UPS fan replacement - electrical guidance needed

[StephenFry]

Computer hardware is not something I'm usually scared of, but I know little to nothing of electrical components and until I do, will stick to the 'better safe than sorry' approach. My question comes from me being completely ignorant and confused about currents and amps and volts and the like. Well, nearly completely, so please be gentle.

This is the issue at hand: my trusty UPS, an old(ish) APC 3000 XL beast, has a fan that, judging by its noises, is expelling its last breaths.

It never was the quietest, so ideally, replacing this fan is an opportunity to silence the unit a bit.

If my information is correct, the culprit is a 24VDC, 10W fan. It is connected to the UPS main board by only two wires. The UPS has two, and only two, settings for the fan: low and high. It is never off (even if the UPS is turned off - it needs to be "braindead", with disconnected battery, for the fan to stop).

The two settings and two wires indicate to me that there is no 'intelligent' steering (like PWN) going on and the fan speed is getting adjusted by changing the voltage...?

Does this setup allow me to replace the old fan by a lower speed / lower noise fan with *different specs*? Say, a 24VDC 5W fan? Or will the UPS likely "send" it 10W and destroy it? Don't laugh, I really have no clue.

These are some images by 5mall5nail5 I found, from the same UPS:

 

[BigDave]

My question comes from me being completely ignorant and confused about currents and amps and volts and the like. Well, nearly completely, so please be gentle.

@StephenFry
What can I say my good fellow, you have come straight out and professed "nearly completely ignorant" for mucking around with this!!!!!
Why, oh WHY would you risk damage/destruction for the cost of a visit to a repair technician OR replacement?
Having said that, If I just had to do this myself I would as follows.

1. Take pictures/label wires before turning one screw
2. remove fan from enclosure
3. get label info from fan
4. find EXACT model number matching replacement if possible (some times these units have proprietary parts)
5. If you did not like the noise level before, BUY A NEW UPS
   
6. Was that gentle enough for you, sorry for yelling that last part... :p

 

[Dice]

Does this setup allow me to replace the old fan by a lower speed / lower noise fan with *different specs*? Say, a 24VDC 5W fan? Or will the UPS likely "send" it 10W and destroy it? Don't laugh, I really have no clue.

Replacing a 10w fan with a 5w fan is not a problem. The fan does not overcook. It just runs slower.
But mind you, the fans might not be "needed" when idle. When you put load on the unit ...things can get pretty damn hot.
I recommend you to test how hot the unit runs off when put on a load surpassing your intended usecase (but remains within spec of UPS) to evaluate if it is feasible to conduct any modifications.
Anyhow, if the fans are straight connected to a solid 24v rail (from what I see, that's the casE) without any sort of 3rd wire to a PCB, the machine won't notice.
Just make DAMN sure you don't cause any shorts while working on it. Remember, it is designed to hold voltage when ....shut off.

 

[Spearfoot]

Get a can of compressed air and blow the dust out of that rascal! :D

 

[wblock]

I advise people not to be messing around inside a UPS. At least not without removing the battery, and even then, there is a potential for surprise. If you had the make and model number of the fan, it would be possible to search for a replacement of the same voltage and, importantly, airflow. The sound level of fans is usually specified, so it might be possible to find a quieter replacement that can move the same amount of air. However, note that people who design fan grills tend to be unconcerned about the noise they generate, so even a quieter fan might be loud inside that case.

Finally, ball-bearing fans are slightly louder than cheap bushing fans, but last many times longer.

 

[StephenFry]

@StephenFry
Why, oh WHY would you risk damage/destruction for the cost of a visit to a repair technician OR replacement?

We all know why -- DIY is fun! And learning new things is, too. :D

find EXACT model number matching replacement if possible (some times these units have proprietary parts)

Thank you for being gentle ;) Finding an exact replacement is not difficult, I'd have done that had the noise not been an issue before. Or if it would have been totally inadvisable to use a different spec fan, which others quoted below say, it isn't... Hm.

Replacing a 10w fan with a 5w fan is not a problem. The fan does not overcook. It just runs slower.

I recommend you to test how hot the unit runs off when put on a load surpassing your intended usecase (but remains within spec of UPS) to evaluate if it is feasible to conduct any modifications.

Though I can claim ignorance when it comes to electrical matters, I am pragmatic enough - the existence of this fan seemed an indication it may be necessary. It's not super critical, though. This exact same model UPS was first delivered *without* fan(s). The second iteration had my 2-speed fan added, while the third iteration has a fan that only kicks in at a certain battery load and/or temperature.

My own tests showed that when my connected equipment is shut off or running, the temperature of the air inside various parts of the UPS as well as the exhaust is 1C above room temp. Discharging or charging adds 3 to 5C. I am confident in my scenario totally passive cooling will be adequate (power outages are maybe once in two years here, and 30s after power out everything is shut down anyway, so barely a load on the batteries ever), but because I like tinkering, would like to have a fan, only quiet.

Anyhow, if the fans are straight connected to a solid 24v rail (from what I see, that's the casE) without any sort of 3rd wire to a PCB, the machine won't notice.
Just make DAMN sure you don't cause any shorts while working on it. Remember, it is designed to hold voltage when ....shut off.

This is good to know, thank you.

When I replace the fan and do not die, I will report back. Could be a few weeks though, 24V fans are few and far between and there is never time to literally "screw around".
I will certainly put on a pair of rubber gloves and boots...

Get a can of compressed air and blow the dust out of that rascal! :D

Hahaha, these pictures are from user 5mall5nail5 on another forum, my unit is much neater, I swear!

