9c.1 Recall that a ladder should be used at the correct angle (4:1 height-to-base ratio).
9c.2 Understand that ladders must be secured at the top or securely held at the bottom by an adult to prevent them slipping.
9c.3 Understand why it is important not to overreach from a ladder, to prevent falling off.
9c.4 Understand why a tool belt or similar device to carry tools should
be used, and that it will help prevent falling objects. Understand the
need to wear hard hats when working at height or when others are
working at height.
Putting up antennas can include working at heights. A fall from a ladder can lead to serious injury or death.
1. Ladders should be used at the correct angle (4:1 height to base ratio)
2. Ladders should be secured at the top if possible or held by an adult at the bottom to prevent them slipping.
3. Never over reach when at the top of the ladder. This can cause a
shift in the centre of gravity which causes the ladder to shift and the
risk of the user falling off.
4. A tool belt should be used to hold tools when working on a ladder to
prevent tools slipping out pockets etc and causing injuries to those
below.
5. Wear hard hats when working at heights to protect you from hitting
your head. When working at ground level below people on ladders wear a
hard hat in case they drop anything.
Safety - Electricity 9d.1 Recall that a dangerous electric shock can result from antennas and ladders coming into contact with or attracting arcing from overhead lines. 9d.2 Understand that a fuse must be correctly rated for proper protection, and be able to select an appropriate fuse using the formula: current = power/230 where 230 is the nominal mains voltage. 9d.3 Understand that a residual current device (RCD) will give better protection against electric shock than relying solely on a conventional fuse (which only protects against excessive current) and earth system. Note: The student should appreciate that an RCD will detect currents to earth of about 30mA whereas a fuse will only blow at several amps and only when the fault is a short circuit (L-N or L-E). The mechanics of RCD operation (differential current sensing) is not examinable.
1. Dangerous electric shocks can be caused by ladders, poles and
antennas coming into contact with overhead lines. Always check the site
before putting up ladders or antennas.
2.Using an appropriate fuse in mains powered equipment is important.
Too small a value will blow when turned on. Too high a value will work,
but under fault conditions will allow too much current to pass through
the equipment causing damage to the equipment.
To calculate the size of fuse required use the following formula:
Current = Power / 230 (the nominal mains voltage)
So for a fire that uses 2kW (2000W)
Current = 2000 / 230
= 8.7amps
So, you would probably use a 10amp fuse
Although a conventional fuse will give some protection using a residual current device( RCD) will provide greater protection. An RCD will detect currents to earth of about 30mA within a period of a few milliseconds much before electrocution can take place A
fuse protects against excessive current of several amps, along with an
earth system and only when the fault is a short circuit (L-N or L-E).
9d.4 Understand that large or high-voltage capacitors can store
dangerous electric charges and must be discharged before working on
equipment. Large, high value capacitors can store enough electricity to give someone an electric shock.
They should have a high value bleed resistor across them to discharge
the capacitor, but this can take a while, so for safety these should
always be discharged before working on them or nearby parts. This can be done by
shorting the positive lead to earth, but can result in a blue flash an
a bang! It is better to use a resistor to slow down the rate of
discharge.
