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Scorched Neutral on shower isolation switch
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Good article thatRECI also recommended contactor switching (page6)
https://safeelectric.ie/contractors/wp-content/uploads/sites/2/2018/09/2016dec_news.pdf
The risk is low in fairness of the contactor becoming emergized
Anyone mixing up the cooker and shower like they said should be thrown out
Like they said check the readings at the shower after working on the circuit0 -
Isn't it high time that cookers should be RCD protected?. I have everything in my house (including lighting) protected with one RCD, shower is separately RCBO protected, and have never had a (10 year old) cooker induced trip. My last cooker was a Creeda Cavalier with those spiral rings and in those pre RCD days one always got a weeks warning that one of them had worn through by means of a tickle through the finger tips when removing the saucepan.0
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Isn't it high time that cookers should be RCD protected?. I have everything in my house (including lighting) protected with one RCD, shower is separately RCBO protected, and have never had a (10 year old) cooker induced trip. My last cooker was a Creeda Cavalier with those spiral rings and in those pre RCD days one always got a weeks warning that one of them had worn through by means of a tickle through the finger tips when removing the saucepan.
You're not doing yourself any favours with that one rcd0 -
Join Date:Posts: 5746
In light of some of the recent slightly off topic comments, I will just mention something that happened a few years ago.
At the time table top raclet cookers were popular, and used regularly for a while, then as is often the case, things moved on, and they were not used for a while.
One that hadn't been used for a while was taken out and put on the table to use by a member of my family, when it was switched on, the relevant earth leakage trip blew out, and that was the end of that raclet session.
It came to me for a look at, and I rang the relevant supplier to see if spare elements were available, in that there was nothing else that could fail other than the element.
On speaking to the service department, the fix was suggested was somewhat different. "Put it on the bench, and connect it to power without an earth connected, and leave it to run for about 30 minutes, let it cool, then test it again. The elements absorb moisture over time if they are not used, and that causes them to trip earth breakers, once it warms up and dries out the insulation, it should be fine again for another 12 months".
They were right, put it on the bench, and connected it to power, as suggested, with appropriate protection around it, and yes, after 30 minutes on power, when tested with a correct connection including earth, it was fine, no tripping, and it is still working some 5 or more years later, albeit that if it's not been used for a while, the special lead I made up for correcting the problem (kept under lock here) gets used for a while before it's used on the table again, just to avoid aggravation.
From comments made by other people, some heating elements on ovens can also have the same issue, which historically was the reason then were not put through earth leakage protection. That may not be the case now, I'm not involved with domestic wiring so don't keep up to date with all the changes that are going on.Shore, if it was easy, everybody would be doin it.😁
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That was definitely the case with elements0
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If a circuit is supply a large load such as a 9 kW shower and the isolator is switched then an electric arc will occur across the switch contacts. Every time this happens it will cause some damage. Although this damage is small it gradually accumulates, eventually causing the isolator to fail. Some wear and tear (although far less) also occurs when this switch is operated under no load condition. This damage manifests itself as resistance which gradually leads to more and more heating within the switch can eventually result in what we see in this example.
Therefore, in my view the isolator should only be used to switch off the shower when maintenance is being carried out on the shower unit itself and at no other time.
Wouldnt/shouldnt switching occur under no load all the time? otherwise isn't that like suggesting people are switching their showers on/off with the isolator? which would seem like bad practice, maybe it happens with pullcord isolators, dont think its a good idea.
I'll have to dig out the manual for my triton shower which I saw recently, but Im sure it recommends (or even states) turning off the isolator when not in use (I suppose they would err on the most safe side).
My first isolator switch was only replaced after maybe 7 years, I think it was only replaced when the 3rd shower was fitted (I dont think it had even failed, just replaced as a matter of course, and I switch it off after every use and Ive learned anyone else to also).A lot of the switch problems are probably poor install to begin with.
10 square into these switches wont be helping.
No real reason for one contact to open before the other in a single phase breaker, but there would be good reason for the N to close first and open last in a 3 phase one. Perhaps this mechanism is also used in single phase devices.
