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Old 18-01-2021, 10:42   #1
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Exhaust Fan Recommendation

I ewant to install a small exhaust fan in my battery compartment. Its in the living area under the settee. I was wondering if anyone knew of a very quiet one that had a relatively small amp draw.
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Old 18-01-2021, 10:54   #2
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Re: Exhaust Fan Recommendation

Computer fan
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Old 18-01-2021, 11:18   #3
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Re: Exhaust Fan Recommendation

Thanks Bill. I thought of that but i was thinking i need to vent the fumes overboard. I have a scupper vent on the stern that my engine blower connects to to dump engine heat overboard. I figured i would try and tee off another line into that hose and bring another section of hose into the battery compartment. i guess i would need an inline fan but the ones on West Marine's website seem to have a very short service life and i have never used one so not sure how loud they are?

I wasnt sure if a computer fan would have the strength to get the air through the hose.
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Old 18-01-2021, 11:45   #4
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Re: Exhaust Fan Recommendation

"I wasnt sure if a computer fan would have the strength to get the air through the hose."

You don’t need a hurricane to draw some outventing from your batteries, a regular modest airflow will do fine.
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Old 18-01-2021, 12:21   #5
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Re: Exhaust Fan Recommendation

Pancake (computer) Fan Duct Mounting Plate

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Old 18-01-2021, 12:33   #6
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Re: Exhaust Fan Recommendation

Quote:
Originally Posted by er9 View Post
Thanks Bill. I thought of that but i was thinking i need to vent the fumes overboard. I have a scupper vent on the stern that my engine blower connects to to dump engine heat overboard. I figured i would try and tee off another line into that hose and bring another section of hose into the battery compartment. i guess i would need an inline fan but the ones on West Marine's website seem to have a very short service life and i have never used one so not sure how loud they are?

I wasnt sure if a computer fan would have the strength to get the air through the hose.
Without a diverter of some kind at the T, there is no way to prevent the air from getting routed down the blower duct that goes into the bilge. You'd basically create a weird loop which would potentially go inboard rather than outboard.

A blower fan would be loud IMHO.

They do make large, high volume PC fans. Look at a 250MM or 360MM pc fan.
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Old 18-01-2021, 12:54   #7
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Re: Exhaust Fan Recommendation

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Without a diverter of some kind at the T, there is no way to prevent the air from getting routed down the blower duct that goes into the bilge. You'd basically create a weird loop which would potentially go inboard rather than outboard.

A blower fan would be loud IMHO.

They do make large, high volume PC fans. Look at a 250MM or 360MM pc fan.
yeah good point. i didnt think about that. thanks for all the replies. i think i might give the pc fan a try with that adaptor Gord May linked to. If it doesnt work it will be a cheap experiment.
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Old 18-01-2021, 13:11   #8
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Re: Exhaust Fan Recommendation

Computer fan. However, if some sort of routing is available for a hose, just a hose to the compartment routed to a higher exit , 4-5 ft, gives a surprising amount of air movement through the "chimney effect" and no fan. Even a 2" hose or something like that.
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Old 18-01-2021, 18:36   #9
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Re: Exhaust Fan Recommendation

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Originally Posted by Cheechako View Post
Computer fan. However, if some sort of routing is available for a hose, just a hose to the compartment routed to a higher exit , 4-5 ft, gives a surprising amount of air movement through the "chimney effect" and no fan. Even a 2" hose or something like that.
thanks. unfortunately no.

i leaning towards creating a ducting network from rigid pvc pipe and ditching the old, deteriorated flexible ducting. im thinking of at least a sort of 'backbone' rigid duct pipe with built in tee's out of pvc that i can tee in short runs of flexible hose. i have several areas i want to ventilate and this will let me. i can simple close off or plug un-used areas while not in use.

not a project i intended to get into for at least a couple more years but oh well...such is sailboat life.
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Old 22-01-2021, 11:26   #10
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Re: Exhaust Fan Recommendation

To prevent backflow, I believe there are bathroom exhaust flaps that might help, but they are used with 120v higher cfm fans, maybe you can find or make something similar.
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Old 22-01-2021, 13:07   #11
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Re: Exhaust Fan Recommendation

I added a small interior air circulation fan inside my 1.8 cubic foot DC fridge.

