SimonD

Yes... I have two heating manifolds, one for upstairs, one for downstairs. My longest run however it a lot longer than yours at approx 17m on 15mm pipe and vary from about 3m to 17m across the house. I use the Danfoss self balancing trvs with lockshields fully open. The self-balancing trvs make balancing a dream as you simply download the app, input your flow and return temps together with the size and type of radiator (or required output) and the app will give you the setting on the valve and its equivalent flow rate - it then provides the required flow to each rad. House balanced in 20 minutes rather than 6 hours and then some on following days. Then if you need to increase or decrease the flow to any rads for finetuning its a very simply turn of the self-balancing dial (which is numbered) rather than nuisance lockshields. Obviously it's a bit of work changing out the trvs but balancing even with lockshields is always going to help - it used to have the normal trvs & lockshield setup.

I did, and I still got it wrong 🙄😊 23-24 is exactly what my wife now knows she wants while I'm walking around in shorts and t-shirt.

I've got to go old school with a leftfield approach - I have several air nail guns used with a compressor. Yes, the air line can be annoying sometimes but it's all so reliable. The guns are fairly light weight and they'll run and run and run, even down to -6, then it got too cold for me.... I've also found the support fantastic - next day delivery on all parts and simple to fix.

I kind of knew I'd get some kickback from what I said and I'm not surprised from whom 😉 I'm an approved Viessmann installer so I'm fairly familiar with how they work and most of my installations with Viessmanns are with unvented cylinders and PDHW bla bla bla.... and I don't treat them like a heat pump. CH and DHW need to be considered differently in both design and commissioning and it's not uncommon to see lower DTs when in DHW mode in PDHW but then flow temperatures are much higher .and @JohnMo you have repeatedly talked about the problems you had getting your ATAG to run as you wished it to which wasn't as it was out of the box and it didn't run like a heat pump...e.g.

Yes, the boiler pump is almost certainly able to deal with the index circuit press drop. The reason you need the hydraulic separation is that your flow rates will be different when you have a different Delta T - the difference between flow temperature and return temperatue. So even if you ran your rads and underfloor heating at a Delta T of 7 (7 degrees temperature difference between flow and return) for example, your boiler still wants to ideally see 20. At a Delta 7T you will have almost 3x the flow rate through the system than at Delta 20T and this will cause problems at the boiler side because of the way gas boilers run - typically if the Delta T across the boiler becomes too small it will tend to short cycle. This change in flow rate between what the boiler wants to see and the emitter system will need the addition of a pump post hydraulic separation. A case in point about boiler Delta T is with my current gas boiler. On Opentherm this is set to run at a maximum flow temperature of 53C. On very cold days, I have a typical return temperature of 37C (even though I have a perfect Delta T of 20 across both of my system manifolds - make of that what you will) - I can't get the settings to work any lower on this boiler. When the return temperature at the boiler reaches 41-42C the boiler begins to short cycle with a max flow temperature of 53C. But it will continue to run fine if I increase the max flow temperature to 55 or 60C. So my boiler just will not run well when the Delta T gets to minimum 11-12C. At minimum 16 it will run for long periods of time. IMHO it isn't worth trying to make a gas boiler run like a heat pump, they are different technologies and thus need to be treated that way. No, it wouldn't because it doesn't have the inputs and outputs for temperature sensors and electronic circuit mixing which you need for the ESBE, unless you use an ESBE product that has its own weather comp/room load compensation controls.

I read loads of books....then I just booked myself onto a self-build project management course for 2 days. I attended the one run at the Centre for Alternative Technology and it was very well worth it. There were even a few professionals involved in building on the course, including architects, which made for interesting discussion. Plus we got a site visit to an existing project to talk it all through with the self-builder. So it was all down to earth and applicable.

I have distribution manifolds as central to the house as possible and from these manifolds I run individual pipes to each outlet. This means I can run small 10mm pipe to basins/wcs ect. and 15mm to showers etc. For maintenance it works great as each outlet can be isolated but the rest of the room can be used - e.g. servicing the basin taps while still being able to have a shower and now of those terrible isolation valves that always leaks after a few years. You really don't need 15mm to go to sinks/wc flush etc. and with decent pressure you don't need 22mm to go to a bath either. We have a couple of long runs and as I've used 10mm pipe, the hot water is there very quickly. If you run 22mm to a bathroom and then split from there, every time you need hot water you have to draw a lot of volume to purge to pipe of cold before you get hot.

