MAJOR electrical issues in 5 year old house - any ideas?

[jack]

My parents-in-law moved into a newbuild house about 5 years ago. It’s a large house with quite a lot in the way of electrical gubbins, including (3-phase) ASHP, wet UFH, a Control4 home automation system, electric gates, etc.

 

They had an issue a couple of years ago with the electric gate control board blowing. They also lost a control board for their electric garage door. However, these seemed to be one-off issues.

 

That changed about 3 weeks ago, when they suddenly lost several devices in their house at once. This included all of the electronic valve actuators on their UFH manifold, in-room controllers for the UFH, the gate control board and a few other bits and pieces.

 

The company that wired their house and installed the Control4 system visited, and concluded that some sort of surge appeared to have taken out these items. All were replaced, and a surge protector was installed right as it comes into the consumer unit.

 

Unfortunately, about 2 weeks after this happened, the wheels comprehensively fell off again. This time, the lights started flickering periodically one evening at around 9 pm. By just after midnight, a large number of electrical items appear to have malfunctioned, including all of the items mentioned above, as well as two sky boxes (smoke coming out of one of them), the electric garage doors, the lighting system, the mains-powered water softener, the boiler (apparently the fault code suggests the fan has blown), the ASHP and various other things.

 

The surge protector indicated a fault at this time. I’ve just learned that the fault code indicates a voltage between neutral and earth exceeding 30 V.

 

We’ve just had the DNO (SSE) visit this morning to check the voltage logging equipment that’s been in place since shortly after the latest problem. We had a look at the trace, and there is no unexpected behaviour over the time that they were monitoring.

 

Of course, if the problem was intermittent, this would be expected. However, the SSE guy said that he had reviewed all of their logs for the last month, and there is no evidence of anyone else in the area suffering from problems, nor were there any local network problems logged during that period. Checks with other neighbours (including their next-door neighbour who is also on the same 3 phase supply) confirm that no one else has suffered any problems during this period.

 

Of course, nearly everything is still turned off at the moment, so if there is a problematic circuit or device causing the problem, it’s presently disconnected.

 

The SSE guy said he'd never seen anything quite like this in over a decade of dealing with SSE fault complaints.

 

I have the electrician who did my place coming over tomorrow to see if he can get to the bottom of what’s gone on. However, from a chat with the SSE guy this morning, it really isn’t immediately apparent what could be causing such significant issues (including smoke and pop/banging failures) to so many different installed devices. I had a very quick look this morning, and it seems that the devices are not even all on the same phase of the 3 phase power supply.

 

The only device that is connected across all 3 phases is the ASHP. It failed during this latest event, and now cannot be turned on without immediately tripping the circuit. It didn't fail during any previous event.

 

Given the extent of the damage, my parents in law are naturally very concerned about the situation. There’s the obvious safety concern if a specific problem can't be identified, but there’s also the potential costs associated with replacing all of the damaged components. Of course, these can be claimed on household insurance, but if the problem returns, I suspect their insurer may be less than happy to pay out again.

 

Based on the admittedly technically light explanation of the problem above, can anyone think of a possible mechanism that could lead to the outcome above?

 

The ASHP engineer is coming by tomorrow morning to install a new board in the ASHP. Is there anything I should be asking him in relation to this situation?

 

Many thanks as always.

[Triassic]

What was the weather like on the day of these events, electrical storm and lightning  by any chance?

[jack]

Thanks.

 

I should have said, there was no nasty weather of any sort anywhere near when this happened. Lightning was the only thing I could think of, and we've written that off as a possibility.

[ProDave]

My inclination is high impedance neutral, so the neutral is floating about all over the place, making one phase too high in voltage and another phase too low, depending on what loads are applied to each phase.  Neutral faults are very common due to the abundant use of concentric cable.

 

But you would have thought (hoped) the electrician would do a loop impedance test from each phase to N to confirm this.  Also you would hope SSE's monitor is measuring each phase to neutral and logging it. If it is measuring phase to phase, then it would miss that fault.

 

Get a basic multimeter and measure each phase voltage with respect to neutral. Also measure neutral voltage with respect to earth and report back.

