SimonD

Hang on, serious alarm bells going on here. What has your installer done? The installer cannot complete a proper system design without a full heat loss calculation. Whatever anyone else tries to tell you, you absolutely need a proper room-by-room heat loss calculation to inform your system design. To plug my own tool again - you, or your installer can produce a proper one to current standards for free at openheatloss.com Not at all Nick, rooms will by their very nature have varied heat load requirements due to lots of things like exposed area, perimeter length/area ratio in floors, size and shape and they all need sizing according to their individual needs, otherwise you'll take a hit on system efficiency and comfort, even if you design for 21C across the whole house.

Maybe I've missed something but that linked document appears only to outline a revised Cfd arrangement. Where is the gas marginal pricing de-linking mechanism? And for taxing extra-ordinary profits? Why not just cap the profits in the first place?

Is it that Panasonic are not being helpful for him or for you? So far my experience of Panasonic tech (I'm a Panasonic pro installer too) has been very good, and when I needed an extra push for some assistance, my rep was amazing and followed through on all promises. So I'm a bit surprised to hear this. The problem is that we really need to know more details about the design issues and what they're referring to as much more power, which will depend on the design parameters too.

It really depends on your budget. Stiebel Eltron, and Nibe both do heating and cooling and are very nice units. Viessmann currently requires an indoor unit, but also very nice and some of the best controls in the business. My Viessmann rep told me there is a monobloc coming, probably in the Autumn. Panasonic also do some nice units with cooling and these can be paired with their fan coils. And as you've listed, Vaillant. I think Vaillant is probably the cheapest on this list, but there may be a Panasonic about the same price. Most people like and choose Vaillant because of the standards of support available. Daikin also do cooling but I don't know much about them as I'm not an installer for Daikin and haven't had their training.

Why are you trying so hard to make the discussion so unpleasant and personal John? All I've done is quoted what you've said and reasonably replied and questioned it, and asked you for some data. It's just very curious.

It's a shame there isn't more granularity, but definitely interesting to look at the behaviour of the system and charts.

This just gets weirder and weirder, as it seems you're trying to prove a pointless point, so probably not even worth engaging in further discussion. However.. Sorry for confirming what I said? So in @jack's case, I can presume that the UFH works well to keep the upstairs warm in winter, but from the charts, shows it has no effect on upstairs for cooling and as he says 'unsurprisingly.' This demonstrates it isn't a whole house cooling strategy, even if it does provide comfort downstairs. Forgive me if I'm wrong @jack? Like I think I've said a couple of times in this thread, cooling is difficult to define, and must be defined and quantified as well as it can be so everyone is on the same page. It's fundamentals like cooling what (how big), by how much, for how long, etc. that need to be determined, understood and agreed at the outset, even in a short conversation like this. And then being explicit about the system parameters used to achieve the aims. In your instance for example, we don't know what kind of heat input your system is dealing with when you make your claims, is outdoor temperature at 21, 23, 29, or even 32C, what are the heat gains such as through windows or elsewhere. What temperature are you seeking indoors? When does your house actually start needing the active cooling input for your comfort? What actual kW heat transfer is your system able to deal with during cooling? What time periods are you running? I think cooling design is just as much of a heat loss & design task as heating. Which is why I asked for data, as on the data, I'm very happy to change my views, which are not based on 'my' theory but standards, calculations, and some knowledge from the wider industry. Views and passive cooling are not mutually exclusive, and my comments about passive cooling are not a criticism of your design decisions. I add in my comments about this as I hope it helps self-builders in the early stages consider heat gain and how to deal with it in the early phase as there have been plenty of threads over the years where this has caught people out, and following completion have struggled with over-heating.

My comments are absolutely justifiable in the context of this discussion. The discussion was about heat pumps that are designed for heating, not heat pumps that are designed for cooling. Yes, they're both heat pumps in so far as they move heat from one place to another, but a heat pump does not function in and of itself without a wider system that is designed either for heating, or for cooling, or as we've seen recently heating with some cooling capacity. This is where the conversation started: Then @saveasteading asked a question about cooling to which I answered: Here, you can clearly see that I'm actually using a distinction between an ASHP (implied for heating) versus a split a/c unit (which is also a heat pump), in the hope that it would help to clarify the difference, but clearly not. However, despite going round the houses, @JohnMo then confirms exactly what I said: As for reversing valves, yes they exist and they're used in ASHP designed for heating, but often the reversing valves have slightly different designs for the purposes of either mainly heating or mainly cooling, and they have different control strategies. So the fact that an ASHP heat pump for heating can reverse cycle, doesn't mean it's going to be great at cooling, or that it can do cooling at all. (and then approach to the design of controls is yet another matter where there are differences between 'cooling' and 'heating' based manufacturers in how they implement heating controls) But beyond this, the cooling effectiveness, as I've clarified above, of a heat pump for heating, is dependent upon the design of the whole system, not just the unit. And a system designed for heating has multiple drawbacks when it comes to reversing the flow of heat, due to a number of factors. Hence why what we're seeing here is exactly what I said - a reduction of a few degrees that increases comfort, but if you're in a position where adding cooling requires a huge amount of investment in infrastructure etc. to make your heating heat pump cool, you're better off installing a multi-split, which is of course is a heat pump, but it's a system designed to do a different thing mainly and would be far cheaper. 😉😏 But like I also said, fundamentally, you're probably better off designing passive cooling strategies into a house at the design stage....than relying on the heat pump, except for in exceptional circumstances.

