Rcd head scratcher

[Welchyboy1]

Farm job im at has a problem


three phase tt system comes into main barn area, three phase main distribution board (with 100mA s type 4 pole rcd as main switch) supplying barns and general farm buildings

Swa single phase supply to farm house(around 40meters away), supplied directly from meter side of distribution board on henly blocks to switchfuse/rcd

so house supply is totally independent from the barn supply

however everytime there is a fault on the barn distribution board and its main rcd operates it takes out the rcd at the farm house too

i havent been over to the farmhouse yet but i cant understand why it would be knocking out the rcd in the house?

any ideas?

 

[R G]

This reads plain to me but a few are not reading the OP properly ...

At mains there is a 3ph board with 100mA rcd main switch
Also a 1 phase supply straight of the meter via a henley block to a sw/f + RCD ...lets assume 100mA

When a fault trips the rcd of the 3ph board the rcd IN THE house trips so assuming a 30mA is tripping in the house possibly 17th edition board....






can the OP confirm this!?

Thats how I read it as well ...

 

[MDJ]

I thought I had read it right, what I thought was, "what is protecting the single phase supply"? it is from henley blocks to a switch fuse then to the house where there is a rcd?? or does he mean there is a rcd in the barn at the supply, oh dear I am now getting confused too

 

[Welchyboy1]

Where abouts is the suppliers transformer ...is it close up a pole?
What kind of rcd's are they - are they modern type that measure inbalance between L/N?

Have you ensured all your customer side connections are sound and tight... check busbar tabs are on the correct side of any mcb, rcd and main switch terminal clamps.

rcds/mcbs are mem old 3871/4293 type, dunno about house end ive not been able to get access in there yet but assuming they are of similiar age

also not sure of tx location

 

[Welchyboy1]

This reads plain to me but a few are not reading the OP properly ...

At mains there is a 3ph board with 100mA rcd main switch
Also a 1 phase supply straight of the meter via a henley block to a sw/f + RCD ...lets assume 100mA

When a fault trips the rcd of the 3ph board the rcd IN THE house trips so assuming a 30mA is tripping in the house possibly 17th edition board.... can the OP confirm this!?


Edit confirmed in post 15.

Spot on darkwood yes 100mA s type sp protecting submain(this is holding fine but the 30ma rcd in house is tripping out with the 3pn board in the barn)

 

[MDJ]

Ah I now get it after seeing the last post

 

[Darkwood]

Now we have the correct set-up as confirmed in my post 13 any chance the OP can answer y questions way back in post 2 :juggle2: ill just wait then!!

 

[Deleted member 9648]

head scratcher alright, but I think I would be eliminating any N-E faults on both installations in the absence of any better ideas. N-E faults do funny things to RCD's.......

 

[R G]

You need access to the house , to confirm what RCDs are there and earthing arrangements at the house,,,

 

[MDJ]

well certainely a headscratcher alright, seems very strange, maybe the fact both supplys connect to the rod and the fact a surge to earth trips the one may mean the other is over sensitive, must admit it is a funny situation which I am struggling with at the moment.

 

[Welchyboy1]

You need access to the house , to confirm what RCDs are there and earthing arrangements at the house,,,

Yes i am due back there saturday

 

[Welchyboy1]

he said henleys, switchfuse, rcd.

then i hear TP board and TT the first thing i think of, is the first (RCD) enclosure insulated?

No the enclosures are not insulated or the dist board, its an old install and a stubborn farmer

first thing i mentioned to him

 

[Darkwood]

La de da da da ....any chance of responding to post 2 yet its getting further away as we speak... might be using the 18th edition by the time you respond to it :juggle2:

Please refer to post 21 for guidance.

 

[jackhammerJIM]

A strange one indeed .

first thing to do would be confirm this is actually happening with test meter .

you know how customers can somehow get the wrong end of the stick .

 

[Welchyboy1]

well certainely a headscratcher alright, seems very strange, maybe the fact both supplys connect to the rod and the fact a surge to earth trips the one may mean the other is over sensitive, must admit it is a funny situation which I am struggling with at the moment.

It is a pain

im thinking of isolating the two earthing systems from each other, having a rod for each and insulating the SWA sheath at the house end from the barn see what happens

just wanted a few ideas for when i get back there

Ramp test the house RCD

 

[Welchyboy1]

La de da da da ....any chance of responding to post 2 yet its getting further away as we speak... might be using the 18th edition by the time you respond to it :juggle2:

Please refer to post 21 for guidance.

post 18