Anyone come across this very often ?

Plumber just phoned me ... hes installing a wet floor heating system somewhere ,  he's  limited scope qualified for boiler  electrics  .  

Part of the system is a RF stat  which he traced to being the cause of tripping the RCD .  

Fitted another one , same thing ,   multimeter shows 50V   on the Earth wire of both stats.       (Meter between  disconnected E wire & E bar .)        Manufacturer tells him to get an electrician in.  

This what I'm asking .    

He says the terminals on the stat  are marked   L  E   N    clearly .        I'm thinking we don't see that very often  and  its just waiting  for someone to  connect   it L N E  .  

I'm thinking fluorescent light fittings  are often  like that  but not devices  like his stat .   

I'm also thinking as the stat is apparently plastic  , why does it need an E connection  unless its to dump data down ?    Or is it trying to use the E wire as an aerial . ? 

Evans Electric said:

he's  limited intelligence

Part of the system is a RF stat  which he traced to being the cause of tripping the RCD .  

Fitted another one , same thing ,   multimeter shows 50V   on the Earth wire of both stats.       (Meter between  disconnected E wire & E bar .)        Manufacturer tells him to get an electrician in.  

This what I'm asking .    

He says the terminals on the stat  are marked   L  E   N    clearly .        I'm thinking we don't see that very often  and  its just waiting  for someone to  connect   it L N E  .  

I'm thinking fluorescent light fittings  are often  like that  but not devices  like his stat .   

I'm also thinking as the stat is apparently plastic  , why does it need an E connection  unless its to dump data down ?    Or is it trying to use the E wire as an aerial . ? 

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I/ I doubt he's proved anything to be the cause..

2/ A floating earth wire could have any "apparent voltage" floating on it with a cheapo plumbers meter..

3/ There is a requirement in the regs to run a CPC to all accessory points.. If said item is ClassII they generally have a clump of brass with a hole in it and screw as somewhere the park the unused CPC. Other than that the CPC is doing nowt!

4/ The order of the LEN,  LNE, NLE, NEL, ELN, ENL  is purely down to the logistics and costs of the circuitry inside the accessory and how their gubbins connects easiest.

5/ Assume plumb-bob is an incompetent baffoon until you have proved other wise..

6/ Could easily be an earth fault anywhere else on the heating system, that only goes live because the thermostat has kicked in. thus causing a current to trip the RCD..

7/ Has the full circuit been IR tested...  Has the RCD been tested...  If Not..  BACK TO BASICS!

Guinness  

or he could have ballsed up a fused spur? those terminals tend to be oddly spaced.

He could have damaged the mat, what tests has he done to prove it's the stat, linked it out and system runs? I had a lad ring me up after fitting an outside light, when you switched it on it took out the RCD, he'd swapped the fitting twice, it still tripped, he concluded it was the light because if you removed the lamp it didn't trip.It was a Crabtree Starbreaker board , what he'd actually done was taken the live off the downstairs lighting MCB, but the neutral bar was full, so there was another one at the other side with only a couple of wires in, he'd stuck it in there. The problem was that 'there' happened to be on the  non RCD side of the board, hence the tripping, it was a lesson learned for him, lol

I doubt he has damaged the mat as it is a Wet system  :innocent

kerching said:

I doubt he has damaged the mat as it is a Wet system  :innocent

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Ok, so I'm getting old and bewildered, lol

A nail through a wet system is easier to spot, the damp patch gives it away.

SPECIAL LOCATION said:

6/ Could easily be an earth fault anywhere else on the heating system, that only goes live because the thermostat has kicked in. thus causing a current to trip the RCD..

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Apparently he,s  tried powering it  with a flex via a second RCD  which also trips  ..... the heating circuit remains on .  

This made me think he'd isolated the device as the problem .

He,s servicing my boiler next week sometime  , I'll be interested in what the manufacturer says. 

Has he actually tested continuity between the L -N and L-E terminals to ensure it does what it’s supposed to as per markings? I’ve had quite a few items that are described LEN and have actually been LNE once tested out.  I put it down to cheap manufacturing processes. 

Bloke  contacted me to get him some light fittings like "I had supplied his sister with 5 years previously. You know the ones, they are made by LENNEL"

it took me a a while to twig it

Sharpend said:

Has he actually tested continuity between the L -N and L-E terminals to ensure it does what it’s supposed to as per markings? I’ve had quite a few items that are described LEN and have actually been LNE once tested out.  I put it down to cheap manufacturing processes. 

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That was my opening question  Sharpie ,    I was thinking how easy it would be  without double checking , to connect  your flex  L N E    and the device would be powered between L  & E .  

I don't know how he's tested it  ....he confirmed the E  terminal had a  G/Y connection to it .   

My brain works in straight lines and the easiest routes so ,  if you unpack a new device  , confirm its 240V ,   connect it as described by manufacturer  and it keeps going bang  ...     same with a second one ...theres something wrong with it . 

if boiler is still on, perhaps he's pinched a nuetral?

No he's eliminated all the heating controls by connecting the stat with a flex  . 

Spoke to him today ,  his wiring was fine  ,  both units were  faulty , third one  was OK .