Rack door fans - quiet fix or alternative?

virulent

New Member
Jul 3, 2019
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Hey all.

I have this rack: https://assets.tripplite.com/product-pdfs/en/sr24ubffd.pdf

Great rack. However the 8 door fans are way too loud for my liking so they are always off. The air intake for servers was a bit too toasty and their fans were spooling up to compensate (5+C above ambient) so I installed 2 120mm exhaust fans (AC Infinity) at the top which fixed the temps and fan noise immediately.

I'd still like to use the front fans to help force airflow through the filters (and really... to have the option just because they are there :')). I don't have a 'harsh' environment, but the dust and hair control would be nice to keep the server intakes cleaner.

Problem is: they're 120V. Model MQ12038HBL 110/120V AC 50/60 Hz. Each fan draws ~30W, so seemingly a ton of room to slow these puppies down but I'm not sure how. It just has a power switch so I would need to change this.
When I was researching google I got the impression that I CANNOT use a ceiling/lamp style dimmer (voltage reducer) and would need a PWM style or frequency speed control or else it can overheat? Maybe someone can confirm? I'm an electronics noob and this sort of fan config (120V AC 120mm) seems rare so finding any sort of info was difficult as there are zillions of other kinds of fan motors that are definitely not this one.

Alternative: swap them all with off the shelf 12v 120mm fans and a fan controller + power supply (PoE?). Wiring all of that up isn't a problem, and is probably the better option as I can use fans I KNOW are affordable and quite quiet at max speed (e.g. Arctic). It won't get nearly the same pressure or cfm through it, but I also don't have 24U of dense gear inside the rack (or will I ever).

Any alternative suggestions are great too!

TIA!
 
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