replace elcb with rcd?

manus30

hopefully some of you experts here can help me. i was doing a fair bit of welding recently from socket in house, and an electrician friend commented that it was amazing that the rcd did not trip.
a few days later i checked my distribution boards and pressed the button on the 40amp 30 ma elcb. it did not trip, so i went to my local wholesaler and asked for a like for like unit. he gave me a different make similar spec rcd which i presume is the same as my old elcb?
anyway, i wired it in and turned it on. all ok so far. then plugged in the fridge and it tripped. started the kettle and it tripped. tried the tv which is on a different mcb circuit but uses the lecb and bang again. however, i could turn on the table lamps alright, anything more it would trip.
i thought the new rcd might be faulty so exchanged it for another one, but same result.
i also noticed that the new rcd only trips when under load, ie tv fridge etc. and if i press the test button on the new rcd it does not trip.
can anyone shed some light on this.
thanks in advance for help.

2011

Ok it sounds like you have the neutrals connected incorrectly. The RCD will have 4 terminals, neutral in, neutral out, live in, live out. Here is how it should be connected:

neutral in: Connected to main neutral bar

live in: Connected to the busbar supplied by the main switch fuse. The lights and cooker will also be on this

Neutral out: Connected to the RCD neutral bar. You should see all of the neutrals for socket circuits connected here. Normally they are 2.5mm sq.

Live out: This will go to the RCD busbar. The sockets will be connected here.

I would guess that the old ELCB has the neutral connections (or the live) located in a different position than on the new RCD.

If you can't sort it PM me a number and I will ring you.

Note ensure that all connections are tight and use at least 10mm sq. cable to connect the RCD.

manus30

thanks a million 2001, i will try it later and see how it goes.

2011

No problem. Be careful! Don't just turn off the main switch fuse, remove the fuse. It is easy to hit the switch by mistake when you are connecting up and then everything becomes live.

Also check all connections in the board are tight, even the ones you have not touched. Often other connections will work loose when you are connecting something like this into the board.

Good luck!

manus30

just tried that and no joy 2011, although when i connect the way you said, when the upstairs sockets mcb is turned on it does not trip. it trips when either of the 2 downstairs mcbs are turned on.
if i turn everything off downstairs, i can set the rcd and power up the mcbs and everything is fine.
if i turn on a few table lights powered from sockets everything is still fine.
problem happens if i power up fridge, kettle, toaster ot tv unit.

mazthespark

ya i think 2011 is right sounds like the connections are mixed up on your rcd. it wont trip with table lamps etc on as there isnt enough current flowing to cause enough of an imbalance to trip the rcd. when an appliance is used it draws a lot more so will cause rcd to trip. have you the live and neutral sides mixed up? or possibly your old elcb was fed the incoming from the top and the new one is incoming from bottom. shouldnt make a difference but possibly

2011

if i press the test button on the new rcd it does not trip.
can anyone shed some light on this.

This indicates that the RCD is not conneted correctly. An RCD measures the difference between the current flowing through it on the live and compares it to the current flowing back through it on the neutra. lf the difference is large enough then it operates. Pressing the test button intrudues a fault. However if the RCD has either the phase (live) o the neutral connected backwards than the test button will not introduce a fault, so it will not trip.

it wont trip with table lamps etc on as there isnt enough current flowing to cause enough of an imbalance to trip the rcd.

Exactly.



Look at the way the test button is connected. It takes a live connection from the incomming side and a neutral from the outgoing. With yours connected incorrectly both sides of the test button are connected to the outgoing side.

manus30

thanks lads, i will try again but i am fairly sure i tried every way of wiring.
ps just a thought, the live side is just marked 1 on top and 2 on bottom of rcd. i presume the live from the main switch connects here on 1 yes?
both neutral connections are just marked N. i also presumed the supply neutral would be beside the L1 connection, but then again i have presumed a lot today.
thanks lads

manus30

ok tried every way of wiring the rcd but still trips. i better call an electrician to look

Bruthal

mazthespark wrote: »

ya i think 2011 is right sounds like the connections are mixed up on your rcd. it wont trip with table lamps etc on as there isnt enough current flowing to cause enough of an imbalance to trip the rcd. when an appliance is used it draws a lot more so will cause rcd to trip. have you the live and neutral sides mixed up? or possibly your old elcb was fed the incoming from the top and the new one is incoming from bottom. shouldnt make a difference but possibly

If the neutrals are mixed up or the live feed and neutral feed are not in the same side of RCD, anything what so ever plugged in will trip the RCD including table lamps.

Sounds like the neutrals are connected wrong into RCD compared to live`s.
Whichever side the Live feed is into should also have the neutral feed into, otherwise test button wont work and RCD will trip with anything plugged in. And i would of thought anything including lights would trip it. After all it only needs an imbalance of 30ma to trip while a 100 watt bulb takes about 430ma, and if the neutrals are in reverse compared to lives then it only takes 15ma to trip RCD then. On a normal slight earth fault then larger appliances are more likely to trip an RCD on a given earth fault than smaller appliances or lights. But on a wrongly connected RCD or neutrals mixed up to wrong neutral bars etc then anything at all plugged in should trip the RCD so it sounds like more than just an RCD wrongly connected maybe an earth fault as well or some sockets not connected through the RCD at all, an RCD with in/out mixed up can cause strange results. Anyway an electrician needs to look at it now.

