$400 fan failed because of $1 cap - Page 1
Forum section: electronics / general

author: Axk
author_rank: Regular Contributor
timestamp: August 12, 2019, 10:51:58 pm
content: Got this s&p td-silent fan and it lost power over time.Turned out the capacitor failed.Is this inavitable or have they saved on the capacitor? Just unlucky with a bad capacitor? Running overloaded?I've got another (cata) fan slightly older, still running fine. And it has been only 2 years.Not sure what happedned to the cap, but replacing it fixed the power loss issue.

author: Stray Electron
author_rank: Super Contributor
timestamp: August 12, 2019, 11:55:43 pm
content: That's common. I've replaced the caps in my A/C compressor, my well pump and in my attic fanseveraltimes each. Now I keep spares on hand for all of them. Replacements are expensive when you NEED one on short notice but I can pick new ones cheaply occasionally so I keep a variety on hand.

author: james_s
author_rank: Super Contributor
timestamp: August 13, 2019, 12:02:06 am
content: Same here, I've replaced the run caps in the heat pumps at both my mom's place and mine. I also keep a spare around because they usually crap out on the hottest day of the year when you'd most like to have AC.

author: coppercone2
author_rank: Super Contributor
timestamp: August 13, 2019, 12:04:56 am
content: if you do HVAC work, its kind of a standard part to replace after time.

author: golden_labels
author_rank: Super Contributor
timestamp: August 13, 2019, 01:52:53 am
content: What a coincidence: the same model (though 1µF/450V) has failed in my room fan last week. I’m waiting for a new one to arrive, along with a thermal cutoff that died with the capacitor. It seems that you’re luckier than me: yours have solderable pins, while my have wires potted. Actually the whole fan, from the wall plug to the windings, is made as a monolithic unit. Not even a single point where you could probe it without cutting wires.That is not something unusual and is not an indicator of a bad design, unless you can prove that in some model they fail considerably more often than the typical rate. Run capacitors are under stress even higher than start capacitors and they break from time to time. Just replace with another one of the same capacitance and voltage rating. Preferably with the same model — run caps need possibly low serial resistance and take not very favourable working conditions, so using just any 0.8µF/400V cap may not be the best idea.

author: wraper
author_rank: Unknown
timestamp: August 13, 2019, 02:13:53 am
content: QuoteI repaired $200k+ equipment which failed because of $0.20 part. So what?

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 13, 2019, 02:19:08 am
content: I'm having a hard time thinking of why a fan with a run cap under 1uF would cost $400. At that price, I would expect it to be BLDC, and a very fancy one at that.

author: wraper
author_rank: Unknown
timestamp: August 13, 2019, 02:23:33 am
content: Quote from: NiHaoMike on August 13, 2019, 02:19:08 amWould you also expect built in SMPS and driver to power that BLDC? or VFD?. It might be surprise for you but fans/motors are quite expensive once you want something more than small noisy fan.

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 13, 2019, 03:06:25 am
content: Quote from: wraper on August 13, 2019, 02:23:33 am0.8uF implies a very small motor, for reference 5uF seems to be the standard for the fan motor in a window A/C unit. The last time I opened up a desk fan, the capacitor was 2.2uF.$400 for a low tech fan is quite high unless we're talking about something much bigger than what uses a 0.8uF run cap. BTW, in the HVAC industry, BLDC motors are very common, sometimes called ECM when they are designed to be drop in replacements for the inefficient induction motors.

author: Brumby
author_rank: Unknown
timestamp: August 13, 2019, 04:48:38 am
content: Then there's the one about a $50 SCR blowing to protect a 50 cent fuse.

author: Gyro
author_rank: Super Contributor
timestamp: August 13, 2019, 12:29:16 pm
content: Quote from: Brumby on August 13, 2019, 04:48:38 amActually, semiconductors make excellentanti-fuses. They usually fail short, taking out your precious 50 cent fuse too!Those special 'FF' fuses for semiconductor protection are often just shorthand for FFS!

author: james_s
author_rank: Super Contributor
timestamp: August 13, 2019, 06:06:30 pm
content: Quote from: NiHaoMike on August 13, 2019, 03:06:25 amInduction motors (ignoring the shaded pole type) are surprisingly efficient machines. The gains from BLDC in HVAC applications comes mostly from being able to easily adjust the fan speed to suit conditions, but this requires the system to be designed to take advantage of this.

author: Axk
author_rank: Regular Contributor
timestamp: August 13, 2019, 10:25:40 pm
content: Sorry for lying to you guys ) It is around $200 actually. The price is for it being extra quiet I suppose. No fancy BLDC motors.https://www.amazon.co.uk/Ultra-inline-SILENT-Soler-Palau/dp/B010B9QYZ4

author: Axk
author_rank: Regular Contributor
timestamp: August 13, 2019, 10:45:55 pm
content: Wrapped in a kind of a rubber apron, or how do you call it. To damp noise I suppose.

author: Axk
author_rank: Regular Contributor
timestamp: August 13, 2019, 10:48:13 pm
content: Rubber on the outside.

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 14, 2019, 01:04:21 am
content: Quote from: james_s on August 13, 2019, 06:06:30 pmThe big ones are pretty efficient, but the small ones are pretty poor even for the PSC type. In particular, most multi speed induction motors are a bit of a kludge that are lossy by design.I would have expected a quiet fan to use a bigger capacitor in order to have the quadrature phase be of closer power to the main phase, to reduce torque ripple. Or just use a sinusoidal driven 3 phase BLDC that's inherently constant torque, as Noctua does.

author: james_s
author_rank: Super Contributor
timestamp: August 14, 2019, 01:46:57 am
content: Almost every fan I've seen uses a shaded pole motor. The typical customer would never know the difference, blade and housing design plays a large part in noise output but even a cheap shaded pole motor is pretty quiet. The appearance, brand name and claims printed on the box have much more sway with a normal consumer than the type of motor.