New In Line Extractor Fans Running Slow Woes

[Mouse1903]

Hi all, I've done a bit of research online to my problem but can't seem to find an answer hence my post on here

My en suite installed in 2011 has a shower with a built in light above that led to an in line extractor which was simply piped into the loft, causing a damp patch in a bedroom wall where the pipe extended.

End of 2022 I had the original small Manrose fan replaced with a larger Addvent one using a local electrician, and now with it being piped to a roof vent with double insulated flex pipes. This worked fine until a couple of months in where I would switch it on and it would just hum without turning before slowly kicking into gear. This gradually got worse with it taking longer to kick in before it stopped completely. I checked the fan and there was no water in the pipes and no dirt whatsoever and the blade turned freely. Reading up on the fan I read the circuitary was known to fail early so put it down to that.

Couple of months ago I replaced the fan with a Blauberg unit hoping it was better quality, using a different electrician. It has only been used about 5 times before having a similar problem where it would power up but very slowly and only run at about 1/3rd of the speed. I went up again and everything still ok, no water in pipes or dust. I hit the top of the unit a few times and it sprung back to full speed and worked the next day fine before reverting to the same problem the day after.

I'm not an electrician however I'm thinking this may be some issue with the voltage potentially and the light above the shower? The original light is also a Manrose unit like the original fan, and both this light and the fan are manually operated by a separate fan on / off switch next to the separate light switch. Is this a case of the voltage not being sufficient to power the larger fan and light, it being wired up wrong, or possibly an issue with air pressure?

Any suggestions before I call my electrician again would be appreciated

 

[EFLImpudence]

. I hit the top of the unit a few times and it sprung back to full speed and worked the next day fine before reverting to the same problem the day after.

Loose wire - or part?

 

[JohnD]

Does the impellor spin freely by finger?

 

[Mouse1903]

Can't see any loose wiring and yeah the blades spin freely (same as the previously upgraded one which I actually still have in my garage)

 

[EFLImpudence]

Wire the old fan to a plug and see what happens.

 

[ebee]

Can't see any loose wiring and yeah the blades spin freely (same as the previously upgraded one which I actually still have in my garage)

Those two suggestions are the first any electrician should look for.
Bear in mind that the loose connection(s) could be anywhere on its path from the origin of the circuit (Consumer unit for example) right up to the fan itself, any high resistance ( loose connection) could cause this effect.
In fact I did once deliberately put a resistor in series to avoid start up surge surge on a motor to avoid blowing a 1 amp very fast acting fuse blowing at 12v, it started slow but gained regular speed after a second or two and although made the motor a bit weaker at final speed caused no discernible difference to users - it was actually a 12v siren for an intruder alarm system but the result is not totally unlike what you are describing so possibly a similar reason.

Your Electricians should be looking for all this anyway though if they are actually electricians rather than someone simply wanting to sell you a new fan

 

[JohnD]

if the light works well, any faulty connection is likely to be quite near. Might be the switch or FCU. Is there a junction box or ceiling rose?