Hi DJ
Will do. give me a couple of days maybe weekend and I'll reply
Short answer is I am very happy with it.
I wrote most of my experience in an earlier post and still have the same view.
There is a lot on the net about inverter pumps vs single speed pumps. A lot favour inverter pumps but they cost a fortune and in my opinion have a lot more things that can go wrong. Think about how long a single speed fridge compressor runs, starting and stopping for years without problems
My view is get a fixed speed heat pump and as big a buffer tank (DHW Tank, Thermal store) as you can get. Run the UFH from that and have the Heat Pump start/stop from the tank temp about 10 degrees apart. That will stop any short cycling.
Mine is connected so the hot return to the 350 litre tank is about 250 mm off the bottom and flow to the Heat pump was about 150mm directly below that (tank is 2000mm). I thought that was short circuiting, so I changed it to come off the return from the UFH, which is at the opposite side about 150mm from the bottom. So now the cold to the Heat pump is about as cold as it can get which helps efficiency. When the UFH starts shutting down the flow comes back from the tank until the tank heats up and the heat pump shuts down. So start/stop is greatly reduced.
During the colder weather <5 degrees, it never stopped running, it still heated the tank up, be it all more slowly.
It gets the tank up to about 50 degrees which is fine for showers but needs an hour with the immersion heater on for a decent bath….we’ve got a big bath…
I haven’t got the solar system working yet so can’t comment on that as a heat input to the tank.
I chose an 8kw in the end to slightly undersize the system which works OK but 10kw might have been a little better, nevertheless the woodburner back boiler helps when it gets colder. I am most likely going to get another 8kw and run it in parallel, that way when it gets colder it can assist and I will have a standby unit in case one fails.
I think these dream heat pumps are OK but as Brambles said earlier the spares back up is appalling. I needed some spares… something I did, not because it failed (why do we sometimes do stupid things doh :-/ ) but had to wait far too long and they are the only supplier and don’t pick up the phone so very frustrating.
That said when they are running they are very good, I left the heating on 24/7 setting back the UFH at night by a couple of degrees only and it used about 30kw a day. CoP I haven’t work out but even when outside temp was about 7 degrees the temp across the pump was 8 degrees on one occasion so was impressed by that.
You cant beat a nice big Thermal store in my opinion. Connect a heat pump at the bottom for base load, then you can get heat from solar, boiler, immersion heat with iboost or wood burner all adding to a big pot of heat to do what you like with. Also mine is vented, I don’t like unvented cylinders, like having a big bomb in your house and they need testing every year, what’s the point?
There’s a lot of comment about heat pumps are only effective in well insulated houses. Because of the lower temp they are slower to bring the temp up so there is an element of truth in that but at the end of the day a heat pump gives heat into the house like any heat source. If the house is getting cold then you need to put more KW in, that hasn’t changed so get a bigger heat pump. Mine is an older house and this is the reason why I left mine on 24/7. However you do need larger rads and definitely works better with a well zoned UFH system.
Incidentally flow to the heating system is also at the bottom about 250mm up so takes full advantage of the Heat pump and leaves the rest of the tank to warm up.
Happy to send pics if anyone wants.