Its been a while since I studied 3 phase theory, although Im not an Electrician, it sounds like it'd be right regarding the N (assuming there is one?) Im not sure if thats because current that might still flow through the N or something else, I know its unrelated to the OP can you elaborate? Currently I just operate switches on/off on circuits that need to be isolated (in work) and lock them when power is required to be off, when carrying out other work, so Im not privy to the design features.Very cheapo effort in whole house really. Switches and backboxes crooked and any i have seen would have no grommets.
One thing that pisses my off is there were never any circuits ran to hotpress, so an immersion or pumped shower would need a whole new circuit run back to fuseboard
Is that in the regs? circuits to a hotpress? (other than for an immersion).
I always thought it wasn't allowed? I came across that as someone I knew was told so when they wanted their alarm wiring centre located in their hotpress (where there is no water present) but they queried why it'd matter as it was already wired up to a downstairs toilet where it was close to a sink.The counter argument to what you have stated above is that a fire is far more likely to occur in the first place if the isolator is operated before and after the use of the shower. Although I accept the argument that replacing an isolator every year or two is not that expensive this ignores the fact that the fire that may occur due to the failure of this device is the real cost.
My next point is where does this end? Does the fire officer (or others sharing this view) only insist on this practice for the shower or does it extend to other fixed appliances? If not, why not? Surely only a consistent approach makes sense? In many homes fixed appliances typically include:- Hob
- Oven
- Boiler
- Intruder alarm
- Immersion
- Zone valves
Also there are many devices that are left plugged in for years in homes up and down the country such as:- Washing machine
- Tumble dryer
- Dish washer
- Microwave
- TV
- Satellite box
If all of the above are to be unplugged or their isolator switched off it would take at least an hour to leave the house each day:D
As I have already stated, I accept fully that there are differing opinions on this. That is why I made it clear in post #13 that what is stated is just an opinion (by using the words "in my view").
Isnt the isolator switch just as likely to just fail and or the protective device to operate? than actually cause a fire?
I have always turned off my shower isolator when not in use, but like anything that might be unused for a period of time, I think it's best to physically cycle or operate occasionally.
Other than the oven/cooker, none of those devices would approach the power consumption of a shower, I certainly would be concerned about the potential for fire with a dryer or washing machine running at night, Ive a fairly decent washing machine brand and imo its too noticeable a noise at night anyway.Its function is to isolate the shower to allow safe working on it. Down at DB doesn't do that.
To allow easier wiring of isolator beside showers it was recommended contactors be fitted at the DB and small control wiring up to isolator.
My opinion at the time this is not proper isolation. Very bad actually imo.
I think 10 square with 10 square earth is over the top as well.
Doesn't that depend on the specific installation, 10sq or not, the power and the length of run of wiring to the consumer unit?
A contactor at the DB and the switch operating it at or near the shower? is not proper isolation, how? isn't the on/off control location the same as an isolator? Doesn't that add an extra (but different) safety feature.
Other than my own, I haven't particularly looked at domestic devices, I think a discreet hole through the switch where a pin and tag could be placed (and even locked) would be a good idea, I dont know if any domestic hardware has anything like that?
I had thought there could be some No Volt protection on showers themselves or recommended to be wired in (I can see adding extra features in would have affects not least of which could be an additional component to fail, or maybe it allows them to be region dependant for regulations?), but it seems like a sensible safety measure in some form.If by "turn off" you mean using the local isolator and / or unplugging everything I think that we can agree that nobody ever follows this advice.
If you turn off your cooker switch the clock needs to be reset. I don't think that was the manufactures intention, they designed the cooker to be left powered.
What about gas boilers? Do you know anyone that turns them off at the isolator before going to bed?
I have seen washing machines and other appliances go on fire alright, but never because the isolator was left on when the appliance was not in use.
