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2ACH, isn't that a terrible number? Or is it different than the european ACH50, 50Pa passivhaus measurement method? The goal is 0.5ach there, and as far as our construction goals go, it can be easily achieved with RAL window installs, sealed vapour stop foil barriers etc, not some space tech solutions.

The fundamental approach was like supplying 7°C to the fancoils, and 16-18°C for the underfloor cooling. I get it what you say, omitting the 7°C side deletes the need for buffering. I am not sure if a fancoil gets any meaningful cooling power when fed with 18 water, but I get the idea!

Thanks to all for the replies! The more I ask (and read) the more obvious it is for me that my ideas are not practically doable in a small-scale family home sized building, with a single heatpump. My initial plan was to use UFH for heating and use fancoils for heating at the same time, but the fancoils could be used for cooling(at 7 degs) alone, or combined with UFC(at 18deg). So that every system could be used for heating and cooling, separate or combined. I thought there are come clever hydraulics that solves this maintaining the advantages, but as You say, it cannot be done without normal buffer tanks, right?

There is no problem with heating. The problem is that we don't want to cool the whole house all day, and using only a single fancoil/radiant panel at a time needs way less flow than any heatpump's minimum.

Thanks for the reply! We plan to use the heat pump for both floor heating and cooling with floor and fancoils, so omitting the buffer completely might not be possible, that is why I seek an Optimum method using it. With a friend, on a test setup we came up with a pwm controlled 4 port buffered floor heating solution, but it uses a condensing boiler. It should work with a HP as well, since it is only a pwm circulator, 2 temp sensors and an Arduino, but We've yet to try it. With a pwm secondary pump, One can preserve the buffering possibility in case of any unexpected heating anomaly, but eliminate the diluton of flow temperature. I posted the question to hopefully better understand the possible pump concepts built into the machines.

Hello again! Sorry for posting a new thread, if it is inappropriate here, please move it to the right section. It is a very technical question, and the more engineering-related heating forums still don't answer it. I have a few weeks in the studying or planning of my own heat pump heating-cooling system, and as an engineer, I came across some questions that are basically unanswered throughout the net, or hardy reachable. The question is that how heatpumps control their inbuilt circulators? I'm sure there are many solutions to this, but I seek reply from those that studied/installed more units. AFAIK, most heat pumps use some kind of PWM controlled circulators now, at least the name-brand ones do. Panasonic Aquarea uses fixed "power" percentage, that can be set from the menu, according to the manual. LG ThermaV uses either fixed capacity,fixed flow, or fixed deltaT(5°C), or some "optimal" flow control method, it can be changed from the menu. The cheaper chinese HPs that I came across does not have control change possibility, but they seem to use fixed-ish deltaT. For those models that need external circulators, how would you set it? What if you must use a buffer/LLH, because you have both fancoils, radiators and UFH, or separate wall/ceiling heat-cool and UFH, or multiple heat sources? The best available articles(like John Siegenthaler's) only describes systems, buffer connection schemes at their nominal performance. Even heating design engineers specify components based on max load. If sized well, at maximum capacity the primary flow is usually greater than secondary(given a 5°C dT HP and 5-7°C dT for UFH) the LLH works flawlessly.. But as a heat pump modulates, it usually reduces its pwm pump's speed, so primary flow becomes less(maintaining dT). The secondary pump, which is usually fixed speed, or constant height type, pumps more water than the HP, so flow mixing occurs. The same thing scould occur with antifreeze monobloc heat pumps with plate heat exchanger. It might be sized to have minusculeloss at nominal flowrates. The heat pump reduces flow, but the secondary pump is fixed, so dT on the secondary side should increase(??), because of the still high flow, but lower capacity. Or the forward temperature drops on the secondary side? Or it follows the primary side with a lag? Or it induces "mixing", just as well with a LLH? IN my opinion, the whole anti-buffer hunt is because of this flow modulation problem during part-load. A fixed-deltaT type secondary pump would be the ideal, but only the most expensive Wilo and Grundfos pumps have that feature. If you set a fixed capacity in the heat pump menu, does this means that the Design deltaT(5°C) increases to 15°C when the heat pump modulates to 1/3 capacity? There is only one 2 minute long video about this topic on the HeatGeek YT channel, but no other source talks about this problem, but it would solve all the buffer-related problems nonetheless.

