PAT TESTING

Question 1

what is class 1 equipment

Answer 1

class 1 equipment is equipment that is earthed. it relies on an earth to protect it from an electric shock it doesn’t rely on basic insulation. so any exposed metal work WILL be connected to earth unless there is supplementary insulation ( 2 layers of insulation )

Question 2

what is class 2 equipment

Answer 2

class 2 equipment is equipment that doesn't require an earth , but do rely on both basic and supplementary insulation ( or one layer of reinforced 
insulation ) theres no provision for the connection of exposed metalwork to a  protective conductor.

Question 3

what is class 3 equipment

Answer 3

equipment which protection from electric shock that relies on a separated extra low voltage source.

Question 4

what is SELV

Answer 4

separated extra low voltage. anything up to 50V is ELV., and isn’t strong enough to harm our skin and give us a electric shock.

Question 5

what is class 0 equipment

Answer 5

relies solely on basic insulation. dangerous as hasn’t been earthed have any additional protection

Question 6

class 01 equipment

Answer 6

class 0 characteristics but earthing is similar to class 1 equipment

Question 7

Portable appliances

Answer 7

less than 18kg and intended to be moved in operation..

Question 8

moveable appliances

Answer 8

still less than 18 kg and has the means to be moved

equipment with wheels or other means to facilitate movement.

Question 9

Hand held equipment

Answer 9

equipment that’s designed to be held whilst in use. you’re holding it so greater chance of electric shock. e.g hairdryer

Question 10

stationary equipment

Answer 10

more than 18kg. NOT intended to be moved. e.g fridge, washing machine , vending machine

Question 11

fixed appliances

Answer 11

equipment that are fixed directly to the wall and are often hard wired (not plugged in , connected to the system and not meant to be moved at all) requires more effort to inspect and test in PAT testing as we’d have to physically disconnect it from the system. e.g a boiler is connected via a flex to a fused connection unit, we would have to unscrew the FCU from the wall and disconnect the flex from it and then in order to test it you’d have to plug it into your machine to see whether its safe to be in service

Question 12

IT equipment

Answer 12

computer equipment , can be portable. hand held , moveable , stationary but has its own equipment type.

Question 13

Extension Leads. pg140

pg 98 table15.4 shows max lengths of extension cables.
if extension leads excede these lengths then a 30ma rcd should protect it.

Answer 13

should never be class 2 extension lead ( there shouldn’t be a 2 core flex going to the plug top) it should be a 3 pin plug. has to have a connection to earth , so class 1 equipment can go into it.

Question 14

manufacturers type testing

Answer 14

testing is carried out to see if it complies with British standards.

Question 15

manufacturers production testing

Answer 15

every hundred or so items that get produced get tested.

Question 16

in service inspection and test

table 7.1 pg52 - gives intervals for user checks.

Answer 16

involves a preliminary visual inspection , earth continuity test , insulation testing and functional testing. done by a competent person. no tests. results - satisfactory ? unsatisfactory ?

Question 17

testing after repair

Answer 17

self explanotary

Question 18

factors that affect the frequency of inspection and testing

Answer 18

1. the environment in which the equipment is used
2. the user
3. the equipment type - moveable , stationary ?
4. equipment construction - class 1, 2 , 3 etc
5. frequency of use
6. installation methods
7. previous methods.

interval checks should be kept under review.

Question 19

what is the only test that doesn’t have to be dead

Answer 19

functional test

Question 20

what is GS38

Answer 20

it Is guidance on the safe use of probes and leads. test equipment has probes and leads tested into it.

Question 21

explain the earth continuity test - pg91
uses a small amount of current and sends It up the cpc of a flex , and around the outer casing of the appliance and then have a different earth probe in that returns the current and the machine measures how much resistance there is .
there are 2 different test currents
1. low current ( soft test ) between 20 and 200 ma
2. high current - not more than 1,5X the fuse rating and not more than 26 amps

Answer 21

it is carried out to ensure exposed conductive parts of class 1 equipment are reliably connected to the earth pin of the equipment plug via the flex or connector. basically it is to see whether the flex of a CPC is continuous and connects to all exposed metal parts

max allowable results for earth continuity shown on pg 93 table 15.1

my appliance should not have more than 0.1 ohms of resistance between outer casing and top cpc plug top pin

Question 22

insulation resistance test. pg 93

Answer 22

the purpose of the test is to prove their is sufficient insulation around the conductors and live parts. the only place I want to see conductors joining together is at the load. 500 v into the item of equipment between line and neutral conductor and making sure any exposed parts or metal or cpc doesn’t touch these things.

Question 23

what is the hard test.

pg 94 insulation readings.

Answer 23

send 500 v down the line and neutral at the same time. the test probe should be attached to all exposed conductive parts. want to see a resistance of greater than 1 meg ohm.

Question 24

what is the soft test

pg 96

Answer 24

instead of sending 500v into the equipment which may damage it we can produce a soft current test. e.g it equipment

Question 25

what is functional checks

Answer 25

simply a check to see if it works, and everything works accordingly. faulty equipment brought to responsible person immediately & labelled.

RCD’s should be checked every 6 months. pg 99 max operating times for 30ma rcd.