keeps tripping rcd

[panny300]

had a phone call,from someone i used to work for,he helped a neighbour to put some power to a garage,
(i know it is under part p but they have already done it)
they took a feed from a mcb which was being used for a couple of other sockets in the house,they had no spare one.,(i know they should'nt but they have) it goes to a small consumer in garage.
the problem is it trips the rcd in the house whatever they plug into a socket in the garage,
so they took out the connection to the couple of sockets from the mcb in the house so that only the garage feed was in it, still tripped,
they put the original cable back into mcb that fed the couple of sockets and took out the garage feed,
they put a plugged lead into one of the sockets that was fed from the same mcb in the house out to the garage consumer,put a load into a socket in the garage,nothing tripped.
so they replaced the original feed to the garage,put it back into the mcb,it tripped the rcd in the house again.
anyone know why it would trip the house rcd if it is wired directly into the mcb but not if they use a socket that is on the same mcb.

 

[securespark]

The feed to the garage has the neutral in the wrong busbar.

 

[garlicbread]

neutral not connected to the rcd side

 

[ban-all-sheds]

a small consumer in garage.

 

[panny300]

thanks i will pass the info on,anyone think of any other reason?
minime,good one

 

[RF Lighting]

There is no other reason. You have been told exactly what you've done wrong.

 

[Taylortwocities]

thanks i will pass the info on,anyone think of any other reason?
minime,good one

Yes. incompetent people messing around with what they do not understand and putting themselves and others in danger.

Do they have ANY idea why Part P is necessary. Good grief