40 years old? Wired in PVC/PVC sheathed cables? What trip time at x1? 

360ms at 1x. The RCD seems to be also somewhat sticky with regards to the test button. Pvc cable, copper black and red....

So you have assessed the earthing, bonding. Will you be increasing the maximum demand ? A MEIWC may be issued to certify a ‘like-for-like’ replacement of the lights & RCD. Is There a CPC in the lighting circuit? I would have thought so.   

I would give him a price for replacing the RCD first.

Main RCD device is installed upstream but exceeds the time stipulation. At 5x about 236ms.

Is it a 30mA device? and was it tested with everything downstream switched off?

I don't see any immediate need for a new CU - BS 3036 fuses are usually still compliant with BS 7671 requirements. Even if you decide to add SPDs and/or upgrade the RCCB, that can be done alongside the existing CU as long as space and aesthetics permit.

   - Andy.

There is CPC in all the lighting circuits.

The RCD is a 30ma and tested at the board.

Do I subject the installation to an IR test. My anxiety is that if it fails the minimum 1Mohms, it becomes problematic. Do I let sleeping doga lay or open the pandora box? 

I assumed the RCD was remote to the board ? So you can’t just replace the RCD ? You would have to replace the consumer unit ? 

Sorry. It is separate to the cu. In its own enclosure but meant to say that RCD test was on its load side and not via a socket.  .

If you suspect that the Residual Current Device is faulty and have conducted the necessary tests in accordance with Guidance Note 3, I recommend providing a quote for replacing the RCD before proceeding with any additional work

If you can replace the RCD and leave the fuses as they are, do so, and  ideally do a wander lead earth test (R2 check) and then swap the light fittings,

I'd suggest if you do any IR test at all, you only do it on the lighting circuits or at reduced voltage L+N to E  as finding and removing all the legitimate loads between L and N is a mugs game and there is a risk of damaging something that got left plugged in by mistake,

Mike

I would welcome your views as to what are the necessary checks for the RCD change. I hope its Not that battery of all the tests that you would do for a consumer unit change? Ze is done, Ipfc is good, bonding visually checked, will do a R2 wander lead. Any others for the RCD change?? With the light change R2 and IR on the lighting circuits if I proceed with the changes???