Burnt Main Downstream Neutral

[Squid]

Sheaving???

Sheathing, damn spell check on the Mac + Sausage Fingers.......

 

[The Ghost]

"guilty knowledge"

I suppose we are now implicated by also knowing and share the guilt. Oh oh!

 

[ennaress]

There are two immersion heaters in one insulated tank. The first is a Heatrae Centerbrand Superloy 800 and is 2.8kW @ 230V. The other is a Backer 2.7kW @ 230V.
The owner was told that evening and I disconnected one of the immersions. I then replaced the burnt neutral with a new tail and terminated it to one of the non-melted points as a temporary, safe fix. The EICR has amongst over 20 other observations, a C1 for this....obviously!
A replacement 7671-3 CU is going to be done. I'll also run the immersions on an indep circuit protected with a 20A breaker as will the oven.
No - the outer sheathing had melted and globbed down the conductor.
Yes - the R1-R2 were fine but rubbish / null IR readings which is a real head-scratcher and I'd welcome any sensible avenues of investigation.

 

[westward10]

What do you mean by null IR readings.

 

[Pete999]

There are two immersion heaters in one insulated tank. The first is a Heatrae Centerbrand Superloy 800 and is 2.8kW @ 230V. The other is a Backer 2.7kW @ 230V.
The owner was told that evening and I disconnected one of the immersions. I then replaced the burnt neutral with a new tail and terminated it to one of the non-melted points as a temporary, safe fix. The EICR has amongst over 20 other observations, a C1 for this....obviously!
A replacement 7671-3 CU is going to be done. I'll also run the immersions on an indep circuit protected with a 20A breaker as will the oven.
No - the outer sheathing had melted and globbed down the conductor.
Yes - the R1-R2 were fine but rubbish / null IR readings which is a real head-scratcher and I'd welcome any sensible avenues of investigation.

Can you explain the last paragraph in greater detail? R1+R2 were fine but rubbish/null IR readings?????

 

[static zap]

/ null IR readings which is a real head-scratcher and I'd welcome any sensible avenues of investigation.

Measured on what ?
, would it progress no further -Error ?

 

[davesparks]

I'll also run the immersions on an indep circuit protected with a 20A breaker as will the oven.
.

Both immersion a on one circuit? How's that going to work?

 

[Dave OCD]

Wire them through a 20a 2 way switch so one can have a rest every other day.

 

[davesparks]

To cover you behind send the customer a Danger Notice without delay. It looks too far gone to be cured by tightening the screw up. What do you mean by IR is open circuit (OC) ?, if it is how have you got satisfactory r1+r2 ? You have what is known as "guilty knowledge" of a potential fire risk. Ideally tell them it must be isolated and the C.U. replaced immediately, I realise that may not be practical, so send the Danger Notice and make it their problem not yours ! Sorry if I sound like an arse but where there's a blame, there's a claim !! .

I wouldn't rely too much on this 'danger notice' to cover your arse, I think it is more likely to be used to prove that you left a known danger in place rather than help you get away with it if the worst did happen.
Don't forget that this 'danger notice' (if you are referring to what I think you are) is something invented by the nic which has no basis in the regulation or law.

 

[davesparks]

There are two immersion heaters in one insulated tank. The first is a Heatrae Centerbrand Superloy 800 and is 2.8kW @ 230V. The other is a Backer 2.7kW @ 230V.
The owner was told that evening and I disconnected one of the immersions. I then replaced the burnt neutral with a new tail and terminated it to one of the non-melted points as a temporary, safe fix. The EICR has amongst over 20 other observations, a C1 for this....obviously!
A replacement 7671-3 CU is going to be done. I'll also run the immersions on an indep circuit protected with a 20A breaker as will the oven.
No - the outer sheathing had melted and globbed down the conductor.
Yes - the R1-R2 were fine but rubbish / null IR readings which is a real head-scratcher and I'd welcome any sensible avenues of investigation.

Only the lower heater should be connected in a two immersion heater cylinder if no off-peak/E7 supply is available.
The upper heater is only there to be a boost element in an off-peak/E7 setup. It will do little to no work if it is switched on at the same time as the lower heater, the heat from the lower heater will quite quickly operate the thermostat of the upper heater and switch it off. Also with modern immersion heaters the lower element can operate the overheat trip of the upper element and switch it off permanently (until reset)

Why are you quoting the 230V power ratings? The public electricity supply in the U.K. is 240V, the mythical 230V only exists on paper and not in the real world. These immersion are will be operating at 3kW and using the lower power ratings will lead to you designing and installing a circuit with a small overload which is a dangerous situation.

