Why have a central vac system? (What's wrong with my upright/cylinder cleaner?)
I saw them when I was in America once and always thought it was a good idea, plus I love gadgets!
There are lots of benefits too! Not least the fact that old air and dust aren't recirculated around the house. (these units vent externally, or into a non living area)
Additionally they are almost silent in operation, the unit needs very infrequent maintenance, the dust collector is so large that it only needs emptying every few months and you don't have to carry a large heavy vacuum around the house with you. Cleaning the stairs is especially easy (and especially difficult with a normal vacuum cleaner)

Step 1: Design

I spent absolutely ages planning this, I had originally intended to fit a central vacuum system when we first bought the house, but never did. Recently I've boarded out and reinsulated the loft, and it seemed like an ideal location for a central vacuum system, so the idea was reborn.
The main things to consider are the pipe run itself (and trying to hide as much of it as possible) the location of the outlets to provide best coverage of the house and the vacuum unit itself.

Step 2: Installation

Ok, I started with the installation of the vacuum unit itself, I decided to fit this in my loft, as I have a lot of space in there and it is now nicely boarded and easily accesible.
I already have some stuff in the corner of the loft, such as a fileserver and bathroom extractor fan so this seemed like an ideal location, it is also near the external wall I'd planned to run the pipework down and close to a source of power (these units need a standard 13amp socket or fused spur)
The first job was to build a small mounting frame for the vacuum unit that would support its weight. For this I biscuit jointed up some planed softwood to make a pretty simple mounting frame that was then screwed to both the loft floor and the roof timbers.

Step 3: Installation2

Once the unit is mounted I connected it up to the mains (easy really, just plug in an IEC power lead) and also connected the 12volt low voltage switching connections too. The 12v side connects to all vacuum sockets and triggers the vacuum unit when the two contacts are closed.
I then mounted the first socket, this is a utility socket in the loft, I decided to have one in the loft as I quite like the look of those vacuum storage bags for duvets and blankets, so having a vacuum point in the loft will be useful, also for dusting things off before bringing them from the loft back into the house.

Step 4: Installation3

All pipework is simply joined together using solvent weld glue in much the same way that some plastic plumbing fittings are connected, in fact the tubing used is remarkably similar, except that this tubing is 50mm Outside Diameter, which is a slighly unusual size.

Step 5: Installation4

The low voltage electrical connections are made using simple 2core flex, I chose to crimp connectors on to it, but the norm seems to be just to wrap the wire around the terminal screws. I think crimping is neater.
You might notice that all bends are swept and made using 45degree bends rather than tight 90degree elbows, there is good reason for this, tight 90degree bends are only used immediately behind each socket, this means that any obstruction or blockage should only occur at the socket (where it can be easily cleared) but once inside the main pipework, the diameter of the pipework is slighly larger than the hose or the socket inlets and the bends are more gradual so in theory a blockage should never occur in the difficult to get to pipework.
My pipework runs around the loft a bit, and then through the foil insulation, down the roof timbers and through the soffet. From here it runs down an exterior wall alongside the soil pipe and makes two entries into the building. One is into the upstairs landing, the other goes under the kitchen units.

Step 6: Installation5

The upstairs landing fitting is fairly straight forward, this just goes into a socket on the other side of the wall (notice the 90degree tight elbow on the outside) As well as the pipework, the low voltage cable has to be ran to all sockets as well (as it is this that triggers the vacuum unit) the approach I took was simply to cable tie it as neatly as possible to the pipework
As for the kitchen, this pipework runs under the kitchen cabinets, where it branches off to a vacpan under one of the kitchen units and also to another socket on the ajoining wall in the downstairs hallway.
Fitting the vacpan is fairly straight forward, as is fitting the sockets, but as I was fitting into a partition wall (well actually a blocked off doorway) the job was even easier. I did opt to use washers as well as screws to mount the sockets to the wall as when pulled sideways it is possible to put quite a lot of force through these sockets and I don't want mine coming off the wall!! (There is also a nice strong wooden frame behind)

Step 7: Sockets

The socket flaps on the front are spring loaded and sealed with an O-ring, once closed they form an airtight seal so there are no vacuum leaks when the other sockets are in use.
Once closed they are fairly unobtrusive and are about the same size as a single electrical socket

Step 8: In Use

I cannot begin to tell you how excited I was to switch this baby on for the first time!
My first surprise was how silent the unit it, granted mine is located in the loft (which is well insulated) but the system really is quiet - which is great if the person not doing the vacuuming is watching the TV!
The first issue that needed addressing when the installation was finished was 'where to store the hose and accesories?'
They all fit quite nicely into our settle in the dining room - so that was easy (once the 4 phone books, hats, scarves and fancy dress outfits that used to be in there had been 'filed' elsewhere)

Step 9: Vacpan

Notice that the vacuum handle has a valve on it to adjust the suction, unlike the ones on many vacuums that are really just there for show, this one is required!! Using the smaller attachments such as the crevice tool or upholstry brushes is nearly impossible at full suction, the attachments just stick to whatever you are cleaning and refuse to budge... I've opted for 4 outlets throughout the house, one is a vacpan, one is in the loft (and probably won't get much use) and the other two are on the upstairs and downstairs landings.

Step 10: In Use2

I paid the extra for the 'deluxe' hose kit, this means the hose is a little lighter, more flexible and has an on-off switch on it.
Getting started is a simple affair of opening the socket and inserting the hose so that the two brass pins are connected to the hose connector (these pins when bridged activate the vacuum unit)
Hoses without a switch just bridge these contacts when plugged in, meaning that the only way to stop the vac is to unplug the hose.

I did go a bit over the top and buy a turbocat brush head, they are expensive but it is a great bit of kit, the brush action is really quite amazing, and the device actually pulls you forward!!

The vacpan is an interesting idea, and is quite useful, quite simply it is a dustpan that never needs to be emptied! When the door at the front is kicked open, the vacuum is operated and anything swept into the pan gets sucked up into the vacuum unit - it really is quite useful for small stuff such as spilt rice, crumbs and breakfast cereals etc...

Step 11: Conclusion

I was amazed how much dirt we picked up in the first week, especially considering that our house has always been vacuumed almost every day, and that the carpets are reasonably new (and pale in colour, so do show any dirt)
The dust bucket shown below is 25 litres in size!! It's about half full (or is that half empty?) after a week of vacuuming

Well, I hope you've enjoyed what I've done, I love my central vac system.
Good luck if you decide to do something similar, you really don't realise how inferior a normal vac is, until you've tried one of these.
Gone are the days of scrubbing the floor backwards and forwards with the vacuum to pick up a stubborn bit of fluff, one pass with the turbo cat and it's gone!! (Seriously)

You might be interested in my other projects on http://www.yourmissus.com (there is a bit more info on this project there too)

Cheers
-Dan