And the graphs above, one is a defrost. The other wobbly ones are unit at temp, but can’t give the heat out quite  fast enough so adjusts up and down a bit. No massive deal if it settles down 

Posted by: @sandman1600

↑

I’ll take a look at the buffer tanks and see if I can figure out what’s what. We have a white one and a red one and I think the red one was for the UFH. 

How many pipes go in/out of those tanks? Buffer tanks normally have four pipes but if there's only one pipe per tank then they are expansion tanks, hence separate ones for CH and DHW.

Posted by: @johnr

↑

Posted by: @sandman1600

↑

I’ll take a look at the buffer tanks and see if I can figure out what’s what. We have a white one and a red one and I think the red one was for the UFH. 

How many pipes go in/out of those tanks? Buffer tanks normally have four pipes but if there's only one pipe per tank then they are expansion tanks, hence separate ones for CH and DHW.

 

A pair of similar tanks one white and one red are expansion tanks.  You can tell because they have a filling nipple at the top and only one pipe leading to them.  Red for space heating, white for the DHW and balanced cold.

@davidnolan22 I think most installers do want to do a good job but when we originally had the UFH specced, we got in 5 different people to quote and every one of them varied quite a bit on advice when it came to ASHPs. In the end we gave up and stuck to oil.

This heat pump installation now has come about from a council grant as they want people off oil. So we’re trying to make it work with what was specced for an oil boiler.

I don’t know if it makes any difference but the bungalow is over two levels. Upper level is living space, lower lever are bedrooms and bathroom.

The upper level has lots of high vaulted ceilings and large windows. But yes, the heated area only amounts to 130m2.

The original design document was based on a 50 degree flow and outputs 5554 W.

The same design for ASHP shows a flow temp of 40 and an output of 3192 W.

I’ve looked at the WTC7 panel and can’t see any settings that you’re referring to.

I’ve been in every menu I’ve got access to  is there some trick to access hidden menus that I’m not seeing?

And as @johnr pointed out, theses are expansion tanks, not buffer tanks. Apologies  

https://m.youtube.com/watch?v=GzZsTwT60gA

can you take a picture of the outdoor unit. Has it got 2 fans? 

@davidnolan22 Thanks for that. I wasn’t getting into the service menu. I’m in now.

I’ve attached photos of the last 5 readings as that’s all it holds. If you need to se the graphs for the same period, I can do that.

I’ve also reduced the weather comp to -3/43 this morning to see how it goes. 

@sandman1600  Id be interested to hear how are things going in terms of flow temperature and stability of house temperature?  You may find that, as you get closer to the 'right' flow temperature, it takes two or three days for the house to settle (during which time it will very gently warm up by half a degree or so).  Thus once you think you have found the 'right' temperature it may be possible to turn it down another half or one degree once the fabric has fully adjusted (or you may have to turn it up by half or one degree!

Once you have found the right temperature it will, with a bit of luck, be possible just to leave it.  This is where it does depend on the house dynamics and in particular solar gain, wind and cooking.  Also once you have stablished the optimum flow temp for heating, you can take a look at cycling (which with a 14kW unit is likely) and assess whether it might make sense to heat part time on a time of use electricity tarrif.  It would help for this if you get a feel for how quickly your house heats/cools. 

@jamespa Thanks for that. At the minute it's become an all consuming stress. I just trusted that we were being given the correct ASHP for our needs. If it wasn't for seeing our electricity usage quadruple, I'd probably not even have investigated this deeply. I never expected to have it all so fine tuned that we'd have heat pump perfection but I want it to run as well as it can given what we're dealing with.

It was only installed last week so I'm wondering if I need to speak to the company and challenge the heat pump size.

At the moment, the house feels great. Aside from a couple of rooms, it's more comfortable than it's ever been but I suspect that the electricity usage is still excessive.

I'm planning on reducing the weather compensation temp slowly until we feel like it's as low as we can go. Every time we adjust this, it does appear to cause a sudden drop and then a bit of fluctuation to the flow temperature graph which I'm hoping will settle.

Posted by: @sandman1600

↑

@jamespa Thanks for that. At the minute it's become an all consuming stress. I just trusted that we were being given the correct ASHP for our needs. If it wasn't for seeing our electricity usage quadruple, I'd probably not even have investigated this deeply. I never expected to have it all so fine tuned that we'd have heat pump perfection but I want it to run as well as it can given what we're dealing with.