What is a rubbish/null IR reading? All of the IR testers I have used have only ever had a numerical scale so I haven't a clue what those readings equate to.

 

[Ian1981]

Only the lower heater should be connected in a two immersion heater cylinder if no off-peak/E7 supply is available.
The upper heater is only there to be a boost element in an off-peak/E7 setup. It will do little to no work if it is switched on at the same time as the lower heater, the heat from the lower heater will quite quickly operate the thermostat of the upper heater and switch it off. Also with modern immersion heaters the lower element can operate the overheat trip of the upper element and switch it off permanently (until reset)

Why are you quoting the 230V power ratings? The public electricity supply in the U.K. is 240V, the mythical 230V only exists on paper and not in the real world. These immersion are will be operating at 3kW and using the lower power ratings will lead to you designing and installing a circuit with a small overload which is a dangerous situation.

What is a rubbish/null IR reading? All of the IR testers I have used have only ever had a numerical scale so I haven't a clue what those readings equate to.

He's probably using 230 v because that is what we are taught to use from college and bs7671.
We are required to record the nominal voltage on our test certificates as 230 volts and not the measured value.
Also voltage drop calculations are based on 230 volts it's 3% of lighting etc based on 230 volts yes it takes the worst case scenario.
Maximum zs values calculations require it to be 230 x 0.95.
Where I do agree that most of the time the voltage is around 240-245 volts it's not the voltage we are told to use maybe common sense tells us different.
Maybe it's not 'the real world' but it is whAt it is.

 

[static zap]

....Maybe it's not 'the real world' but it is whAt it is.

Maybe a harmonized EUROPE ... or What it WAS ...
(did we ever intend to comply -or just upped the + to 10%)

 

[Ian1981]

Maybe a harmonized EUROPE ... or What it WAS ...
(did we ever intend to comply -or just upped the + to 10%)

Yes it was to harmonise if you read page 316 of bs 7671 it was agreed by CENELEC within Europe from as early as 1988.

 

[static zap]

CENELEC within Europe from as early as 1988.

Politicians promises , (-sounds good-) !!!

 

[telectrix]

latest one being corbyn's u turn on student fees. promise.. we'll scrap them.. now you students have voted labour, we wouldn't.

 

[static zap]

Was it about all debt , vs future debt ?
(Just heard U turn ,and sighed/switched off)
Vagueness is normal in their arean.

 

[ennaress]

Typical....someone mentions a relatively minor point* about Voltage (each immersion carried a plate stating 230v...not because that's what I was taught at college - thanks all) and the thread goes way off into Labour party election promises...

The IR readings for the Ring Final returned 0 and 5.5 and 5 MegOhms (must I state that these were for readings through L-E, L-N and N-E...?) and c.350 MOhms or thereabouts for the other circuits - 6A lighting and 2 No. 32A Radial (yes, I know a 32A on a radial is unusual). Either way, they're rubbish so that's why I assumed (wrongly) that you'd all be able to assume I knew what was a good, reasonable, unacceptable and utterly rubbish reading.

*Please - do not start arguing the ---- - of course Voltage is a critical element of everything we do - I mean minor as in the relevance to the problem - low/no IR readings.

 

[DPG]

Are you saying the IR reading between Live and Earth on the RFC was zero ohms ??

 

[westward10]

On the ring final did you unplug / remove all loads to get the L/N reading.

 

[davesparks]

He's probably using 230 v because that is what we are taught to use from college and bs7671.
We are required to record the nominal voltage on our test certificates as 230 volts and not the measured value.
Also voltage drop calculations are based on 230 volts it's 3% of lighting etc based on 230 volts yes it takes the worst case scenario.
Maximum zs values calculations require it to be 230 x 0.95.
Where I do agree that most of the time the voltage is around 240-245 volts it's not the voltage we are told to use maybe common sense tells us different.
Maybe it's not 'the real world' but it is whAt it is.

We are given 230V as the nominal voltage yes, but that is nominal.
Nothing in the regulations tells us that it must be used to calculate current ratings, as far as I know the regulations don't tell us anything about how to calculate current.
The regulations do state at various points that nominal values should be used when no better information is available, the actual voltage is always readily available to us.

The regulations do however require that we do not allow small overloads to be designed in to a circuit.
Designing a circuit based on 230V power ratings when the actual voltage is higher will lead to such small overloads being designed in to the circuit, which is dangerous as the ocpd will not operate on such overloads.