Beets82 Posted July 31, 2011 Report Share Posted July 31, 2011 I have had a bit of a fungal problem in my stand. I put a cover over my sump a couple of months ago and it has really helped but not 100%. So I have brought a small fan kind of like for a computer. http://www.jaycar.co.nz/productView.asp?ID=YX2509&keywords=80+mm+fan&form=KEYWORD Question - Is it better to have the air flow sucking out of the cabinet creating -ve pressure or have it blowing in +ve pressure like a HRV or DVS in a home. I will prob just run it on a time clock a few hours per day. fanx Rob Quote Link to comment Share on other sites More sharing options...
Ira Posted July 31, 2011 Report Share Posted July 31, 2011 So I have brought a small fan kind of like for a computer. Whrere drid yrou bruy irt from? Question - Is it better to have the air flow sucking out of the cabinet creating -ve pressure or have it blowing in +ve pressure like a HRV or DVS in a home. I will prob just run it on a time clock a few hours per day. I'd have it blowing in, otherwise you're sucking damp air through the fan which can corrode it. Quote Link to comment Share on other sites More sharing options...
Warren Posted July 31, 2011 Report Share Posted July 31, 2011 If it's a 12V fan you could also leave it running all the time but power it of 5-6V. All you will need is a very small airflow to stop the damp. This has the added bonus of making the fan almost silent. A cheap plugpack will do the job. Quote Link to comment Share on other sites More sharing options...
Beets82 Posted August 2, 2011 Author Report Share Posted August 2, 2011 Its exactly the fan in the link, only 14w so wont use much power maybe 7 cents a day if it was going 24/7. I think I won't need it running too much and in summer when the heaters in the sump do go much it can prob stay off. I'm going to put it in so it is blowing into the cabinet -so its not sucking wet air through as Ira pointed out and also I don't want a gross moldy patch on my wall. Quote Link to comment Share on other sites More sharing options...
Warren Posted August 2, 2011 Report Share Posted August 2, 2011 Jaycars specs are wrong - it's not 14W. At 23 cfm it's only 1.4W - also confirmed by the current of 100mA (12V x 0.1A = 1.2W - close). However, at 2800RPM (if this is acurate) it might be a bit noisy. If it is you have 2 options - get a lower voltage PSU or add a series resistor. Every 10 Ohms will give you about 1V drop @ 100mA. Heat loss in the resistor is propotional to V² so there's 4 x the heat for double the voltage drop. eg: 1V drop (10ohms) = 100mW, 2V drop (20 ohms) = 400mW, 3V drop (30 Ohms) = 900mW, 4V drop (40 ohms) = 1.6W etc. If you use the resistor voltage drop method you will need to size the resistor correctly. Pick a resistor wattage about 3x the power loss. Resistors run at about 200'C+ at their rated wattage. Derating to 1/3 means they operate at a sensible temperature instead. eg, 4V drop (40 ohms - use 39 ohms as it's a standard size) = 1.6W so use a 5W resistor... 23cfm is heaps for your application and you will only need a fraction of this. Quote Link to comment Share on other sites More sharing options...
MalcolmX Posted August 2, 2011 Report Share Posted August 2, 2011 i use the variable 3.5-12v adaptors on my fans so i can find just the right level of noise and air movement. they are slightly more to buy though. Quote Link to comment Share on other sites More sharing options...
Beets82 Posted August 4, 2011 Author Report Share Posted August 4, 2011 All done. :thup: I biffed the 240v fan back into the dark closest whence it came from and got a cheap 12V fan. I already had a variable 3.5 -12v adapter which was unused. :happy2: Thanks for the help guys Warren - your over my head dude :hail: I'm swimming in the shallow end when it comes to electrical stuff :oops: , but i did learn something new, amps x volts = watts. Now only 3 more days off work and so many more projects to do ahhhhhh :digH: . Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.