 

I had this once after a storm, SSE installed a mobile generator to a care home to get power back quickly and blew up half the stuff in the house because they habe neutral and a phase swapped over.  When I called them out to show the problem, unbelievably the guy started the generator and waved a volt stick over each phase and said "what's the problem" I had to show him with my meter.  They had a big bill for repairs, including several televisions, a computer and a new fire alarm system.

[Jeremy Harris]

The relatively high voltage measured between N and E is a possible clue.  If this was a true measurement, then it indicates a range of possible fault conditions, but the one that would concern me is if Ze, the earth loop impedance, has risen to an unacceptably high level for some reason.  This should be a low value, less than 0.35 ohms if the house earth protection scheme is TN-C-S, or PME (should be if the house is only 5 years old).  Do you happen to know what the earth system is?  Alternatively, is the house in a very rural area, where the DNO may have been unable to provide a TN-C-S supply, so the house could be using a TT system?

 

Clearly there seems to be an electrical installation problem somewhere, either on the consumer side or the supplier side, as everything seems to point towards an event that has caused the supply to go outside an acceptable range for some reason.  Having a 3 phase supply introduces some other possible causes, as 3 phase will be 400 VAC (in harmonised terms; it's really still 415 VAC as we fudged the tolerance to comply with the EU requirement, as we did with 230 VAC single phase).  As the 3 phase ASHP has failed and now trips the circuit, do you know if it's tripping the 3 phase RCD or the MCB? 

 

Your chap can check Ze quickly and see if that odd 30 VAC measured between the house N and the incomer PEN (I'm assuming this is what was checked) is real or not.  I suspect that, if the 30 VAC measured is correct, then Ze can't be within limits, as if the installation is TN-C-S then with with the max allowable Ze of 0.35 ohms, 30 VAC between N and E indicates an earth fault current flowing at the time of the measurement of just under 86 A, which would be producing a host of other symptoms.

 

I'm with @ProDave on this (I've typed most of this before he posted) but would suggest that it may well be worth getting the whole installation inspected and tested, for reassurance as much as fault finding.

 

[ProDave]

I suspect it is not TNC-S. Since N and E are the same cable and usually even the same terminal at the supply head, it's virtually impossible to get a difference between N and E.

 

What usually happens with a N break in a TNC-S is the whole installation rises to near 230V but you bizarrely don't notice it or get a shock from anything as everything has risen so there is no potential difference.  Last one of these I found, the DNO then spent days digging up the guys drive and a lot of the street until they found the fault.

 

I am really disappointed the electrician who has already been has not found the fault.  I suggest the next one measures Phase to neutral voltage on all phases, phase to earth voltage on all phases, and neutral to earth voltage. 

 

He also needs to measure Ze on each phase, and also do a phase to neutral loop impedance test on each phase. This is one aspect of the wiring regs I disagree with. They are fixated with measuring Ze which is the loop impedance from phase to earth.  If this is a TNS or TT supply, that could still measure perfectly fine with an open circuit neutral. I think it is very important, particularly when looking for a fault, to measure phase to neutral loop impedance.

[jack]

Interesting, thanks Dave.

 

1 minute ago, ProDave said:

My inclination is high impedance neutral, so the neutral is floating about all over the place, making one phase too high in voltage and another phase too low, depending on what loads are applied to each phase. ...Also you would hope SSE's monitor is measuring each phase to neutral and logging it. If it is measuring phase to phase, then it would miss that fault.

 

The results SSE was measuring gave range of something like 235-250V over the time they were monitoring, so I assume they must have been measuring to neutral.

 

6 minutes ago, ProDave said:

But you would have thought (hoped) the electrician would do a loop impedance test from each phase to N to confirm this. 

 

I was astonished to learn this morning that the electrician who's been out so far (from the company that wired the house originally) has spent only a couple of hours onsite, all of it spent seeing whether he can get various things like lighting going again. According to my parents in law, he hasn't done any further testing that they're aware of. There was talk (prompted by my father in law) of them giving the electrics a general health check, but based on what I've seen so far I've discouraged them from using these guys any further.

 

4 minutes ago, JSHarris said:

This should be a low value, less than 0.35 ohms if the house earth protection scheme is TN-C-S, or PME (should be if the house is only 5 years old).  Do you happen to know what the earth system is?

