second RCD tripping

carrick

have a problem with an rcd tripping have installed a sub board in a garage using 10sq+6sq earth,installed six workshop sockets and two appliance sockets,trying to keep both circuits independent so as not to lose power to freezer,the problem is the tumble dryer works perfectly on 63A 30mA rcd appliance circuit,as soon as anything is plugged into the workshop circuit it trips both rcd's,the second rcd is a 16A 30mA rcd
-both rcds wired independently
-wired direct from 63A fuse and main neutral in main board

any ideas thanks

user1842

Sorry why do you have two RCD's in you garage?

Surely you should have wired one RCD and two MCB's. Each of the MCB's feeding your two ring mains (circuits). The RCD should feed both MCB's. Relying on the 63A fuse on the main fuse board is bad practice. An MCB should always be at the end of a circuit and rated just above the max laod intended for that circuit.

An RCD will only trip when a current flows to earth (anywhere but the return neutral), this may not always happen hence we still uses fuses (MCB's)

carrick

sorry should have pointed out that there is a seperate 63A switch fuse,two rcds and mcb protecting each circuit since the person was getting the lower rated rcds from an existing refurb why not use them and stop the problem of losing the freezer if the work sockets were tripped,so everything is above board from what i can tell but it still doesnt explain why the lower rated rcd is tripping both the rcds out whenever anything is plugged into it.

user1842

Great,

Only can think of two possibilities:

1. The RCD is faulty and is nuisance tripping.
2. The wiring is faulty, the installer might have connected a live/neutral to an earth or some of the live/neutral wires are damaged and are exposed tipping off a metal/conductive material.

Test the RCD first then if no joy you need to look at the wiring. I would start with the sub board and then to the sockets

"whenever anything is plugged into it" Make sure that this is the case as you never know you might have a lot of faulty items

carrick

thanks dmclean1842
didnt get a chance to get back to it since saturday so will check everything again,having fun with this one,first time ive ever come across a total rewire where the fella who done the job never bothered putting any earth rod,just all socket,light earths back to earth terminal with no connection to earth not even on the esb side.

user1842

You need to put an earth rod down , cant believe there is none. A lot of dodgy people use the copper pipes in the house as an earth. They should be earthed but never be the ground earth.

Good luck, hopefully it will be something simple.

M cebee

you're allowed feed a deep freeze from a dedicated cct-no rcd

that's the simplest way to avoid losing the contents

sounds like you need a sparkie anyhow

beanie10

You need a proper electrician you have no neutralising earth very dangerous. Point it out to the "electrician" that done it. Was he qualified or apprentice doing a nixer.

Bruthal

dmclean1842 wrote: »

An RCD will only trip when a current flows to earth (anywhere but the return neutral), this may not always happen hence we still uses fuses (MCB's)

We use fuses/mcb`s because RCD`s dont trip on L-N overload, only L-N differential.

Bruthal

Sounds like a bit of a cowboy job is the cause probably. The 2 rcd`s should have both socket neutrals completely seperate for a start anyway. So if they have a neutral bar each then another neutral bar would be needed for lights etc, maybe the socket circuit neutrals are into each RCD neutral terminal direct which would be ok.

2 seperate RCD`s like the OP`s can have neutral mix up problems anyway, such as second RCD neutral feed taken ffrom the neutral bar of the first one, but there would have to be another problem in the circuits to trip both.

Get a proper sparks in. 2 RCBO`s would of been a lot better for your above setup. Or a dedicated circuit to a spur for the freezer which needs no RCD on it.