Gravity grille not opening when bathroom fan on

7 Apr 2015
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United Kingdom
I have just had a bathroom installed, and a Ventaxia extractor fan put in.
It has a plastic gravity grille on the outside, and a flat cover on the front.

I noticed that it is not doing much to clear steam, and checked the outside grille while the fan is on. It doesn't move. I'm guessing it's supposed to open, otherwise no air can flow to the outside correct?

If so, is this a common problem. Better solutions or products?
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show us which fan you've got, and which cover.

what is the duct length?
I'm guessing it is out of reach & that you are unable to try to open it by hand to check it is not physically jammed. If so try to stick a cane through the fan from the inside & see if it opens that way.
Does the grill open if the bathroom door is open when the fan is running ?

No matter how powerful the extractor fan it cannot extract air from the bathrooon if there is no way for replacement air to enter the bathroom. A gap under the door is the most common way for the air to get to the bathroom.
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I checked again this morning and it is lifting up very slightly, a few mm. The top one seems loose, the middle one is a bit stiff (tested with a stick) and the bottom one is fixed in place, designed that way it seems. Opening the door makes no difference. It looks like probably the fan is just not powerful enough. Elsewhere someone recommended centrifugal over axial fans.

I asked the builder and he said it's not meant to open, only keep wind out. I do wonder how can someone be so ignorant of their own trade!
It's a VentAxia VASF 100B

This is how much the flaps open when the fan is on. I think the fan has its own spring loaded backdraft flaps as well.

The duct length is to fill a Victorian brick cavity


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It looks a funny shape, perhaps that's the camera angle. If it is square, all three flaps should swing. However, on that model, they will rattle annoyingly in the wind, until they fall off. It should be attached with four non rusting screws, not glued onto the wall.

A cowl vent is not so noisy and has better weather protection. I like the brown ones. It has one large, free-swinging flap.
I see from the silicone that your builder is a bodger. Is there a plastic duct in the hole drilled through the wall?

The fan you have is one of the modern ones, fairly expensive, and its power should be adequate
P.s. I think your fan may have two speed settings. Have a look at the instructions, or ask on the "Q&A" section of that link.
can you open fully manually? looks like it may be obstructed by poor fit, excess silicon fouling it.If there is slightest restriction it will not open correctly.
Thanks for the reply. Yes, it's square.
My neighbours downstairs have one of these and exactly what you described has happened to it.
The flaps have blown off and ended up in the gutter.
Cowl vent looks like a better design.
At this point all I can do is switch off the electric and unscrew the fan to have a look at it from the inside.
I can check if there is a plastic duct and whether it is set to the high setting. I did ask about this but since I've had lots of contradictory answers to my questions I am trusting what they say less and less. The latest response was that the flaps do not need to open, which is clearly nonsense.

After a couple of leaks from the bath plumbing into downstairs' flat I doubt the builder is willing to make any more changes.
After the second leak, the bath plug also no longer closes properly. I'm wondering if anything can be done about that?
The bath panel is tiled and they have removed it and resealed twice already.
Bodge sounds about right. I suspect even the leak fixes may have been bodged too.

When people don't take pride in doing good work I just find it disgraceful.
The three flaps all open , if bottom is stuck then its a bodge job. Either distorted or silicon fouling.
I managed to remove the flat cover, but can't find any info on how to remove the main front cover.
These things are flimsy plastic so I don't want to force it and break anything.
The manual doesn'r explain how to get the front cover off to access the pcb.
Any ideas?

I found a picture from Amazon of what it looks like inside


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I think you will find the round screw (usually on the bottom, but on the LHS of your pic) retains the cover. The cover will then hinge from the opposite end, so you pull out the side that was formerly held by the screw, and it will then lift off tabs (on the RHS of your pic)

The round black thing facing you looks like it is an adjuster, probably for the timer, if yours has one.

But you must find the instructions, or put a question on the Q&A of that link I gave you, to see how the power is adjusted. It looks like there is a high and a low setting, "wall and ducted," what he calls "bath or toilet" but I don't know if your model is the same.

I mostly use a Spanish brand that is not quite the same.

some items on the Q&A tab already say:

the manual suggests that speed can only be adjusted during installation. is this correct?
1 Answer

Yes, that is correct. You select either toilet or bathroom running speed.

Vent-Axia Product Expert,

The information on flow rates for this fan will be updated shortly to refect the current generation - as below.
Low speed is 60 m3/h
High speed is 108 m3/h
Note that these flow rates are given at free air.
14 Oct 2016
Vent-Axia Product Expert,

Last edited:
The pcb settings I'm sure I would be able to figure out, or it's in the manual.
But the cover doesn't want to budge. Unless it's designed to snap off with pressure, and in that case you need to be willing to risk breaking it.
The screw is removed but it's not hinging or sliding.
Rubbish design..

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