggested. All solid state devices, have a heat/ time curve for longevity. So the cooler you keep it the longer it will last and the less problems you will have.

 

[mph]

You have used power going to the speakers for calculation, this is not correct.

Well, I knew something was wrong. The tag on the unit says 7.2 amps. I could not find the wattage in the owners manual either. It only shows wattage to the speakers. I did a little searching on the net an found a couple of reviews that state the power consumption at 550 watts. Thanks for pointing that out. I should have known better and taken a little more time. Using the 550W brings the waste heat down to 1500btu's/hr and the total cooling down to about 340 CFM. I still think this is a bit high.

I've looked at fans and fan cooling units, and peltier cooling devices. I favor the peltier because the $35.00 unit with heat sinks has a hot side of 190F cool side of 55F w/o fans. Add a fan to hot side and the cool side temp. drops, add a fan to the cool side and you have a ventless cooling system. Add an inexpensive thermostat and you have a hands off cooling system that's independent of the equipment it's cooling and keeps a more stable temperature in the enclosure.

I'm trying to use a few fans as possible to keep the noise down. In this case 2 120mm fans can do more cooling than 4 or more of the same size fans. There are fewer holes in the cabinet and less worry about dust being sucked in. Dust is a big issue in my house. It's almost 100 years old and falling apart 1 dust bunny at a time.

Bottom line is; I know this is probably way over kill... But I'm a glutton for punishment.

 

[TLS Guy]

Well, I knew something was wrong. The tag on the unit says 7.2 amps. I could not find the wattage in the owners manual either. It only shows wattage to the speakers. I did a little searching on the net an found a couple of reviews that state the power consumption at 550 watts. Thanks for pointing that out. I should have known better and taken a little more time. Using the 550W brings the waste heat down to 1500btu's/hr and the total cooling down to about 340 CFM. I still think this is a bit high.

I've looked at fans and fan cooling units, and peltier cooling devices. I favor the peltier because the $35.00 unit with heat sinks has a hot side of 190F cool side of 55F w/o fans. Add a fan to hot side and the cool side temp. drops, add a fan to the cool side and you have a ventless cooling system. Add an inexpensive thermostat and you have a hands off cooling system that's independent of the equipment it's cooling and keeps a more stable temperature in the enclosure.

I'm trying to use a few fans as possible to keep the noise down. In this case 2 120mm fans can do more cooling than 4 or more of the same size fans. There are fewer holes in the cabinet and less worry about dust being sucked in. Dust is a big issue in my house. It's almost 100 years old and falling apart 1 dust bunny at a time.

Bottom line is; I know this is probably way over kill... But I'm a glutton for punishment.

I think your plan makes perfect sense. You are a little high on the BTU as that 7.2 amps will be the max draw. However I would use that number. Not being close to the edge is good. Modern engineers have a habit of cutting tolerances to the bone. If you follow your plan you know you will be OK.

If that house has not had a wiring update fairly recently, I would get a dedicated circuit to that equipment cabinet. That is always a good idea anyway. Modern audio gear presents a nonlinear load, and it will stress the neutrals, which may cause you problems, and be a fire hazard.

 

[mph]

If that house has not had a wiring update fairly recently, I would get a dedicated circuit to that equipment cabinet. That is always a good idea anyway. Modern audio gear presents a nonlinear load, and it will stress the neutrals, which may cause you problems, and be a fire hazard.

Very good point! I hadn't thought of that(yet). I just got circuit breakers put in within the past 2 years. Some of the house has been rewired. Most of it is 3 wire, but there's still some 2 wire where it's hard to get at. Fortunately, the first floor is easy as there's no ceiling in the basement. The only things that are on that circuit are two plugs in the same corner. One plug isn't used except for a battery and cordless phone charger. Worst case, I made sure that the panel had extra space in it when I had the breakers put in.

Ya gotta love it. Every time I get one problem solved, one or two more show up!

-- I'd rather have a bottle in front of me, than a frontal labotomy.