I think its sensible to turn off/isolate items that consume the amount of power that a shower does, when not in use, certainly a shower. I dont think a cooker approaches the power consumption of a shower, unless the oven and grill was capable of being turned on at the same time? but cookers do have isolators, I dont turn mine off (because of the clock reason, resetting would be a pain), but I think it would be a sensible feature to have a small rechargeable power supply that could maintain that aspect for a period of time SO the cooker could be isolated.0 -
That was or still is an issue I think with showers, the lack of a no-volt release
It meant that you can switch the load with the isolator, some users like to start it with the pull cord before they go in
I also was warned by my inspector not to design+ install a priority controller as you may be responsible if there was a flood caused by it when a secondary shower was interrupted, someone might walk out of shower and it later restarts automatically0 -
You answered your own question about the contactor at the DB when you said " control"
It's a method of controlling the supply to the shower , not physically isolating it
They're 2 different things0 -
That was or still is an issue I think with showers, the lack of a no-volt release
It meant that you can switch the load with the isolator
I also was warned by my inspector not to design+ install a priority controller as you may be responsible if there was a flood caused by it when a secondary shower was interrupted
I hadn't thought of that around a situation with 2 showers, but is it actually a problem? not 100%, but if there is load on one side/circuit, doesnt that prevent the other circuit/shower operating, and as such, the second shower couldnt come on at all, if the first one was running, the first one in effect interlocks the second one, by the same token, the first one could not come on if the second one was running.
I think I can see where the person was coming from, Interesting (to me), but Im not 100% sure its applicable, but for sure built in No Volt protection would eliminate that, but having a contactor in each circuit would also do the same I think, seems like it would be a lot of extra components, but I think it could be the right way to do things?
not so sure about the flood either, given it should be drained away, unless it didnt drain away or a fault occurred in the unit itself causing a leak,
Interesting though
Adding No Volt protection seems like a good idea in some form (to me), but I suppose within the shower, it adds something to fail and potentially bulk in a shower unit. I havent thought about it in a while, I think it could be a good idea to be fitted (or maybe required to be fitted) externally to the shower as it can then be replaced easier and with standard components if it doesnt function.
Maybe someone could highlight the potential problems, I cant see any?0 -
You answered your own question about the contactor at the DB when you said " control"
It's a method of controlling the supply to the shower , not physically isolating it
They're 2 different things
In effect, wouldnt the switch (at or near the shower unit) in such a set up, operating the control aspect of the contactor be the isolator? as it acts on the contactor, turning it off and locking it out if that was possible prevents the contactor functioning,
It acts in the same way as a traditional isolator, in that it turns the supply on and off, just indirectly. If anything if that control circuit is faulty or damaged, the contactor will not operate, essentially making it fail-safe.
Where the actual isolator component is, doesnt make a difference really? does it? if anything if it's remote from the person operating it that seems to be potentially better.0 -
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I hadn't thought of that around a situation with 2 showers, but is it actually a problem? not 100%, but if there is load on one side/circuit, doesnt that prevent the other circuit/shower operating, and as such, the second shower couldnt come on at all, if the first one was running, the first one in effect interlocks the second one, by the same token, the first one could not come on if the second one was running.
I think I can see where the person was coming from, Interesting (to me), but Im not 100% sure its applicable, but for sure built in No Volt protection would eliminate that, but having a contactor in each circuit would also do the same I think, seems like it would be a lot of extra components, but I think it could be the right way to do things?
not so sure about the flood either, given it should be drained away, unless it didnt drain away or a fault occurred in the unit itself causing a leak,
Interesting though
Adding No Volt protection seems like a good idea in some form (to me), but I suppose within the shower, it adds something to fail and potentially bulk in a shower unit. I havent thought about it in a while, I think it could be a good idea to be fitted (or maybe required to be fitted) externally to the shower as it can then be replaced easier and with standard components if it doesnt function.
Maybe someone could highlight the potential problems, I cant see any?