Yes, the concrete floors will help a lot, but I'd be curious to know how the floor temps are when the ASHP is not running? Have you taken any comparative measurements? What we ideally need are specific figures to understand the W/m2 can be gained from a floor during cooling

That's the big red flag for me too. I can't find much in the way of useful reference and those references I can find from journals, the process is quite complex. But basically the standard used to calculate cooling is the same standard as is used for calculating UFH output - BS EN 1264. So the calculation goes that essentially the floor output for the same given floor depends on Mean Water - Air Temperature difference - give or take some details. If you're running heating you'll typically have a higher dT for heating than for cooling simply because you need to keep flow temps above dew point and a floor that's tool cold is uncomfortable. This means that the floor heat out (or actually input in this case) is going to be less that with heating. One way to think about this is that a thick slab is highly unlikely to reach parity with air temps during a heat wave, for example and will almost always provide some natural cooling effect due to its mass, so even when running cooler temp fluid through this the temperature difference is going to be even smaller. Then there is the effect of floor coverings and heat transfer. Add to this that heat pumps are designed and developed primarily for heating and you have a system that can do something else - a little bit of cooling, but it's questionable how much it's been developed and tested for this. So there's an optimisation question, then there's a control question because heating controls aren't really designed for cooling control. Etc. etc. Then there is the question as to whether, if you're building a new house anyway, you're better off designing passive cooling measures into the design in the first place. In our house, for example, the top floor is timber frame and it takes about 3 days during a heat wave for the heat to equalise and become uncomfortable when it's over 28C outside. Downstairs we have EWI coupled with brick/brick, brick/stone walls and this area maintains a nice cool temperature throughout heat waves. My sons always comment on this when they come home from school on hot days and how fresh the downstairs feels even after days of heat - this is where all our bedrooms are. We are just installing a smaller split aircon unit centrally upstairs for the living room which gets a lot of heat gain through large windows. There's also another element that's overlooked in effective cooling, which is dehumidification and the role that plays in our experience of heat. Aircon units dehumidify as a natural consequence of condensation. A heat pump using cooling does not, and will not do this especially if it's running safely above dew point - fan coils condensing can of course dehumidify. This is an effect that is important when we experience high humidity heat. So for me the conclusion is that in a well designed and highly efficient house, running cooler water through the UFH will have a positive effect, of course it will, but in terms of designing a whole house system that does efficient optimised heating and cooling through the same system, it is not a simple or easy thing to do. And as we know, how do you find an installer that'll do it and then properly support it? Anyone doing it just has to have a realistic expectation of what they're going to get and the scant public information out there is not massively helpful.

This is exactly the shifting argument I've come to expect from you. In one statement you say just run fan coils at 6C and get as cold as you want and then when it's pointed out the measure you have to take to get this working, in the next you say something is dead simple and no problem at all, but use reference temps that are wildly different at 17C. Once you then run at 17C the cooling effect is dramatically different and goes back to what I originally said was marginal cooling that may bring uncomfortable temps back to okay and not like aircon at all. The other issue is that your doing this in your own home, you're not running a company providing design and installation in other peoples' houses that may have vastly different expectations and understanding of the system, or none at all and then completely undermine the original strategy. What customers often understand as cooling is very difficult to quantify and can easily lead to big misunderstandings, because they often assume it's like aircon.

For radiation you need to ignore the air (as that can actually hinder radiative heating and cooling). It's the radiation of heat between different bodies. For UFH the warm floor radiates heat to our bodies and the surrounding walls/floors which then radiate the heat back into the space. A similar thing happens with cooling. When the floor temperature is reduced, the walls and ceilings, and our bodies radiate heat toward the colder surface. Hence we feel cooler (even if the air isn't necessarily any cooler). It's the same reason intermittent heat isn't very good for comfort because it heats the air not solid bodies so when the heating is turned off, it feels cold very quickly because the surfaces draw heat away from the body through radiation. Passive cooling using radiation can be very effective but it has to be carefully designed for cooling. If you happen to have the infrastructure, like UFH and your heat pump has the necessary controls/sensors for relative humidity and dew point calculation, then of course you can use it. I've had conversations with the tech people at a couple of large and well known heat pump manufacturers who, whilst they confirm the heat pumps do cooling, it's not like aircon, it will temper the room temperature. In many circumstances this is okay. And the other side is finding the design resources to do the cooling side properly - if heating using heat pumps is difficult, just imagine trying to find the knowledge and skill for cooling. And I'd argue that if there is any risk of condensation forming on pipes, then detailing the system is even more painstaking than insulating for heating.

Like I said: If you're going to run fan coils with a flow of 6C then be prepared not only for condensate drainage throughout, but also to very carefully lag all pipework through the house etc. So it's a lot of work to make sure the system is properly installed.

You're not far off. Cooling effectiveness of ASHP isn't that great, you may get a few degrees drop during the hottest days, so it might take the house from uncomfortably hot to okay, but that's about it. If you're in a position where you need to drop time, money and resources on infrastructure for an ASHP to do cooling, you're better of just getting a split a/c unit. I made that choice.

The MCS design and installation requirements are that the Heat Pump can provide all the heating/how water requirements, which does mean the unit has to be sized according to the heat loss, but that doesn't necessarily mean that your heat pump will be over-sized. Good design also makes sure that the heat pump can modulate down far enough to deal with typical temperatures without short cycling.