Some advice regarding 125mm hole for cooker hood fan please?

[HappyHippyDad]

Morning all..

I am about to quote for a cooker hood installation including core drilling for the vent. The fan is 125mm.

I have checked upon the sizes of core drill bits and 127mm is the closest fit. I cant see the 125mm ducting getting through that due to the outer diameter of the ducting being greater than 127mm. Does it fit through?

How much of an impact would it have on the motor if I used a 125mm-100mm reducer for the ducting?

Could I cut a 152mm hole and use a larger vent on the outside wall, also using a 150mm-125mm reducer for the ducting?

Cheers.

 

[Midwest]

This seems like the best option but if the the motor is designed to remove air through a 125mm hole will it not be straining to remove through a 100mm hole?

Think the 90' bend in the ducting would have a worse effect.

 

[HandySparks]

.... and rember to drill from both sides not just from one

Why?

 

[HandySparks]

.... and rember to drill from both sides not just from one

Why?

 

[HandySparks]

This seems like the best option but if the the motor is designed to remove air through a 125mm hole will it not be straining to remove through a 100mm hole?

It won't strain the motor (might even reduce the load slightly, depending on the characteristics of the motor) but it will reduce the flow for a given fan speed (as will more duct length or bends). Whether this matters to you or your customer is hard to judge.

 

[Pete999]

Why?

To stop break of the material you are drilling through

 

[valleybilly]

+ 2mm addition to core drill sizes is more than enough for fitting flexi ducting . The bigger ducting size also reduces dB when in full power mode so 150mm is even better on a 100mm system.

 

[LankyWill]

127mm is the standard for cookerhood extracts, if your struggling to fit the duct through get a hammer and block of wood and wack it.

 

[Pete999]

127mm is the standard for cookerhood extracts, if your struggling to fit the duct through get a hammer and block of wood and wack it.

Like the technical talk there Will, "get a hammer and a block of wood and wack it out" nice bit of engineering speak like it.

 

[egg67]

A lot of MI will say core size 5mm bigger than ducting it allows for movement and gives you a bit of leeway to set the duct so condensation does not flow back to fan.
Handyspacks as pete999 said saves a lot of making good

 

[Midwest]

It won't strain the motor (might even reduce the load slightly, depending on the characteristics of the motor) but it will reduce the flow for a given fan speed (as will more duct length or bends). Whether this matters to you or your customer is hard to judge.

A mate of mine, had to route his ducting through 2 x 45' bends and 3.5m of ducting. Still stops his kitchen steaming up.

 

[HandySparks]

To stop break of the material you are drilling through

Handyspacks as pete999 said saves a lot of making good

I've never had any break away of material on the exit side when using a core drill.

I guess if you have the drill on 'hammer' you would, but that's not how most core drills are used.

Surely, getting a core drilled hole to meet up accurately when drilled from both ends would be difficult?

 

[Pete999]

I've never had any break away of material on the exit side when using a core drill.

I guess if you have the drill on 'hammer' you would, but that's not how most core drills are used.

Surely, getting a core drilled hole to meet up accurately when drilled from both ends would be difficult?

Not really drill through from one side until the pilot shows and then drill through from the other side with the core drill engaged, rocket science is not required.

 

[HandySparks]

Not really drill through from one side until the pilot shows and then drill through from the other side with the core drill engaged, rocket science is not required.

But why would you bother? I've never had any problems with drilling from one side only with a core drill.

 

[Midwest]

I've done both ways, ones okay for flexible ducting not for solid. Let the machine do the work, and don't be so impatient

 

[Pete999]

But why would you bother? I've never had any problems with drilling from one side only with a core drill.

Do what's best for you Mate I'm only explaining the right way of doing it, if your way suits you carry on.