Hi, I am Hus.

In this video I want to share with you a scenario where it’s possible to charge a dead installation when you’re conducting an IR test. Let’s get started. So this scenario is when you have an active to earth short, somewhere on the installation and you’re doing an IR test across neutral and earth. Let’s have a look at simulated installation and see what’s going on. So here we have a switchboard. As you can see, there is nothing else connected here. What we’re going to do is we’re going to conduct an IR test between the neutral and earth bars while we have an Earth to active short. So you can see there is a short here going from earth. So this basically a simulation. So we’ve got a short between the active of this circuit and earth. So when I conduct that IR test, what essentially I’m doing is putting the 500 volts across the active and neutral of this RCD. But let’s look at different scenarios and what happens to the voltage across this circuit where there’s nothing connected and how it’s charging and holding the charge in the circuit.

Let’s look at the first scenario, which is all circuits on, and we conduct an IR test between neutral and earth and we’ll also measure the voltage across it. So let’s turn that on. I’ve got my IR tester set to 500. I’ll just check if the tester is working. Yes, it is. So the tester is on. I’m going to put my voltmeter. Turn this off. I’m going to put my voltmeter across this bar and the neutral bar here. As you notice that this bar isn’t really connected to earth, but I want to do a test where there is no fault and when there is a fault. So let’s just say that will be when there is no fault. My voltmeter is set to dc, my IR tester is on, testing the tester again, it works. Okay, I’ll put it across the earth bar, which is not connected, but let’s say earth bar and neutral. And I’m seeing about 526 volts. And if I disconnected, the voltage disappears, which is what you would expect to happen if the installation didn’t have any faults.

But let’s just say we go to this earth bar where there is a short between active and the earth bar here, and let’s connect that now. Just like before, we still have 527 volts, which is coming from the IR tester, but as soon as I remove my IR tester, what you will notice, instead of going straight to zero, it’s slowly dropping. So it’s at 60 volts, 40 volts, 30 volts. Now let’s try the same scenario when the fault circuit is off. So I’ll turn this fault circuit off and then we will conduct the same IR test. So I’ll test the tester, still working, and I will do that test, and I’m seeing 526 volts. And if I remove that, you can see how the voltage went straight to zero. So we know that there was a problem here. Let’s flip this test now, we’ll turn everything off and then leave just that fault circuit on and see what happens. Okay, we’re going to repeat that test again where we will put 500 volts across earth bar and neutral.

And the only circuit that’s on is where the active and earth short exists. So we do that and we can see 526. As soon as I let go, you can see that it’s slowly dropping. It was much faster than the first scenario, but it did charge up, which goes to show that there is something inside the RCD that is holding charge. And we pulled one RCD apart and found out that there is a capacitor inside. Now, there is another scenario that I want to conduct tests on where, how much peak voltage it holds once I remove the IR tester and how much voltage it holds in different situations. Thanks for watching.