Read Online SAS Urban Survival Handbook by John Wiseman - Free Book Online Page A
Authors: John Wiseman
Tags: Fiction, General, Reference, Survival, Survival skills, Self-Help, Health & Fitness, safety, Personal & Practical Guides
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voltage is plugged into a lower power supply, it probably won’t work—or will operate at reduced speed and efficiency. Plugging in an appliance into too high a power supply may result in overheating, fire or explosion. DON’T GUESS!
Major differences
Power supplies, electrical sockets and plugs vary the world over. In the UK and Australia, for example, voltages are very similar and both use three-pin plugs. The important difference is that plugs are not fused in Australia—whereas they always are in the UK. In the US, not only is the voltage lower, but plugs are two-pin and unfused. Switches on lamps may be turn buttons, not rocker switches or press buttons. Room switches may operate in the opposite direction to the UK. ‘Up’ may be ON, while ‘down’ is OFF. All could lead to confusion and mistakes could be dangerous.
If travelling or emigrating, be aware of national variations. KNOW YOUR DESTINATION!
Types of domestic circuit
The electricity supply enters a premises through a sealed service fuse box (to which only the electricity company has access), passes through the meter (which records the current used) and travels through a set of fuses, before being distributed about the building.
Very old systems had separate fuses for each outlet. Power (socket) and lighting circuits, even quite recently, had separate fuse boxes. A messy fuse board may indicate old, messy or dangerous wiring.
A modern system usually has a single fuse box, or consumer unit, linked to a smaller number of circuits, with each circuit protected by a fuse or circuit-breaker. Each appliance is protected by a fuse in its plug. Alternatively the actual socket (or special switch) may also be fused.
Heavy cable is used to serve a number of outlets, which are usually arranged as a ring—starting and ending at the consumer unit. This is known as a ring main.
A less-common domestic arrangement—a radial circuit—passes the current from one outlet to another, but ends at the last outlet.
Spurs or extensions may have been taken off either of these types of circuit at any point, to serve another outlet.
Special circuits may be run off to serve rooms such as kitchens, where demand for power is high, or for individual appliances such as cookers. It is unlikely that you will overload a circuit, unless you use a lot of demanding equipment such as electrical heaters.
Power limits
A 13-amp socket will be able to supply up to, but not more than, 3000 watts power if safely and correctly installed. Most ring mains carry a fuse of 30 amps. This should tolerate a total load of 7200 watts—on the whole circuit.
The following box should help you work out if you are within safe limits:
POWER CONSUMPTION
Here are some approximate ratings for different types of appliance. The information is designed to be for rough guidance only. Most appliances will have information/specific ratings marked on them. CHECK!
■ Low-rated appliances—5 to 50 watts
Bedside clocks, clock radios, answering machines, electric razors, personal computers
■ Up to 125 watts
Televisions, fridges, hi-fi equipment, video recorders, low-rated food mixers, (most) plug-in lamps
■ 200 to 350 watts
Medium-rated food mixers, do-it-yourself equipment such as circular saws and jigsaws, low-rated electric drills, sanders, very low-rated lawnmowers, freezers, very low-rated vacuum cleaners, low-rated hairdryers
■ Up to 1250 watts
More-powerful food mixers, vacuum cleaners, lawn mowers, hairdryers and electric drills, plus microwave ovens, coffee makers, irons, low-rated toasters, low-rated electric heaters
■ Up to 2500 watts
More-powerful electric heaters, fan heaters, tumbledryers, washing machines, low-rated ovens, low-rated kettles
■ Over 2500 watts
Powerful electric heaters and fan heaters, ovens, powerful kettles
► Even from this list you can see that a 13-amp socket could not be used with an adaptor to take a 3000-watt kettle
Major differences
Power supplies, electrical sockets and plugs vary the world over. In the UK and Australia, for example, voltages are very similar and both use three-pin plugs. The important difference is that plugs are not fused in Australia—whereas they always are in the UK. In the US, not only is the voltage lower, but plugs are two-pin and unfused. Switches on lamps may be turn buttons, not rocker switches or press buttons. Room switches may operate in the opposite direction to the UK. ‘Up’ may be ON, while ‘down’ is OFF. All could lead to confusion and mistakes could be dangerous.
If travelling or emigrating, be aware of national variations. KNOW YOUR DESTINATION!
Types of domestic circuit
The electricity supply enters a premises through a sealed service fuse box (to which only the electricity company has access), passes through the meter (which records the current used) and travels through a set of fuses, before being distributed about the building.
Very old systems had separate fuses for each outlet. Power (socket) and lighting circuits, even quite recently, had separate fuse boxes. A messy fuse board may indicate old, messy or dangerous wiring.
A modern system usually has a single fuse box, or consumer unit, linked to a smaller number of circuits, with each circuit protected by a fuse or circuit-breaker. Each appliance is protected by a fuse in its plug. Alternatively the actual socket (or special switch) may also be fused.
Heavy cable is used to serve a number of outlets, which are usually arranged as a ring—starting and ending at the consumer unit. This is known as a ring main.
A less-common domestic arrangement—a radial circuit—passes the current from one outlet to another, but ends at the last outlet.
Spurs or extensions may have been taken off either of these types of circuit at any point, to serve another outlet.
Special circuits may be run off to serve rooms such as kitchens, where demand for power is high, or for individual appliances such as cookers. It is unlikely that you will overload a circuit, unless you use a lot of demanding equipment such as electrical heaters.
Power limits
A 13-amp socket will be able to supply up to, but not more than, 3000 watts power if safely and correctly installed. Most ring mains carry a fuse of 30 amps. This should tolerate a total load of 7200 watts—on the whole circuit.
The following box should help you work out if you are within safe limits:
POWER CONSUMPTION
Here are some approximate ratings for different types of appliance. The information is designed to be for rough guidance only. Most appliances will have information/specific ratings marked on them. CHECK!
■ Low-rated appliances—5 to 50 watts
Bedside clocks, clock radios, answering machines, electric razors, personal computers
■ Up to 125 watts
Televisions, fridges, hi-fi equipment, video recorders, low-rated food mixers, (most) plug-in lamps
■ 200 to 350 watts
Medium-rated food mixers, do-it-yourself equipment such as circular saws and jigsaws, low-rated electric drills, sanders, very low-rated lawnmowers, freezers, very low-rated vacuum cleaners, low-rated hairdryers
■ Up to 1250 watts
More-powerful food mixers, vacuum cleaners, lawn mowers, hairdryers and electric drills, plus microwave ovens, coffee makers, irons, low-rated toasters, low-rated electric heaters
■ Up to 2500 watts
More-powerful electric heaters, fan heaters, tumbledryers, washing machines, low-rated ovens, low-rated kettles
■ Over 2500 watts
Powerful electric heaters and fan heaters, ovens, powerful kettles
► Even from this list you can see that a 13-amp socket could not be used with an adaptor to take a 3000-watt kettle
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