Block of 200+ flats, eleven single channel hot water timers blown this week alone.

[marconi]

I’ll add this to my long list of other things I have got wrong. Yours humbly……

 

[Mike Johnson]

Don't think it's been asked, but did all eleven flats loose their timers at the same time, or was it cumulative over a period.

 

[marconi]

Don't think it's been asked, but did all eleven flats loose their timers at the same time, or was it cumulative over a period.

Following MJ’s theme - MOVs do degrade each time they react to over voltages. It is not unknown for them to eventually suffer thermal runaway which is when their quiescent current rises over time, the MOV warms up, its resistance reduces, it passes more current, it warms up even more…until it cannot dissipate the heat quickly enough to its surroundings and it destructs. All of which can happen in the absence of any overvoltage.

 

[GBDamo]

Don't think it's been asked, but did all eleven flats loose their timers at the same time, or was it cumulative over a period.

That is a good question but impossible to get a definitive answer as we don't know when they "went" only when the tenant discovered and reported them.

The first was reported on Tuesday, I was called on Thursday and by then there were eleven.

All we've got is the times they were reported.

But judging by the crazy disco lights I witnessed the issue is still ongoing and more will go.

 

[Lucien Nunes]

@marconi I'll let you off if you can find a SIL through-hole bridge rec in a white package made in the last 25 years.?

We can now confirm from the PCB pics that the failed part is across the mains input. In theory it could have been a small filter capacitor but:
a) The part shape and burst pattern are more consistent with an MOV
b) A cap of those dimensions would typically be a Y-class part of a few nF which is not appropriate there.
c) An MOV is not a bad idea where a capacitive dropper is tapped off the supply to a relay-switched 16A load of unspecified characteristics.

What it will hopefully have been doing, before it popped, was shaving off transients likely to damage the dielectric of the X2 dropper cap, that would otherwise cause a progressive loss of capacitance to the self-healing process.

But judging by the crazy disco lights I witnessed the issue is still ongoing and more will go.

Somebody needs to switch this lot off now.

 

[GBDamo]

Somebody needs to switch this lot off now.

Twice I have told them it needs attention, verbally and in writing via the job card.

I will chase it up on Monday as the lass who I was dealing with didn't convince me she understood the potential gravity of the situation.

 

[UNG]

Just curious if you did any more voltage checks when you went back although I think to catch any major voltage peaks or dips you would probably need to put some logging equipment in across all three phases


Had a similar problem to this at a business premises I used to work from many years ago although no equipment was damaged the voltage would very often dip to 170 - 185v on one phase around 8:15 - 9:00 in a morning and around 17:30 - 18:30 in an evening but not everyday, after a few weeks we got the DNO involved who put a voltage logger in for a week who told us there was no problem found, a week later 4 DNO vans appeared one afternoon and dug up the link box at the end of the street about 50m away, talking to the DNO lads they said that the box was close to failing due to thermal damage and was being replaced with a resin joint, The voltage problem disappeared after that

 

[Dave OCD]

Could it all have been caused by a one off surge as the power was restored following the reported mains failure across the entire block ?

 

[roper_ni]

They are rated at 16A. The hot water cylinders are on a dedicated circuit off their own 16A MCB, isolated via a 20A double pole switch, length is a couple of meters.

Couldn't see a rating on the element but looking into that now.

Edit to add,

The elements are 3kW but looking at the plumbing I think they're on a central hot water system as there seems to be a coil on the cylinders.

I'm back there tonight two replace a couple and grab some more info.

Time to get the Megger out and 1000v dc @ the heater could be cable or heater.

 

[roper_ni]

Time to get the Megger out and 1000v dc @ the heater could be cable or heater.

Sorry wrong post

 

[Fender]

There's some really clever people on this forum. I had to Google the electronic references, and, after reading them for a few minutes, I realised I was mentally debating tea or coffee to start the day (I went for tea).

So I can't help you there. But I will try to using my old favourite, Ockhams Razor ie go for the bleeding obvious.

Lights flickering, different flats affected, electronic gizmos feeling unwell (my knowledge of such things shines). And all about the same time.

It stinks of a neutral connection. It's the only common denominator. I can't see 11 Sangamo clocks packing up at the same time (Greenbrook, maybe..)

I was (un)lucky enough to see a neutral on a three phase supply go AWAL first hand ('tis a long story) and it is frightening. Voltage between phase and (apparent) neutral 270. Nope, 370. Nope 300. Nope 280 etc. Modular fittings jumping up in the suspended ceiling. Vending machines dying in agony.

Ok, this was for a period of minutes. Bit it's proof that the voltage goes crazy with a naughty neutral. It may be the case that your neutral was just a bit cheeky and went missing for a second or so.

One to watch out for.

 

[roper_ni]

There's some really clever people on this forum. I had to Google the electronic references, and, after reading them for a few minutes, I realised I was mentally debating tea or coffee to start the day (I went for tea).

So I can't help you there. But I will try to using my old favourite, Ockhams Razor ie go for the bleeding obvious.

Lights flickering, different flats affected, electronic gizmos feeling unwell (my knowledge of such things shines). And all about the same time.

It stinks of a neutral connection. It's the only common denominator. I can't see 11 Sangamo clocks packing up at the same time (Greenbrook, maybe..)

I was (un)lucky enough to see a neutral on a three phase supply go AWAL first hand ('tis a long story) and it is frightening. Voltage between phase and (apparent) neutral 270. Nope, 370. Nope 300. Nope 280 etc. Modular fittings jumping up in the suspended ceiling. Vending machines dying in agony.

