Has Anyone Ever Replaced the Fan in a APC UPS?

Zarathustra[H]

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Oct 29, 2000
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Hey all,

I have an aging APC Smart-UPS SUA1500 desktop model which I got used on eBay in like 2014 or so.

1602603430068.png

(Example pic from Google, not mine)

It's a great unit, built like a tank, and just incredibly reliable. Couldn't be happier with it.

That said, the thing has likely been in service for many years (I do not know what the manyfacture date was, or how the first owner used it), and all good fan bearings come to an end. It is starting to make those groaning noises and starting to annoy me.

Before I shut down all the stuff I have running off of it, and disassemble it to inspect it, has anyone ever replaced the fan in one of these?

Are we talking standard PWM 4pin PC fan in a standard PC size? Is the fan close to those happy little potentially life-ending capacitors?

Appreciate any thoughts.
 
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GiGaBiTe

[H]ard|Gawd
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Apr 26, 2013
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I've replaced fans in similar units, and they generally use 80mm fans, but the gotcha is they're usually 24v and not 12v like PCs use. They'll either be two or three wire fans.

24v 80mm fans aren't terribly difficult to find, but if you can't, you can use a cheap LM2596 buck converter module and splice it on the pigtail to drop the voltage down. Double sided tape or hot glue to stick it to the fan. You'll definitely want to pre-set the voltage before you connect the fan up to avoid killing the hall effect sensor.

As for spicy voltages inside, just make sure the batteries and mains are disconnected before you open the unit. If you see any juicy capacitors, stick a multimeter across them to see if they have any charge left. If they do, you can use the quick and dirty method of a screwdriver across them. Just be aware that capacitors can self-recharge after discharging, so it's best to leave them shorted out with croc clip leads while working on them.
 

Zarathustra[H]

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Joined
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I've replaced fans in similar units, and they generally use 80mm fans, but the gotcha is they're usually 24v and not 12v like PCs use. They'll either be two or three wire fans.

24v 80mm fans aren't terribly difficult to find, but if you can't, you can use a cheap LM2596 buck converter module and splice it on the pigtail to drop the voltage down. Double sided tape or hot glue to stick it to the fan. You'll definitely want to pre-set the voltage before you connect the fan up to avoid killing the hall effect sensor.

As for spicy voltages inside, just make sure the batteries and mains are disconnected before you open the unit. If you see any juicy capacitors, stick a multimeter across them to see if they have any charge left. If they do, you can use the quick and dirty method of a screwdriver across them. Just be aware that capacitors can self-recharge after discharging, so it's best to leave them shorted out with croc clip leads while working on them.


Thank you for that suggestion.

I pulled the battery out today to see if I could access the fan, but couldn't It's in the back of the unit, so I am going to have to take the back cover off. Didn't have time for that today.

Unless there is more than one fan and they operate at different speeds (I can only see one through th event from the outside) the fan in this particular model is definitely changes speeds based on load.

So, either it is pwm adjusted, or changes speed base3d on voltage. If it uses voltage to change the speed, will one of these buck converters still work, or will they just output a fixed voltage?


For instance, if it winds up being a 24v fan, and at idle it runs at - say - 12v, but goes up to 24v at max speed. If I use a buck converter to bring it from 24v down to 12v at max speed, and the PSU then drops voltage to slow the fan, will th econverter also drop the voltage, or will it maintain it at 12v as the voltage drops?

(Bear with me here, I am not familiar with these types of regulators)
 

GiGaBiTe

[H]ard|Gawd
Joined
Apr 26, 2013
Messages
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You'll definitely have to take the metal shell off the UPS to get at the fans. Usually it's just four or six screws on the bottom of the unit and the shell slides backwards off the base.

As for fan speed control, the units I worked on only had fixed speed fans that came on under load. A buck converter will work with variable voltage controlled fans, but it depends on the buck converter as to how the fan will act. Some buck converters will have the output voltage follow the input voltage as it rises and falls, while others will try and maintain a fixed output voltage until the input voltage drops too low to maintain the desired output voltage and then start dropping. The only advice I can recommend is test the buck converters you buy because even though many look near identical, they can all function differently. Though in the case of a variable speed fan, it'd be better to just replace it with another 24v fan.
 

drescherjm

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Nov 19, 2008
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14,850
It will be easier to just get a 24V fan.

Also be careful what you touch inside the unit.

Edit: I see you were already warned about that!

I just looked at Amazon and they have a few 24V 80mm fans available.
 

pendragon1

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Oct 7, 2000
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Your last link for some reason points to pchub
when i pasted in the link i hit the wrong line and it went in behind the pchub url, so i hit the undo button and repasted it to the bottom but for some reason it still pulled the url with it. odd, but fixed.
 
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