Sure, you can check many manufacturer's website: Uponor Thermatop M Look for Wavin Comfia CD-4, it is not yet released in the UK Rehau chilled ceiling Somehow these radiant cooling systems are not widely introduced to your Country, idk why. As far as I know, it is now widely used across europe, even in our almost-third-world county, compared to the UK or Germany. Interestingly, underfloor cooling is strongly not recommended in Hungary, because you may slip on wet floors if condensation occurs, cool floor is unhealthy to the feet, "warm air rises to the ceiling", etc. Btw, condensation is prevented by using RH metering thermostats. On simple systems, you can set a maximum RH level that shuts down the cooling in the room. With advanced bus-type controllers, you set the buffer tank flow temp to a low temperature ( e.g. 5-7°C), and use a motorized mixing valve to constantly adjust the flow temp to be above the dew point for the highest RH room. It maximizes cooling effect, preventing condensation, while acts as a further "buffer" when it uses up the 5°C water to mix it up to 16-18°C. Yes, it works. It has moderately high costs, but can provide the peculiar cool "church feeling", if done right. To better understand its problems: Combining radiant heating and cooling makes the system not ideal to either tasks. As many of you advised, UFH should be as open as possible, and use the heat pump's inbuilt circulator without any buffers. You basically heat the whole home, every room. This radiant cooling system always use some kind of room thermostat, and unless you have every ceiling full with these panels working all the time, you don't necessarily have the necessary flow rates to prevent short cycling. I planned to install these panels only in the Bedrooms, but it results in less than 9l/min flow all bedrooms engaged. A single room uses about 2-3l/min, so you either cool the whole house, or nothing. We are starting to be a Mediterranean country in terms of summer weather, but still, cooling is not used for more than 2 weeks at a time, and it can be switched off at night. Why am I bothering with all these unnecessary hassles? Because a very good, silent fancoil(Like the Innova Airleaf that Panasonic sells rebranded to their Aquarea lineup) costs more than these radiant panels for a given square meters of room. The fancoil costs as much as the panels, but you must buy overpriced modulating thermostats, specific comm. boards, drain pans, etc. Still, the small flow problem persists if you plan to cool 1-2 rooms at a time, and a buffer is needed. If anyone has any engineering data regarding radiant floor cooling, I could awfully thank if he/she could share with me.

But the cooling does not only take place in the UF slab, but also in the suspended ceiling radiant panels, which needs approximately the same flow as a slab UFH, but has zero mass. (Uponor Thermatop system)

I downloaded the LoopCAD trial version, modeled the house, so I got very useful results, I really suggest everyone doing this, it is really straightforward, albeit i studied building physics for a year. Basically the program suggested 100mm CTC piping for rooms with many outside walls, and 150mm CTC for rooms with few outside walls. Even using this variable floor piping, there is about 30% difference in flow quantities accordig to the program, that is why I asked if this "all open" method works. How would you combine it with zoned cooling (perhaps only one room at a time with ~0.15m3/h flow)? The manufacturer of the slab/drwall radiant cooling panel suggested a separate cooling buffer tank. The radiant panel needs about 18°C water, so filling the buffer with 5-7°C flow, then up-mixing it may provide the buffering solution. At least it is their idea.

You should have very good insulation! My house is perfectly good with the latest insulation and lifetime emission regulations, although not a certified Passive House. The heat loss per calculations greatly depend on the filtration number between 5.5-7.5kW. If you open all flowmeters, and you don't use zoning, how do you balance the system for "equal" room temperatures? The "standard" UFH layout per my studies uses a Constant Head circulator, but according to your suggestion it is not needed without zoning, right?

