Newby to the forum so apologies if I'm putting this in the wrong place.

We are trying to get a heat pump installed under the grant system now available to us here in n Wales.

It is a long and frustrating battle as the would-be installers have talked a lot but given us no real technical info as to choices, what actual equipment will be supplied etc.  As a semi-retired engineer all I see is a disastrous way to step into a project of this type.  They want to throw in an 8kW Samsung heat pump, a pre-plumbed cylinder, change all our existing 15mm pipe to 22mm and make all the T11 radiators T22.

The basics of that seem to be OK BUT our biggest bugbear is that we have a perfectly good H/W cylinder already, fed via a Dunsley neutraliser from our existing lpg boiler (Potterton P50e) with an input from a back boiler too.  Now I know the purpose of this grant is to get us to drop lpg so we are fine with disconnecting the Potterton  and locking it off (the grant system won't allow hybrid installations). However we aren't happy with having to have that pre-plumbed cylinder and the space it takes up when we already have a perfectly good cylinder of our own.

Yes, I know the coil could be too small so hot water heating time would be longer and finally we get to the question: does anybody know why we can't take the hot water feed from the Samsung 3 way valve into a heat exchanger and take the output from the heat exchanger (pumped if necessary) directly into the hot water connection on our tank? It does mean some cutting and capping of the existing connections and completely isolating them from the Dunsley too.

Even better we would like to take the heat exchanger output into the Dunsley using the back boiler connections which are no longer in use as that would mean almost no pipework changes.  I know we can't plumb the 3way direct to the Dunsley at the Samsung side is pressurised (to keep out "contaminants/foreign material" according to their installation manual, so as to avoid heat exchanger corrosion in their heat pump they claim).  So far all I've got from the installers is they have checked with some mysterious "coordinator" and he/she said it doesn't meet specification yet we've not seen any "specification" to prove this.

I am still trying to find a way to put this question direct to Samsung but their very big and very glossy site does its damnedest to make doing so impossible.

Any thoughts/ideas/suggestions?

Regards

Peter