feedback on Daikin altherma HT please

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!

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:

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Originally Posted by nennyrainbow

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!

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Sorry - a miscalculation on answer number 1 above. The Daikin HT uses 200W on standby which is 4.8kWh per day. The hot water is another 1.5 - 2 kWh per day so in summer it is very inefficient. It's a good job my PV panels provide most of that 200W load!

I've fitted a few of each with good results.

Using your Sq m at an average 70w/m2 the LT Altherma (size 16) comes out in the Simulator software at an estimated annual energy cost of £1518, whereas the HT (size 11) comes out at £1724.
A difference of £206/yr or £2060 over a 10 year period.

Both systems have different benefits and drawbacks and you should consider which one fits your requirements - not just the cheapest price.

For LT
Benefits: Less expensive to run, lower flow temps for underfloor heating
Drawbacks: Circuit temp max at 55C, Radiators may need upgrading

For HT
Benefits: Higher flow temps without electric backup, existing radiators can be used
Drawbacks: More expensive to run (2x compressors)

For RHI, you need to check on the MCS Equipment List to see if your product is listed
Your installer must be MCS registered for your installation to be eligible for the RHI....when it comes out.
You can read up about the RHI here

OP

We have run a 16kW HT since 2010.

House is 3 storey 6 Bed 4 Bath and 308m2.

Good insulation and DG windows.

2 Adults 3 Kids, 2 Showers and 1 250 litre Bath a day on average.

Keep house at 22 degrees C on 3 x programmable thermostats on each floor.

Running cost over last 2 years comes out at just under £2K

HiWe'll have our HT ( 14kW ) for 3 years now in April... And all I can say that we choose the right thing. House 150m2, 2 small kids ( lots of warm water consumed ).We kept the "old" high temp radiators, and set the "weather dependant" outlet temp to vary from 45-max 60C .Keeping 22C in the house... even if it's -20 outside.And the power consumption is 7400kWh / year ( heating and warm water ).I'd say that as a replacement of old boiler and together with "old" type radiators... Altherma HT would be the one to have. ;)

We have installed alot of LT and HT.
Every system we install is metered so our annual maintenance contracts collect running costs.
Both are very good. HT does use alot of standby power.
Would not use HT tank. Use a standard unvented tank with an immersion heater
The ERLQ models are much more efficient if designed for max flow 40 degrees. We always recommend rad upgrades.
If your heating system uses micro bore or old system- make sure you flush and flush and flush the system before you install either LT or HT. You will have nothing but pain and flow head aches- HT and LT are all inverter pump set to dT control. Flow must be spot on.

Quote:

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Originally Posted by sinewave

OP

We have run a 16kW HT since 2010.

House is 3 storey 6 Bed 4 Bath and 308m2.

Good insulation and DG windows.

2 Adults 3 Kids, 2 Showers and 1 250 litre Bath a day on average.

Keep house at 22 degrees C on 3 x programmable thermostats on each floor.

Running cost over last 2 years comes out at just under £2K

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Hi

2000£ doesn't tell me much:)
Would you have any record of annual kWh consumption by the HT.
How much do you pay for 1 kWh in UK... the total cost i.e kWh used / bill ;)

Ande eventually... how much do you need to pay for a complete HT set in UK?

If I may ask of course :)

Quote:

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Originally Posted by nec0310

We have installed alot of LT and HT.
Every system we install is metered so our annual maintenance contracts collect running costs.
Both are very good. HT does use alot of standby power.
Would not use HT tank. Use a standard unvented tank with an immersion heater
The ERLQ models are much more efficient if designed for max flow 40 degrees. We always recommend rad upgrades.
If your heating system uses micro bore or old system- make sure you flush and flush and flush the system before you install either LT or HT. You will have nothing but pain and flow head aches- HT and LT are all inverter pump set to dT control. Flow must be spot on.

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Very interesting.

Based on your metering, what sort of COPs are you seeing either seasonal or instantaneous (e.g. at 7 deg C rated temp or lower temps)?

Are you only installing with u/f or also with HT rads? If so, what has user experience been?

Thanks

I have put some experiential information on the other HT thread that might be of interest to anyone viewing this thread.