cooling and sytem evaluation

Hello Everyone, I'm getting ready to start my build and need some advice before i settle on a amp rack design.
the rack will be a false floor with 2 concealed amps inside.
 I normally wouldn't have ever attempted to encase any amps. but I'm very lImited on space.This is going to be in the cargo area of my 91' Nissan 300zx along with a pair of 10" Subs. PLUS I need to be able to store the T-tops there 3or4 days out of the year, when then sun comes out in Seattle.
 Anyway i was planning on running two Pac CF-1 cross cooling fans in the push/pull configuration. and putting a dividing center wall between the amps left open on the end. Id say kinda like a "U" shaped air path. I'm going to build a small set of baffles to help silence the fans both intake and exhaust.
 Now a few question's..
1.Is Push/pull the right orientations to use?
2.Should i not cool both amps in the same air stream?
3.Ill be incorperating some acrylic into the amp rack for viewing. Although most of the tIme there will be a lid covering it flush with the floor, Id like it to be as dust free as possible inside. So I'm wondering what kind of material everyone uses for a pre fan Filter?
  I assume that it cant be to restrictive for the sake of the fans life span?
I think that's all for now. ill give you the equipment list and my thoughts on configuration of. For your consideration as well. Thank you All very much for your time. I appreciate your help.

91' Nissan 300zx x/32
140 amp alternator
1/0 Stinger HPM power Wire
Stinger HPM RCA's  (series 2)
Pioneer N-3 DVD/Nav H.U.
Diamond Audio Hex 6.5 components(silk tweet)(doors)
Diamond Audio D-6 700.4(Bridged into 4ohms for 350w x2)
Diamond Audio D-6 1500.1(Wired into 1ohm Mono for 1500w x1)
2 Diamond Audio D-6 10's (sealed in two separate boxes)
2 Pac CF-1 brushless cross-flow cooling fans

It probably won't effect the fans life. When blocked, they speed up and use LESS current.

The problem with filters is they require maintenance. They will block.

If the circuits are conformally coated and components are dust rated, etc, then dusty air can be blown thru the device. Now and again you may need to blow the dust out if it settled & blocks heat-sinking fins etc.


But hopefully the amps are thermal overload protected - not that that means "pre-circuit" protection.
Otherwise air temp sensors, air-flow alarms, etc.

Wow, great Info OldSpark. I Had to google to find out what conformal coating was. Ive Never heard of such a process. Is this treatment common place in the 12v field for situations like mine? Sounds pretty expensive.
 Really wasn't planning on alarms, temp sensors and such, But now that I'm thinking about it , I don't think it would be a bad idea to be able to monitor temps.
Would you recommend i monitor the amps surface temp, exhaust air temp, both?
 And as for the fans speeding up and drawing less current if restricted, Shows me i have allot more to learn. i would have thought that I'mpossible. Could you help me understand why that is. I'm very curious.
Thanks.

I work at an arcade at the beach and we use the white 3M A/C filters and just cut them down to size to cover the intakes on all of the arcade games it works great. You could buy one filter and cut several replacements the size you need. Then I would put them in a bag and hide them in your car so you don't loose them. We replace ours every 3 months but the arcade is seasonal and wide open to the boardwalk so you could probably get away with 6 months or more. Just check em every month until they get grey.

I believe I was just reading a post from soundsecurity who was replacing the tweeters of those component set because one of them was failing. Just FYI if you haven't bought or installed them already.

Other than that nice set up!

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Dodge Magnum in progress:
Pioneer DEH-80PRS - PPI Amps - Dayton Subwoofer(s) - Exodus Anarchy's - Vifa Tweeters - Kinetik Battery

if the fans have less air to BEAT against then it is easier for them to turn...hence less demand for electricity. If you are doing the install think about some flexible ducting or remote ducting to make it easier to get to the filters. make sure the surface area is large enough to support the flow you deem necessary.

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The RIGHT way is the ONLY way.

As far as monitoring temperature, the amp surface temp is more likely to provide usefull information than the exhaust air temp. afterall if the fans were to stop and the temp gauge read a normal range the amps could be COOKING and thats the component you wish to save.