All it takes for a flood is the shower head to point at the door if it comes back on automatically
"It'll work in practice but will it work in theory", is an old saying i like0 -
All it takes for a flood is the shower head to point at the door if it comes back on automatically
"It'll work in practice but will it work in theory", is an old saying i like
Yeh, I had thought that could be the first and most likely way to go wrong, Ive a shower curtain up in my bathroom where my own electric shower is as the shower door doesnt manage its job, its still possible for the shower to drench the floor,
Id have said that the other way around, but if its a way of saying things and people will find a way to make it go wrong, then yeh, I get it, if not Im off to find out in google0 -
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Wouldnt/shouldnt switching occur under no load all the time?
Yes, but in the real world this is not always what happens. Just like testing RCD's every once in a while, despite the advice this is frequently ignored.Its been a while since I studied 3 phase theory, although Im not an Electrician, it sounds like it'd be right regarding the N (assuming there is one?) Im not sure if thats because current that might still flow through the N or something else, I know its unrelated to the OP can you elaborate?
Once either the N or phase pole of the isolator is opened the circuit is open therefore currents stops flowing so the 2nd pole will not arc. The same does apply to 3 phase circuits.Isnt the isolator switch just as likely to just fail and or the protective device to operate? than actually cause a fire?
The protective device may or may not operate. Most likely it won't. Isolators can fail in many different ways.I have always turned off my shower isolator when not in use, but like anything that might be unused for a period of time, I think it's best to physically cycle or operate occasionally.
I believe frequent use to be the issue especially under load conditions.Other than the oven/cooker, none of those devices would approach the power consumption of a shower, I certainly would be concerned about the potential for fire with a dryer or washing machine running at night, Ive a fairly decent washing machine brand and imo its too noticeable a noise at night anyway.
I certainly would not conclude that only appliances that draw a high current can go on fire although I accept it is more likely. The last washing machine fire I dealt with was a good quality brand, Siemens.Doesn't that depend on the specific installation, 10sq or not, the power and the length of run of wiring to the consumer unit?
It depends on several factors but mainly the two you mentioned.
10 sq. cables are very common in domestic installations now especially for 9.5 kW showers and iridium hobs.A contactor at the DB and the switch operating it at or near the shower? is not proper isolation, how?
As stated above this is considered control, not isolation.Other than my own, I haven't particularly looked at domestic devices, I think a discreet hole through the switch where a pin and tag could be placed (and even locked) would be a good idea, I dont know if any domestic hardware has anything like that?
Why do you see the need for this?I had thought there could be some No Volt protection on showers themselves
What do you mean? How would this work?I dont think a cooker approaches the power consumption of a shower
That depends on the cooker.
Besides with all of these items you need to consider what is consumed under fault conditions, not normal conditions. Fault currents can be many multiples of normal currents.I think it would be a sensible feature to have a small rechargeable power supply that could maintain that aspect for a period of time SO the cooker could be isolated.
Or if you are genuinely concerned about appliances going on fire you could install AFDD's (Arc Fault Detection Devices). I believe these mitigate the risk to a far greater extent and in time I believe these will become the norm.0 -
Loads in 3 phase with a Neutral are connected in star. Take away the Neutral with non balanced loads and you have the 400v dividing up so more than the 230v is on the higher resistance loads. (impedance for the fanatical terminology poster(s))Its been a while since I studied 3 phase theory, although Im not an Electrician, it sounds like it'd be right regarding the N (assuming there is one?) Im not sure if thats because current that might still flow through the N or something else, I know its unrelated to the OP can you elaborate?
If the Neutral opened before the phases, this would happen momentarily.
Yes, but no need imo for 10 square earth with 10 square circuit.Doesn't that depend on the specific installation, 10sq or not, the power and the length of run of wiring to the consumer unit?
If the run requires a 10 square circuit due to length, then a 6 square will be ok on a shorter run, so the breaker is likely rated for 6 square, so no need for a 10 square earth.
If the load requires 10 square due to the load, then its short enough that 10 square is enough, so again no need for 10 square earth.
If they used flex, it would not be too bad, but 10 square t&e is troublesome to terminate into the isolators used in domestic installations. I would say it is causing a good many `forced on` switch plates unless a very deep back box is used. But I dont know. I have nothing to do with domestic works anymore, except in my own house if needs be.
