I’m not really sure what you’re talking about Shaun. Have you logged onto gas Safe website recently. It’s all there mate. AR and ID. No mention of NCS because it’s gone Shaun.
Could be a wiring fault, where the pump and boiler get switch live from the stat, not from the auxiliary circuit of motorised valve (2port) grey & orange
Good bit of kit, but So expensive though! Couldn’t you just get a cold water accumulator?
I fitted a Stuart Turner ‘Mains Boost’ a few months back. I phoned Stuart Turner and with a few simple measurements and questions they were able to specify the correct product. Very helpful company and...