How to properly do an RCD time trip test

[swaRRR]

I've seen several videos on these, half of them show an MCB in the 'on' position protected by an RCD also in the 'on' position, earth lead on the earth bar, neutral on the neutral bar, and live on the MCB's line screw terminal.

But then i've seen other videos where the earth bar and the line/neutral terminals on the load/outgoing side of the RCD is used. John Ward for example shows this test with a standalone RCD on a rig board with two pieces of wire coming from line and neutral.

Which one is right?

 

[plugsandsparks]

Ideally, RCD powered up and both outgoing lines disconnected. Probes on Outgoing L and N, with Earth on earth bar.

 

[davesparks]

Which one is right?

Both are right, as long as the live lead is connected to the outgoing side of the RCD the test will work.

If you're testing standard SP RCBO's then the neutral is solid anyway and it won't matter which side of it the neutral is connected.

And if you have an RCD which is downstream of another RCD you can connect the earth lead of the tester to the incoming N to avoid tripping the upstream RCD.

 

[timhoward]

I don't have it with me but I think GN3 says test on load side of device with loads disconnected.

 

[loz2754]

I don't have it with me but I think GN3 says test on load side of device with loads disconnected.

So does the On Site Guide. Section 11.1

 

[swaRRR]

I don't have it with me but I think GN3 says test on load side of device with loads disconnected.

So when they leave a circuit on and test that it's technically not allowed?

 

[loz2754]

So when they leave a circuit on and test that it's technically not allowed?

The reason for the guidance to test with no load on the outgoing terminals of the RCD, is because we just need to test the RCD itself. If there is a load connected, the test results may be influenced.

However, this is guidance, not regulation.

 

[timhoward]

So when they leave a circuit on and test that it's technically not allowed?

In some circumstances it can be useful to see if an RCD is actually working in normal operating conditions too, e.g. that it isn't being blinded by DC leakage. A ramp test can be very helpful under load to see how close it is to tripping "normally"
No point signing off an RCD that works perfectly until you connect any loads!

 

[swaRRR]

In some circumstances it can be useful to see if an RCD is actually working in normal operating conditions too, e.g. that it isn't being blinded by DC leakage. A ramp test can be very helpful under load to see how close it is to tripping "normally"
No point signing off an RCD that works perfectly until you connect any loads!

Thanks for the help mate appreciate it. So i'm right in thinking that for test sheet purposes on an RCD time test we should try to test without a load, for the certs results box?

 

[loz2754]

Thanks for the help mate appreciate it. So i'm right in thinking that for test sheet purposes on an RCD time test we should try to test without a load, for the certs results box?

Yes

 

[swaRRR]

Yes

Very much appreciated my mate