 

Thanks Jeremy.

 

It's on the outskirts of a suburban area (just around the corner from where I live). The SSE guy said this morning that was a PME scheme, which was part of why he found what had happened surprising.

 

6 minutes ago, JSHarris said:

As the 3 phase ASHP has failed and now trips the circuit, do you know if it's tripping the 3 phase RCD or the MCB? 

 

I believe it's tripping its MCB. By 3 phase RCD, do you mean an RCD protecting the three phase as it comes in? If so, then I believe there isn't one connected - the SSE guy mentioned this morning that getting an RCD on the incoming three phase would be useful, quite aside from the other issues. 

 

I'm not really up on all of this stuff, but I couldn't actually see any RCD protection from a 10 second look at the CU. I may just have missed it. I'm sure my electrician will be able to tell me more tomorrow - I'll be onsite with him for the first hour to see what I can learn.

 

11 minutes ago, JSHarris said:

I'm with @ProDave on this (I've typed most of this before he posted) but would suggest that it may well be worth getting the whole installation inspected and tested, for reassurance as much as fault finding.

 

This is exactly what I've already recommended to my parents in law, and what the electrician (the guy who you met when you visited) will be doing.

 

I'll let you all know what we find tomorrow.

 

Thanks as always 

[Jeremy Harris]

OK, PME = TN-C-S in this case (strictly speaking it's not exactly the same, but PME is often used to describe what's really a TN-C-S installation).

 

No RCD on the 3 phase supply is another clue, as if there had been, and if N really is 30 VAC above PE (Protective Earth), then the RCD would certainly have tripped long before the fault condition got to the point where equipment has been damaged.

 

Number one priority would seem to be to measure Ze, to see if there's an earth loop fault.  If the N isn't sitting at the same potential as E, then it sounds as if there could be a problem with the PEN in the head (Protective Earth and Neutral) or the CPC (Circuit Protective Conductor) from there to the installation PE.  Normally, the PE are N and connected together (hence the term PEN) at the head, and the incoming N conductor is also the PE conductor. 

 

There will probably be other earth paths within the installation, particularly from things like the ASHP, where the chances are that its earthed metal case will be bolted down to ground.  However, the chances are that the other incidental earth paths may have quite a high impedance, so if the PEN is really just N then this could explain the 30 VAC measured.

 

 

[ProDave]

14 minutes ago, jack said:

Interesting, thanks Dave. The results SSE was measuring gave range of something like 235-250V over the time they were monitoring, so I assume they must have been measuring to neutral.

The important thing as are they all reading the same at one instant, or is one going up when another is going down?

14 minutes ago, jack said:

I was astonished to learn this morning that the electrician who's been out so far (from the company that wired the house originally) has spent only a couple of hours onsite, all of it spent seeing whether he can get various things like lighting going again. According to my parents in law, he hasn't done any further testing that they're aware of. There was talk (prompted by my father in law) of them giving the electrics a general health check, but based on what I've seen so far I've discouraged them from using these guys any further.

Nothing surprises me any more. Some electricians are simply rubbish at fault finding. They seem to be taught how to wire and installation and do a standard set of tests and nothing more.

 

Let us know what they find, and a picture of the CU and supply head would be interesting.

[Jeremy Harris]

Nothing surprises me any more, either, particularly with relatively new builds.

[jack]

9 minutes ago, JSHarris said:

OK, PME = TN-C-S in this case (strictly speaking it's not exactly the same, but PME is often used to describe what's really a TN-C-S installation).

 

The SSE guy has worked for them for over 30 years, and I think a lot of people who've been around a long time call it PME since it's what they're used to and it's perfectly adequate for most applications. I seem to recall a significant argument about the distinction on Buildhub in the past!

 

5 minutes ago, ProDave said:

The important thing as are they all reading the same at one instant, or is one going up when another is going down?

 

I don't know. Best I can recall, they all varied relative to each other, but I wasn't really able to look closely to see what sort of scale was involved, and the SSE guy didn't seem too concerned about what he saw.

 

7 minutes ago, ProDave said:

Nothing surprises me any more. Some electricians are simply rubbish at fault finding. They seem to be taught how to wire and installation and do a standard set of tests and nothing more.

