electrical Flashcards
What document should be referred to for specific wiring details of domestic heating
controls?
Manufacturer’s instructions
What is the most likely supply voltage type and rating used for a central heating
pump?
230 V a.c.
What voltage would be found on a low voltage central heating wiring system?
24 V a.c.
What domestic electrical circuit would incorporate the plug outlets?
Ring main circuit
Which Earthing arrangement uses an installation of an earth electrode as part of
the earth fault path?
TT
Which conductor connects an installation Main Earthing Terminal (MET) to the incoming
metallic Water Supply Service Pipe?
Main Protective Bonding Conductor
Which conductors would normally connect two water pipes together within a bathroom location?
Supplementary Bonding Conductor
Which protective devices operates under earth fault conditions only?
RCD
What protective device operates when the system is overloaded?
circuit breaker
Which fuse cartridge would be selected to provide overcurrent protection to the fused
connection unit to a 230v domestic central heating control system with a total load of 600
Watts?
3 a
What protection method applies when installing circuits using single-core cable?
The cables must be enclosed in conduit
What would most likely be the first thing to be damaged if the current in a cable exceeds
its current carrying capacity?
Cable insulation
What is the recommended method used to secure a circuit breaker in the off position?
Locking device with unique key
A circuit breaker located within a consumer’s control unit controlling a shower circuit
requires replacement. What is the correct part of the installation for carrying out safe
isolation?
The consumer unit main switch
A ring-final circuit requires the addition of a fuse connection unit for a boiler. Where’s the
most suitable location to carry out safe isolation in order to carry out this work?
The consumer unit main switch
What is the correct method of ensuring safety following safe isolation and locking off of
the circuit?
Retain the unique key with you
Which faults is most likely to cause electrocution?
Loose connection
What is the most likely fault if an appliance works intermittently?
Loose connection in the appliance plug
What is the most likely fault that would cause an RCD to trip when an electric shower is
switched on using the local functional switch?
A fault between live and earth within the shower unit
When wiring up a plug top, the connections should be made in a way to ensure that if the
cable is pulled with sufficient force to remove it from the plug. Which wire should be the
last to be broken?
Earth
An intermittent fault exists in hot water immersion heater. It appears that the cable has
become brittle and the circuit keeps shorting out. What is the most likely cause of the
fault?
A non heat-resistant flex being used
What fault is the most likely cause of brown discolouring around the front of a
socket-outlet?
Loose line connection within the plug of an appliance regularly used at the socket
Fault diagnoses reveals a serious fault in a domestic installation which could result in
serious electric shock if not rectified. Which person should be informed immediately in
this situation?
Owner
Fault diagnosis is being undertaken in a building during non-working hours (when the
building is unoccupied). A serious and life-threatening fault is discovered to the wiring of
a circuit and rectification of the fault will require major works. What action would be the
most appropriate in this situation?
The circuit should be securely isolated until the client can be informed of the risk
