SELV extractor fan switching

Feb 02, 2017 5 Replies

Have a need to place an extractor fan within reach of a shower so obviously have to fit a 12V one. No problem there, but I would like it to be humidistat switched, looking around I could only find a limited number of examples.



Has anyone used one of the separate humidistat switches, switching the transformer and does it cause any problems? Or do I have to hunt for a mains powered switch with volt free contacts and switch the 12V side?



I don't see why it should cause any problems switching the PSU.

Manrose humidistats are good (I have one) and also contain a run on timer and auxiliary switch input to which you can wire a pull cored momentary switch[1] to force the fan on for a time if required.

[1] Use the MK disabled alarm switch for this and buy a white cord to replace the red one. Looks like any other pull cored when done.

Besides I don't see a problem with switching anything with a humidity switch. If you are worried use a relay in between. Brian

Maybe I was over-thinking whether the contacts would like the inductive load of the transformer.

But the IP rated mains fan mentioned up-thread looks promising instead :)

The PSU will probably be switch mode and not the big toroidal massive inrush beast you may be thinking of :)

But it is worth checking - does the fan come with its PSU and if so, does it say waht type it is?

Good point, hadn't considered it may have a SMPSU.

The one I was looking at didn't specify and at only 5W the picture of the largish "transformer" box could easily have contained either ;)

Lee

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