Aardvark Daily

Please visit the sponsor!

Fan-tastic fun

On Saturday I was working away editing some video when a loud noise filled my office.

It was the over-temperature alarm on my Siemens Masterguard 1KVA UPS.

This UPS has served me reliably for almost three decades, running 24/7 and protecting a bunch of gear from power outages, spikes and goodness knows what else.

Aside from several replacement SLA batteries and a previous fan change, it has required nothing more than the occasional blow-out with an air compressor to remove accumulated dust and detritus.

In short, this is a pretty solid bit of very high quality electronics that continues to impress me to this day.

However, the fact that it was now screaming at me meant that something had clearly gone wrong.

I have to admit that I knew the overheating situation was likely because when I changed the fan a while back I couldn't find a really suitable replacement.

The fan itself is an 80mm square by 25mm thick unit that operates on 12V DC.

It's not fancy... there's no PWM speed control, it just runs at a constant speed and the original wasn't exactly silent, even before its bearings got lunched by over 20 years of continuous use.

I recall that last time I went searching for a replacement fan I could only find one that seemed about half as powerful -- but it worked for normal loads (two out of five bars on the load meter). However, when the load reached three bars or higher, the new fan was incapable of moving enough air to keep the internals from overheating and the alarm from sounding.

Knowing that I would eventually have to find a better fan I purchased several 80x80x25mm fans in anticipation of the day I'd actually get around to fixing this thing for good.

So, on Saturday I put the UPS on the bench and set about replacing the wimpy fan with something better.

Sadly, none of the replacement fans were actually better than the one I was already using. Even the rather expensive Noctua fan was gutless and although totally silent, moved about as much air as a flea-fart.

I then went online to try and find a stronger replacement... nothing.

Someone suggested I use AI and proffered Grok as perhaps a good agent for such a task -- so I gave it a go.

What a disaster!

Grok confidently came back with a raft of airflow figures and fan options that, on the face of it, looked great. How could I have missed these options in my comprehensive manual search?

Well guess what?

Grok was full of shite.

The fans it suggested as being as good or better than the original were just a waste of time.

Despite claiming these were all the same form-factor as the original, downloading the datasheets showed that most of them were significantly thicker, usually 35mm instead of 25mm which means they simply won't fit the case. When I queried this, Grok, like all AI systems, apologised and acknowledged its mistakes.

After laboriously checking and discarding all of the allegedly suitable options I was back at square one... unable to find a suitable replacement fan. Even Siemens no longer carry parts for this UPS from last century.

So how to solve this problem?

Well I could get a stronger fan with a thicker form-factor but these have awful noise figures and since this UPS is sitting just a couple of metres away from my desk and microphone, that noise would be unacceptable.

Time for some lateral thinking!

Big fans turning slowly tend to be a lot quieter than little fans spinning fast and they can also move a lot more air in a given amount of time. Clearly a bigger fan would be a good idea -- but the case will only take an 80x80x25mm unit and even that's a tight squeeze.

After a little contemplation, a fresh cup of coffee and a moment of inspiration I fired up my CAD program and designed an interface manifold that would allow me to use a 140mm fan on the outside of the case. One end has a flange with 80mm mounting holes and opening, the other side mates to a 140mm fan I also have sitting around -- between the two flanges is a truncated cone.

I created an STL file, sent it to the 3D printer and about 2 hours later I had my solution.

The 140mm fan is still virtually silent but it draws just about as much air as the original (noisy) 80mm unit and far more than any of the replacement options.

Yes, it does stick out the back of the case and look a bit dorky -- but it works a treat and I'll take function over fashion any day of the week.

The other bonus is that all it cost me was a little time and about $2 worth of PETG printer filament.

One of the funnest things you can do in life is solve problems and I actually quite enjoyed this whole experience -- much better than veging out in front of Netflix on a Saturday arvo (not that I've everdone the latter).

Now I can crank up my video editing software to the point where both the CPU and GPU are sucking many watts of power to track objects, grade colours and 3D render objects -- driving the UPS load meter up the scale like never before -- and all I hear is: cool silence!

Carpe Diem folks!

Please visit the sponsor!

Here is a PERMANENT link to this column

Rank This Aardvark Page

Change Font