I wanted the lowest amp draw one I could find, as I run it 24/7, whether the compressor is running or not.

Sunon MagLev KDE1204PKV3.MS.AR.GN

40mm diameter, 20mm thick

0.03 amps, 6.3 cfm

Peel up the sticker on the hub and cover the solder joints where the power wires enter, with clear nail polish or similar.

You could use a higher amp draw larger lower rpm(noise) fan, if you have it activated only at gassing voltages.

I've leaned towards ridiculously powerful computer fans using a 5amp voltage bucker with an XL4015 chip as a speed controller. I can get a 200CFM 120mm fan down to 0.08 amps draw and nearly silent, through the bucker.

These newer xl4015 buckers are quite efficient and turned all the way up, on a 3 amp load, drop only 0.19v across them, the XL4005 drop 0.29v. Older 3 amp LM2596 drop 0.7v.

One could just get a 24v fan and run it at 12v as well and reduce amp draw and noise. Get a Dual ball bearing or a fluid dynamic bearing fan as opposed to a sleeve bearing fan.

Sunon, Nidec, Delta, Noctua are 4 of my favorite computer fan brands. Noctua is very well engineered, but all these fans should have the wire entry at the hub further protected from corrosion.
It is the failure mode of almost every single fan I have used over the last 15 years, and no fan has yet failed that i have added protection here, to.

I imagine one dedicated to exhausting battery fumes, is even more suceptible to corrosion
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Old 22-01-2021, 13:44   #12
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Re: Exhaust Fan Recommendation

Would the larger computer fans be a good replacement for noisy engine room fans like the yellowtail? Ducting heat out of the engine to promote fresh air entering the engine via the cabin?
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Old 22-01-2021, 21:43   #13
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Re: Exhaust Fan Recommendation

I have no direct experience with the yellowtail fan.

Powerful computer fans are noisy too, but a larger fan can move as much air, for less noise and often less amp draw, if that is a factor.

Fan RPM is related to a fan's static pressure rating, and the pressure rating is related to how well it can move air against a resistance, where as a cfm rating is calculated by air velocity and the diameter of the fan aperture.

Often a high CFM fan can have a poor static pressure rating and a fan with a high static pressure rating might not have an impressive CFM rating

The 3 inch(76.2)mm yellowtail claims 120 CFM and gives no static pressure rating.

I have a Delta 92mm computer fan with a 175cfm rating, but it screams like a banshee at 12v as it is spinning 7K rpm. But it is so powerful I rarely run it near full speed.

The computer fans are not as easy to hook ducting to. Their inlets and outlets are not perfectly round either. A perfect aperture for a computer fan has 4 flats

92, 120 and 140mm computer fans are popular sizes with lots of choices, but they could be a poor choice as a bilge blower, especially if they are not hardened by the user for such an environment.

A superpowerful fan with a 21KHZ PWM motor speed controller, can allow one to dial down the noise to tolerable levels or crank it up when it does not matter.
21KHZ, as lesser frequency than this makes the motor windings whine annoyingly at reduced speeds.
I prefer modified voltage buckers for 5 amp or less fans or 10 amp buck/boosters for the 24v fans, opposed to PWM motor speed controllers.
'Modified' as I am removing the tiny jewelers screwdriver potentiometer on teh circuit board and replacing it with wires leading to a remote mounted finger twist potentiometer.

I think if one is annoyed with one bilge blower fan's noise, running two, at half speed via PWM speed controller and some Y shaped or dual ducting is a better solution.

Or a push/pull configuration. Have one bilge blower pushing cold air at the alternator's backside, and one sucking air from engine compartment.

In a tight compartment, two fans at half speed is far superior to one fan at full speed either pushing or pulling, as well as being quieter and drawing less amperage.

I don't think bilge blower fans put the resources into engineering the fan blade design and the brushless motor drivers like computer fans do, but the ease at which a bilge blower fan can be ducted, is quite attractive.

