How do I install a spiral duct? Check out our mounting tips!

Our tips for fitting spiral ducts and fittings

To connect spiral ducts and fittings to each other properly, it helps if they don't all have exactly the same diameter. That's why a duct might have a diameter of 100 mm, for example, while a fitting (anything other than the duct itself, like bends and T-pieces) is slightly smaller, around 98 mm in this case. This lets you slide them together without any hassle.

Which connector you need depends on what you're joining together:

• To join two ducts together, you use a plug-in connector;
• To join two fittings together, you use a connecting sleeve;
• A duct and a fitting can be attached to each other directly.

A connecting sleeve is really nothing more than a short section of duct. A plug-in connector, on the other hand, is smaller in diameter and slides inside a duct. The connection on an inline duct fan works on the same principle. That connection is called either a side end or a channel end. You'll find which type of connection your inline duct fan has for every product on our website, under the specifications for "connection":

• Side end: no plug-in connector needed, you can attach the duct directly to the inline duct fan;
• Channel end: you do need a plug-in connector, because the diameter here matches that of the duct.

All our spiral fittings come with a SAFE connection (sealing rubber), so you know for sure your connection is airtight. You won't need any tape or sealant for this. Even so, there are situations where you might want to seal that connection a bit further, for example with a long run of ducting or a connection outside. You'll find out how to do that below.

How do you seal connections airtight?

A SAFE connection usually already makes for an airtight joint, but in some situations you'll want extra peace of mind. Think of ducting that runs outside or in an unheated space, where temperature differences can cause condensation, or a connection that has to withstand a lot of tension. For these situations, you have two options:

• Aluminium insulation tape: stick this around the seam of the connection to seal any small gaps, while also giving the duct a bit of extra insulation against condensation;
• Mounting sealant or adhesive: this makes the connection permanent and airtight, handy for joints you'll never need to take apart again.

Using a regular duct or fitting without a SAFE connection? Then we'd recommend sealing the seam with insulation tape or sealant either way, so you don't lose any air along the whole duct run.

How do you cut a spiral duct to size?

The spiral ducts in our range are typically available in lengths of 1.5 metres, but in practice you won't always need exactly that length. Luckily, you can easily cut a spiral duct to size yourself. Here's how:

1. Measure the length you need precisely and mark a straight line around the duct, for example using a marker and a piece of card or a pipe clamp as a guide;
2. Cut the duct along this line with a hacksaw or an angle grinder fitted with a metal-cutting disc. Make sure you cut straight, so the duct still fits neatly and squarely into the connector afterwards;
3. File or sand the cut edge lightly, so there are no sharp edges or burrs left that could damage the sealing rubbers.

This way, you can adjust any spiral duct exactly to the space you have, without compromising on an airtight, sturdy connection.

Supporting and mounting spiral ducts

It's best not to leave a spiral duct lying loose, not even in a crawl space or loft. Without support, the duct can sag, which can cause connections to come loose or seams to leak. That's why you mount a spiral duct using brackets with rubber. The rubber also stops the duct from vibrating or rattling against the bracket. Exactly how you position the brackets depends on the situation:

• For a horizontal position, for example along a loft joist, fit a bracket roughly every 1 to 1.5 metres to stop the duct from sagging;
• For a vertical position, such as in a service shaft, secure the duct to the wall roughly every 1.5 to 2 metres so it can't shift;
• Is the duct supported by the floor or a duct channel? Then a single bracket at each joint is often enough.

As a rule of thumb: the longer the run and the heavier the duct, the more often you'll need a bracket. Not sure about the right distance for your situation? Our customer service team is happy to think it through with you.

Combining a spiral duct with a flexible hose

You can easily combine a spiral duct with a flexible hose or an air distribution system, for example if you need to bridge the last bit to a grille or valve somewhere a rigid duct won't fit around the corner. Here's how:

• Use a reducer or adapter that fits both the diameter of your spiral duct and that of your flexible hose;
• Slide the flexible hose over the adapter and secure it with a hose clamp, so it can't come loose;
• Seal the join with extra insulation tape, since a flexible hose usually doesn't have a SAFE rubber seal.

This way, you combine the sturdiness of a spiral duct with the flexibility of a hose, exactly where you need it.

With these tips, you can get started fitting, sealing and mounting your own spiral ducts. Can't quite figure it out, or not sure which parts you need exactly? Our customer service team is happy to help.

FAQ

The FAQ below covers the most common questions about installing and fitting spiral ducts, laid out clearly for you. Do you have questions about your specific situation, or can't you quite figure it out? Our experts are ready to help, so feel free to get in touch!