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Deleted member 105166
Today I have three 13A 30mA RCD plugtop adaptors to test - two around 5-7 years old and one brand new. When testing these I insert a Seaward NTB1 isolation transformer to prevent tripping any upstream CPDs.
The two old adaptors would not energise when connected to the isolation transformer, however they would energise when connected direct to the mains (they were both immediately tripping, indicated be the repeated 'clicking' sound when connected to the isolation transformer.) However the new adaptor energised as normal when connected to the isolation transformer.
I then took the questionable two adaptors and tested them connected direct to the mains and they both gave good readings, tripping within acceptable times for I and 5I at 0° and 180° (also - as expected - tripping an upstream RCD).
Tests carried out with two separate instruments, a Megger MFT1741 and a Kewtech KTD50, gave the same results.
This has left me confused...
- if the isolation transformer was at fault, why would the third (new) adaptor energise?
- if there is another problem with the two old adaptors, then what could that problem be, since they give credible results when tested without the isolation transformer?
Any help & suggestions welcomed.
The two old adaptors would not energise when connected to the isolation transformer, however they would energise when connected direct to the mains (they were both immediately tripping, indicated be the repeated 'clicking' sound when connected to the isolation transformer.) However the new adaptor energised as normal when connected to the isolation transformer.
I then took the questionable two adaptors and tested them connected direct to the mains and they both gave good readings, tripping within acceptable times for I and 5I at 0° and 180° (also - as expected - tripping an upstream RCD).
Tests carried out with two separate instruments, a Megger MFT1741 and a Kewtech KTD50, gave the same results.
This has left me confused...
- if the isolation transformer was at fault, why would the third (new) adaptor energise?
- if there is another problem with the two old adaptors, then what could that problem be, since they give credible results when tested without the isolation transformer?
Any help & suggestions welcomed.
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