I agree, definitely no C1, failing to trip on button or >300mS with instrument test at 1xI∆n I would give a C2, but absence of evidence of biannual function test (common in domestic environments) or instrument test within 5 years (max recommended industrial EICR period) or missing labels is surely only a C3 at most.

Definition of C2 :-

C2 - Potentially dangerous - urgent remedial action required.
This means that this fault is not immediately dangerous in the same way as a C1 code is, but it could quickly become a hazard in the future.

Even if due to production constraints, they couldn’t test the RCD/RCBO, that does not indicate that it is potentially dangerous and need urgent remedial action.

It would surely have to be a C3 at most?

Thank you, this echoes my thoughts on the matter. 
Photos for example evidence of test in 2018 and 2020, EICR gave a C2 for absence of evidence of RCBO testing.

Second image shows, tested recently and indicates trip time.

That's fine, but where is the notice please?

ETA: Don't RCDs come with a copy of the notice, so there shouldn't be any difficulty installing one.

Incidentally, they used call for testing the test button quarterly.

The notice is on the outside of the door as there isn’t any suitable place inside/around the breakers. The C2 wasn’t about lack of labelling (which would be C3)

On the EICR it was stated that there is no evidence of periodic testing of RCD/RCBOs and thus was recorded as a C2.

What then is the remedial action that must be taken to rectify this potential danger?

Taken word for word from EICR:- 

“Introduce recorded maintenance test and inspection programme”

We have started recording trip times every three years and recording function tests every 6 months on a spread sheet. We have about 500 RCD/RCBOs on site. Not counting RCD socket outlets in control panels for programming use. 

I have no issue with recording trip times and functional tests, I just don’t think the absence of them is a C2, I doubt anyone would give a domestic EICR a C2 if there was no evidence of functional tests being carried out. 

But why would a "User Test" be coded as you listed in your comments?

I suspect you and JP are at cross purposes with the words and are actually in agreement. I think JP actually said "the user test device" rather than "user test" - i.e. he was referring to the T button - operation of which should be checked as part of ordinary BS 7671 RCD testing (col 29 of the schedule of test results).

  - Andy.

A very good point!

Press the test button and record the result, but hang on - you just did that as part of your EICR. :-)

The instrument tested at I delta n is the softer test than the test button. The user test facility tests the RCD at 2 x I delta n so should be done after the instrument test. If it passes the instrument test but fails the T button test then a C3 as the user cannot carry out the regular user test. Not unknown as the test resistor or sometimes goes open circuit but the RCD operates on a test with a test instrument.

JP

AJJewsbury said:

Interesting one. BS 7671 recommends biannual RCD testing

Indeed interesting ... some RCDs have "test monthly" printed on them by the manufacturer.