We replaced our old oil boiler in July 2012 with a Daikin HT. I did a lot of comparisons and had shortlisted the HT and an ECODAN LT. At first I was going for the LT but once I had an accurate comparison I realised I would need very large increases in the radiators so I went with the HT. We have a victorian cottage with solid walls. I increased the loft insulation and fitted double galzing throughout at the same time. We have an open fire downstairs for colder evenings but otherwise the 14KW HT provides all the heating and hot water and is coping well, even over this last week where the average temperature has been zeroC.
In answer to your questions:-
1) There is a significant standby use. The Daikin calculations ignore it which is annoying. There is a continual load of 200W when it is doing nothing - 2.4kWh a day. The hot water in summer is another 3.5 - 4 units per day, though there are only two of us.
2) No buffer tank. We have the Daikin storage tank which fits on top of the indoor unit and looks quite neat next to our large fridge/freezer. We had no changes to the rads.
3) That is a question I spent a long time thinking about. In the end I calculated that the LT would spend too much of its time working at 45 rather than 35 and so the COP for the two systems would be comparable. At the moment with outside temperatures below zero the radiators are running at 70C and the house is nice and warm.
4) I don't think the rules for RHI are set yet but we were successful in getting the full RHPP grant and I believe that means we are eligible for RHI. Based on the performance so far I think our electricity bill will be about the same or slightly less than our previous oil + electricity bill. I am happy with that, I never really believed that there would be significant savings, I'm just glad it has worked out no more expensive. The supply and installation was around £12K, but I needed a new oil boiler, tank and a new flue which would have been approaching that amount.
5) I'm not sure about a deaerator, but they might have fitted one. There is a magnetic particle trap which is deemed essential

Quote Originally Posted by nennyrainbow View Post
Hi
We are thinking of replacing our oil fired boiler with a heat pump in the next few months. We have been quoted by 2 different companies for a Daikin HT and a Daikin LT. Contrary to what you might expect, the HT is coming out cheaper. I have been reading other people's posts with interest and was wondering if anyone can comment on how their HT is performing (wiffola?).

Currently a 3 bed detached with cavity wall insulation, 270mm loft insulation, double glazing. Have planning permission for an extension which will take it up to 5 beds (total 168m2) with underfloor heating in the downstairs part of the extension (34m2). 5 people but water usage probably more like 3 people as bundle all the kids in the bath together for the time being. Have 2 (will be 3) woodburners downstairs which we use during winter to supplement heating, particulalry in winter. And large southwest facing windows. We also have 2.85kW solar PV.

The main questions I have are:
1) How much power does the HT use on standby in the summer when only used for DHW? I have heard it's in the region of 100-200W for older models but don't know if this is true for newer models and Daikin don't seem to publish the figure anywhere. Is there any way to reduce this?

2) Did you have a buffer tank? We don't seem to have been quoted for one but I have read on here and another forum that it's more or less essential with the HT. And did you have to change any pipework to rads?

3) Does the HT cost the same to run as the LT if run at the same temp?

4) Does anyone know if the HT will be eligible for the RHI if it ever comes into being? Published COP for the 16kW model is 2.88, although our SPF was calculated as 3.1. Would be nice to think that we'd get some of the money back over the cost of installing a new oil boiler.

5) The installer recommended fitting a deaerator to improve efficiency - any ideas on this?

Any comments / feedback much appreciated. Preferably in layman's terms as I have no background in this technology!