JohnMo

I know when I was running a boiler last year (Atag A325ECX), the flow temp was set to 36 degs, the pump speed was being modulated by the boiler and it set the dT at about 6 degs. This also coincides with the part load performance data on the datasheet (30/36). But also think min modulation kW allowed is also considerably higher than the 50/30 flow temps. Think it must try to keep the return temp at 30 and above, but just reduces the dT to accommodate a lower flow temp set point.

Fundamentally a heat pump runs as detailed below 1. you or it sets a target flow temp, depending on fixed flow or a compensated flow temp. 2. Heat pump starts and monitors return temp and delta T 3. First it maintains delta T, so if you have a target flow temp of 40 and delta T of 5, but the return temp is 25, it will flow 30 degs until the delta T reduces below 5. As the delta T reduces the heat pump add more flow temp until it gets to 40 degs, while maintaining the delta T. 4. Once at 40 degs the ASHP will modulate down from full power to a lower setting to maintain, 40 deg and the delta T. Two things cause a slow ramp up, the heating system has been off for too long, or you are trying to bring temp up too quick. How exactly do you operate the heating? Do you have a buffer, if so how big? How long does the DHW heating cycle take? How many loops of UFH do you have?

Sounds rip off, my Triton fan/motor was £276, incl vat and delivery. I thought that was expensive.

Looks to be a split unit and only the outdoor unit being provided. You will need a refrigeration engineer to install also.

I would just go elsewhere for a quote. I have panels on a hill 70m from the inverter, it's then another 20m to house, plus panels on the roof again about 15m to the inverter. Mine are all coupled to a GivEnergy All in one. Works great.

Was driving the UFH from a heat pump, and flow temps needed to be higher than I was prepared to run. Now use a fan coil, way better.

Not sure about that due to contamination for later use. Plenty of cheap cylinders on gumtree.

More like flow temps in the 40s, I had some in my well insulated summer house (now ufh decommissioned because it was rubbish), high 30s flow room below 16.

You have dT 25 radiators, that means the difference between room temp and radiator temp, flow and and return dT would be in the region of 20. It's not

A better heat geek video on how to do your UFH connections https://www.google.co.uk/url?sa=t&source=web&rct=j&opi=89978449&url=https://m.youtube.com/watch%3Fv%3DK_OWE2dJht0&ved=2ahUKEwj57Zj31OGEAxWqQUEAHROIC2cQwqsBegQIDhAG&usg=AOvVaw3Kv9nfBIKtwsPqVzMirE55

Only thing I would say is once signed off you are likely to reduce flow rates. Because building regs rates tend to be a bit excessive. Even with our rates reduced by 30% we are still dropping to mid 30s relative humidity when it's cold which is getting a bit low. I would be tempted to go with the smaller unit.

Certainly doable, throttling not really, but the heat pump will modulate to reduce output. Depending on ASHP size and heating duty and system volume a buffer/volumiser is going to be required. A possible solution would be a fan coil these run on a just about fixed 35 degs water temperature. So easy to set up, we have one in our summer house (used 365 days a year) and UFH in the house, all run from a single ASHP. It was a bit of a learning curve setting up, but works well now.

I got mine from eBay. It's a matter of doing your due diligence. Find the manual on line and as much technical data as you can. Do other manufacturers rebadge the unit (do a Google image search) you are looking at. Mine was from the original manufacturer, but was also rebadged by Viessmann. You may not get a warranty. If you building to a half decent spec of house you should only need a small unit. Many retailers online are very competitive on pricing.

I worked with a guy that used to use Wikipedia as a reference tool, for marine engineering project He started quoting something he found on there in a large meeting, unfortunately the information was duff and he was nearly sacked. Internet is awash with rubbish information, you need to do your due diligence to verify stuff.

I don't bum pluck numbers, CoP numbers for different flow temps and outside temps. With this I will bow out and let you dream on.

Wish it was true. It would be nice, my 57 tonnes of concrete floor and about 65 tonnes in the walls would beg to differ.

So confused - what are you doing now and trying to do. What has the heat pump got to do with your boiler?

And what benefits are the changes making? If you are flowing a high temp into UFH most of the flow going through the pump is recycling with some hot water being introduced. They provide a hydraulic null point in the system and hydraulic separation so pumps do not see each other. For UFH the mixer does that already, so adding a cct to an already working system adds no value.

Not sure where that snippet came from. An ASHP uses a fan to make high winds local to the heat exchanger to ensure good heat transfer. General wind make no difference to frosting of the coil.

Unless you want to cool also, then efficiency drops. So working the argument through Biggest difference between the OP and the reference property, is the reference property only did DHW for around 1 hour per day. OP will be heating, cooling and DHW, so a different use case. So let's assume the sun exposed, heavily build stone area that's designed to trap the sun's heat, ASHP installed close to a south facing wall to get max perceived gains. Heating by ASHP running with an internal thermostat. Typical nice winters day, cold overnight, zero degs, bright morning, sun out and air temp increases to 7 degs, then by 5pm temp starts to drop quite fast. Overnight the stone area reduces to match ambient air temp of zero, ASHP gets no negative or positive effects from this. Morning air temperature start to rise, stone area remains at close to zero for a prolonged period as sun not high enough in the sky to have any heating effect. ASHP in an area below air temp, negative impact on CoP. Late morning to late afternoon, sun out and heating stone, sun also on house windows warming house, heating clicks off. DHW clicks on and heat pump starts at 2pm. Localised area could warm air flow to ASHP by say 5 degs (if you are lucky), giving a 0.3 CoP benefit. Heating benefit zero as heat pump is off. Early to late evening, temperature outside drop back, some residual heat in stone, but the benefits are marginal, CoP gains for a short period but would guess almost nil. Cooling case case almost the opposite, sun out you need cooling, ASHP is hot sun trap, EER (CoP when cooling), takes a hit. When flowing 12 degs changing air temp from 20 to 25 has a 1.2 negative impact on EER. Another negative is weather compensation becomes screwed up, if the temperature probe becomes exposed to artificial low or high temperatures.

Assume the UVC is via a diverter valve and it will only have when a call for heat. So DHW or heating never both together. Your LPM flow rates sound very low especially for the UVC and your UFH. If you need 10kW into the floor with dT of 7 the flow is 20l/min. So then you only need to look at rads and UFH. The issue is likely you will have two distinct flow temps for your heating, UFH and radiators. So you need a mixer on the UFH, so you also need a pump on the UFH. Why? All depends how you plump as long as the return to the boiler always exists there is zero issue. Just follow the attached. CCT WORCESTER BOSCH.pdf

Depending on what's installed now, adding fins or extra panels keeps the radiator size but increases output as if the radiator is bigger. The lower the return temperature to the boiler the better efficiency you get. Also see https://www.heatgeek.com/does-my-pipework-need-upgrading-for-a-heat-pump-with-cheat-sheet/

Although heat pumps modulate, that isn't the only means they match output to heat required, they also cycle. Your cycles really need to be a minimum on time of around 10 minutes. So for example if your heat pump modulates to 6kW, you need an engaged volume of water of around 100L. This can via limiting zones (no small zones) or via a volumiser.

A bit a write up here https://www.linkedin.com/pulse/does-heat-pump-work-better-its-sunshine-graham-hendra

It certainly would be heated, the air used to provide the heat passes through a heat exchanger not the casing. Either way take or leave anything said here or anywhere else. You going have so much excess solar not sure if will make a difference what the CoP is anyway. I've only around 7kW in the north of Scotland and my battery was full and cylinder heated by immersion to 70 degs by 3pm on a sunny day in March, you could be doing that most days of the year.