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

[HandySparks]

I tend to core from the outside to the inside, this due to the dust levels.

Could always get yourself one of these (and a hollow extension, if required):
http://www.NoLinkingToThis/p/marcrist-dust-extraction-unit-150mm-3-pcs/4441F

 

[NDG Elecs]

Could always get yourself one of these (and a hollow extension, if required):
Marcrist Dust Extraction Unit 150mm 3 Pcs - http://www.NoLinkingToThis/p/marcrist-dust-extraction-unit-150mm-3-pcs/4441F

Would be an excellent idea but I would need a vac too Handy!

 

[HappyHippyDad]

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

I'm guessing drilling all the way from one side is better if using solid ducting?

 

[HappyHippyDad]

I shall be adding a FCU next to a kitchen socket then chasing perhaps 1.5m (no filling), fitting the cooker hood, core drilling and fitting ducting and outside vent.

I've estimated 4 hours but am thinking it may be closer to 5? Just trying to work out the quote!

 

[NDG Elecs]

I'm guessing drilling all the way from one side is better if using solid ducting?

Yeah defo. The actual shape of the core drill helps to keep the hole straight. If you core from both sides it is easy to deviate off from a nice straight line. Don't forget to angle it slightly to prevent water any water from coming in from the outside.

I think four hours sounds about right. 30-90mins on the core itself. 60-90mins chasing, fcu etc. Remainder for testing and tidying up.

 

[HandySparks]

Would be an excellent idea but I would need a vac too Handy!

I've used mine with a Henry. Works pretty well.

 

[Dave OCD]

Deleted double post.

 

[Dave OCD]

I shall be adding a FCU next to a kitchen socket then chasing perhaps 1.5m (no filling), fitting the cooker hood, core drilling and fitting ducting and outside vent.

I've estimated 4 hours but am thinking it may be closer to 5? Just trying to work out the quote!

£160-£170, a good bit of cleaning up too.

 

[HappyHippyDad]

I've actually just had a look under my cooker hood chimney. It has a 125mm ducting vent coming out of the top of the cooker hood, followed by 100mm flexible ducting siliconed inside it! NOT the way I am going to do it.

I've just this second fitted the reducer on (had one hanging around, as you do. What else are you going to do on a Tuesday night! ) and it looks much better

Decision made for the job!

Cheers everyone.

 

[johnduffell]

Reducing the duct size has a ridiculous amount of effect compared with what you'd think on the air flow. Look up the pressure loss. And to illustrate:
100mm duct its 7850mm2 Free area and 125 is 12265mm2 free area so almost double.
The resistance (pressure drop) is also related to the diameter, so you can see the noise level due to pressure and the flow rate will be compromised. And the power usage isn't going to meet part L if you're interested in regs.
Flexi duct is a disaster and you won't find many manufacturers recommending it. It's the ducting equivalent of those canoe rapids you see people paddling down with water sloshing everywhere.