Some help for course work info needed

digiman · Sep 12, 2012

Hi there,

I am new on here,Great place !

Can someone explain to me how to do an earth continuity test and earth loop test on an electric cooker where the cooker point is already installed.

Our college tutor has asked us to find out the info for next weeks lesson ,where we will be asked some questions to see if we have the right answers.

We will then be installing an electric cooker after we have ascertained that the supply is good and that the earthing from socket to cooker shell is correctly earthed .Any info appreciated so i have a better understanding for next week.

Thanks in advance

trev · Sep 12, 2012

Rather than spoon feeding you the answer, tell us how you think it should be done then we can either put you right or say well done

telectrix · Sep 12, 2012

you do your R1+R2 on the terminals of the switch, after disconnecting the cables in the CU and shorting L and E (in CU). your easrth loop test is a live test, and so it may be advisable to calculate the Zs from Ze+ (R1+R2). you test the cooker and it's cable separately. ( as in PAT testing)

edit: sorry trev, forgot it's a schooldasy. LOL. :19:

SirKit Breaker · Sep 12, 2012

I will guide you on the earth continuity test for the cooker with the flex connected to it.

If you have access to the 3rd edition of Inservice inspection and testing of electrical equipment (this is the book for the pat testing course), look in it, in there you will find the maximum allowable value of earth continuity for all class one appliances (all earthed equipment is class 1). It will be (0.1 ohm + R). You need to know the value of R. R is the resistance of the CPC within the appliance flex, this is given in milliohms per meter in a table in the aforementioned book. 0.1ohm is the maximum value of earth continuity of the appliance only i.e earth terminal to the farthest part of the exposed metalwork on your cooker. Once you have found out what the milliohm per metre of your particular diameter of CPC is, multiply it by the length of the flex, and divide the sum by 1000 to give ohms per metre. Take an earth continuity measurement from the part of the cooker which is farthest away from the end of your flex, to the cpc at the end of the flex which will be connected to the supply. The result obtained is the combined value of the appliance and its connected flex. You know the value of R, so deduct it from the overall result, this will leave a value, this value is the earth continuity of the appliance, and it should be 0.1ohm or lower.

Cheers.............Howard

digiman · Sep 12, 2012

SirKit Breaker said:
I will guide you on the earth continuity test for the cooker with the flex connected to it.

If you have access to the 3rd edition of Inservice inspection and testing of electrical equipment (this is the book for the pat testing course), look in it, in there you will find the maximum allowable value of earth continuity for all class one appliances (all earthed equipment is class 1). It will be (0.1 ohm + R). You need to know the value of R. R is the resistance of the CPC within the appliance flex, this is given in milliohms per meter in a table in the aforementioned book. 0.1ohm is the maximum value of earth continuity of the appliance only i.e earth terminal to the farthest part of the exposed metalwork on your cooker. Once you have found out what the milliohm per metre of your particular diameter of CPC is, multiply it by the length of the flex, and divide the sum by 1000 to give ohms per metre. Take an earth continuity measurement from the part of the cooker which is farthest away from the end of your flex, to the cpc at the end of the flex which will be connected to the supply. The result obtained is the combined value of the appliance and its connected flex. You know the value of R, so deduct it from the overall result, this will leave a value, this value is the earth continuity of the appliance, and it should be 0.1ohm or lower.

Cheers.............Howard

Thanks for the info ,not got 3rd edition of In-service inspection and testing of electrical equipment book. Will have a look out for it or see if it's anywhere on the net.cheers

Carl

SirKit Breaker · Sep 18, 2012

digiman said:
Thanks for the info ,not got 3rd edition of In-service inspection and testing of electrical equipment book. Will have a look out for it or see if it's anywhere on the net.cheers

Carl

Try get a secondhand book, the new one is out in November.

oldtimer · Sep 18, 2012

digiman said:
Thanks for the info ,not got 3rd edition of In-service inspection and testing of electrical equipment book. Will have a look out for it or see if it's anywhere on the net.cheers

Carl

How in hells name are you meant to learn when you dont have a book ?? Trev was right you should have said how you would have done it and before you say I am having a pop forget it the whole idea of college is for you to learn how to figure it out yourself instead of googling this forum. If you want to be an electrician or if there is anybody else reading this who is in the same position then listen up you need to apply yourself and show the forum how you have figured it out and then they can help if not its just plain lazy in my view

trev · Sep 18, 2012

When I did my 16th course I couldn't afford to buy my own copy of the regs, then I remembered these things called libraries. Most colleges have them, they're great places and the staff are usually really nice. They let you borrow the books

oldtimer · Sep 18, 2012

trev said:
When I did my 16th course I couldn't afford to buy my own copy of the regs, then I remembered these things called libraries. Most colleges have them, they're great places and the staff are usually really nice. They let you borrow the books

Trev no offence but when we were starting yep it was tough and yep I had my regs book and any and all handouts from the college but come on I am sorry I just dont get it when I hear I cant afford or I dont have a £30 book but funny enough I have a £300 phone in my pocket but I aint going to trade it in for a £100 phone so I can afford some books its called PRIORITIES and SELF DISCIPLINE and if you aint got it then stop wasting my time and your own by trying to be an electrician.