Ducting FAQ

The following points should be kept in mind when choosing ducting or planning ventilation systems:

1. The length of ducting and number of bends will effect performance and should therefore be kept to a minimum.

2. Long runs of flexible duct are not recommended for use on cooker hoods.

3. Ducting components have a simple push fit connection. Flat channel can be easily cut to length using a hacksaw.

4. When installing a rectangular to round adaptor, it is important that the flat side is fixed uppermost. The flap operation of a grille/fan would otherwise be obstructed.

5. When installing a circular through-the-wall duct a core drill can be used.

6. Ducts passing through an unheated roof void should be insulated to minimise condensate formation and must include a condensation trap and means of running off condensate. 

7. Vertical ducts should be fitted with a condensation trap for low power systems and a weather proof cowl of sufficient free area for the air volume.

8. Horizontal ducts should fall away from the fan unit.

9. Choice of the right system will ensure quiet and efficient operation of fans and or cooker hoods

10. All internal system parts manufactured with self-extinguishing materials to meet fire retardancy standard UL94V2

11. Plastic materials do not corrode leading to a clean and long lasting life

12. Wall outlets are made with UV stable materials to delay colour fade

13. The choice of ducting system will depend on a number of factors including: the power of the cooker hood or fan to be connected to, its location, the configuration of the duct run, the space available and others.

14. Ductwork diameters are normally internal diameters – if unsure contact us

For a full list of ducting (including galvanized and stainless steel) or colours please contact our sales line on 020 463 9696 or to discuss your personal requirements, contact us.

Ducting Size Guide: View Full Table Here

Ducting System	Actual dimensions (mm)	Space requirements (mm)	Airflow mm²
For 4″ (100mm) extractor fans or for low power cooker hoods Up to 250m³/hour
System 100 – Round	100	106	7,854
System 100 – Rectangular	110 x 54	116 x 60	5,940
For medium extraction rates or if available depth is limited Up to 500m³/hour
System 125 – Round	125	131	12,272
System 125 – Rectangular	150 x 70	156 x 76	10,500
For 6″ (150mm) extractor fans or for high power cooker hoods Up to 500m³/hour & above
Megaduct 220 – Rectangular	220 x 90	227 x 97	17,968
System 204 – Rectangular	204 x 60	210 x 66	12,240
System 150 – Round	150	156	17,671
System 150 – Rectangular	180 x 90	186 x 96	16,200
For a shallow space, such as ceiling voids or under floor, where high extraction rates are not needed:
System 300 – Rectangular	308 x 29	314 x 35	8,932
System 225 – Rectangular	234 x 29	240 x 35	6,786

System 100 Round/Rectangle	System 125 Round/Rectangle	System 150 Round/Rectangle	System 204	System 225
			System 220	System 300
Actual Dimensions (mm)  Space Requirements (mm)

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The best method is to use a jigsaw with a quality blade suited to cutting thin sheet metal.

Mark your pipe in multiple places to provide a cutting guide / line – Drill a small hole to allow you to insert the blade and cut away from you.

Alternatively you can use a hacksaw, but for large ducting or quantities this can be somewhat frustrating. Obviously take suitable safety precautions.

We do offer a cut to size service if you know your measurements and we can ship these ready cut to save you the time and hassle – just let us know quantities / diameter / length etc.