"I bought this to replace a similar Xpelair fan of 30 years because the timer gave up. This 180t has a timer but is not adjustable like the previous one,where I could adjust between 2 and 20 minutes.It runs for 12 minutes instead of the 20 mentioned in the instructions, which is lucky, as 20 is far too long for our application. In our installation It is ceiling mounted, and as in another review somewhere, on the second run the fan fell off an jammed against the casing. The fan is a push and pinch fit on a smooth shaft, it gets warm and just slides off. I have stuck it with silicone which is working so far. All this for a trade customer would be a pain in the backside. It's also noisier than the previous one,and of poor build quality."