New Ceramic Hob wont power up

[sjolley]

hi, ive just renewed my ceramic hob with an indesit VRA640X. i've used my existing supply and connected to the pre connected electric cable designed for single phase. switched on my cooker MCB and nothing happens. the hob is suppose to beep and should turn on using the touch controls but mine seems DEAD. i have double checked my electric connections and tested with volt meter.

the hob has L1,L2 and L3 (3 lives). the pre made up cable has a red and brown cable joint together at the end, at the hob end they are connected to L1 and L3 with a link between L3 and L2.

It has 2 blue cables, again jointed together at the connection end and at the hob end goes to L5 and L4, which are the 2 neutrals. the earth is connected to L6.

voltmeter says 245v ac between earth and all other connections.

seems like a fault hob.

 

[ColJack]

read through the instructions carefully, there may be a specific sequence of buttons to press when you power it on to "unlock" it.. perhaps?

 

[nelectric]

Have you followed the instructions regarding wiring?

page with link to instruction for Indesit VRA640X

 

[TicklyT]

.....voltmeter says 245v ac between earth and all other connections....

That bit doesn't sound right. The Neutral connection(s) should be at, or close to the same potential as the earth connection.

That would get me looking for a fault in the neutral connection, allowing the live to backfeed mains voltage onto the Neutral via the hob - Very dangerous if you are poking around and not expecting it, so make sure you turn the power OFF before investigating.

 

[sjolley]

read through the instructions carefully, there may be a specific sequence of buttons to press when you power it on to "unlock" it.. perhaps?

read through instructions several times, hob should give a beep when power is turned on, unfortunately no beeps can be heard.

 

[sjolley]

Have you followed the instructions regarding wiring?

page with link to instruction for Indesit VRA640X

yes i beleave i have followed the correct wiring instructions. to be honest not very difficult considering they was a pre connected cable for single phase supply.

 

[sjolley]

read through the instructions carefully, there may be a specific sequence of buttons to press when you power it on to "unlock" it.. perhaps?

read through instructions several times, hob should give a beep when power is turned on, unfortunately no beeps can be heard.

just doubled check my voltages. so at my hob i have L1, L2, L2 (Live) L4, L5 (Neutral) L6 Earth

going from L6 earth to all over connections (live & neutral) i get approx 245v ac.

between live and neutral i get 0v ac.

also just disconnected my hob from cooker socket. at cooker socket i get 245 between live and earth, 0 between neutral and earth, 0 between live and neutral. which i guess i right so fault must lie on hob..

a resistance check on the hob shows open circuit between N&E, L&E and approx 1.5M between L&N

 

[jj4091]

Not the hob thats faulty but the supply at the cooker switch. You should read the same voltage between live & neutral as you do between live & earth ie 240v so it would appear that you are loosing the neutral to the cooker switch. Power off at the consumer unit & check that the connections in the cooker switch are ok IE screwed to the wire & not the insulation. If you cannot find a fault there & you are competant & confident enough to look in the consumer unit you need to check the cable going from there to the cooker switch.

 

[sjolley]

Not the hob thats faulty but the supply at the cooker switch. You should read the same voltage between live & neutral as you do between live & earth ie 240v so it would appear that you are loosing the neutral to the cooker switch. Power off at the consumer unit & check that the connections in the cooker switch are ok IE screwed to the wire & not the insulation. If you cannot find a fault there & you are competant & confident enough to look in the consumer unit you need to check the cable going from there to the cooker switch.

a second voltage check at cooker switch shows LE 240v LN80v NE 0v

 

[TicklyT]

That definitely sounds like a neutral fault. Bereft of any electrical conection to complete the circuit, the neutral conductor will 'float' at any voltage it sees fit at the time. sometimes 240 V, sometimes 80 V, maybe sometimes 160 V, and maybe sometimes 0 Volts, just to confuse things. Testing with a high impedance meter often shows these spurious voltages on unterminated conductors, with the values often changing beteen tests.

To recognise some of these faults you need to be aware of the limitations of the testing rechniques you have available.

As jj4091 said, finding anything other than the same voltage L-E and L-N, and virtually no voltage N-E. indicates a fault in the supply. As it is the voltage on the neutral conductor that seems to be changing, that suggests a problem with the neutral connection somewhere 'upstream' of the point where you are testing.

 

[sjolley]

thank you every one who has contributed to my problem . it turns out i had some hidden terminal blocks in my stud wall where the neutral was loose.

all repaired and hob works ok now.

once again, many thanks. keep up the good work in the forums.

 

[flameport]

some hidden terminal blocks in my stud wall

Hopefully not hidden any more?

 

[nelectric]

Teminal blocks?

I would not be happy about that, particularly on cooker circuit. Depends on what sort of terminal block though. And why would there be a need? Has the cooker been re-sited? If the circuit really did need extending, then it ought to be done properly, with suitably rated junction box or similar. Otherwise you end up with more faults like the one you have found - possibly even more serious. Can you post a pic of the 'terminal block' used so we can advise further?