I think computer fans are best when pushing air into a restriction, or are not restricted. They seem to perform worst when there is restriction close to the back of their blades.
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Old 23-01-2021, 06:43   #14
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Re: Exhaust Fan Recommendation

Thank you for the great ideas. How would you control the speed sensor ones, a twist potentiometer?

Sunon MagLev KDE1204PKV3.MS.AR.GN
40mm diameter, 20mm thick, 0.03 amps, 6.3 cfm, noise 18 db A

xl4015 buck step down converter $7
3pcs XL4015 4~38V to 1.25-36V 5A DC-DC Buck Converter Step Down Module 5A DC-DC Adjustable Step-Down Module XL4015 4~38v

Ultra Quiet 140mm fans. Noctua is listed. It looks like fans from this list might be the best to use.

Werleo 12vdc 200cfm 12cm 120mm Werleo fan $26
Model: FFC1212DE, Size: 120mm x 120mm x 38mm, Dual Ball Bearing, Speed: 4000 RPM, Air Flow: 200 CFM, Noise Level: 59dBA. Power: 12VDC 3.0A 36W, 3-Wire 3-Pin Connector with Speed Sensor.

Noctua NF-P12 redux-900, Ultra Quiet Silent Fan, 3-Pin, 900 RPM $30
120mm Ultra low noise fan, 120x120x25mm, 12V, 1200/900 RPM, max. 12.1 dB(A), >150,000 h MTTF, ideal for CPU coolers and watercooling radiators, Flow Acceleration Channels, record tight 0.5mm tip clearance, anti-vibration mounts, radiator gasket. Does not state 200cfm

Noctua NF-P12 redux-1700 PWM, High Performance Cooling Fan, $13 4-Pin, 1700 RPM 120mm, 12V, 4-pin PWM, max. 1700 RPM, max. 25.1 dB(A), >150,000 h MTTF, Pressure-optimised blade design, high static pressure and strong CFM for air-based CPU coolers, water cooling radiators or low-noise chassis ventilation, 1700rpm 4-pin PWM version supports automatic motherboard speed control, optional accessories (anti-vibration mounts, S-ATA adaptors, y-splitters)
- Would these work with a twist potentiometer?

Noctua NF A14 Industrial PPC 140x140x25mm PWM Fan IP52 Rated
4-pin PWM, Bearing SSO2, 2000 RPM, Min speed (PWM, +/-20%) 500 RPM, Airflow 182,5 m³/h, 31,5 dB(A), Static Pressure 4,18 mm H2O, Max. Input Power 2,16 W Max. Input Current 0,18 A, 12 V, Motor type Three-phase
- Would this work with a twist potentiometer?

DC 12V 24V 3A 21kHz PWM DC Motor Speed Regulator Controller $8.25 Adjustable Speed Control Reversible Relay Module 6V-28V 1203BS
For more powerful fans, more than 5a?

21KHz 6-28V DC Motor Controller, Reversible Switch 3A PWM Controller $8

Mini DC Motor PWM Speed Controller 3V 6V 12V 24V 35VDC 90W 5a DC Motor O9V9 $6 on ebay. Would it work? (Probably not as efficient)

I would find a cowl for two of these and, as you suggest mount a pusher and a puller fan. I also like the idea of two pusher fans at lower RPM using my 3" vent. Would I need separate twist potentiometers or separate DC motor controllers? What about the ones with PWM speed control?

140mm is 5.5", I have (2) 3" dia vents at the stern, but I could blow into the cabin and move air in from the two 3" vents at the stern.
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Old 23-01-2021, 06:57   #15
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Re: Exhaust Fan Recommendation

This one has a higher static pressure rating than some of the others, it is about 4.15mm h20, cooler fresh air will flow in from the cabin openings.

Noctua NF-A14 iPPC PWM 12V 2000RPM 140mm High Performance Fan
so would it be a better choice for a 6' duct situation?

I think it might be best to mount two of these, each one pushing into its own separate 3" flex duct connected to separate 3" vents at the stern.
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