Opinions differ, but imo it is not proper isolation. It is possible for the contactor to be operated from locations other than the switch that controls it. It may be a remote possibility, but it exists. In an industrial situation, it certainly would not be accepted imo.A contactor at the DB and the switch operating it at or near the shower? is not proper isolation, how? isn't the on/off control location the same as an isolator? Doesn't that add an extra (but different) safety feature.
MCBs can be locked off.Other than my own, I haven't particularly looked at domestic devices, I think a discreet hole through the switch where a pin and tag could be placed (and even locked) would be a good idea, I dont know if any domestic hardware has anything like that?
I have suggested this for years, a relay in the shower, wires as a DOL setup with start and stop.I had thought there could be some No Volt protection on showers themselves
Power goes, returns, shower will not restart. And, with the shower stopped, there is no power past the relay.
Again, its a debatable point. I dont believe the ability to start a fire when the device is off, relates that much to the power is uses when on. A tv for example, would be likely a higher risk when in standby.I think its sensible to turn off/isolate items that consume the amount of power that a shower does, when not in use, certainly a shower.
Cookers, microwaves and washing machines/dryers are the biggest causes of electrical fires apparently. Likely when in use though.0 -
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Actually, I had my own shower installed for about 3 years before I "discovered" that it didn't have a relay until my relation was in her shower during a power outage, she left the shower, went away for a few hours during the outage and returned later to find (power restored) her bathroom like a sauna. I was just about to go off and investigate but decided to check my own first.0
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Quote: Other than my own, I haven't particularly looked at domestic devices, I think a discreet hole through the switch where a pin and tag could be placed (and even locked) would be a good idea, I dont know if any domestic hardware has anything like that?
Why do you see the need for this? Quote:
I think it would be a sensible feature to have a small rechargeable power supply that could maintain that aspect for a period of time SO the cooker could be isolated.
Or if you are genuinely concerned about appliances going on fire you could install AFDD's (Arc Fault Detection Devices). I believe these mitigate the risk to a far greater extent and in time I believe these will become the norm.
I was thinking the need was Safety, regarding the ability to have a switch (on something with a double pole aspect to it, not just a light switch) kept in an off position and ensure it stays that way, so that anyone who might work on it can ensure it stayed off for the duration of any work.
edit --> I didnt see any ability to keep an MCB off (but a quick google/as below, shows there are devices for that purpose).
Opinions differ, but imo it is not proper isolation. It is possible for the contactor to be operated from locations other than the switch that controls it. It may be a remote possibility, but it exists. In an industrial situation, it certainly would not be accepted imo.
MCBs can be locked off.
When you say it like that, ie an industrial application, I wouldnt be satisfied with locking out a control aspect, Id want the device switching the power locked.
I still feel it would be ok for a domestic application (a shower or maybe anything else) because generally it'd be switched off for the purpose of shutting it down completely in the short term, where no work is going to be carried out as its for the user of the device, not someone taking covers off and working on it.
I just had a quick google and I see a few different device types of lock out that fit into domestic MCBs, hadnt thought such items existed, as a quick scan over my own consumer unit (has some grooves on the MCBs but didnt appear they could be locked out, just used to lockout so not something most people might even think about or know).
Interesting, thanks for the replies, I also think the REC pdf linked to is good information, even for a homeowner to be informed on some points, surprised at some of the things mentioned in there, but it does seem if things can go wrong they will.0 -
Sometimes the device (isolator) switching the power, may need to be changed or worked on.When you say it like that, ie an industrial application, I wouldnt be satisfied with locking out a control aspect, Id want the device switching the power locked.
Or a light switch, or many things, that require MCBs locked off.0 -
Domestic isolation is just 2 pole switching within 2m
That keeps it simple and failsafe in a domestic environment
In an industrial environment you might be switching off for mechanical-maintenance or electrical isolation remotely with a lock+sign and may not be switching the N pole
Emergency switching might just be using a emergency stop which is a control device0
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