Multiple RCBO's tripped??

[apprentice87]

Hi All,

What you make of this..??

Where i work in the hospital we have a area in the kitchen with various 13A sockets to power trolleys for keeping the food warm. They are all powered from a three phase DB, with each of the three circuits on a different phase with a separate rcbo for each circuit.

Earlier on today they all tripped off.

I had a look, and the the three RCBO's had all tripped off together. How would that happen?? Some sort of neutral fault?? [as i know that neutral/earth faults can cause trips on entirely different circuits.. Wiring is singles in conduit if that helps..

I reset them, and they seemed ok, but what will happen when they cook breakfast in the morning!!!

john..

 

[SPECIAL LOCATION]

Well, as most RCBO's don't actually switch the neutral, if one RCBO has tripped the 'N' is probably still connected.....

So I am guessing it is something 'N' -> 'E' related.....

What type of Earthing are we talking about?

What if you had some sort of external fault coming up the earth & making its return via the Neutral..?

One RCBO trips... but N still connected so another RCBO trips...   etc...  etc...  etc....

Dunno..

just guessing??

:coffee

 

[Murdoch]

I would be looking closely at the incoming supply to the board rather than load side off the rcbo's

 

[apprentice87]

Thanks all!!

I have no idea where the origin of the supply is, so i have no idea of earthing type. I would guess TNS as the place was built in 1903/6

The board itself is fed from god knows where by a rather hefty looking length of SWA, modernish looking stuff as the original would have been PILC i would think..

Poor old works and estates will have to sort it out, but that might take them a while i think.. Would be WAAAYYYYYYY beyond me!!

Might pop in shortly and see if it all worked ok this morning!!

john..

 

[Phoenix]

What make are the RCBOS? and are these the only RCBOS in the board?

Thinking in terms of interference, I'm sure there was one brand that has been known to trip if a PMR radio was used right next to it. And I've been called out to a load of RCBOS all tripping off when a thunderstorm passed overhead

 

[Evans Electric]

I can only offer  the following .    Two MK  RCD  sockets  on a stage used for amps etc .      My RCD tester knocked them both off every time .     No idea why .  

 

[apprentice87]

Hi All,

Well, i think i have solved it!! It would appear that when they wired this bit of the kitchen, [it is about 25 feet square] they they decided that it would be a great idea to put each pair of sockets on a different circuit all protected by its own RCBO, That way, nothing can go wrong and put the place out of action..

Well, it turns out that one of the dinner trolleys has an earth fault, and yesterday, one of the kitchen staff, when they could not get it to work, tried it in every socket in the place, and hence, tripped all three RCBO's off and a fourth one in a different board too. one after the other!!

john!!!

 

[ProDave]

Hi All,

Well, i think i have solved it!! It would appear that when they wired this bit of the kitchen, [it is about 25 feet square] they they decided that it would be a great idea to put each pair of sockets on a different circuit all protected by its own RCBO, That way, nothing can go wrong and put the place out of action..

Well, it turns out that one of the dinner trolleys has an earth fault, and yesterday, one of the kitchen staff, when they could not get it to work, tried it in every socket in the place, and hence, tripped all three RCBO's off and a fourth one in a different board too. one after the other!!

john!!!

Related to that, I had to hard wire the fridge at our village hall, also used by the nursery, into a hard wired switched FCU, after the cleaner kept unplugging it to plug in the hoover, then did not plug it back in again.

 

[Geoff1946]

after the cleaner kept unplugging it to plug in the hoover, then did not plug it back in again.

That in turn reminds me of an amusing incident.

My son helps at the local scouts gang show, setting up and operating sound and lighting, for which they have a fairly sophisticated control desk at the rear of the auditorium. 

First night and just into the last act before interval, comes a sudden and total blackout;  complete silence and darkness.

Turned out the ice cream lady had arrived, wheeled her freezer into her customary place only to find that her usual socket had been appropriated by my son for the control desk. 

Worse, she couldn't understand how her unplugging one plug could possibly have had such drastic effect, and concluded she was just being blamed for someone else's failure. She was all set to repeat her action the next night until stopped by a wisely appointed guard.

 

[ProDave]

That in turn reminds me of an amusing incident.

My son helps at the local scouts gang show, setting up and operating sound and lighting, for which they have a fairly sophisticated control desk at the rear of the auditorium. 

First night and just into the last act before interval, comes a sudden and total blackout;  complete silence and darkness.

Turned out the ice cream lady had arrived, wheeled her freezer into her customary place only to find that her usual socket had been appropriated by my son for the control desk. 

Worse, she couldn't understand how her unplugging one plug could possibly have had such drastic effect, and concluded she was just being blamed for someone else's failure. She was all set to repeat her action the next night until stopped by a wisely appointed guard.

Well on holiday on the Western Isles we went to a pub on a live music night. Typical one man, a guitar and a rhythm box.

Old pub, not many sockets, fed from an extension lead.

An old lady gets up from her seat wanders around the room looking for a socket, unplugs the musicians extension lead to plug her phone charger in.

 

[UNG]

Reminds me of the days when I was installing data radio links, on one job the customer complained that the radio link went offline about the same time everyday week day for about 20 minutes it was suggested he checked the power that the radio link was connected to but he insisted it was a faulty radio and wanted us on site to check it

So it was a 200 mile trip to the site checked the uptime on both ends of the link to identify which end was going down and then it was grab a brew while waiting and watching for the problem to occur, bang on the normal failure time in comes the cleaner unplugs the comms rack and plugs her hoover in. So the customer was advised that an invoice would be raised for an engineer for a day a plus travel expenses as there was no fault with the radio