Thanks for the reply John! In our climate, almost every installer use some kind of buffering technology. It's because we have to size the HP to a greater span of heat loss. It needs to be sized for winter loads(-15°C sometimes), so heating without cycling is almost nonexistent. In my example: I need about 8-9kWatts of heating at 35°C flow temp for the winter. A 9kW unit might be a good choice, but even a good quality unit can only modulate down to say, ~4kW which might be exactly the load you size the machines there at the UK -2°C. Above freezing(about 5kW for me) the heat pump will eventually cycle. With this "oversized" approach, a second problem comes. If I set the WC curve to supply 30°C water in 0 ambient, The 5kW power with 5 deg deltaT results in so little flow that with your "all open" approach, the secondary(UFH) flowrate surpasses the heat pump's builtin pump, thus severe mixing occurs. Mixing can be avoided only if you fix the flowrate at a constant maximum, but it increases deltaT in low-load conditons. I've been learning about sizing hydronic equipment for quite a few weeks, and I am more and more convinced that part-load calculations are basically nonexistent. Everyone talks about inverter-driven heat pumps, but no one about the fixed speed secondary circuits.

What do you think, how much energy is lost in the 4-way tank reversing valves? I mean the flow and return essentially contacts the same brass body, heating/cooling each other. I am still confused with the 3-port vs 2-port configurations, many articles describe that the 3-port method is the neater, because at least the lower portion of the tank is engaged at all times.

Thanks for the reply! By 'Managing buffer temperature' you mean the start/stop of the HP? Do you think the 2 port is better instead of the 3-port?

Yes, almost all new homes, apart from the very basic, low-cost ones use these panels. It is either a metal sheet with small heating pipes embedded, with drywall overlays or drywall boards with pipes embedded from the factory. It is fixed to the ceiling, or cast in the concrete ceiling. They work very well, but only with ventilation and dehumidification included.

Here we size the heating system to -15°C, so the heat loss of the building is around 8.5kw net, maybe 9kW with losses in the distribution system. Frankly, a modulating condensing boiler is a way better approach in our climatic area, because in winter it is often foggy and around 0°C. ASHPs are way better in UK and warmer climates. Many heatpumps struggle with defrosts and keeping the performance at low ambients, that is why we need to size a 10-12kW ASHP that can still provide 9kW at -15. Due to EU regulations, condensing boilers cannot be installed in new homes alone, only along with 3-4 minisplits or PV panels(with very low return of investment). Buying a heat pump only for heating, and installing air conditioners for cooling seems to be a waste of money. There isn't enough space for floorstanding ultra-quiet fancoils, but the looks and noise of the high-wall, minisplit-like fancoils are very disappointing. The radiant panel ceiling heating and cooling becomes more and more common here. It has very good thermal comfort without any noise. Its only weakness is the humidity factor, because we use 15-18°C flow temps to cool, either with humidity sensors, or condensations switches. Btw a fancoil "indoor" unit costs alone as much as a complete minisplit set, with more noise, less eficiency and more pipework.

Dear Buildhub'ers! I am quite new here, and I've already learnt a lot from you regarding the proper heat pump design principles, which I thank You very much! One thing that comes to my mind again and again, is that how would you place the buffer tank for a zoned UFH and zoned radiant ceiling cooling. For the "traditional" 4-pipe configuration, it is quite straightforward, you need several ball valves(6 or 8 IIRC) manual or motorized on the primary side to change that the cooler or warmer water goes to the top of the buffer. The more modern, 2 or 3-port configurations really caught my mind, but I simply cannot imagine how would anyone pipe these layouts for both buffered heating or cooling. The Caleffi article describes a 2-port config with cooling, but it does not reverse the cool-warm ports of the tank, so the cooler goes to the top. What would you advise in terms of energy efficiency, but with realistic costs at the same time? Should I stick with the traditional 4-port method? Perhaps a 4-port with custom internal baffles to prevent mixing? What is the way to go ? My home will be about 150sq.m newly built low energy type, with only UFH in all rooms, and radiant ceiling in bedrooms with A2A split heat pump in the living room for dehumidifying. According to the initial plans, the heat pump may be 2-2.5m3/h flow on full load, while the house needs 1.5-1.8m3/h all zones engaged, at 35°C flow temp. Thanks in advance!

What makes "adequate" an install in your terms?

Thanks for the reply! What's your thought on combining it with separate room control possibility for cooling? Adjustable cooling is mandatory in every room, as We don't feel like operating the whole cooling system nonstop, just on demand for some hours on the hottest days. The Innove "airleaf" fancoil is the most attractive for me, but IR remote control would be the best, missing from every cabinet type fancoil.

