Small Cooling Fan for Electrical Compartment

[wlooper89]

I am thinking about putting a cooling fan in my tongue box electrical compartment to keep things cooler for the converter and clear out any battery gas. The battery is sealed but I believe it can still give off a little gas if a pressure relief valve opens. There are two 2" openings in the back of my tongue box so one could allow air to enter and the other for the fan to blow air out. This is one link that shows a 12V 2” fan pretty cheap. The fan is intended to cool fish aquarium lighting. There were some 120V fans but they were said to make more noise.
http://www.marinedepot.com/ps_ViewItem~ ... tab~2.html
I believe the fan would only need to run when there is AC hookup for the converter. I would like for that to happen automatically so as to avoid an added drain on the battery when there is no AC. It would be better not to need to remember to turn a switch on or off.

It may require a 120V powered relay to turn the fan on, even though I would rather not do the extra wiring. Does anyone have thoughts or suggestions?

Thanks! Bill

[Dale M.]

Why not his one....

http://www.radioshack.com/product/index ... Id=2102824

Its 12 volt dc, could run off battery, and probably run for a year with out draining battery if you forget to turn switch off.... And you can probably get it locally, and not pay shipping...

Dale

[wlooper89]

Dale,

Thank you for your suggestion. It would be very nice to be able to buy the fan locally. That one is a little smaller than the holes in my tongue box but I will check stores in my area. The 2" fan draws a little over 1 watt and using the handy formula Amps=Watts/Volts it will use about 2 ampere hours from the battery in 24 hours. That would be a bit of drain on a long weekend.

I guess I will bite the bullet and buy this to make the fan automatic. That was a good idea to look at Radio Shack. A web search for something like this turns up a bewildering array of industrial stuff.
http://www.radioshack.com/product/index ... Id=2049721
Using the two terminals for the AC coil and two of the others as a switch for the DC fan it will not be much more trouble than putting in a regular DC switch.

The converter has an automatic internal fan that blows warm air into the compartment when it needs to cool itself. When the battery needs charging or there are a lot of lights on I can hear the converter fan running more. The electrical compartment is well sealed except for the two vent holes in the back and there probably is not much airflow in and out of the compartment. I think adding a new cooling fan will help keep things cooler.

Bill

[aggie79]

Computer fans are 12 volt. The 80 mm ones are about 3 1/4" though.

[wannabefree]

Go to your local computer repair guy and ask him for a junk power supply with a good fan. It should be free, but a couple bucks wouldn't be inappropriate.

[bg]

My local northern tool sells 12 volt computer fans.
Fans - Northern Tool

[Trackstriper]

May have a solution for you:



Approx 3-1/4" square x 1-5/8" deep. 0.06 amps @ 115 volts. Alloy housing and it is pretty quiet.

This fan is as old as some of the folks on the forum (8 March '82) but appears to still run fine. Been collecting dust in my garage. It's yours if you want it. PM or email me your address, or you can pick it up in Marietta.

Bruce

[wlooper89]

Bruce,

Thank you very much. That is a very nice offer. I have read that the DC fans are more quiet so I think I will go with one of those. Although when I listen to my computer power supply fan churning away I wonder. It will mean adding a 120V powered relay to turn the fan on when AC is available, but wiring is a sort of second hobby for me after camping.

The tongue electrical box is just behind our heads on the other side of the trailer wall when sleeping so I am thinking quiet will be a plus. I can definitely hear the converter fan when it runs. The 12V fans for fish aquarium lighting are meant to be quiet inside the house so I will probably get that one. It is also 2" the size of the holes already in the back of the tongue box.
http://www.marinedepot.com/ps_ViewItem~ ... tab~2.html

Bill

[Trackstriper]

Bill,

Don't understand why DC would be quieter than AC. Fan blade design and rpm would be huge factors though. Some 12v computer fans can be quite noisy. I had a small micro fan in my Vector inverter that would just whine...finally replace it with a small brushless blower and to make it very quiet I dropped the voltage with a variable resistor to the point where the fan would just reliably start. Can hardly hear it run but it moves air.

The AC fan that I offered was pretty quite by itself (about like a standard case fan) but if you put it against a sounding board it would transmit some noise. It would have been best insulated with a foam type mount. The small fan you are planning on getting will fit your existing ports better. BTW, the local Microcenter has a whole slew of various computer fans.

Best wishes with your project.

Bruce

[wlooper89]

Doing some searching on the web I learned a little more about 12V cooling fans. The quietest were said to have bearings of a type called hydra-flow that have fluid in the bearings. The next quietest are ball bearing followed by sleeve bearings. Panasonic makes the hydra-flow ones under the brand name Panaflo. Unfortunately they do not make the 2" size. The closest metric to 2" is 50mm but the smallest by Panaflo is 80mm. 2" is just less than 51mm so 50 is close enough. I found a ball bearing one for 6.95 with $.99 shipping and handling. Pretty amazing!

The airflow on this one is 19.5 CFM and noise is 32 db. This seems pretty good. The lowest noise level I saw was 25 db and I'm not sure how much difference that is. But this fan moves a lot more air. Some of the sites that sell fans give a lot of technical info such as RPM, CFM airflow, bearing type and noise level while others only the fan size. The site I used gives more info and is also very cheap on the shipping & handling. www.buyextras.com

I plan to mount the fan and the controlling relay inside an existing compartment inside my tongue box with a short hose to one of the vents in the back of the larger box. Hopefully this will help to dampen noise in the trailer. This existing compartment has a larger hole for wires that will allow air from the tongue box to enter.
Bill

[wlooper89]

I tried to sort out the difference in noise level between 25 and 32 decibels. The math involves logarithms and is way beyond me now. Apparently the human ear can detect an enormous range of sounds, beginning with a mosquito flying at 3' to a rock concert and beyond. One Google search found a comparison chart. Library whisper level noise is 30 db while normal human conversation level is 60-70 db.

As near as I can tell a 32 db sound would be about 4 times as loud as a 25 db sound. Hopefully still not too loud for sleeping in the trailer that is somewhat insulated from the tongue box. If not there is always the possibility of a new plan.

Bill

[Micro469]

I tried to sort out the difference in noise level between 25 and 32 decibels. The math involves logarithms and is way beyond me now. Apparently the human ear can detect an enormous range of sounds, beginning with a mosquito flying at 3' to a rock concert and beyond. One Google search found a comparison chart. Library whisper level noise is 30 db while normal human conversation level is 60-70 db.

As near as I can tell a 32 db sound would be about 4 times as loud as a 25 db sound. Hopefully still not too loud for sleeping in the trailer that is somewhat insulated from the tongue box. If not there is always the possibility of a new plan.

Bill

I put two small computer fans in an icebox in the galley. The icebox is made with 2" of pink foam insulation. When standing in the galley, you can't hear them, but at night in the tear, they sound like a 747 going overhead. I have to turn them off to sleep because they reverberate right through the walls...... just a thought......

[wlooper89]

John,

Many thanks! I will do that too so we can turn the fan off at night. I am not normally using a lot of power at night and everything is cooler, so with an added spare switch that I already have we can turn off the fan if it is too loud.

Paige generously agreed to help with photo of small cooling fan parts. The hose ends will have clamps not shown. The relay is powered by 120V AC if the converter is powered. 12V DC then goes to the fan through the relay contacts and switch if the relay is powered and the switch on.

Bill

[BrwBier]

I would think that the mounting of the fan would make as much or more difference than the fan it self. I would experiment with some way of soft mounting the fan.

[wlooper89]

Thank you for your idea about a soft mounting for the fan. That could help.

Bill