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The RIGHT way is the ONLY way.

seattlejoe1970 wrote:

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... as for the fans speeding up and drawing less current if restricted.... i would have thought that Impossible. Could you help me understand why that is....

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Uncomfortable Politician getting a pain-in-the-butt question wrote:

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I'm glad you asked!    

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First - the proof:
Block the suction of a vacuum cleaner with your hand.
What happens - the motor slows & grinds to a halt (as "common sense" dictates)??
NO!!! It speeds up! (Can you hear the whir getting faster or higher pitched? I know it from memory!)

Why? Cavitation. Air stops, fan "chops" through air and doesn't move it. Hence less friction (speeds up) and less power required (current down).
Cavitation - same happens in powerful propellor boats - connect power too quick and the prop just spins a while before it starts to "grip" and push water thru - the boat equivalent of a wheel-spin (burn out, snakey, etc).   

And that too is ONE reason cars can overheat when revving too high OR thermostats are removed. (The other/s being jet-streaming, and changed hydrodynamic flow profiles.) That's another story - but some still think overheating is because the water travels "so fast" it hasn't got time to "lose the heat". (LOL!)
I tried arguing the car overheating, but it wasn't till ~3 years later I learned why [Thanks Dean!] . (I just knew intuitively etc that it wasn't the "not enough time to dump the heat..." Like what - yet is had time to pick it up? Does that mean to heat a house faster, keep the heater fan on LOW? Etc.)


There are conformal sprays - maybe $20 a can? But I would not "conform" a commercial product (warranty etc) - they should be doing that themselves whether for dust or moisture.
But I had the same dilemna years ago for some critical equipment (UPS) - specify filters and hence FORCE maintenance else failure?
And it was Dene or Dean that convinced me (just as above) that monitoring for HIGHER fan current (to indicate blockage) would NOT work! (So very D'Oh! In retrospect that is!)

The final solution - conformal coating but with filter supplied (at base of unit). The site could decide whether to keep or remove filters.
The 2 or 4 fans on top of the units each had a spring-loaded air-flap that would trigger an alarm after a few seconds. IE - allo for flapping, but if no air, then flap closed and alarm was raised.

FYI - air-flaps seem primitive or inelegant, but it's another brilliant design.
What are you trying to measure? Airflow. Not current or fan speed etc.... (Sure - maybe hot-wire sensors etc, but as long as it is air-flow that is measured.)



As to what temp to measure... oh boy!
Components cannot exceed their maximum operating temperature hence sensors are place on the components or heatsinks etc. But that is an "averaging" method - even if one sensor per device, it still won't sense instantaneous overheating (eg current).

And usually it's the big components you monitor - eg, output transistors or FETs etc, input transformers or chokes.
Individual components cannot be monitored economically. Besides, it they overheat, it is usually some failure which you will find out about anyhow...

The other temp consideration is not immediate failure, but lifetime.
A common rule for electronics & electrical is that every 10C or 15C increase is a HALVING of its life. EG - maybe a battery at 45C lasts half as long as at 35C (lifespan - not capacity!), or an amp at 50C lasts half as long as at 35C.   
And also, the higher the temp, the greater the chance of failure (which may be another way of stating the above "lifetime" reduction).


So - what to measure?
Intake air? (Will you shut it down if it's too hot? Or to meet warranty conditions - if it's warranted up to 45C, then have a 45C intake-air sensor?)   
Exhaust air?
Case temp? (If output heatsinks are ok and inputs are okay, but case to "too hot", is there a problem or just a hot car?)

