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Our Diesel Generators can be used for residential or small commercial installations.  The best way to provide an outdoor mains supply is to use proper outdoor cabling accessories, with a supply derived from the main distribution board via an RCD. As always, you will need to ensure that the cabling is adequate for the current load you anticipate.

A particular problem is that of meeting the voltage drop regulations when the cable is likely to be quite long. You may find that you have to use a cable that is heavier than you would expect, not to carry the current, but to meet the voltage drop requirements. This is particularly likely if you plan to use the outdoor system to supply power tools.

For example, a 2.5 mm cable carrying 20 amps can only be 27 metres long before it fails the voltage drop requirements.

You can derive the outdoor supply from a power ring, using a fused spur unit, if the load is expected be less than 13 amps. You may need to include an RCD in the circuit at the point the spur is taken, if the power ring itself is not RCD protected.

Miscellaneous

Earth conductor

You'll notice that the earth conductor in two-core-and-earth cable is not insulated. This is because the earth cannot carry any dangerous voltage (if it is properly installed). However, there is a risk in a crowded junction box or socket outlet that the earth conductor could come into contact with a live part. This is a particular risk with socket outlets, where one would normally wire the outlet and then push it back into its mounting box. This can easily cause the earth conductor to deviate from its original position and touch something it shouldn't. To prevent this, it's customary to push a length of insulating sleeve over the earth conductor before fixing it to a terminal. The standard colour for this sleeve is green and yellow.

Trimming lengths

When stripping the ends off the insulation on the live and neutral conductors, there is a `right' amount of insulator to strip. It is the length which allows the conductor to be firmly gripped by the terminal, but leaves no conductor visible outside the terminal shroud. If an excessive length of stripped conductor protrudes, clearly this increases the risk of it's coming into contact with something else. The length of insulation to strip will vary according to the type of fitting, so it's worth practising first.

Terminal contact

Cable protection

Mounting box depth

A particular important type of spur is the fused spur. In this arrangement the spur is connected to the ring by a fuse and, optionally, a switch. A fused spur becomes, in effect, a separate circuit, because its fuse limits the load it places on the main ring. Fused spurs are very important where we need to connect appliances designed for a lower-current circuit into a higher-current one.

For example, suppose we have a wall-mounted lamp designed to be fitted on a 5-amp lighting circuit. The lamp will be constructed in such a way that it can stand a current of 5 amps (in a fault), but will expect never to see more than 5 amps, because somewhere a fuse or MCB will trip.

Suppose we want to connect two such lamps to a 30-amp power circuit. We can't take a simple spur from the power ring, because it has a 30-amp fuse or MCB protecting it (and we need to restrict current to 5 amps). So what we do is fit a fused spur unit and connect the lamps to that. The fused spur unit will be fitted with a 5-amp fuse. The spur unit will cost about three pounds, and fit the same mounting as a standard lightswitch. For an extra few pounds you can get one that contains a switch as well, so it could be the lightswitch.

You may be wondering why we would want to connect lamps to a power circuit, rather than a lighting circuit. First, it is sometimes simply more convenient to do this, especially with wall lamps. Second, some lamps - especially security floodlamps - may take as much as 4 amps. Although one of them will run on a 5 amp lighting circuit, it doesn't leave a lot of current over for the rest of the lamps. And, clearly, two 4-amp security lamps will overload a 5-amp lighting circuit.

Electric Generator Store Networking computers involves connecting them together with cables and connectors. At the time of writing all practical small networks are based on electrical cables, although optical fibres may soon be competitive. Although in principle there is a number of different connection schemes to choose from, in practice everyone uses a scheme called ethernet.

Ethernet has been around for about 30 years, and completely dominates the local-area networking market. Although ethernet derived from a proprietary standard (Xerox Corporation) it is now non-proprietary, and many companies make ethernet equipment. Therefore it is relatively inexpensive.

   The ethernet system defines a signalling strategy (the way signals are carried on wires) and a low-level protocol (the way data is converted into signals). It does not define the type of cable or the speed of transmission.

In practice, however, everyone now uses twisted pair cables, with speeds of either 10 megabits per second, or 100 megabits per second. For a domestic installation, the earlier `coaxial' cabling scheme may be more appropriate, but it is getting increasingly difficult to find compatible equipment, so I will assume that you are going to use twisted pair cabling like everyone else. Happily, the hard part of the installation (laying the cables and connecting the hubs) is the same whether you go for the 10 or the 100 mbits/sec option.

Twisted pair cable is available in various categories and either with, or without, a screen (`shield' in the US). The category dictates the maximum transmission speed and distance that the cable will tolerate. The most common sort of cable, which is used in nearly all domestic and commercial installations, is category 5 unscreened twisted pair.

You will usually see this abbreviated to `CAT5 UTP' in trade publications. Although in principle CAT3 cable could be used with the lower-speed ethernet, there is no real advantage to this as it isn't any cheaper. Screened twisted pair cable is used in some industrial installations, where there is a high level of electrical interference. There is unlikely to be a good reason to use it in domestic or commercial work.

  So, in practice, you will almost certainly need to use CAT5 UTP cable for your installation. At the time of writing this cable costs about Ј40 for a 1000-foot drum. If you are wiring your entire house then you probably do need this much. If you have only two PCs, and they are side-by-side, then you should probably buy pre-assembled `patch cables', rather than a cable drum, as described below.