 

My surprise was mainly that he seemed content not actually knowing what the problem was. This was clearly a serious event, with smouldering/buzzing from at least one AV component (Sky box maybe). As a matter of safety, you'd have thought he'd have advised finding the fault as a priority rather than just trying to get the lights back on.  

 

6 minutes ago, ProDave said:

Let us know what they find, and a picture of the CU and supply head would be interesting.

 

Will do, thanks.

[Triassic]

Do you actually need three phase, or is this a throwback to a time when ASHPs had to have s 3 phases supply due to high start loads? If the ASHP I’d fried, maybe it’s time to change it for an inverter based unit!?

[Onoff]

Sad as it sounds a vast number of cus / dis boards get thrown in but nobody bothers to check the manufacturers terminal within are properly tightened! 

[jack]

16 minutes ago, Triassic said:

Do you actually need three phase, or is this a throwback to a time when ASHPs had to have s 3 phases supply due to high start loads? If the ASHP I’d fried, maybe it’s time to change it for an inverter based unit!?

 

No idea. It's a 5 year old Mitsubishi - I've always assumed that an ASHP from a mainstream brand of that era would be inverter driven. At this stage, we don't know what's actually fried. It might be just a small control board.

 

14 minutes ago, Onoff said:

Sad as it sounds a vast number of cus / dis boards get thrown in but nobody bothers to check the manufacturers terminal within are properly tightened! 

 

I'm sure all connections will be tested thoroughly this time!

[Jeremy Harris]

14 minutes ago, Onoff said:

Sad as it sounds a vast number of cus / dis boards get thrown in but nobody bothers to check the manufacturers terminal within are properly tightened! 

 

Too true, and that's despite every one having a label on telling the installer to check the tightness and, I very strongly suspect, loose terminals being the cause of a fair few CU-related fires, hence the amendment 3 metal cases.  The latter seems to be treating the symptom, not the cause, to me.

[ProDave]

5 minutes ago, jack said:

 

No idea. It's a 5 year old Mitsubishi - I've always assumed that an ASHP from a mainstream brand of that era would be inverter driven. At this stage, we don't know what's actually fried. It might be just a small control board.

 

Even though it is 3 phase, I will bet it has a neutral connection and used that and 1 phase for the control circuitry (so it can use the same controls as the single phase version) so if it is a floating neutral that would be as likely to go pop as your sky box.

[Jeremy Harris]

1 hour ago, jack said:

I'm sure all connections will be tested thoroughly this time!

 

Do they have a copy of the EIC/Part P certificate that was lodged with the building control body?  They can get this from the accreditation body for the electrician/company that wired the house and it may be useful, in as much as it will give some of the measured values from the installation testing.  It's not comprehensive, in that not every measured value is recorded, but key ones are, including Ze and the highest Zs for each circuit, and as the house is 5 years old one would assume that there is still a warranty of some kind.  If it turns out to be a long standing fault in the installation, then it may well be possible to try and claim on the warranty (although frankly I suspect that's a lost cause).

 

 

[ProDave]

5 minutes ago, JSHarris said:

 

Too true, and that's despite every one having a label on telling the installer to check the tightness and, I very strongly suspect, loose terminals being the cause of a fair few CU-related fires, hence the amendment 3 metal cases.  The latter seems to be treating the symptom, not the cause, to me.

There was much discussion at the time of rather than fix the problem, they "solved" it by putting it in a tin box.  Won't stop CU fires just might stop them spreading.

 

There is much wrong with modern CU's that nobody seems bothered about fixing, like nothing to stop a busbar finger going the wrong side of the cage clamp, and what happened to having 2 screws on the incoming L and N connections?

[ProDave]

6 minutes ago, JSHarris said:

Do they have a copy of the EIC/Part P certificate that was lodged with the building control body?  They can get this from the accreditation body for the electrician/company that wired the house and it may be useful, in as much as it will give some of the measured values from the installation testing.  It's not comprehensive, in that not every measured value is recorded, but key ones are, including Ze, and as the house is 5 years old one would assume that there is still a warranty of some kind.  If it turns out to be a long standing fault in the installation, then it may well be possible to try and claim on the warranty (although frankly I suspect that's a lost cause).

