12v transformer for fan

[Crofter]

So... I've picked up a cheap 2nd hand single room MVHR unit off eBay. It's incomplete, hence the low price. The major bit missing is the control unit, but upon opening it up it appears that there are just two small computer-type fans inside, each wanting 4w at 12v. I've powered it up off a car battery and it works just fine.

Plan is to wire it into the bathroom lighting circuit... yes I know there will be no hysteresis...  but it will get me up and running easily.

 

I can pick up a cheap 12v transformer off eBay, like this:

https://www.ebay.co.uk/itm/DC12V-LED-Driver-Power-Supply-Transformer-6W-12W-36W-48W-60W-Strip-MR16-G4-CCTV/272777976696?hash=item3f82d59b78:m:mITRanGIZh6GiuSn_zCgkFw:rk:11:pf:0

 

Question is- is there anything to be gained or lost by buying an oversized transformer? They all cost the same anyway.

[ProDave]

The 12W version of that will probably be okay. I doubt it's well regulated but should be okay for a couple of fans.

 

I suspect they are unregulated, so a larger one, with just a small load, may output more than 12V but the only way to tell would be to try it.

[MikeSharp01]

Not much but a slightly bigger one will run cooler as it won't be working so hard. As Dave says it won't be smooth but it will run just fine.

[PeterW]

You could always stick a Sonoff TH in the circuit and use it to control the on/off by humidity.  That plus the transformer is change of £20 all in