Noisy Fan
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Back in October 2023 I decided that my old UPS
was becoming too unreliable and as we regularly get power cuts
I decided to buy a new one. For those that haven't used a UPS
let me explain what it is...
If you're using a PC and the incoming mains supply
suddenly fails the PC will instantly turn off losing whatever
you're working on and also perhaps getting so corrupted it will
fail to boot up. An "Uninterruptible Power
Supply" develops a mains equivalent voltage from
internal batteries at a power level of your choice. Connect your
PC plus display etc to your UPS and you'll have enough time to
finish what you're doing and close down correctly. The more you
invest the longer the time you can rely on your UPS for power.
In fact with one rated at say 2KVA you can also connect your
router, a table lamp and whatever you deem necessary.
A UPS doesn't last for ever though because its lead
acid batteries will eventually degrade. This will be progressive...
meaning that you may lose UPS power fairly quickly after several
years of use.
My last UPS blew up because of a surge in the mains
supply during its loss. Fortunately my protestations to Scottish
Power, who oddly are in charge of distributing power on the South
coast, paid me compensation to cover new batteries and new power
transistors so I was able to repair it without forking out for
a new one.
By October I'd lost the display and, before then,
both the USB and RJ45 comms had failed... plus the batteries
failed to charge properly so I bought a brand new one. |
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The new UPS is a Powercool 2000VA and worked
perfectly well when I'd installed it.
After a week or so I noticed slight fan noise was
now definitely not slightly noisy.. it was getting distracting.
I had several options.. get the UPS replaced (it would take about
a month through my supplier and the replacement may not be any
different), unplug the fan (but the UPS might get too hot), insert
a resistor in the 2-wire fan lead to reduce its speed (a bit
hit and miss), or add a thermal device to control the fan (my
chosen option). |
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I opened the case and unplugged the fan. I'd
done some rough calculations and purchased a couple of thermal
switches type KSD9700 rated at 55 degrees Centigrade with normally
open contacts.
I glued one to each of the two heat sinks accommodating
its power transistors (the UPS has just two large heatsinks).
Because my plan was to turn on the fan if either heatsink
reached 55 degrees I connected the devices in parallel in the
fan's opened red lead. That means if either heatsink got too
warm the fan would power up. The aim was to silence the unit
when the PC was off or when the ambient temperature wasn't too
warm.
Now the UPS is generally silent. A fall back option
I'd considered was to add a resistor across the thermal cut-outs
which would allow a slow and maybe an almost silent fan.
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