Quiz 2 – ‘PAT Testing’ Basics

Insulation Resistance Testing is always carried out with Direct Current (dc). Surge protection is designed to protect against higher voltages, so if we test using 500Vdc, we will trigger the surge protection, so 250Vdc is used.

Power / Voltage = Current

2300W / 230V = 10 Amps

• Current - Amps
• EMF / Potential Difference - Volts
• Resistance - Ohms
• Power - Watts

• Current - Amps
• EMF / Potential Difference - Volts
• Resistance - Ohms
• Power - Watts

By definition, an Extra Low Voltage item has a reduced input voltage and is not powered by the mains supply

The BS1362 fuse is designed to protect the cord.  Therefore, the fuse has to be of a lower rating than the cord to ensure it blows before the cord sets on fire

Under fault conditions, we would expect current to pass down the earth path to ground.  If there is too much resistance in the earth path, the fault current will find an alternative path to ground e.g. through the user.

The supply voltage is influenced by a number of factors, including the number of items being fed by the supply.  The more items we switch on, the lower the voltage will go

The safety of the item is dependent upon the safety of the socket.  If the socket is damaged, it could make a safe item, unsafe.  Therefore, prior to using the item, the user should check the condition of the socket

The industry standard states that an item with a power rating of up to 700 Watts will draw up to 3 Amps.  From 701 Watts to 3,000 Watts it will draw up to 13 Amps.

"H05VV-F" - for indoor mobile installations and household appliances with medium mechanical strain.  "3G" - 3 conductors.  "NSW24982" - product code.  "1.0mm² " - the cross sectional area of each conductor.

If a flex has a moulded plug, it isn't possible to open the plug and count the number of conductors.  However, we look at the flex for 3G or 3X to indicate 3-core or 2G or 2X to indicate 2-core.

The appliance itself has to identify the type of construction.  Opening the plug and counting the conductors tells us whether there is a 2-core or 3-core flex...not whether it is the correct flex for the item - it could have been changed at some point.

"H05VV-F" - for indoor mobile installations and household appliances with medium mechanical strain.  "3G" - 3 conductors.  "NSW24982" - product code.  "1.0mm² " - the cross sectional area of each conductor.

An earth path is designed to take fault current to ground and away from the equipment user.  Resistance in an earth path will affect its effectiveness putting the equipment user at risk.  As electricity will always take the path of least resistance, low resistance in the earth path is always required.

By definition a Class II item is mains powered and has 2 distinct layers of insulation (basic and supplementary) or 1 layer of reinforced insulation.

Energy cannot be made or destroyed, but it can be changed from one for to another, for example, electrical energy to heat

The key 'safety feature' of a Class II item is two distinct layers of insulation (or one layer of reinforced insulation) around live parts.  Also known as double insulated.

The user doesn't need a qualification to carry out a User Check, but they do need common sense and attention to detail

The 'box inside a box' symbol represents 2 layers of insulation