Ok, this was for a period of minutes. Bit it's proof that the voltage goes crazy with a naughty neutral. It may be the case that your neutral was just a bit cheeky and went missing for a second or so.

One to watch out for.

Have never seen that happen, don't know what supply type is being used over here we use TT

There's some really clever people on this forum. I had to Google the electronic references, and, after reading them for a few minutes, I realised I was mentally debating tea or coffee to start the day (I went for tea).

So I can't help you there. But I will try to using my old favourite, Ockhams Razor ie go for the bleeding obvious.

Lights flickering, different flats affected, electronic gizmos feeling unwell (my knowledge of such things shines). And all about the same time.

It stinks of a neutral connection. It's the only common denominator. I can't see 11 Sangamo clocks packing up at the same time (Greenbrook, maybe..)

I was (un)lucky enough to see a neutral on a three phase supply go AWAL first hand ('tis a long story) and it is frightening. Voltage between phase and (apparent) neutral 270. Nope, 370. Nope 300. Nope 280 etc. Modular fittings jumping up in the suspended ceiling. Vending machines dying in agony.

Ok, this was for a period of minutes. Bit it's proof that the voltage goes crazy with a naughty neutral. It may be the case that your neutral was just a bit cheeky and went missing for a second or so.

One to watch out for.

Must say that have never seen that happen, the reason that said about the Megger i

 

[pc1966]

Have never seen that happen, don't know what supply type is being used over here we use TT

The TT or TN supply type won't make any difference to equipment damage if you have an neutral fault on a 3-phase group of circuits. What is more likely to make a difference to the stats is the types of cable/joints used that might alter just how common such a fault is.

Oh and the number of scroats stealing neutral links from sub-stations...

However at least with TT you don't have the open PEN risk for TN-C-S elevating external metalwork to tens or hundreds of volts...

 

[nicebutdim]

over here we use TT

Was that a typo?

 

[GBDamo]

Final update.

First thing, we have plague in the house so this may be my last post. We have one positive test and I'm fairly sure I've got it now, did my test this morning.

Interestingly my missus who, is a double jabbed devotee, is in bed (three days now) with it after catching it on a camping trip.

What exactly does this vaccine do?

-*-

Anyway had a chat with the contact at the flats this morning and to be honest I'm befuddled by her explanation.

They have had the situation looked at and resolved. Apparently it was "some flat plugging in too many appliances and burnt out a fuse and some wires"

I find this highly implausible.

Any overload should have been dealt with by the OCPDs in the flats and not downstream. Unless the design of the installation was seriously FUBAR.

More likely they got the installers back in to check it over and they've tightened up their loose neutrals.

 

[DPG]

Final update.

First thing, we have plague in the house so this may be my last post. We have one positive test and I'm fairly sure I've got it now, did my test this morning.

Interestingly my missus who, is a double jabbed devotee, is in bed (three days now) with it after catching it on a camping trip.

What exactly does this vaccine do?

-*-

Anyway had a chat with the contact at the flats this morning and to be honest I'm befuddled by her explanation.

They have had the situation looked at and resolved. Apparently it was "some flat plugging in too many appliances and burnt out a fuse and some wires"

I find this highly implausible.

Any overload should have been dealt with by the OCPDs in the flats and not downstream. Unless the design of the installation was seriously FUBAR.

More likely they got the installers back in to check it over and they've tightened up their loose neutrals.

Thanks for the update.

Hope the Covid doesn't get you too bad. I know some people who were affected for months.

Don't forget the vaccine is not 100% effective - no vaccine is.

 

[littlespark]

The vaccine stops you from being as ill as you would without it.
Can still get COVID, but not as severe.

“severe” being in ICU
“not severe” is being laid up in a bed a few days.

 

[nicebutdim]

What makes little sense is the different rules about self isolation between people who have been vaccinated and people who have not - both can spread it around and I doubt it would be of little comfort to those ending up severly ill to know that the person they caught it from had been vaccinated.

 

[Mike Johnson]

Double vaccinated before I went to France three week ago, impossible to get a PCR test before I left my area, six different test laboratories refused to give me a test without an appointment, not much good as they only had appointments two weeks hence, went into Calais and had a test while I waited, all of this took hours, my normal six hour journey turned into thirteen and a half hours, the rules at Calais are very strict on the tests, at the UK side they did not want to see any documentation, just my passport, seems the French side is more strict than the UK side, hence letting all those FIFA people in without any checks, seems to be daft to me.

 

[LukeD]

Final update.

First thing, we have plague in the house so this may be my last post. We have one positive test and I'm fairly sure I've got it now, did my test this morning.

Interestingly my missus who, is a double jabbed devotee, is in bed (three days now) with it after catching it on a camping trip.

What exactly does this vaccine do?

-*-

Anyway had a chat with the contact at the flats this morning and to be honest I'm befuddled by her explanation.

They have had the situation looked at and resolved. Apparently it was "some flat plugging in too many appliances and burnt out a fuse and some wires"

I find this highly implausible.

Any overload should have been dealt with by the OCPDs in the flats and not downstream. Unless the design of the installation was seriously FUBAR.

More likely they got the installers back in to check it over and they've tightened up their loose neutrals.

SKunk farm ? Anyway , i would like to know how their explanation would cause this issue (From a learning perspective )