MORE ABOUT CENTRAL VACUUMING. Last month we discussed vacuum systems in broad outline, and now is the time to look at some of the finer detail.

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1 MORE ABOUT CENTRAL VACUUMING Last month we discussed vacuum systems in broad outline, and now is the time to look at some of the finer detail. Choices to be made The hose with or without a switch? A plain hose is cheaper than one with a switch by about 50, or so. The act of plugging it into the inlet completes the electrical circuit and starts up the vacuum unit. But many people prefer to pay extra for the convenience of a switch on the handle of their hose. (This is especially useful if you wish to leave the hose plugged in while it is stored inside a cupboard.) Accessories A standard kit of accessories usually consists of: Telescopic chromium tube and floor brush. Usually the brush has two settings, one for carpets and the other for hard floors. Small circular brush for cleaning furniture, skirtings, etc. Crevice tool a narrow tube for cleaning into awkward places. Other accessories are offered as extras. For example: Turbo brush. A turbo brush cleans carpets with extra thoroughness. Air power is used to rotate the brush, sweeping up the dust and grit into the air stream. The use of air power in this way reduces suction, so if you expect to be using this tool extensively you may wish to fit a more powerful vacuum unit. But bear in mind that the whine of a turbo brush nullifies one of the advantages of central vacuuming its quietness. Extra long crevice tool. For cleaning beneath washing machines, fridges, etc Vibrating upholstery brush. Pet grooming brushes Fleas bite the dust! Another convenient accessory is the so-called vacpan, a sort of automatic dustpan which can be built into the plinth of a kitchen unit. Any debris on the kitchen floor can be swept into the vacpan and sucked away. (Remember to put in the pipework at first fix.) A rather different extra is a muffler to quieten the exhaust from the vacuum unit. This would be important if the vacuum unit were fitted inside the house, rather than the garage. And another optional silencer is a motor muffler for the air intake of a bypass motor. MORE ABOUT CENTRAL VACUUMING 1 JANUARY 2004.

2 Special features Although all vacuum systems are basically the same, each manufacturer offers some special features: Vacuum unit: Transparent dust canister This allows you to keep an eye on the dirt level. Filters Some filters need no attention when you empty the dust canister, while others may need to be brushed or even washed. Some are paper bags that need to be changed will a supply of suitable bags be assured for many years to come? (A self-cleaning, textile filter is the most convenient.) Motor Almost all vacuum units are based on an American-made motor from the specialist range made by Ametek Lamb. When comparing vacuum units from different manufacturers, compare their motors if they have the same motor they will produce about the same air power. (And motors with bypass motor cooling can be expected to last longer than those with thru-flow, whereby the exhaust air stream is used for motor cooling.) Automatic cut-out This protects the motor if it becomes overloaded due to a blockage, etc. Utility inlet This enables the hose to be plugged directly into the vacuum unit. This might be convenient for cleaning the car, etc. (As an alternative, it is easy enough to incorporate an inlet socket into the pipework in the garage.) On/off switch This bypasses the normal circuit and switches on the motor. (This can be useful for clearing blockages, as described in the next issue.) Inlet sockets: Some manufacturers offer sockets which match UK electrical sockets in size, making them less obtrusive than the standard American sockets. And a variety of finishes other than white plastic are available. Hose: The switched hose of the Nilfisk system has the wiring embedded into the hose material, offering advantages over the American hoses. Swivel heads: Attachments with swivel heads are more convenient in use than those with fixed heads. MORE ABOUT CENTRAL VACUUMING 2 JANUARY 2004.

3 Installing a central vacuum system Most suppliers of central vacuum systems can also arrange for them to be installed. Ask for quotations. Alternatively, they supply installation manuals some better than others so that you can subcontract the work, or do it yourself. The obvious subbie to do the work is the plumber the PVC pipework is very similar to PVC waste pipe. But plumbers, like other building tradesmen, are seldom eager to embrace anything new, so their quotes for what is basically easy work might be over-high. If you are the hands-on type of selfbuilder, installing the vacuum system may well be a job for you. So here is an outline of what is involved. Inlet sockets FIRST FIX As mentioned last month, most suppliers will draw up a layout for your system showing the pipe runs, inlet sockets and vacuum unit. Fix the inlet sockets in the required positions, generally at the same height as the electrical sockets. In studwork, a socket can be screwed to the side of a stud. When the plasterboard is fitted, cut a hole in the board to suit the socket. In blockwork, the socket can be fixed in position by screws or Gripfill (or similar). Make sure that each socket is fitted with a plasterguard to prevent the inlets becoming bunged up during plastering. Pipework The 2" PVC pipe comes in rigid 5' lengths and is joined to fittings by solvent cement, as used with PVC waste pipe. A 90 sharp bend should be placed at the back of every inlet socket. The purpose of this is to trap any long thin object such as a pencil that gets sucked in. (The object can be recovered by opening the inlet flap.) Elsewhere, only slow (ie, gradual) bends should be used to minimise the resistance to air flow. For a junction, a swept Tee is used, with the sweep towards the vacuum unit obvious enough in theory, but in practice it is easy to install one the wrong way round. (I know I ve done it!) Some points to note: Cutting pipe Cut pipe squarely, using, for example, a fine tenon saw. If necessary, de-bur the cut end with coarse sand-paper. Dry assembly Dry assemble a run of pipework first, and check that it is satisfactory before cementing it together. Make sure that each pipe is pushed fully home into its fitting so that there is a smooth bore inside it s a good idea to mark the pipe with a felt-tip pen to show the depth to which the pipe must be pushed home. Jointing Smear the cement all round a pipe; push it into the fitting and rotate the pipe a quarter turn to spread the cement evenly; then leave the fitting undisturbed MORE ABOUT CENTRAL VACUUMING 3 JANUARY 2004.

