Oven Isolation and heating element.?

[cfcdoc]

Ok i have a belling xou178 single electric oven. I have a switch on the wall for the oven which cuts the power to the oven so that nothing comes on. I believe the heating element has gone for the fan oven not the grill as both the grill and fan still work as does the oven light, however, no heat with the fan oven on only. I clicked this oven switch on the wall near the cooker to off and i took the back plate off and saw a cracked element on the surface. It appears that the element is screwed in from the rear so i took the fixing screws out and pulled the oven out. Before i go any further am i right in assuming that by switching the switch on the wall near the oven off that no electricity is now passing through the wires so i can safely disconnect the heating element without becoming a heating element for all that electricity myself

 

[Chivers7]

As long as it's double poled - which it's likely to be the answer is yes.

 

[cfcdoc]

how do i know if its double poled, i pulled the oven out there seems to be like a brown box with a "lid" on the back of the oven with a brown cable coming out to a white box on the back wall in the oven recess then a white cable running up out of this white box on the wall behind the worktop to the oven switch on the wall

 

[Steve]

Do you have a multimeter? I suggest you stop now, and go and buy one from Maplin. About £10, it is invaluable for prooving dead, and testing resistance, across heating elements, for example

 

[Taylortwocities]

Or turn off the main switch to the fusboard for the house.

You should also check the circuit is dead using test meter or proper voltage indicator (NOT a neon screwdriver!)

 

[cfcdoc]

the heating element is dead its got a cracked surface. Surely the oven switch isolates the power does it not. When i switched it off the oven wouldnt come on, i`m not an electrician but surely that must mean there is no power coming to the oven

 

[bernardgreen]

When i switched it off the oven wouldnt come on, i`m not an electrician but surely that must mean there is no power coming to the oven

The oven ( and any electrical appliance ) needs Live and Neutral connected to work ( and Earth as a safety factor ).

If the switch turns off only the Neutral then all the wiring in the appliance is Live and therefore extremely hazardous with a almost 100% certainty of electric shock and possible fatality.

Hence NEVER trust an isolator has disconnected the LIVE until you have proven it with a measurement of voltage between Live in appliance and earth. It is no good measuring between Live and Neutral as that will show ZERO as both are LIVE since the neutral is disconnected.

I once had an isolator switch in which the LIVE contacts had welded together. Good thing I tested for live before working on the appliance

 

[Steve]

the heating element is dead its got a cracked surface. Surely the oven switch isolates the power does it not. When i switched it off the oven wouldnt come on, i`m not an electrician but surely that must mean there is no power coming to the oven

It was you that asked for confirmation on this. I was giving you a solution to confirm it.

 

[cfcdoc]

sorry mate but the element just looks dead, its not really that that i wanted confirmation about, it really was just about the switch and whether it was safe to now work on the appliance

 

[cfcdoc]

bernard what is the easiest way of confirming what you said. Is there a dummies guide for people like me. is it simple, dont really want to pay the 70 call out fee when the part is only 20

 

[bernardgreen]

bernard what is the easiest way of confirming what you said.

Using a voltmeter to measure the voltage on the wiring relative to the earth.

Is there a dummies guide for people like me. is it simple, dont really want to pay the 70 call out fee when the part is only 20

If there was it would be a very large book. But to test your element there are two resistance measurements you need to make using an ohm meter.

[1] The resistance from one terminal to the other will indicate the condition of the element as broken or intact. A one Kilowatt element will have a resistance of around 60 ohms. A two Kilowatt will be around 30 ohms. If this measure is far from those value then the element has broken.

[2] The resistance between the element's terminal and the metal casing of the element. This should be many millions of ohms as there should be no current flow possible between the terminals and the case which is earthed.

A multimeter can do both voltage and resistance tests. So buy one for around £10 and read the instructions a few times. And then measure some batteries for voltage and some un plugged appliances for resistance between the pins of the plug as practise till you understand what the meter is telling you.


The test for the high resistance [2] is not really correct with an average multimeter as these meters only test resistance at a low voltage ( around 3 to 9 ) and not at 230 volts. Insulation in the element can be good at 9 volts and fail at 230 volts. But it will show most insulation failures, anything less than 5 Megohms ( 5 million ohms ) at 9 volts and I would change the element.

 

[Taylortwocities]

And disconnect the wires from the element before you test its resistance otherwise you may pick up readings from the rest of the wiring!

You can check the reading you get on the suspect element with the reading on a known working one. That will confirm if its faulty or not.

 

[cfcdoc]

thank you all, just ended up switching the mains supply off instead of hoping the isolating switch did what it was meant to. Didnt really want to fry myself. Element came out, almost corroded on side like someone had taken a hacksaw to it. New element now in. Cheers all.