RCD polarity testing

[Desmond Downs]

Hi, I've recently done a PAT course after the large company I work at discovered we have a Deltapat 3309 kit tucked away.
I'm actually an automotive electrician maintaining the electric forklifts and pallet shuttle 'robots' at the factory but they decided to expand my skills which I appreciate.
I was also assigned to make up a short "quick guide" to using the unit once I learned how.
While going through the testing procedures I saw that a "Portable RCD [power latching switch]" does not require a polarity test while a "Portable RCD - EPOD type" does have a polarity test.
During the course I had questioned why the RCD we were testing failed a polarity test and I was told that we can't do a polarity test on an RCD because it needs to be connected to power to close the contacts. My question then is why the EPOD type portable RCD can do a polarity test when it seems to be the same thing just with more power outlets?
Thanks in advance.

 

[Desmond Downs]

Ok, so I found out that the RCD on the EPOD type is the same used on houses, so is always continuous, while the PRCD leads need power to be able to engage which is where the difference comes in.