4 for a few minutes for the cement to set. (Don t smear inside the socket, otherwise excess cement will be squeezed out of the joint into the interior of the pipework.) Underground pipework The best place to locate a vacuum unit is in the back of the garage, and if the garage is detached, this means that the vacuum pipe will probably be laid underground. In this case, the pipe needs some sort of protection, and one way of achieving this is to place it inside plastic drain pipe (110 mm). Does it also need insulation? Some people in the industry are saying yes, and some saying no. The theory is that, in wintertime, when the central vacuuming system has just been switched off, the underground pipe contains warm air from the house. As this cools to the temperature of the cold earth, moisture condenses on the side of the pipe. And when the system is next used, dust will become stuck to the damp pipe. After many repetitions, a blockage can build up in the pipe. However, I don t find the argument convincing. The vacuum pipe inside the garage is likely to be as cold as the underground pipe, or even colder, and it has not been found necessary to insulate this pipe. Wiring Bell wire can be used as the cable that carries the on/off signal from the inlet valves to the vacuum unit. (The voltage is a safe 12 V or 24 V, as produced by the vacuum unit.) The cable should be taped or strapped to the pipework every couple of metres. Where two pipes from different inlets join to merge into one, the two cables from the different inlets need to be joined by connector blocks to form one cable going towards the vacuum unit. Leave about 15 cm of cable spare at each inlet socket, to be connected later. Inlet sockets SECOND FIX At a socket, cut the bell wire to a suitable length, and connect the twin wires to the two terminals on the face plate. Then screw the face plate to the body of the inlet socket with the screws supplied. It is personal choice whether the inlet flap opens upwards or downwards, but most people find the latter more convenient. With all the inlet sockets in place, check the wiring. With a circuit tester, first make sure that there is an open circuit between the twin wires that are to be connected to the vacuum unit. Then connect a hose into an inlet (and if it has a switch set it to the ON position). Testing the twin wires again should show that the circuit has been completed. Repeat this test for each inlet. Vacuum unit Purpose-made brackets are supplied for attaching the vacuum unit to a wall. A convenient height has the top of the canister at waist height. (Bear in mind that there may be a minimum amount of space required below or above your particular unit.) Remember: you should have installed an electrical socket nearby to power the vacuum unit. MORE ABOUT CENTRAL VACUUMING 4 JANUARY 2004.

5 You may need to crimp spade connectors onto the ends of the bell wire to connect to the vacuum unit. But don t cement the vacuum pipe into the socket on the unit. Just leave this as a dry fit so that you can easily remove the unit if required or so that you can carry out a procedure for clearing blockages that we will describe in the next issue. Correction Last month I wrote that air watts are the product of air flow and pressure differential each side of a 50 mm diameter orifice. This is not totally incorrect, but it is misleading. In fact, the air watts can be measured for any size of orifice, and it is usually greatest for an orifice of about 19 mm 24 mm diameter. The air watts quoted by manufacturers is this maximum value. To be even more sophisticated and probably over-precise, in choosing a vacuum unit you can attempt to match the orifice area of your usual attachment frequently the floor cleaner with the area of the orifice for maximum air watts of the particular motor under consideration. (By now, you may be totally confused about air watts, but the technically inclined reader can find a fuller explanation at the relevant web site below.) FURTHER INFO: Smart Vacuums Installation manual smartvacuums.co.uk. Built In Vacuums Explanation of 'air watts' and other terms. builtinvacuum.com. Ametek Ametek Lamb motors are used in nearly all central vacuum units. ametek.com Words Copyright article by Robert Matthews in SelfBuild & Design magazine, January, MORE ABOUT CENTRAL VACUUMING 5 JANUARY 2004.