Amps should have thermal protection. Usually a bi-metal temp switch (Klixon etc) on their heatsinks etc. These are usually cheap on-off switches ($4-$6 retail).
I'm experimenting with a 90C klixon as my car's fan switch (the car uses an 82C thermostat).

z03mz03m,
          I was thinking along the same lines as that , and I've had my eye and mind open while I'm in the stores. Ive been back and forth to the hardware, automotive,lumberyard,big box....  Cause its not just the audio that's getting the upgrade I'm also reupholstering the interior of the car, So a filter mod of some sort is very doable with the vast selection of choices out there, still looking.
     And i think i might have read the same thing about the tweeter fail, I think it even failed twice on him if its the same guy. But weren't they the aluminum tweets? Yes there all ready paid for and I  have the drivers side tweet installed.
thanks

resquchas,
           Ive also thought about the flex ducting unfortunately my Car is way to fast to have that kind of extra room. Theres just no place to duct them to or from.
Although get this....  A Friend of mine came up with this idea, He says, Because I'm pretty much deleting the spare tire because the amp rack is going to be so bulky its just not worth packing around the weight of the space saver spare . So take the spare tire out, and make some sort of fresh air scoop under the car that diverts the air into the spare tire well, Which would make it a ?fresh air tire well manifold thing? ...  er  ..anyways then put a K&N Cone shape /pop charger style air filter at the end of the duct but inside the tire well. To filter the road debre/moisture. then my #1 Fan intake would pull its air from the tire well. and be getting cool air. Oh and you need to seal the top of the tire well so its not just a massive air leak  into the car..   LOL... 

thanks

OldSpark,
          I'm picking up what your laying down,
But on the vacuum analogy, the motor definitely gets loud , but i guess I've always figured that it was more like the motor was bogging or testing its limits there for pulling many more amps, A situation that would shortly trip the breaker if aloud to go unchecked?

 From the brief amount of reading i did on the conformal sprays, I didn't think this was a do it yourself type project, Isn't it a 100& dismantle of every component and spray them then reassemble? 5-7days shop labor. I don't think id want a aerosol rattle can job on my amps...   Ewww!

The Flapper Is Fool Proof, and undeniably nothing less than  perfection.  some times there is no technological upgrade available ya know?

And in response to what temp to measure.....
Oh WOW you just made it so very difficult with all valid points you brought up.. I'm going to have to think about all that for a while.    Whoa...
thanks
           

You should hear the blocked vacuum motor SPEED up as well as get louder.
Hence why circuit breaker (or current) WILL NOT WORK to detect blockage - the current drops because the load is less (cavitation) and it speeds up too...

I understand the whole "no room thing" but there is always a way. I just put a sub in a 61 vette that you can not see, but it is there. took some fabrication but i did it. Think outside the box as you clearly have begun to do. I would not do the fresh air scoop thing if that is what you are talking about, as under the car gets very dirty and wet. maybe mold a cool filter shape into a panel and then cover it with paint/upholstery. Hide it in plain sight, people freak when they look at something and still have to be told what it is.

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The RIGHT way is the ONLY way.

resquchas wrote:

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I understand the whole "no room thing" but there is always a way. I just put a sub in a 61 vette that you can not see, but it is there. took some fabrication but i did it. Think outside the box as you clearly have begun to do. I would not do the fresh air scoop thing if that is what you are talking about, as under the car gets very dirty and wet. maybe mold a cool filter shape into a panel and then cover it with paint/upholstery. Hide it in plain sight, people freak when they look at something and still have to be told what it is.

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I wish there was a like button on here like Facebook lol.

that was inspirational

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Dodge Magnum in progress:
Pioneer DEH-80PRS - PPI Amps - Dayton Subwoofer(s) - Exodus Anarchy's - Vifa Tweeters - Kinetik Battery

OldSpark,
         So then it wouldn't be putting a load on it in the same way as :If you were to take a computer fan and put your finger in the center of the fan slowing it down?
I totally get what your saying though, and all the analogies make perfect sense.
Its kinda funny how the mind has trouble letting go of certain thoughts or beliefs that you have thought to be correct for so many years. ya know?
Thanks

resquchas,
          So what diameter of ducting are you thinking would be in order? the amps measure #1= 11"x17"x2.5" and #2= 9.5"x18.5"x2.5" and i was thinking about making the space around them about 1-2" on all sides. and the fan measures at Intake opening is 6.5"x2.5" and exhaust is 6.5"x.75"

Thanks

Oh and i forgot to mention that I'm not, nor was i ever considering the air scoop thing. Just thought it was funny.

My friend still thinks it would be a great idea, and cant believe I'm not on the same page as him.

seattlejoe1970 wrote:

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So then it wouldn't be putting a load on it in the same way as If you were to take a computer fan and put your finger in the center of the fan slowing it down?

