Rcd Tripping When Carry Out Prospective Fault Current Test

[electrics_new]

I have installed a Wylex 17th Edition DB at a property and everything has tested fine (both dead tests and live).

I've then used a MCB (RCD protected to supply) a DB in the garage.  No RCD present in the garage as it's under the RCD in the main property.

However, when I perform the Prospective Fault Current Test – between Earth, Live & Neutral – the RCD in the house trips.

Any ideas ???

 

[Andy™]

 

[electrics_new]

I've just found another post with someone else having the same issue.

I'll give it a shot.

Read from sparkeytim

ow to test Zs on a RCD protected radial circuit.

Turn OFF RCD, short L to E at the end of line of the circuit (Furthest point from supply)

Connect one lead of your tester and connect to OUT GOING line terminal of the RCD ( RCD SWITCHED OFF)

CAREFULLY Connect the other lead to the INCOMING Line terminal and take reading.

Your Meter bypasses the RCD so it will not trip and you get a reading using the full 25 Amp test current.

Remove leads, remove short at end of line and you have it, accurate direct reading

Ps 

I had to draw it out to prove to myself it would be a true reading when shown this Method.

Try it and see for yourself 

 

[Blue Duck]

Hmmmm prospective fault current test. what are you doing when you are testing for a prospective fault current? Creating a fault current that will be picked up by an rcd and it will disconnect supply.

I'm sure I have written this before? Maybe I'm going mad?

Main RCD 100mA?

 

[Doc Hudson]

I have installed a Wylex 17th Edition DB at a property and everything has tested fine (both dead tests and live).

I've then used a MCB (RCD protected to supply) a DB in the garage.  No RCD present in the garage as it's under the RCD in the main property.

However, when I perform the Prospective Fault Current Test – between Earth, Live & Neutral – the RCD in the house trips.

Any ideas ???

I've just found another post with someone else having the same issue.

I'll give it a shot.

Read from sparkeytim

ow to test Zs on a RCD protected radial circuit.

turn OFF RCD, short L to E at the end of line of the circuit (Furthest point from upply)

Connect one lead of your tester and connect to OUT GOING line terminal of the RCD ( RCD SWITCHED OFF)

CAREFULLY Connect the other lead to the INCOMING Line terminal and take reading.

Your Meter bypasses the RCD so it will not trip and you get a reading using the full 25 Amp test current.

Remove leads, remove short at end of line and you have it, accurate direct reading

Ps 

 I had to draw it out to prove to myself it would be a true reading when shown this Method.

Try it and see for yourself 

By virtue of the fact that you had to ask, clearly you do not appear to understand what happens during PFC or an earth loop impedance test, with regard to the path of test currents. As such I strongly suggest for your own safety, and more so the safety of any third parties who may be present at you installation, do not attempt any such fiddling around with test procedures that are outside of your scope of ability and competence. I fear that you could end up energising all the exposed conductive parts at the installation. Test procedure methods and an understanding of how they operate should be basic concepts grasped before working alone. During some tests exposed parts can become energised, which I doubt you understand as you question why an RCD has operated. Please seek some professional guidance, maybe with a competent electrician who can supervise and guide you with your testing. 

Even more worrying; Why do you ask about Prospective fault current, then suggest that a Zs, (earth loop impedance test) will give you the results that you need?

Doc H.

 

[m4tty]

What tester are you using mate? My megger mft1552 does a low current 'no trip' test for rcd protected circuits hth

 

[Andy™]

My megger mft1552 does a low current 'no trip' test for rcd protected circuits hth

dont confuse him with the features of a test kit

 

[m4tty]

 

[Steve3948]

I have installed a Wylex 17th Edition DB at a property and everything has tested fine (both dead tests and live).

Really, how sure are you about this ?

I have a feeling you do not fully understand how and what testing is all about.

 

[Andy™]

id love to see all these other test results...

or can it all be summed up in

'all 3 lights on plug in tester lit'?

 

[Blue Duck]

'all 3 lights on plug in tester lit'?

The socket n see test!

 

[Andy™]

or maybe it was a table lamp and it lit up?

 

[steptoe]

just what exactly is a 17th edition DB  ?

and surely a consumer unit would have been more suited to a domestic property anyway?

 

[Sharpend]

DB= Domestic Board !

 

[batty]

CCU was cooker control unit when I went to college nowadays its customers consumer unit. All very confusing.

 

[steptoe]

CCU was cooker control unit when I went to college nowadays its customers consumer unit. All very confusing.

really?

is it?

since when?

CU is consumer unit,

CKR is cooker sw for me,  :|

a consumer unit was CU , and it always will be for me, CCU next tuesday as to it ever being CCU,  :shakehead

 

[Blue Duck]

Its hardly a distribution board at least not the way I see it. Not sure about 17th ed either as you get old (80's) dorman smith boards with RCDs protecting more than one circuit.  :C  

Although Asking a customer where their consumer unit is usually gets a blank response so I ask for fuseboard/box.

The fact that they change the names of everything every year makes it all very confusing. Least it may help us weed out the 5ww's