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? 

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

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???

RCD functional test, trip time at rated current, polarity check, loop impedance, fault currents, bonding etc all  recorded on a minor electrical installation works certificate with a full description of what the certificate covers only (Replacement of RCD). 

I think that you have to do what is reasonable.

I would say that you test upstream of the replacement RCD, but are not obliged to test downstream.

If you were to test the lot, even at mate's rates for a family friend, you really could open a can of worms. The property could potentially become uninhabitable.

The MEIWC does not exactly help - see the paragraph at the top of page 514 of the BBB.

I would have thought the work fell under  replacing individual item of switchgear- replacing single protective device 

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

But was the main (downstream) CU main switch OFF at the time (or all the fuses pulled)? A consistent slowness in apparent RCD operating times seems a little unlikely if it's just due to it sticking - in my experience they tend to free up after a few operations. On the other hand, many loads (whether capacitive or inductive), if connected at the moment of the test, can result in the voltage on the load terminals not collapsing as promptly as expected - fooling the tester into thinking that the RCD hasn't opened yet when in fact it has. There might be that the RCD is good after all - which presumably would make life simpler all round.

   - Andy.

Seconded - before condemning the RCD, that should be checked with all loads removed- the meter can only look for voltage to fall away, it cannot know if the contacts have opened on time, but the voltage persists due to something elsewhere - things with motor-run capacitors can be especially odd at this.

Or you may already have done that.

An RCD that has not been operated often, sometimes needs a few shots to polish the moving parts, and gradually speeds up again, but total failures are more commonly never trip or occasionally trip without a fault.

Depending on the cost of the thing it may be simpler to replace it as a  lump.

Mike.