In Line Centrifugal Fan

[doni]

Just trying to plan the ventilation in the kitchen and bathroom in a refurbishment I am doing.

No soffits and property is a top flat, so too costly to go through the roof.

I'd like to use a standard extractor fan and cooker hood to extract out, but the main problem is that the length of ducting I will need is about 9m to get to the outside wall, for both kitchen and bathroom.

Manrose do an in-line centrifugal fan that can cope with 10m of ducting, and is powerful enough to extract enough volume for the rooms (9sq m and 11sq m) to comply with Part F.

http://www.screwfix.com/prods/63459...or-Fans/Manrose-150mm-In-Line-Centrifugal-Fan

I am thinking about running ducting from the bathroom and kitchen and Y join to the in-line fan, and then run the majority of the rest of the run (8m) to the outside wall.

This would have the effect of ventilating both bathroom and kitchen whenever the fan is on (which I guess is ok).

I was thinking about having two switches in parallel (not linked to one another) operating the fan, using standard switches (the bathroom one sited outside the bathroom)

I know this is not a standard way to extract from these rooms, but my long length of ducting is limiting my options.

Problem is I have never use one of these fans before, so if anyone has any experience of using them, or has any ideas about my proposed set up, I'd appreciate it.

Do I also assume that I can forget about zones if I site the in-line fan in the attic void not directly above the bathroom?

 

[flameport]

This would have the effect of ventilating both bathroom and kitchen whenever the fan is on

It also means when the fan is not on, all of the bathroom smells end up in the kitchen.

 

[doni]

Oh balls - two fans then?

... and two runs of ducting - and two holes in the wall?

 

[doni]

... or just have another standard bathroom fan as well, operated by the same switch ...

 

[bernardgreen]

Oh balls - two fans then?

... and two runs of ducting - and two holes in the wall?

Two fans, use a Y junction to combine their outputs into one duct to the wall vent. You will need to fit backdraft shutters to each intake grill.

Also remember that the air sucked out of a room has to be replaced by air coming into the room, normally under the door or through a vent in the door. Without that the fan will not achieve the amount of air movement required.

 

[SimonH2]

It also means when the fan is not on, all of the bathroom smells end up in the kitchen.

Backdraft shutters in each leg ?

 

[doni]

Ah ... like this ...

http://www.edwardes.co.uk/externalIndex.jsp?skid=MAN1230L

Looks like a possible solution.

So would that be ok - two backdraft shutters and a single in-line fan, opearted by two standard switches in parallel?

Would it obviate the need to consider the bathroom zones, as the electrics would be in the attic - possibly not even above the bathroom?

 

[doni]

Sorry bernard - didn't see your response.

In fact it seems sensible to have two separate fans, I'll just downgrade the power and get a slightly cheaper one - yes I think thge regs says e.g. 10mm gap at bottomof door.

Are regular switches on outside of bathroom still allowed?

 

[doni]

OK - bought the fan, and the instructions say use a 3A FCU to isolate outside the bathroom, but I thought that sometimes a triple pole switch is used.

I have tried to draw out both how the instructions say to wire the fan and light (A), and how I thought a triple pole would operate (B).

Untitled

• doni
• 29 Mar 2011
• 1

It seems a triple pole has the advantage of isolating the fan, but not the light, whilst a DP switch isolates fan and light, but do the regulations care what is done?

 

[bernardgreen]

Your diagram B is correct.

Use TRIPLE and Earth to and from the isolator.

Sleeve the switched live with brown sleeve to indicate it is a live.

Take the earth to the fan and, if not required in the fan terminate it in a terminal block in case you change the fan to one that requires an earth.

Sleeve the earth in green / yellow.

 

[bernardgreen]

Your diagram B is correct.

Use TRIPLE and Earth to and from the isolator.

Sleeve the switched live with brown sleeve to indicate it is a live.

Take the earth to the fan and, if not required in the fan terminate it in a terminal block in case you change the fan to one that requires an earth.

Sleeve the earth in green / yellow.

 

[doni]

Thanks - Yes, left earth out for ease.

BUT, if I followed the instructions in the Manrose Fan, they say use Diagram A - that's the DP version - would that still be OK, even though the 3A FCU isolates Light and Fan?

 

[doni]

OK - As the MANROSE in-line fan instructions reads:

"A DP fused spur having min contact separaton of 3mm in all poles must be used and fitted with a 3 amp fuse".

I have to oblige - so I suggest to combine both diagram A and B - as such :

Untitled

• doni
• 29 Mar 2011
• 1

It seems daft to me that the fan has to have a 3amp FCU, as it appears that triple pole diagram B is what is normal.

The fan is a Manrose one, a fairly standard in-line fan from what I can see.

I plan to site the FCU and Triple Pole switch in a double back box above the door on the entrance into the bathroom.

Are there any thoughts on this please?

 

[seasickstevie]

It seems daft to me that the fan has to have a 3amp FCU, as it appears that triple pole diagram B is what is normal.

I believe it's the in-built timer that's probably rated at less than 6A or so, therefore needs protecting should there be a fault.