Multi vent fan not working.

HappyHippyDad · Mar 20, 2021

Morning all..

I have just been to a regular customer who has a problem with their extractor fan, i.e it doesn't work. I have not come across these types of fans before. usually they are the small wall or ceiling mounted ones, or an in-line fan, all of which are cheap enough to just change. This one is a multi-vent fan situated in the loft extracting from 2 bathrooms (and a third going down somewhere else!).

This was purely a quick pop in and out, so I haven't investigated at all. I don't really know where to begin, past making sure the unit is still receiving power (which I think it is as I heard a low hum coming from it).

What are the common problems with these larger, multi vent fans and how are they fixed? Pictures below.

[ElectriciansForums.net] Multi vent fan not working.

telectrix · Mar 20, 2021

humming could be a stalled motor due to bearings.

loz2754 · Mar 20, 2021

There's possibly a wiring diagram inside the cover. If not, take a picture of the rating plate and research the model.

Mike Johnson · Mar 20, 2021

In France they are Called a VMC (Ventilation Mechanical Control) usually suspended from the roof rafters to help eliminate noise nuisance, inside the unit will be a phylum chamber that can become clogged with debris from fluff in the bathroom or fat from the Kitchen, the one you have there is made by Vent Axia perhaps a run through their web site will help.

It's not a heat recovery version, but may have a humidity control and multiple speeds, so a controller problem is not out of the ball park.

mattg4321 · Mar 20, 2021

Fitted a Greenwood CMEV for a customer recently in a similar situation. Seems a well built piece of kit.

Constant running and then boost from any of the bathrooms it extracts from when the light switch is on. Usually via a double pole switch. (So all the lights in different bathrooms don’t come on together)

HappyHippyDad · Mar 20, 2021

How do these things switch themselves on? In this case the customer said it has a will of it's own and just comes on by itself. I'm guessing this must be a humidistat, but i could not see any humidistat sensors in any of the bathrooms. Does the unit itself somehow monitor the humidity of the bathrooms? perhaps in the vent in the ceiling?

UNG · Mar 20, 2021

loz2754 said:
There's possibly a wiring diagram inside the cover. If not, take a picture of the rating plate and research the model.

Looking at the cover it looks like something should be clipped into it, possibly the instructions

Can't find that model on Vent Axia website but looking at a similar model some variants have a built in humidistat and run continuously at low speed with a variable speed increase as needed / required

Mike Johnson · Mar 21, 2021

happyhippydad said:
How do these things switch themselves on? In this case the customer said it has a will of it's own and just comes on by itself. I'm guessing this must be a humidistat, but i could not see any humidistat sensors in any of the bathrooms. Does the unit itself somehow monitor the humidity of the bathrooms? perhaps in the vent in the ceiling?

The humidistat could be in the unit itself or even in one of the rooms or ceiling vents and wired back to the unit, some run constantly at a low trickle and boost on demand when one of the humidistats tells it too, you really need a model number to find the installation guide, Vent Axia are usually very good at that sort of information.

Timbo · Mar 21, 2021

This is the nearest I found on the Vent Axia website:

Product Search Results | Vent-Axia

www.vent-axia.com

Not exactly the same...

HappyHippyDad · Mar 21, 2021

I think this may be the model. (see attachment)

It looks different in the actual pictures that come up on the net if you type the model number in, but in this PDF it shows the rectangle in the middle (as in my photoghraphs).

It looks like there is an over heating function that can switch the fan off, it doesn't go in to great detail though.

Mike Johnson · Mar 21, 2021

Good investigation to find the model, I note the unit has a condensate trap may have a level switch, worth a look to see if it has a container and it's full, or as you suspect a build up of fluff restricting the motor/fan.

Multi vent fan not working.

HappyHippyDad

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telectrix

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loz2754

Mike Johnson

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mattg4321

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HappyHippyDad

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UNG

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Mike Johnson

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Timbo

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Product Search Results | Vent-Axia

HappyHippyDad

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Mike Johnson

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