help on home made heat pump

hi folks,

i am based in Ireland and at the moment i am building my new home a 250 sq meter story and half domer. I have been looking at air to water heat pumps for the underfloor heating side of things on both floors and also dhw for showers and bath there is 3 ladies in the house so lots of hot water wasted. prices of a 13 kw air to water heat pump are around €12,000 to € 15,000 c/w a 300 litre storage tank. After picking myself up from the ground after receiving the prices i said what is really in these units that make them so dear, i have decieded that i am going to build one of these unit. So lads and lassies can some one point me where to start sizing this.

i hope to use a copeland scroll ( what size), gas R410A, plate exchanger ( but what size) a 300 litre hot water sorage tank ( i will have solar as well to heat water in summer and 5 kw back boiler on a stove to help in winter. Any and all advise welcome and i know i have overlooked somethings so please be kind with your comments.

thanking you all in advance Engineer Lowe

Hi engineer lowe.
Welcome to the forum. First let me save you on wasting that hot water from the shower down the drain. If you have room below the shower you can install a GFX gravity feed exchange. Very easy to make - use 5/8 cu tube and form it around a 4" or 5" steel tube (you need a little heat from gas tourch) and fill with dry sand to prevent crimping. Make it about 2' long and remove steel tube and sand. Place inside a plastic drain pipe and there you have it. Feed cold tap water into bottom and the outlet at top goes to the water heater. This saves in practice 25% of the heat - reducing the size of heater required. The other guys will help on the heatpump side.

You should be able to get a heat pump for about half that price!

For high temp DHW R410 might not be the best gas to use on the system.

try googling ecoairsource based in hull. have just put four of these in at a nursing home, up to 65 degrees on single phase and we had no trouble at all. Easy life. Also done a stone cottage in north yorks with the same. No probs. For the cottage we paid £2750 for the heat pump and £1200something for the 320 litre DHW cyl, and about £400 for a buffer. Can't be bad.

Daikin wanted the price of a house for the nursing home job as you can imagine. - and last time we rang daikin after a heat pump packed in, we couldnt get a call out for 2 weeks, and they acted like they were doing us a favour!

Is the HP in Scotland so expensive?

Why not put a hotgas heatexchanger to produce hot tapwater?

To get 12kW heat try calculate COP 4 at tops that gives you a 3 kW compressor with 9 kW cooling power.

The heatexhangers should be calculated by your supplier or do you plan to make them yourself as well?