 

It will be interesting to see what the fault is before the finger of blame is pointed.  If it is the DNO's neutral corroded and floating neutral, you can hardly blame the installer.

[Jeremy Harris]

1 minute ago, ProDave said:

It will be interesting to see what the fault is before the finger of blame is pointed.  If it is the DNO's neutral corroded and floating neutral, you can hardly blame the installer.

 

True, my suspicious nature leads me to suspect this is probably a fault on the consumer side, though, given that the incomer can only be around five years old.

[jack]

6 minutes ago, JSHarris said:

Do they have a copy of the EIC/Part P certificate that was lodged with the building control body?  

 

I think I saw that in some paperwork they had out. Will check. They mentioned that they'd seen something about a "platinum" warranty from NICEIC, but as you say, it's a long time to be claiming on a warranty.

 

4 minutes ago, ProDave said:

It will be interesting to see what the fault is before the finger of blame is pointed.  If it is the DNO's neutral corroded and floating neutral, you can hardly blame the installer.

 

The main aim at the moment is to find the source of the problem. If that can be sorted, and it isn't an obvious installation error, I think they'll be happy just to get a definitive answer so they can rest easy living there in the future. 

 

Edited to add: the potential for blame and arse-covering is a major reason for me suggesting getting a neutral (pardon the pun) electrician involved in identifying the problem. The guy I've asked to do it is very thorough and has no axe to grind. He'll give an honest answer without fear or favour.

[Temp]

Can't claim to be an expert but have heard that a bad connection between Neutral and Earth on a three phase system can cause over voltage. It certainly sounds like you had an over voltage event if you have had multiple failures and smoke coming out of a sky box.

 

I think you should also speak to your house insurance company. Perhaps the would consider paying for an investigation to reduce the chances of further claims?

 

 

[Jeremy Harris]

9 minutes ago, Temp said:

Can't claim to be an expert but have heard that a bad connection between Neutral and Earth on a three phase system can cause over voltage. It certainly sounds like you had an over voltage event if you have had multiple failures and smoke coming out of a sky box.

 

I think you should also speak to your house insurance company. Perhaps the would consider paying for an investigation to reduce the chances of further claims?

 

 

 

 

Yes, although the main issue is when there is an imbalance between the phases, caused either by one phase feeding a greater load, or, perhaps more likely in this scenario, harmonic distortion causing a high neutral current in combination with a high N to PE impedance.  When there is a combination of an imbalance and a high impedance in the N, the voltage on the least heavily loaded phase can approach the phase to phase voltage if things get really bad.  This would, perhaps, explain why the phase feeding the house seems to have had a major over-voltage event.  

 

Checking Ze on the incomer should determine whether there is a DNO side problem and checking Zs at the consumer side, perhaps at the ASHP (as I strongly suspect that may be the heaviest load) should show whether there is a N to PE impedance problem somewhere else in the installation.

 

On its own, having an imbalance in a 3 phase system isn't really a problem as far as the consumer is concerned, as all it does is lead to a higher neutral current in a mixed 3 phase/single phase installation.  If the installation is correctly wired and has no faults then there shouldn't be a problem, as the distribution network is sized to deal with phase current imbalance and the consequent current flow in the neutral.

 

 

[jack]

1 hour ago, Temp said:

I think you should also speak to your house insurance company. Perhaps the would consider paying for an investigation to reduce the chances of further claims?

 

They've spoken to their insurer, and the loss adjuster is coming out on Friday with an expert. If possible, they want to know what's going on before then, hence getting someone independent involved now.

 

Whether their insurer will pay for this electrician's time, I'm not sure. I think they're happy to pay themselves if needed the main thing is getting a clear identification of the problem.

[ProDave]

The blame game cannot start until the fault is identified.  If it is a DNO fault, I am absolutely sure the DNO will pay for items damaged in the home. Your insurer may be the vehicle to facilitate that as I am sure they will just pass on the claim. The danger though in going through your insurer is they will deduct the policy excess from the claim, wheras going straight to the DNO (IF it turns out to be their fault) you would likely get the full claim.