replacing diverter: no earth on terminal block, replace cable at timer? also: no isolating valve?

[Berk]

I purchased a Honeywell V4073A to replace an old Potterton PMV3 / Sunvic type valve and actuator. Before I fully disconnect everything I want to be check a couple of things.

As predicted by 45yearsagasman, the Sunvic does not have an earth wire, but it turns out that neither does the terminal block it is connected to. Pretty sure this was all originally wired by British Gas so I assume it's all correct as it should be, but would I be right in thinking that in order to correctly install the Honeywell I need to replace the cable between the programmer and terminal block with a 5 wire version that includes the earth? e.g. Screwfix 68083? I'm guessing the difference is the Sunvic has the plastic housing which doesn't need the earth, but the Honeywell is metal and must be.




Also, while I'm busy wrapping my head around where everything is connected, I wondered if there should be a a valve somewhere on the pipe feeding the A/B port so that the flow can be shut off while the diverter is replaced?



I could put a valve in the system somewhere if there isn't one already, pretty sure I have a couple of 22mm full bore isolating valves amongst my spares (Screwfix 351944) if that would be suitable?

Thanks!

 

[polesapart]

Do make sure that the G/Y sleeved conductor that so clearly "has to be" an earth wire really is.