Central Vacuum Installation

Understanding the principle of a central vacuum system is as important as understanding the mechanics of the installation. Following these guidelines should ensure that the installation is easily accomplished and that the pipework will not become blocked in use.

The Principles

The system is designed so that it will not become blocked in normal domestic use. The narrowest part is the point at which items are sucked into the system, this being the brush or tool on the end of the hand-held wand. The diameter of the tubing gets progressively larger so that if an item can pass through the suction tool, then it will pass through the rest of the system. The diameter of the nozzle on the suction hose is 32mm. This increases to 43mm at the 90 degree elbow and again to an I.D. of 46mm for the main run of pipe. If an item is small enough to pass through the 32mm pipe, then it will generally pass through the 43mm bend and the 50mm pipe easily.

It is possible to suck a long thin item, such as a pencil, into the vacuum system. This could pass through all the pipework until it reached a bend where it could become stuck and cause a blockage. However this is prevented by the use of a sharp right-angle bend behind the vacuum socket. As the pipe immediately after the bend is larger than the socket’s internal diameter and all subsequent bends are 45 degree bends or swept 90 degree bends, then anything that can pass through this sharp 90 degree bend will pass unhindered through the rest of the system. If a pencil is sucked into the system, it will become lodged in the sharp 90 degree bend behind each socket and can be removed through the vacuum socket.

The Pipework

Imagine the pipework as a simple tree with the longest run of pipework as the trunk, the shorter runs as branches and the vacuum unit as the root. The trunk & branches may need to have a few bends in them in order to fit the building and, as with most trees, the branches join the trunk at an angle pointing in the direction of the roots. In a central vacuum system, the branches of the pipework must join the main run at an angle using a swept 90 degree Tee or 45 degree Tee (see diagrams on page 10).

The Pipe Fittings

It is important to use the correct fittings for the pipework. Apart from the 90 degree bend fitted directly behind each socket (see page 6), all bends should be curved or “swept” bends. This also applies to Tee connections (see diagrams of permissible connections - page 10). Use two 45 degree bends to make a swept 90 degree bend and a 45 degree Tee with a 45 degree bend to make a swept 90 degree Tee. In order that this is clear, some pictures of suitable fittings are included.

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