Recently installed in duct extraction fan making hooting/resonance sound.

[piper64]

A few months ago I installled a Manrose 100T in duct fan in the attic. The only noise you could hear was the air moving through the fan, but another noise is becoming more noticeable. It's keeping me awake until the fan cuts off, 1/2 hr after someone has used the bathroom.

It's a pulsing, hooting noise. I've taken the ducting off, but it's still there. I've cleaned the fan blades, but it's still there.

The fan is mounted to chipboard, suspended from the rafters by metal straps, so there is no direct contact wiith the ceiling joists.

Any suggestions chaps?

 

[ree]

The best advice i've googled came from a grow grower - it should, shouldn't it: they are the experts. google "en.jar dinmag.com"

There are actually so many variables for ext's, and failure after a short working life is not uncommon.

Instead of me suggesting this or that why not transfer to the elec forum?

 

[foxhole]

Would most likely be air movement across the outlet, needs a baffle.

 

[piper64]

Would most likely be air movement across the outlet, needs a baffle.

Do you mean the outlet on the unit or on the outside of the wall? Not sure what you mean by baffle, so I googled 'vent outlet baffle' and it shows the backddraft flap that is already fitted in line along the ducting. Not the same?

With the ducting removed, it still makes the noise and slight vibration can be felt by touching the unit and the straps.

I'm intrigued as to why it's just started recently as it was not noticeable initially?

 

[foxhole]

Vibration would suggest the fan is unbalanced, Manrose are not known for quality.You could reduce the timer down to say 5 mins.

 

[piper64]

Hmmm, not sure 5 mins would clear the residual moisture at all and any case I don't want to compromise due to alledged poor quality. Manrose seemed to have a good reputation, better than Ventaxia and the like, which is why I chose them. Any suggestions for a better quality unit?

If it was a balance issue, would it not have been there since install?

How about this 'baffle' that you mentioned, assuming it's airflow not build quality? What is it?

 

[foxhole]

Ventaxia is far superior to Manrose , like comparing M&S with Lidl. Balance issue could arise if the fan was constructed poorly, any slight vibration could cause more as parts become loose.Baffle is for the external part of the vent, but does not seem to be your problem. Of the last three Manrose fans I fitted one failed at installation and one lasted a week.

 

[JohnD]

your description of the noise made me think the blades were touching the casing, perhaps it is twisted or out of shape? Maybe by fixing clamps? Or perhaps it was the motor bearing. Better fans have ball-bearing motors these days, I would have expected them in yours. If the fan is scraping it would leave marks.

 

[piper64]

If you're right foxhole, I may just go back to the supplier and see what they say before the 1 year warranty expires. Actually, it may have a 3 year warranty, I'll have to check...

JohnD, the blades spin freely and there is no roughness or freeplay in the bearing that I can detect. It does have a ball bearing motor.
There was some fluff build up on the blades and the interior of the inlet, so I have cleaned that out. It sounds slightly quieter, but that may be just me as my wife says she can stiill hear it!

 

[piper64]

prenticeboyofderry, I see that you have posted in reply to my post in the electrics sections, for some reason I do not have sufficient priviliges to reply, even though it is my own thread? However, to answer your question, the distance it has to suck is 1m and to blow is 0.5m. I did some calculations regarding volume and came up with a figure that pointed me to an inline unit which is supposed to move 245 cubic mph.