Safety Hazards - Have you ever intervened first and THEN explained?

[Muttley Snickers]

Brumby explained the configuration of this particular power supply to a tee, I did notice in a picture of their later model a sticker above the output sockets indicating no earth connection or similar, anyway all five of the following are terminated together in a single connection on this supply.

1. Mains Protective Earth Input
2. Mains Protective Earth Output
3. Cabinet Metal Chassis Earth
4. Toroidal Transformer Earth
5. Toroidal Centre Tap

[Iwanushka]

From my experience if device is constructed correctly N/L swapping does nothing, but if device is crooked bad things might happend, my oven was tripping breaker (dunno how you call it but its the one which measures leakage current) every time I rurned on the oven so it means that electrolux POS case was live (100% polished steel)

Also all cheap socket extenders have switch only on one side, so if L/N is swapped it does not matter if extender is on or off it's always live....

[Aodhan145]

From my experience if device is constructed correctly N/L swapping does nothing, but if device is crooked bad things might happend, my oven was tripping breaker (dunno how you call it but its the one which measures leakage current) every time I rurned on the oven so it means that electrolux POS case was live (100% polished steel)

Also all cheap socket extenders have switch only on one side, so if L/N is swapped it does not matter if extender is on or off it's always live....

Your thinking of an RCD. How did you discover that the case was live?

[madires]

From my experience if device is constructed correctly N/L swapping does nothing, but if device is crooked bad things might happend, my oven was tripping breaker (dunno how you call it but its the one which measures leakage current) every time I rurned on the oven so it means that electrolux POS case was live (100% polished steel)

I think you mean a RCD. Ovens in Europe usually are designed to run with 3-phase mains (star/Y) and allow different setups, i.e. true 3-phase, 2 phases with one feeding two inputs or 1 phase feeding all 3 inputs. Therefore the oven comes with one or two u-shaped metal strips for paralleling inputs. And all got a PE terminal. If someone bridges that with N (lack of PE in the mains wiring) and swaps L and N, that deserves the Darwin award.

When the wiring is correct a broken heating element is a common cause for tripping the RCD. Another interesting cause is when the oven wasn't used for quite a while. When not used the isolation inside the heating element can worsen to a point at which enough current can flow to PE to trigger the RCD. In that case the element can be fixed by baking it for half an hour at about 200° Celsius. No joke!

Also all cheap socket extenders have switch only on one side, so if L/N is swapped it does not matter if extender is on or off it's always live....

Haven't seen any SPST switches in power strips for quite a while 

[rolycat]

Also all cheap socket extenders have switch only on one side, so if L/N is swapped it does not matter if extender is on or off it's always live....

Haven't seen any SPST switches in power strips for quite a while 

They are ubiquitous in switched UK power strips, since live and neutral are always defined in power circuits.

An example:



with internals exposed for your viewing pleasure:



Neutral is definitely not switched. And if anyone wonders, the strip was purchased from Farnell, not eBay.

[Zero999]

Here in the UK, each plug has a fuse on the phase conductor and the main circuit breaker is often 32A or more. Neutral must be neutral, otherwise there's an increased risk of fire, as there will be appliances with a skinny 0.5mm² connected via a 32A breaker.

No. The current has to go through the appliance in a loop so with neutral and live reversed the current still goes through the fuse.

That's not acceptable since the device would still be live.

Also the fuse wouldn't provide any protection if the RCD failed.

If the RCD fails the 32A break will trip so no problem at all assuming a fault to earth. In most cases the fault is more likely to occur in the circuit between live and neutral and which fuse blows where doesn't matter as long as the current flow is interrupted. Things get hairy if you are opening the appliance without pulling the plug first but if you are that daft you're up for a Darwin award anyway.

No, earth to phase fault is much more common than a phase to neutral fault.

If there's a problem with the RCD, 0.5mm² cable (quite common in appliances fitted with a 3A fuse) may not allow sufficient fault current to trip a 32A breaker (depending on the type used) before melting and/or giving someone a shock due to the appliance's case rising to well above 50VAC.

[Iwanushka]

Also all cheap socket extenders have switch only on one side, so if L/N is swapped it does not matter if extender is on or off it's always live....

Haven't seen any SPST switches in power strips for quite a while 

They are ubiquitous in switched UK power strips, since live and neutral are always defined in power circuits.

An example:



with internals exposed for your viewing pleasure:



Neutral is definitely not switched. And if anyone wonders, the strip was purchased from Farnell, not eBay.

For euro plugs its different, and most so called electicians wire sockets randomly...

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[Iwanushka]

From my experience if device is constructed correctly N/L swapping does nothing, but if device is crooked bad things might happend, my oven was tripping breaker (dunno how you call it but its the one which measures leakage current) every time I rurned on the oven so it means that electrolux POS case was live (100% polished steel)

I think you mean a RCD. Ovens in Europe usually are designed to run with 3-phase mains (star/Y) and allow different setups, i.e. true 3-phase, 2 phases with one feeding two inputs or 1 phase feeding all 3 inputs. Therefore the oven comes with one or two u-shaped metal strips for paralleling inputs. And all got a PE terminal. If someone bridges that with N (lack of PE in the mains wiring) and swaps L and N, that deserves the Darwin award.

When the wiring is correct a broken heating element is a common cause for tripping the RCD. Another interesting cause is when the oven wasn't used for quite a while. When not used the isolation inside the heating element can worsen to a point at which enough current can flow to PE to trigger the RCD. In that case the element can be fixed by baking it for half an hour at about 200° Celsius. No joke!

Also all cheap socket extenders have switch only on one side, so if L/N is swapped it does not matter if extender is on or off it's always live....

Haven't seen any SPST switches in power strips for quite a while 

My oven is single phase, and it was "live" around 20v on case until I swapped N/L the way it suppose to be, never had a chance to open it up and see wtf was wrong.

Also +1 about baking/burning in heating element if it's not used for half a year helps

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[Iwanushka]

Also at least in my country 99,99% apartment buildings are single phase, only houses have 3 phase, go figure exUSSR...

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