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If you think the airflow-restricted fan slows down, then it should be like fingering the fan.   

But my experience is the opposite - ie, cavitation and speeds up - and consumes LESS power.
Maybe the current/power increases as the restriction increases, but eventually it drops.
Hence a "blocked fan" should last longer assuming it doesn't overheat (no air flow) and doesn't out-spin its bearings (too fast).

The ducting needs to be small enough to meet your needs and with as few bends as possible to provide laminar airflow. So a small straight shot is better than large with lots of 90's. Sorry, but there are many variables. Go as large as you can and as smooth as you can. It is ok to make a small sacrifice if you make up for it in another area. I always try to keep the crossectional area near the same as the opening. ( 6x6=36insq)So if i need to make a false passage that is only 3inches high i keep it till i transition before the fan and then the duct itself. In your car I might be tempted to do a false floor as that could get me to the rear inside quarter trim panels then its easy to route a 6in duct in there with a filter that is easily mounted to the NEW upholstered panel. I think you are doing this absolutely correct, in that you are thinking BEFORE doing. That always saves TIME MONEY FRUSTRATION. And you end up with exactly what you want. NICE.

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The RIGHT way is the ONLY way.

OldSpark,
          I feel you growing tired of the lecture, And I'm not trying to beat this into the ground. nor am i trying to test your patience. Just wanted to fully understand the facts of the matter. please know that your words do not fall on deaf ears. And are truly appreciated. Ive always thought that if you don't learn something everyday, It was a wasted day. Thank you very much for your time and knowledge.

resquchas,
          Understood. And I'm definitely going to give this aspect of the project allot more thought,And ill keep your words in mind while doing so. Ive already got a couple thoughts in mind that are going to have to wait till this weekend to investigate.
 Thank you for your encouragement and sharing your own experience with me.

It might take me a few more weeks to complete because I'm only able to work on it during the weekends. but ill try to post picks when i do finish it. And if it finishes out as well as it has started. Ill be very pleased. And it should .
         Thanks again to everyone!

seattlejoe1970 wrote:

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OldSpark, I feel you growing tired of the lecture, And I'm not trying to beat this into the ground. nor am i trying to test your patience...

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No Joe! My intent re "If you think the airflow-restricted fan slows down..." was "if it does slow down" - ie, because you know that or have observed that. (IE - if it slows it is under greater load and should therefore take higher current to compensate. That is generally how motors etc work AFAIK.)

But I have yet to (knowingly) observe that...
But in my experience, blocking "fan air" has always resulted in the fan speeding up. And the few times I have measured it, the current has decreased.

I can't say that I know nor have studied what happens with varying restrictions around normal flow rates, but that was too complicated compared to simpler and more direct or meaningful air-flow detection methods so it was never worth studying (from the POV of detecting blocked filters OR lost flow hence eventual overheating).


Learning something everyday can be a luxury, and the other days simply boring or "a day off" rather than being wasted.
After all, ask enough & you learn enough. Think enough and you may not need to "learn" (from others) - you develop & teach yourself.


But as per resquchas - to think before building etc, isn't that sensible? (It often is in retrospect!)
I'd rather ask a dumb question than do a dumb thing. (Though the "dumb thing" may be enjoyable in itself - and less embarrassing....)

In our boat I did an install that is encased in acryllic so I could use the storeage area without worrying about the amps getting hit with stuff. I used 4 of the stinger cross-flow fans and also wired them with an adjustable temp switch so they come on when the amps reach a specific temp. Going overboard as I normally do I also installed a couple sensors and a Cyperdyne Amp Temp display . I can switch between each of the amps to monitor their temp independently. I raised the amps up off the mounting board by 1/2" so air can flow around all sides of the amp.

I went with a straight cross flow with all fans pushing instead of doing a push pull which I thought about. I have it set so there is an intake on top of the fans and an exit on the other side.  I did not use any filters, but this is in a boat so dust is not really an issue.

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James

The salt is the issue....


But yeah - push is usually better than pull or suck.
Most experimenters etc report that they are either similar ELSE push is better.