Another thing it could be is the neutral bar for the sockets is fed with a direct neutral as well as RCD out neutral in a sort of bypass fashion. This would cause test button to also not work, and would account for bigger loads needed to trip the new RCD.

johnnyjb

There could be a fault some where in the house ,earth leakage etc...The old elcb might not of picked it up and your new rcd is doin its job and tripping out.

Just a thought anyway

manus30

ok so i had a go at this again and spent all day yesterday at it. i unplugged everything in the house, wired up the new rcd a different way which is live in on terminal marked L2 and out to mcb's on L1. N in is beside L2 live in.
turned on main switch and reset mcb's. reset rcd and all ok no tripping.
pressed test button and it worked. eureka i thought to myself.
turned on a table lamp on first mcb circuit, then on second and third mcb ( 3 mcb's run off the rcd ) all ok.
then went around to each socket on each mcb circuit with a fan heater, the rcd tripped every time i turned it on.
then tried various other appliances and rcd tripped every time, so its not the appliances.
it seems if there is any load on the circuit it trips the rcd.
i have tried every way of wiring the mcb just to be sure, so its not wired wrong.
where would i go from here?
thanks in advance.

M cebee

you'd need to megger the wiring really with all loads disconnected

assuming all the neutrals are on the rcd bar correctly and there's no shared neutrals anywhere

sparkie is your best bet

Bruthal

manus30 wrote: »

ok so i had a go at this again and spent all day yesterday at it. i unplugged everything in the house, wired up the new rcd a different way which is live in on terminal marked L2 and out to mcb's on L1. N in is beside L2 live in.
turned on main switch and reset mcb's. reset rcd and all ok no tripping.
pressed test button and it worked. eureka i thought to myself.
turned on a table lamp on first mcb circuit, then on second and third mcb ( 3 mcb's run off the rcd ) all ok.
then went around to each socket on each mcb circuit with a fan heater, the rcd tripped every time i turned it on.
then tried various other appliances and rcd tripped every time, so its not the appliances.
it seems if there is any load on the circuit it trips the rcd.
i have tried every way of wiring the mcb just to be sure, so its not wired wrong.
where would i go from here?
thanks in advance.

Sounds like a neutral earth fault on one socket circuit, in which case even if that circuit is switched off at its MCB, appliances plugged into other socket circuits will trip the RCD although small loads might not. A link between RCD neutral bar and earth bar would have the same effect, or a link between the 2 neutral bars, ye just never know what someone may have done if previous RCD was faulty or tripping, as in bypassed it which on the neutral side could be by connecting the 2 neutral bars together with a link wire.

Continuity tester will find which circuit it is if a neutral earth fault on a circuit is the problem but the neutrals need to be removed from the RCD neutral bar to find which circuit it is if it is a neutral earth fault on one of them. Could even be neutral and earth in together at a socket.

Sparks is best bet alright.

manus30

top class stuff robbie, i disconnected each neutral on the neutral bar one at a time and then reset the rcd. i eventually found which circuit was at fault.
i then began removing sockets on that circuit. found that the gas installer fitted a spur on one socket and ran it up to the boiler and controls. checked the wiring and it was a complete mess. wires twisted together, never even bothered to use connectors and the main culprit, a twin and earth connected to the spur with the live disconnected but the neutral in place.this wire was going outside but was no longer used. i removed the neutral and hey presto! rcd now works!!! the gas installer got away with dodgy wiring due to old elcb not working.
glad i didnt get an electrician, i rang a couple and they were looking for call out rate of at least 100 euro. one said that my insulation was probably at fault and house would need rewiring.
seriously thinking of getting that gas installer back to give him a telling off though. cowboys ted..

Bruthal

manus30 wrote: »

top class stuff robbie, i disconnected each neutral on the neutral bar one at a time and then reset the rcd. i eventually found which circuit was at fault.
i then began removing sockets on that circuit. found that the gas installer fitted a spur on one socket and ran it up to the boiler and controls. checked the wiring and it was a complete mess. wires twisted together, never even bothered to use connectors and the main culprit, a twin and earth connected to the spur with the live disconnected but the neutral in place.this wire was going outside but was no longer used. i removed the neutral and hey presto! rcd now works!!! the gas installer got away with dodgy wiring due to old elcb not working.
glad i didnt get an electrician, i rang a couple and they were looking for call out rate of at least 100 euro. one said that my insulation was probably at fault and house would need rewiring.
seriously thinking of getting that gas installer back to give him a telling off though. cowboys ted..

Cowboys ted,, haha i like that one, ye could talk that into coming down.

But seriously, it never ceases to amaze me the stuff you would see done.