It was only installed last week so I'm wondering if I need to speak to the company and challenge the heat pump size.

At the moment, the house feels great. Aside from a couple of rooms, it's more comfortable than it's ever been but I suspect that the electricity usage is still excessive.

I'm planning on reducing the weather compensation temp slowly until we feel like it's as low as we can go. Every time we adjust this, it does appear to cause a sudden drop and then a bit of fluctuation to the flow temperature graph which I'm hoping will settle.

Im sorry to hear about the stress, just bear in mind that this is an expensive time of year, you wont be paying for heating at all in Summer, and there is plenty of scope for improvement.  Choosing the right tariff can also make a big difference, but best first to get the basics right!  There is absolutely no reason this should end up costing more than oil/gas to run, and with UFH it should be less. I have radiators running at 42C and mine is costing 12% less like for like than gas.

If it was only installed last week I would definitely go back to them.  Even if they swapped it for the 8.5kW model it would be a massive improvement (actually the 8kW R290 ecodan is particularly interesting as it has a very wide modulation range as a result of having 2 compressors).  You need the evidence on house loss though, but it sounds like you have that.  Its an easy swap, one days work tops.  Im really struggling to understand what was going through the installers minds when they fitted 14kW.  The only rationale I can come up with is that they had one kicking around that they needed to shift and thought they might just get away with it - or is that being too cynical?

Im glad to hear that as you get closer to the right flow temperature the house comfort gets better because its more stable.  Thats the thing about low temperature heating, there are fewer on/offs and reduced temperature gradients, which mean that the house is more uniform.  Its a bit of heating magic that is under-estimated for its effect and a very rare occasion where the laws of thermodynamics work in your favour, because lower flow temperature is cheaper as well.

Those flow rates are very low for the 14kw unit.  Youre currently only needing 3.5Kw to keep your house warm.

One problem you may have is the emitter output to minimum output of the unit.  I've looked online, with mean water temp of 50, the poly pipe overlay system is 79w m2.  Lets say you have 120m2 of actual emitter surface area. That 8.7Kw.  With mean water of 38, which is what we're saying to you, you are going to reduce that by quite a lot and quite quickly you will reduce the emitter output lower then the unit can modulate down to.  There will be nowhere for the heat to go and it will start tuning on and off a lot.   

You may need to run this hotter and in batches, but I'd have a good chat with James or someone that knows what they are talking about.

As for cost: I think your heat loss might be close to 5 or 6 (guess).  So a well set up system on day around freezing will cost 5 x24 = 120w, / that by 3.5 = 34kw a day. at 25p per unit, that's £8.50 a day.  so on days like today where its cold, but not freezing. I'd expect £6-7 for heating, £1-2 hot water.

I would want a very good explanation on why the 14kw unit was deemed suitable if it was my property. 

@jamespa Everything we've done in the house has been by trades that we know friends have used and we've trusted their work. Sadly we don't know anyone else with a heat pump so this was a leap of faith. I'm going to challenge the choice of the 14kw unit but I expect they'll use every excuse in the book to justify it. Now who's being cynical? 

They specced the 14kw from the start and to be honest, I was chuffed that we had the big one because I was really concerned that we wouldn't be bale to heat the house on low flow temperatures. It's only seeing it in action that has convinced me it was possible.

Would it make a difference that we have high (3.3 to 3.7 metres at the apex) vaulted ceilings in most of the living spaces with very little roof insulation? We've insulated under the suspended floors before fitting the UFH but because there's no loft space to insulate, we haven't tackled ceilings yet.

Although looking at the calculations @davidnolan22 has just supplied, I'm guessing they pretty much prove that we don't need anything this large anyway.

@davidnolan22  Thanks for those figures David. The calculations are more than I can get my head around at the minute but if 3.5Kw is all that currently being used and its been 0c/-1c overnight, I can see that 14Kw is way too much. Cr*p.

I want this to run as simply as possible so the thought of it having to fiddle around with running it hotter at times just to avoid the cycling isn't appealing at all.

I've attached some of their calculations from the documents they sent over. Does any of this explain why they specced a 14Kw..?