We currently have an oil fired vented ch system supplying a 150ltr HWC, 5 double radiators and 9 singles. The boiler is a Grant 15/26 condensing boiler. The system has two pumps, one on the feed from the boiler, one beyond the zone valve in the ch circuit. There is an open fire with a back boiler connected via a neutraliser. The HWC is permanently connected to the water from the neutraliser/boiler, i.e. there is no valve in that part of the circuit.
We would like to remove the back boiler and neutraliser and turn the system into a sealed system. At the same time we would like to remove the zone valve and use a mid position valve so that we can have the CH on only - at present we have to have the cylinder full of hot water before the heating warms up properly.
My question is what to do with the second pump? It is a relatively large system and the HWC, neutraliser etc are all in the loft, so the water goes up to the loft before going back to under the downstairs floor (where the second pump is). I suspect the second pump is useful, but how would I wire it in?