Ventilation advice

[Buckeyefan 1]

Need some advice. My Denon 3805 gets pretty warm. The family had the tv on most of the day today. I have all 7.1 channels running. My Polks are rated at 89db, so you can imagine the volume I need to set it on to have adequate sound. The problem is my cabinet has little ventilation. The receiver sits in an enclosed cabinet beneath my 36" tv. There's plenty of space above the receiver. There are vent holes in the back of the wall unit, but no cross ventilation with the glass cabinet door shut. It's a $2000 oak wall unit, so putting the receiver outside the cabinet is out of the question. Should I install a small cpu fan somewhere in the cabinet? Are there any companies that make fans for this? Does anyone have any ideas how to ventilate this unit without me keeping the glass door open all day (quite the hazard for my 2 yr old boy!). Thanks in advance!

 

[sjdgpt]

I have the 2805 powering Polk LSi. The 2805 is the same chassis as the 3805 with just less bells and whistles.

The 2805 gets warm to the touch even with an open rack system (three upright legs and glass shelves) and the unit just in standby mode. Leaving the unit in the "on" setting, but no signal being amplified, the case to unit reached 116F in 74F ambient room temperature.

In other words, it runs warm.

(I have not check the temp when the unit is actually working).

By the way, Denon says 4 inches above the unit for the next shelf in the rack. I have mine set at 2 inches, but the bottom of the shelf above is only about 5F hotter than ambient temperture, so I strongly suspect that I have enough cross ventilation to keep the unit as cool as it is ever going to be.

I would compare my temperatures with your temperatures. If you are not much above my temps, I would suspect that you have adaquate heat dispersion.


Yes there are small CPU fans that would provide more air circulation for the display racking. Most electrical and industrial supply businesses will have a wide selection of fans to choose from. You do not need a big fan, just something to get the air to move in the display rack. Install the fan towards the bottom of the cabinet and have the air flow across the unit and towards the top of the cabinet.

(remember, hot air rises, so your fan is to aid the flow of hot air, not work against the flow of the hot air)

Steven

 

[BMXTRIX]

While it is up to you, I would say the number one reason I have seen equipment fail is due to the exact ventilation setup you have. Adding a fan may make air flow better, but don't underestimate how important ventilation and air flow is to your equipment. Not just the receiver, but all of the equipment.

How you get that airflow is up to you. Equipment fans exist for sure, also opening up the back of the cabinet more may be a possibility.

It would piss me off to no end to spend 2 grand on a 'oak wall unit' that just gives a few small holes in the back and calls it 'adequate' ventilation for A/V equipment. I am of a strong opinion that custom buiilders are about 80% clueless since they do not actually check with A/V design engineers before selling their product.

Your equipment though. My stuff is in an open rack in my basement. Don't see it, don't have heat issues.

 

[Buckeyefan 1]

Well, I tore into an old computer and rigged up a cpu fan with a 115v to 9v ac adaptor and it worked! I knew there was a reason to keep that old computer around. It blows hard, but is very directional-probably only 3" in diameter. Probably equivalent to the air expelled when one whistles. Believe it or not, there were no holes in the back of that oak cabinet, so I don't know what they were thinking on how to run A/V wires when they built the thing. I had to cut a bunch of them out with a hole saw attachment on my drill. Pain in the neck going through oak. The fan originally cooled an AMD Athlon 1200 chip directly over the cpu. I wasn't sure how to mount this tiny fan, so for now I have the fan blowing down into the center of the receiver. I don't think this tiny fan is powerful enough to pull air from one compartment to the other. Do you think this stream of air into the unit will damage anything? It's plugged into the "switched" outlet so it only turns on with the receiver. PC's have two and three fans internally with a ton of circuitry, and seem to do fine. The fan on my pc right now seems to blow "in" and not out. What a pain in the neck!

 

[sjdgpt]

Taking your questions backwards.

Yes, your PC fan blows in. It is drawing cool ambient (room) air into the PC, rather than trying to blow hot air out. Mechanically, the amount of force required to draw air versus blow air is essentially the same, BUT cool air has a greater density, so the fan can achieve greater results with the cool air.

Acutally the PC does not have a significant heat producers when compared to the amplication of a receiver. If we removed the amplication stage, as well as the corresponding power supply, the remaining preamp portions of the receiver would be comparable or slightly less heat producing than the PC.

You should not be plugged into the switched outlet. When the receiver has been used, and is hot, and then is turned off, so is the fan. The fan should be independently switched and should be left on whenever the receiver is warm.

Any air flow through the cabinet will not hurt the other components, unless you have a sensitive turntable drive, you will most likely not know the fan is operating.

The amount of air flow through the other compartments is not critical. But you are right, this type of fan, unless used in a closed case environment, is not sufficient to draw any significant amount of air through the cabinent.

The fan needs to be blowing UP. Heat rises. Having the fan blow up will allow natural convection to be used WITH the fan's force, rather than against the force.

Yes, I realize you can not mount the fan directly under the receiver, but you could mount the fan at the rear bottom, blowing the air across and UNDER the receiver. As the air is heated it will rise and displace the hotter air in the receiver.

PS: You need to use a decent thermometer to measure your actual receiver temperature, as well as the air around the receiver.

In other words, if your receiver is measuring 125F, but the blank space just one inch away is only 5 degrees above ambient temperature, it simply means that you are displacing the heat. BUT if the blank space temp just one inch away is 115F, it means your temperature differential is insufficient to remove heat from the unit.

 

[trevorgray]

I don't have a 3805 but I do have a 2500 which probably gets just as hot. I was thinking about doing the exact thing by plugging a fan to the switched plug on the back, but will be rethinking a lot of things after reading the post. Thanks for your insight and help.

 

[Buckeyefan 1]

The small cpu fan really does it's job. The unit doesn't get near as hot now. Wow! I decided to hook it up to the switched outlet in the rear because I'd never remember to turn it off otherwise. It's better than not having one. I haven't experimented with flipping the fan over yet (its blowing into the unit rather than up) because it's doing such a great job now. I still need to create some more vent holes in the cabinet's rear side. It only has one 3" for wires - terrible design. Once I do that, I'll probably flip the fan over as an exhaust fan rather than a direct fan.

 

[NetGeek]

I am in the same boat

Have one of those nice $2,000 oak wall also; mine came with a few, but not nearly enough pre-drilled holes.

What I did was on the bottom shelf where my receiver sits I cut a square hole the size of the receiver in the back of the entertainment centers "pier" to allow me full access to the rear of the receiver, then I cut two holes per shelf; hole on the left for power and one on the right for the interconnects. I am rigging two PC fans for ventilation, using large 120 mm "Stealth" fans because they are quiet and move a lot of air. I am rigging on at top that blows out and one at the bottom that blows in in order to circulate the hot air from the bottom out through the top. The bottom fan also has a "pre-filter" on it to filter out cat hair & big stuff before it gets in.

You can use a CPU fan but since they are usually smaller they run at higer RPM's and produce more noise; the larger the fan the slower it has to turn & therfore the quieter it is.

 

[shokhead]

My 3200 ran twice as hot as my 2805. As long as there is plenty of above room,you'll be fine. Fans are not a must.

 

[Buckeyefan 1]

My 3200 ran twice as hot as my 2805. As long as there is plenty of above room,you'll be fine. Fans are not a must.

To add to that, ...not a must - as long as your cabinet is open in the back or front. 12" above the unit is no good if it's in a coffin.