Combiconnect Ø254 mm - Flexible Air Duct Per Meter

Flexible ventilation ducting in 254 mm, sold by the running metre. Made for installations with a 250 mm connection where you need a short length rather than a whole box.

By the metre or by the box, and why that means something different at this size

At the small sizes you buy a box because you are building a system. At 254 mm it is different: this diameter usually sits at the start or the end of an installation, between a large fan and a filter, or as the transition to rigid duct. That calls for two or three metres, not ten.

That is what this pack form is for. You order the number of metres you need and you get one continuous piece. When ordering, simply enter the number of metres as the quantity: 3 means three metres in one length.

Do measure the run first and add a little. Ducting that fits exactly does not fit: it has to go over the flanges and it has to make the bend without being pulled tight.

Flexible or rigid, a real trade-off at this diameter

At 125 mm nobody weighs it up. At 254 mm they should, because at this diameter rigid spiral duct is a genuine alternative and the choice depends on what you are doing.

Rigid duct has a smooth bore and therefore less resistance over a long distance. The drawbacks are that you need a fitting for every bend, that it has to be cut precisely, and that it absorbs no misalignment at all.

Flexible ducting does the opposite. The ribbed bore costs you some pressure per metre, but it bridges a gap that is not straight, it absorbs fan vibration, and it needs no fittings whatsoever. That is exactly why the per-metre form makes sense: for short sections where the flexibility does the work and the resistance barely registers.

The rule of thumb: long straight sections rigid, short and misaligned sections flexible. The longer your flexible run gets, the more of that resistance you see back in your fan's performance.

Technical Specifications:

• Construction: flexible laminate ducting with encapsulated steel helix
• Laminate: multi-layer aluminium and polyester
• Outer layer: abrasion-resistant plastic jacket
• Temperature: -30 to +140 °C
• Max. air speed: 30 m per second
• Max. working pressure: 3000 Pa
• Nominal size: 254 mm
• Length: per running metre, supplied in one continuous piece

Frequently asked questions

How many metres do I order?
The quantity you enter is the number of metres. Enter 3 and you get three metres in one piece.

Does it fit a 250 mm connection?
Yes. 254 mm is the size that belongs on a 250 connection; a duct clamp takes up the difference.

Should I use rigid duct instead?
For a long straight section, yes, it gives less resistance. For a short or misaligned connection, flexible is easier and needs no fittings.

Do I need tools to cut it down?
Stout scissors or tin snips will do. Watch the steel helix at the cut end, it is sharp.