I am moving and the new house that has tank in the loft for a vented cylinder. I plan to change it to a thermal store, preferably unvented. Since I prefer things DIY, my understanding is that you do not require G3 certification for an unvented store if you use a plate exchanger, but you do if you use a tank with a DHW coil greater than 15 litres.
Is that correct?
Is that correct?