So you don't think advanced TPI algorithms do much good with heat pumps?

And how would you combine these forecasts and WC controls with cooling? I plan either fancoil and/or UFH cooling, maybe a cooled ceiling type system, but controlling the cooling demand per room, and non-zoned UFH heating seems not to have so many off-the-self thermostat options. Making a simple Arduino, or Home Assistant or PLC thermostat system is not too far from me, but then I'll lose the TPI learning feature, I am not experienced enough to program this algorithm.

On the hottest days, we get 37-40°C peaks, and it gets worse as the warming goes on. On a hot day, I expect condensation under 16-17°C floor temps, so UFH cooling in itself is surely not enough. There are stylish, slim fancoils available, but you either oversize it(price), or run at max with 35dB of noise, and no IR remote as far as I've seen thermostat options.

No, I am not sure, but the EN 12831 standard calculation gets this result. At - 5°C, which is closer to the UK design temp., the heat loss is only 5.4kW. Ok, so zoning heating does little to comfort, or energy saving, but what about the cooling? How's you UFH cooling is set up? Does it have dew point sensors, or just works with non-condensing flow temp? The "traditional" plumbers and heating technicians consider it an evil's thing, but I've read many times, that it can be utilized well. Other than that, i don't think cooling the whole house's slab is too efficient, when you need just half an hour of cool breeze in the living room, isn't it?

Greetings BuildHub'ers! 😄 I am grateful to have you here, as in my County, ASHPs are only started to get installed in the recent years, so few experience is available. Now, they are installed like there's no tomorrow, but the hydraulic and control 'finesse' is completely missing from most of the installers inventory. Basic 4 port normal buffer tank with huge coil surface area DHW tank. AA battery powered on-off thermostats, no statified tanks, no 3 port configurations, no external plate DHW heat exchanger like I've read in this site. The most ambitious installers make a H-type route changing circuit from manual ball valves(to have the colder water at the buffer tank bottom when cooling), and that is all, no more than the heat pump reference designs from 10 years ago. I am also an AC and ASHP certified installer, licensed electrician and controls engineer by trade; our family home is under planning and construction now. All solutions should be considered with B2B installer pricing. It is a ~155sq.m2 ground floor house, 4 bedrooms, with normal-to-good insulation for new homes EU regulations.("porotherm" clay brick 30cm walls and 20cm EPS foam sheet insulation on the walls, 35cm rockwool on the ceiling, warm edge, 3-pane glass windows). The heat demand is 7.5kW @-15°C, which is the traditional design temperature here, although very rarely gets this cold. I plan to install the 9kW LG R290 Monoblock heat pump next year for underfloor slab heating, DHW and fancoil heating and cooling. Cooled ceiling is not considered. As a control engineer, i quickly got attached to the super-smart contollers and thermostats, like 0-10V thermostatic actuators, 0-10V fancoil speed controllers, etc. Then I came across the pricing lists.... The initial plan was Siemens RDG200 series thermostats per room, with 0-10V or NC underfloor actuators, and 0-10V fancoil speed control. It is one of the most expensive thermostat available, excluding the KNX ones, but it is possible to run both systems with it, albeit the set of these thermostats costs almost half of another a2w heat pump. I want to control both the heating, and cooling circuits with one controller, if possible in a financially sensible way. Many say here on the forums, that the heating does not need any zoning in this moderate sized home, because with good sizing and weather curves, the heating does not stop at all, so any thermostat is useless. The cooling must be adjusted per room, as it is needed occasionally, during the peak weeks of July and August. Heat pump heating and DHW with split AC cooling would be the most effective solutions, but sticking 2-3-4-5 outdoor units onto the facade does not seem to be an elegant solution; then the ashp is not needed at all as a gas boiler is way cheaper for heating only. My main question is, does a modern, well-built and commissioned heat pump system need high-priced control equipment to run with good comfort, or stick with a good weather compensation setting? Do zoning have any advantages compared to thoughtful hydraulic setting in terms of UFH? What other control options do you suggest to control fancoil cooling, to be as similar to a high wall split AC IR remote control? Every opinion, experience or tip is welcomed here.