Rewire Questions

[ppelec100]

My modus operandi with inline fans has always been to buy the complete kit from the wholesalers.I always go for highest wattage. Nothing as pleasing as watching a sheet of toilet paper stuck to the grill when extractor fan operates. I normally connect fan with flex first and check its operation before installing it in the attic. If fan has a timer I make sure homeowner decides the overrun time before I install it. It can be a nuisance mucking about with a fan timer in a small attic. Lastly a little rubber placed between the fan and the wooden grounds it's mounted to reduces vibration and noise.

soooo do you use the inline fan with just a grill mounted in the ceiling of the bathroom then? you don't use the inline + ordinary extractor fan? could you link me the kit pleaseeee

 

[LastManOnline]

soooo do you use the inline fan with just a grill mounted in the ceiling of the bathroom then? you don't use the inline + ordinary extractor fan? could you link me the kit pleaseeee

Apologies. Misunderstood your question. Your phrase "inline + ordinary extractor fan" is unfamiliar to me. An inline fan by definition is "in the line" of air extraction with a flexi connected to the ceiling grill in the bathroom and a flexi connected to the wall or roof outlet. An ordinary extractor fan has a flexi on one end only. Don't have any links to hand but it's a standard item in any wholesalers

 

[ppelec100]

Apologies. Misunderstood your question. Your phrase "inline + ordinary extractor fan" is unfamiliar to me. An inline fan by definition is "in the line" of air extraction with a flexi connected to the ceiling grill in the bathroom and a flexi connected to the wall or roof outlet. An ordinary extractor fan has a flexi on one end only. Don't have any links to hand but it's a standard item in any wholesalers

so from the grill, how far into the flexi ducting do you install the in line fan? would you recommend straight duct over flexi duct if it is possible? because of the air flow resistance when hitting the grooves of the flexi duct?

 

[Mike Johnson]

Its not the airflow resistance on flexible ducting I find that is the problem, but the condensation that occurs on the grooves if extracting from a bathroom or kitchen, condensation trap and drain needed, if possible I try to always use solid duct, not popular as its more difficult to fit and takes time, any inline fan I also suspend from the rafters in a loft installation as this cuts down the noise considerably.

 

[ppelec100]

Its not the airflow resistance on flexible ducting I find that is the problem, but the condensation that occurs on the grooves if extracting from a bathroom or kitchen, condensation trap and drain needed, if possible I try to always use solid duct, not popular as its more difficult to fit and takes time, any inline fan I also suspend from the rafters in a loft installation as this cuts down the noise considerably.

There is no rafters, this is a flat with a concrete ceiling above the plasterboard. Would you say to suspend it from the concrete ceiling then? Can I not put it in a big enclosure to trap the noise? Suspending seems like a lot of work

 

[Mike Johnson]

Or Lord mount it straight onto an external wall.

 

[LastManOnline]

so from the grill, how far into the flexi ducting do you install the in line fan? would you recommend straight duct over flexi duct if it is possible? because of the air flow resistance when hitting the grooves of the flexi duct?

Straight duct is always preferable but circumstances may limit its use. Your exit hole location (roof, wall or soffit) and your extract fan location will determine what you use. You will want to keep your duct run as short as circumstances allow. From the grill I normally mount the fan approx 2 to 3 feet away using flexi.If the exit is through the roof then I use another section of flexi. If the exit is through the soffit (or wall) it's usually a longer run and here is where straight duct is useful to provide a nice sloping flow to the exit hole with the final foot again in flexi

 

[ppelec100]

Or Lord mount it straight onto an external wall.

? how about I stick a hoover on the other side of the inline super sucker!

 

[ppelec100]

Straight duct is always preferable but circumstances may limit its use. Your exit hole location (roof, wall or soffit) and your extract fan location will determine what you use. You will want to keep your duct run as short as circumstances allow. From the grill I normally mount the fan approx 2 to 3 feet away using flexi.If the exit is through the roof then I use another section of flexi. If the exit is through the soffit (or wall) it's usually a longer run and here is where straight duct is useful to provide a nice sloping flow to the exit hole with the final foot again in flexi

Okay got you! its possible for me to use a straight duct as the rest continuation of the flat pvc duct is above the existing fan location. When doing a 90 degree bend into the duct would you recommend putting 2 x 45 degrees together then for the swooping like you said?

 

[ppelec100]

Straight duct is always preferable but circumstances may limit its use. Your exit hole location (roof, wall or soffit) and your extract fan location will determine what you use. You will want to keep your duct run as short as circumstances allow. From the grill I normally mount the fan approx 2 to 3 feet away using flexi.If the exit is through the roof then I use another section of flexi. If the exit is through the soffit (or wall) it's usually a longer run and here is where straight duct is useful to provide a nice sloping flow to the exit hole with the final foot again in flexi

Or Lord mount it straight onto an external wall.

Do you install a 3amp fuse inline of your extractor fans? they show on the installation instructions to do it...

 

[Mike Johnson]

You should always read the manufacturers instructions, it may be the last thing you do after installation, but you should always read them. ?

 

[LastManOnline]

Okay got you! its possible for me to use a straight duct as the rest continuation of the flat pvc duct is above the existing fan location. When doing a 90 degree bend into the duct would you recommend putting 2 x 45 degrees together then for the swooping like you said?

A 90 degree will work fine. Regarding the 3 amp fuse, you will obviously have to follow manufacturers instructions. I would however check if other makes stipulate a 3 amp fuse. I personally have not come across that

 

[Mike Johnson]

A 90 degree bend laying flat would work, but two 45 degree bends ease the flow and will help prevent condensation at the change in direction, water ladened air hitting a wall will give up some of its content on the surface of the wall, if that wall is at an angle the airflow transitions better and will condensate less, worse is a vertical face, a corrugated face would indues turbulence which would be about the worse case scenario this would most definitely need a condensate trap.

Of the four different types of extractor I have fitted (tend to stay with what works) they have all stipulated the need for a 3amp in line fuse. In France where I do most of my work now, the requirement for VMC (forced mechanical ventilation) is mandatory on new builds and is supplied on its own 5amp MCB circuit.

 

[ppelec100]

You should always read the manufacturers instructions, it may be the last thing you do after installation, but you should always read them. ?

I do always read them. read bottom reply to lastmanonline

A 90 degree will work fine. Regarding the 3 amp fuse, you will obviously have to follow manufacturers instructions. I would however check if other makes stipulate a 3 amp fuse. I personally have not come across that

The inline fan I have come across requires a 3amp switched fuse for the whole circuit (lights included if on the same switch line) which in theory does not make sense as they will be covered by a 6amp RCBO anyway and also the fuse will be doing the same job as the 6amp RCBO (protecting the cable). If they had asked to put it in just before the fan it would make sense, but then I don't see how that would work... (fuse for the permanent live and switched live?) does not seem thought through

 

[Mike Johnson]

Haven't read the whole thread, but has any mention been made of a three pole isolation switch?

 

[ppelec100]

Haven't read the whole thread, but has any mention been made of a three pole isolation switch?

No, which is silly, I guess they expect you to use the double pole isolator at the start of the circuit to isolate the fan?