Odd problem on IR Test.

[Lucien Nunes]

I always think that a requirement to disconnect something for an IR test is a sign of cheap or poor design. Clearly it is possible to make devices that don't need to be disconnected and unnecessary fiddling around with cables leads to wear and tear, errors and the possibility of introducing faults that the test was supposed to detect.

There are two aspects - whether the device will spoil the test result and whether it will be damaged. Anything that is connected to the mains can expect to see an RMS voltage of 253V and hence a peak voltage of 358V continuously for decades. Film caps ought to withstand 500V or else they are not fit for a noisy environment that can see spikes of a few kV. VDRs will give spurious test results but won't be readily damaged by the current-limited output of the IR tester. The weakest links would likely be 400V electrolytics and transistors in SMPSUs, but I don't like electrolytic capacitors hard-wired into my electrical installation e.g. in sockets with USB ports.

Back in the days of big, tough stud-mounted thyristors in theatre lighting dimmers, there would often be notices on the dimmer modules warning not to carry out insulation tests. Even if the thyristors were rated for 800PIV and the suppression capacitors 500V DC, and the primary of the mains transformer would thwart any attempt to test L-N with a resistance of only a few hundred ohms, the warnings would be there.

 

[freddo]

I was fitting Hager ones yesterday and they have a little sticker on them saying you can IR test at the outgoing terminals....

I thought that was great when I first saw those stickers, until I realised you still have to disconnect the neutral as it is still connected through when the RCBO is off. Apparently Wylex now do compact 1 module RCBOs with 2 pole switching where you can test without disconnecting.

 

[Raptor0014]

I thought that was great when I first saw those stickers, until I realised you still have to disconnect the neutral as it is still connected through when the RCBO is off. Apparently Wylex now do compact 1 module RCBOs with 2 pole switching where you can test without disconnecting.

Fusebox do 1 module mini RCBO which are DP.

I normally fit those which is why I think I’ve not normally had an issue. However on this job they were SP.

Just need to remember to read the instructions in future.

 

[mainline]

I always think that a requirement to disconnect something for an IR test is a sign of cheap or poor design. Clearly it is possible to make devices that don't need to be disconnected and unnecessary fiddling around with cables leads to wear and tear, errors and the possibility of introducing faults that the test was supposed to detect.

There are two aspects - whether the device will spoil the test result and whether it will be damaged. Anything that is connected to the mains can expect to see an RMS voltage of 253V and hence a peak voltage of 358V continuously for decades. Film caps ought to withstand 500V or else they are not fit for a noisy environment that can see spikes of a few kV. VDRs will give spurious test results but won't be readily damaged by the current-limited output of the IR tester. The weakest links would likely be 400V electrolytics and transistors in SMPSUs, but I don't like electrolytic capacitors hard-wired into my electrical installation e.g. in sockets with USB ports.

Back in the days of big, tough stud-mounted thyristors in theatre lighting dimmers, there would often be notices on the dimmer modules warning not to carry out insulation tests. Even if the thyristors were rated for 800PIV and the suppression capacitors 500V DC, and the primary of the mains transformer would thwart any attempt to test L-N with a resistance of only a few hundred ohms, the warnings would be there.

It's all down to some little china man selling them the pcb's fully loaded for a £2.00 a go
Oh and we do cases btw for £2.00 with your logo