Finally, ball-bearing fans are slightly louder than cheap bushing fans, but last many times longer.

For years, I've been a big "fan" *badum tish* of Sunon brand fans with 'magnetic levitation' type bearing. My every-day NAS with 11 hot-running 7200rpm Seagates, is perfectly cooled (30C max with room 20+) by just three 120mm 3100rpm Sunons pulling the air through. No pushing, nothing. Super silent apart from the air rush.

 

[wblock]

even then, there is a potential for surprise.

Didn't even realize I did that... "potential", get it? :)

 

[FreeNASftw]

Power in Watts is Volts * Amps. Volts are pushed, Amps are supplied to balance the equation. For easy numbers, 24V supply, 24W fan pulls 1A; 12W fan pulls 0.5A. It is electrically fine in this case to substitute a lower power fan so long as the voltage is correct, a higher power fan will move more air though.

Disconnect all power including batteries, don't touch any electronics as UPS's have some pretty big caps.

 

[Spearfoot]

Disconnect all power including batteries, don't touch any electronics as UPS's have some pretty big caps.

Yep. What @FreeNASftw means by 'caps' is capacitors. Capacitors store charge, and they retain that charge even if the UPS is unplugged. Be very careful poking around the innards of your UPS; touch the wrong spot and you could end up dead.

 

[jgreco]

Bear in mind that a UPS is a device that is storing energy using a chemical process, and this process generates heat. The UPS requires cooling.

The older APC SmartUPS units in particular are well known for generating heat, both because they ran kinda hot (heat from the electronics) and because they had a tendency to overcharge the batteries, causing nice extra toasty warming. Reducing the available cooling increases the stress on the batteries, which will lead to early battery failure, cooking and bulging of the batteries, etc. In the worst cases, it can lead to burning electronics or even fire. APC has gradually improved their designs over the years because their earlier APC SmartUPS units often burned through batteries in a year. Newer ones seem to be able to get 5+ years out of their batteries, and I've not seen any signs of overcharging.

Having owned hundreds of these units,

1) If a fan stalls, replacing is not optional.

2) Use the same or better fan for replacement.

3) The newer gear such as the APC SMX UPS series is much nicer, IMO, though not as-compatible with open software solutions such as NUT.

 

[Ericloewe]

If you're going to replace the fan, replace them both while you're at it. Get a pair of nice Deltas or San Aces.

 

[StephenFry]

After having just tinkered with my UPS, I can happily report that I have not died.

Also, I have not replaced any of the fans. "Whaaaat, Stephen!?? Why go through all this trouble and not do what you set out to do!?"

Well, let me tell you. After opening up the UPS and before purchasing €60 worth of fans, I decided to see if it was possible to confirm if only one of the three made noise.
So I ran the UPS while it was open. Poking at it with metal sticks while blindfolded, so as to be able to fully focus on my hearing.

It turns out the two smaller (80mm) fans are inaudible. They are very low-pressure 0.09A 22dBA fans and are working perfectly. One makes sure the battery compartment always has a bit of air movement, the other does the same for the compartment housing the transformers.

The larger, 120mm, fan, is a 9.6W 0.4A 48dBA 122cfm bad boy, trying to blow away the caps. It was making quite a ruckus, of course, but not the "neighbors-will complain-about-this" excessive noise from before. Just a lot of wind in a constricted space, nothing annoying.

The actual reason for my initial noise complaint? While working on it, I put the UPS in a horizontal orientation, but normally I'm running the unit on its side and apparently the big fan has decided it doesn't like that.

Replacing the fan would be an obvious solution, but the Stephen Fry Way is usually lazy and always cheap. If the fan runs at 90% or less, the noise (either from the fan itself or something resonating, I can't be sure) goes away.

This all means there is a step down buck regulator in this fan's future. A solution that should cost me about 4 minutes to install and 2 euros to acquire.

Mind you: this is me messing about and having fun with my home system, judge it as such :)

 

[Spearfoot]

After having just tinkered with my UPS, I can happily report that I have not died.

Also, I have not replaced any of the fans. "Whaaaat, Stephen!?? Why go through all this trouble and not do what you set out to do!?"

Well, let me tell you. After opening up the UPS and before purchasing €60 worth of fans, I decided to see if it was possible to confirm if only one of the three made noise.
So I ran the UPS while it was open. Poking at it with metal sticks while blindfolded, so as to be able to fully focus on my hearing.

It turns out the two smaller (80mm) fans are inaudible. They are very low-pressure 0.09A 22dBA fans and are working perfectly. One makes sure the battery compartment always has a bit of air movement, the other does the same for the compartment housing the transformers.

The larger, 120mm, fan, is a 9.6W 0.4A 48dBA 122cfm bad boy, trying to blow away the caps. It was making quite a ruckus, of course, but not the "neighbors-will complain-about-this" excessive noise from before. Just a lot of wind in a constricted space, nothing annoying.

The actual reason for my initial noise complaint? While working on it, I put the UPS in a horizontal orientation, but normally I'm running the unit on its side and apparently the big fan has decided it doesn't like that.

Replacing the fan would be an obvious solution, but the Stephen Fry Way is usually lazy and always cheap. If the fan runs at 90% or less, the noise (either from the fan itself or something resonating, I can't be sure) goes away.

This all means there is a step down buck regulator in this fan's future. A solution that should cost me about 4 minutes to install and 2 euros to acquire.

Mind you: this is me messing about and having fun with my home system, judge it as such :)

Very good, Jeeves!