Posted by: @marzipan71

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Would it matter that the UFH is all brand new with new piping, but the radiators are using the original 12 or 15mm pipes?

Pipes smaller than 15mm are going to be tricky to cope with relatively low-temp water. They're usually lumped together under the heading 'microbore'.

When BEIS installed ASHPs in hundreds of trial houses over a year ago, any properties with microbore had to have it replaced.

I suppose you could super-insulate them, assuming they're not below the floor. But the general idea of a HP with UFH is to use low flow-rates. Doing so using a particularly small tube makes it difficult to see how you can deliver the required number of joules to the radiator!

Hi @transparent yes even those DAB pumps in my photo are made in Italy. We are also surprised how much stuff we buy at the DIY stores - plumbing, electrical - here is actually made in Italy. I also imported one wood stove from the UK (pre-Brexit) and one from Poland through ignorance really as there are some fabulous wood burning stoves made here. Reading through the threads in the forum I don't feel so bad about feeling that many of our decisions (or decisions made for us) I'd change if we were ever to undertake a major renovation again (and that's not happening for a good few years for the sake of my sanity!)

Posted by: @marzipan71

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Thanks @transparent they are some very useful alternatives to consider. I will re-do the insulation this winter as its been bothering me that its not up to scratch (or regs). For background, we are expats living in Italy so the un-lagged pipework is possibly entirely normal here (I've seen things that make my non-professional hair curl so heaven knows what an expert would make of things...). Anyhow, trying to find out anything here about heat pumps is next to impossible and this forum is proving a lifeline for us 😀

Hi Steve,

You may be smiling now, but wait till you get the bill!!! 😎 

Posted by: @transparent

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Posted by: @marzipan71

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Would it matter that the UFH is all brand new with new piping, but the radiators are using the original 12 or 15mm pipes?

Pipes smaller than 15mm are going to be tricky to cope with relatively low-temp water. They're usually lumped together under the heading 'microbore'.

When BEIS installed ASHPs in hundreds of trial houses over a year ago, any properties with microbore had to have it replaced.

I suppose you could super-insulate them, assuming they're not below the floor. But the general idea of a HP with UFH is to use low flow-rates. Doing so using a particularly small tube makes it difficult to see how you can deliver the required number of joules to the radiator!

Yes our installers/ builders didn't seem to consider this and I only learned of the radiator pipe size issue post-install (and post-payment). We did have a heating engineer calculate the wattage requirements for the rooms where we have radiators installed, and I bought and they installed aluminium radiators which (supposedly) delivered those reqts at T40. I've not tried them out at anything like that temp - as I've mentioned we were running the ASHP system like a boiler for these past two winters with consequent very high electrical consumption and general perceived dissatisfaction with the system as it stood. The radiator pipework is insulated as far as I'm aware - seems like 1cm insulation - and I'm sure this is very far from super-insulated - pic:

Plumbing schematic for this system is figure 6.1.1 for anyone who's interested.

Posted by: @hughf

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Absolutely you can run the mixed UFH circuit at a different (albeit always lower) temp than the unmixed circuit. The blending valve that you can see in your photo has an adjustment knob on it, this sets the flow temp for the UFH to a fixed value, irrespective of what the weather compensation is doing to the flow temperature into the header and therefore into the radiator circuit.

It's perfectly possible that the system is wired so that when the UFH pump is running, the rad pump is not running - we don't know how this is wired.

You've got a daikin iirc? I don't know if their controller supports full control of both mixed and unmixed pump groups.

 

Hi @hughf we have the Daikin remote controller as they call it which allows us to change the field settings etc., then two in-room 'smart' thermostats. The field settings on the Daikin controller allow for multiple set point modes where a 'temperature reducing device' is installed (what is that? its not just a blending valve, is it?) then the installation manual has lots of diagrams with different set ups that reference different spaces with different temperature set points, and a separate DHW set point. I don't think that's what we have installed - my recollection from the plumber was that we set a single temperature for the water, and if we wanted to say have the rads at high temp and the UFH at low temp, the blending valve on the pump would blend in cold water to reduce the leaving temp of the water for the UFH (which I assume is a very wasteful way to run the system). I don't think that is the same thing as what's illustrated in the manual. We have no idea how its wired up either I'm afraid so I can't tell whether the rads not running when the UFH is running is by design or just coincidence. Either way, I think my aim is to try the weather compensation curve out using as low temp water as we can to try and increase efficiency and reduce our (grid) electrical consumption. For info, our relationship with the builders, plumbers etc broke down (co-incidentally just after the final payment was made) so I don't have an option to talk with them unfortunately.

I've attached the installation manual referenced above - the multiple set point control section is from p29.

@marzipan71 Wow, that's quite the complex beast isn't it. Two F-Gas circuits, an r410a to r134a heat exchanger and another compressor inside the indoor unit. I'll need a bit more time to look over the manual and figure out how it's wired up.

Probably the most complicated system I've ever seen...

Posted by: @hughf

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@marzipan71 Wow, that's quite the complex beast isn't it. Two F-Gas circuits, an r410a to r134a heat exchanger and another compressor inside the indoor unit. I'll need a bit more time to look over the manual and figure out how it's wired up.

Probably the most complicated system I've ever seen...

Hmmm not entirely sure that's something I wanted on my CV...oh well, it is what it is and hopefully it can still keep us warm this winter! 😀 

Posted by: @marzipan71

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... and the UFH at low temp, the blending valve on the pump would blend in cold water to reduce the leaving temp of the water for the UFH (which I assume is a very wasteful way to run the system)

No, that's not wasteful. And I'm unsure whether you meant to say that the the blending valve uses 'cold water'. It would be more usual to blend in water that's from the return pipe of the UFH.

It's a pretty common way of running UFH pipes beneath wooden floors, for example. They mustn't be fed with water that's hot enough to warp them.

It also means that the water being sent back to the HP (or boiler or whatever) is at a lower temperature. In effect the heat has been removed from it twice. The lower the HP return water, the better is the efficiency.

Hi @transparent thanks for this - yes I mis-spoke about the cold water - it may sound a bit daft but I didn't even understand until relatively recently that the heating part of the system was a closed system - so yes, now you've explained it I get that the blending valve is mixing lower temp return water - that makes perfect sense. Thank you!!