Rcd tripping issue.

[Pauldicker]

Can someone shed some light on a problem I'm having.
I changed a CU today as there were only 6 circuits they are all now rcbo's there was no rcd protection prior to that.
On the ground floor circuit the rcd test was x1@ 147ms and x5@ 23ms.
However now when the customer turns the heating on its fine and if they turn the hot water on at the same time it's tripping the rcd.
It is run from a fused connection unit and upon looking all looks good in the fcu.
It's a valiant ecotecplus 618 and the controller is a lifestyle lp522
I'm not a heating engineer but I may be missing something obvious.

 

[Octopus]

The Zs is measured at the extremity of the circuit. The Ze is measured at the DB.

IR readings should NOT be taken with the RCBO connected .......

What was the IR reading ?

 

[Midwest]

In any case I would contact valiant tech before IR boiler even at 250v.

 

[Pauldicker]

The Zs is measured at the extremity of the circuit. The Ze is measured at the DB.

IR readings should NOT be taken with the RCBO connected .......

What was the IR reading ?

Oh sorry misread zs was tested at the sockets 0.55 was my highest reading on the ring. Ir was 10m ohms but this may be because i tested through the line and neutral. Im assuming its wrong now so how do i test a circuit that has an rcbo. Im still new and not used rcbo's until now.

 

[Leesparkykent]

The faults obviously not wit the supply to the switched fused spur its on the control side of the wiring for the heating system. I wouldn't bother doing any insulation resistance testing on any of the control wiring as you will get all sorts of skewed results. What heating system is in place y-plan, s-plan, c-plan etc?

Edit. just read OP again does it trip if hot-water is on independently?

 

[Midwest]

Think its a combi boiler.

 

[Deleted member 9648]

Oh sorry misread zs was tested at the sockets 0.55 was my highest reading on the ring. Ir was 10m ohms but this may be because i tested through the line and neutral. Im assuming its wrong now so how do i test a circuit that has an rcbo. Im still new and not used rcbo's until now.

Disconnect the outgoing line and neutral wires from the RCBO to test,leave the cpc connected to the earth bar with the main earth connected. If you are testing an existing circuit which may have connected equipment unknown to you, to avoid having to remove lamps and disconnect everything DO NOT test L-N. Join L and N together and test between that and earth.

 

[Leesparkykent]

Think its a combi boiler.

I doubt it as the op says it has a drayton lp522 programmer which is a two channel programmer for heating and hot water. A combi wouldn't need a programmer for the hot water.

 

[Midwest]

Ummmh, just googled the model number of boiler.

 

[Pauldicker]

The faults obviously not wit the supply to the switched fused spur its on the control side of the wiring for the heating system. I wouldn't bother doing any insulation resistance testing on any of the control wiring as you will get all sorts of skewed results. What heating system is in place y-plan, s-plan, c-plan etc?

Edit. just read OP again does it trip if hot-water is on independently?

No it does not but the hot water did not fire up but i am not sureif thats because the water was still hot. It worked
I havent got a clue what heating plan it is.
I was pretty sure it was not the supply side but the customer thinks that because ive upgraded the consumer unit to include rcd protection it is something i have done. And as it was working yesterday its somehow my fault. Im thinking there was an earth issue or crossed connection or faulty controller before i changed it.

 

[Pauldicker]

Disconnect the outgoing line and neutral wires from the RCBO to test,leave the cpc connected to the earth bar with the main earth connected. If you are testing an existing circuit which may have connected equipment unknown to you, to avoid having to remove lamps and disconnect everything DO NOT test L-N. Join L and N together and test between that and earth.

So basically take the line and N out of the rcbo, connect L&N together in a connector block and test that and earth together thus completly taking the rcbo out.

 

[Leesparkykent]

No it does not but the hot water did not fire up but i am not sureif thats because the water was still hot. It worked
I havent got a clue what heating plan it is.
I was pretty sure it was not the supply side but the customer thinks that because ive upgraded the consumer unit to include rcd protection it is something i have done. And as it was working yesterday its somehow my fault. Im thinking there was an earth issue or crossed connection or faulty controller before i changed it.

The fault is on the load side and unfortunately its one of those things that would never of been picked up on pre tests or testing whilst swapping the board as the SFCU would of been switched off. You wouldn't find the fault until the hot water/ heating was turned on. Its one of those things that you might just have to suck up and find the fault it shouldn't take that long to locate the fault if its a basic heating system. Do you know how many valves there are?

 

[Pauldicker]

I

The fault is on the load side and unfortunately its one of those things that would never of been picked up on pre tests or testing whilst swapping the board as the SFCU would of been switched off. You wouldn't find the fault until the hot water/ heating was turned on. Its one of those things that you might just have to suck up and find the fault it shouldn't take that long to locate the fault if its a basic heating system. Do you know how many valves there are?

know nothing about heating systems.
Im assuming that with the old circuit breakers if ther was an earth leakage and there was no rcd nothing would trip and would have just worked.

 

[Leesparkykent]

Ummmh, just googled the model number of boiler.

Its a system boiler so more than likely an unvented set up. If its unvented there will be 2 x 2 port valves or a 3 port with a two port for interlock on the cylinder.

 

[Midwest]

Its a system boiler so more than likely an unvented set up. If its unvented there will be 2 x 2 port valves or a 3 port with a two port for interlock on the cylinder.

Well whatever it is, the fault is more probably within the boiler, associated wiring, values etc. Before continuing I would contact Valiant, before proceeding further IMO.

 

[Pauldicker]

Its a system boiler so more than likely an unvented set up. If its unvented there will be 2 x 2 port valves or a 3 port with a two port for interlock on the cylinder.

Ita like talking a different language to me