You haven't really followed what was done in that video. On your system you need: - Vaillant wiring centre to wire in the mixer and additional sensors - really you want the SensoComfort together with the VR71 wiring centre and this has up to three outputs for ESBE mixers and has the inputs for several system temperature sensors that you're going to need as well as the DHW cylinder sensor and pump control output for UFH. - you need a pump on the UFH side of your circuit between the mixer and ufh manifold. This is because as you have a gas boiler you need different flow rates between radiator circuit and UFH circuit because you want a delta T of 20 for rads and delta T of lets say 7 for arguments sake on the UFH but once the flow is outside of the UFH circuit you want a delta T of 20 between boiler flow and return. - you need temperature sensors on your pipework so that the controls can differentiate between the temps of the radiator circuit and the UFH circuit (and provide input to the ESBE mixer). In the video, the first thing he points out is the close couple tee arrangement below the boiler which is to provide hydraulic separation between the two circuits - you really must have this in your system for it to work correctly

No, I said that the research at present suggests that there shouldn't be a great different between heat demand in different areas for this to work effectively. You asked me what the Heat Geek mantra is and I clarified this, then you try to tell me it's not? 🤔

Room influence from a heat pump controls perspective is where a room thermostat is integrated into the manufacturer's control system to provide input data from the thermostat to influence some or all of the below (depending on how you commision it): - the call for demand (i.e. if room temperature is above set room temperature, there is no call for heat) - the system flow temperature based on an combination of weather compensation, actual room temperature and target room temperature - so the heat pump will modulate where necessary. So if my weather compensation curve is set to operate at a flow temperature of 35C at 0C outdoors but room temperature is nearly satifsfied, the room controller modulates the flow temperature of the heat pump accordingly. On some heat pumps you can set the room co-efficient to change the weighting of the room influence to weather compensation. But you can also use modulating mixers for UFH, for example, that can either be wired into the heat pump manufacturers controls to regulate flow temperature going into a specified zone. You can also buy room/weather compensated mixers (like from ESBE) or even room/weather compensated UFH manifolds if necessary that have their own sensor and controls if absolutely necessary. And of course, not forgetting radiator systems, you can employ simple ways of restricting flow using TRVs. Or if you decide on a more permanent turn down of flow to some areas of the home, you can use self-regulating TRVs where you set for flow rate for a specific output and delta T across the radiator. You could also technically use a mixer to the whole radiator circuit, if needed. The main difference in room influence versus the main stream understanding of the zoning term is that with room influence you are not closing down flow to areas of the heating system, simply balancing flow rates and flow temperature, so you don't experience the problems associated with low system volume when zones are closed down. You tend to do this minimally using 1 or 2 room thermostats with proprietary control, but some manufacturers have begun to supply support for up to 6 in their controls. There's nothing particularly complicated about this in terms of overall system install, it just needs a thoughtful design process that understands the building and what the occupants want/needs. As manufacturers now build these into their control systems, it's also something that is fairly straighforward to adapt, should you need to. As a note: @JohnMo's system is technically a system with room influence as it runs very low flow temperatures where there is only a couple of degrees difference between flow and room temperature, which permits a self-regulating effect on the heating system. This is a behaviour of the system that works independently of the controls and heat pump.

Research suggests differently and I'm more likely to trust a balance of trusted research. And you're not doing that John, so you shouldn't pretend that you are. Not quite, it's more subtle than that. The mantra is to use open-loop managed with pure weather compensation on retrofits and less well insulated homes (including some newbuilds) but in highly insulated and airtight homes use weather compensation together with room influence. The balance between weather compensation and room influence is dependant of specific design elements and context of the house. Come one John, I've already said that open-loop is the preference many times. What I've been saying, yet again, yawn, is that the specific circumstances of the building must be considered and that building in room influence is preferrable when dealing with well built, highly insulated homes, with good air tightness, especially if they experience large inputs of energy outside the heating system. This isn't complicated either. Occupants might also like more control in their bedrooms.... Err, so below you're suggesting what? Not room influence by any chance?

There just seems to be some bizarre obfuscating circle going on here John, 1. You are running a very low temperature UFH system that also utilises a specifically designed slab arrangement. 2. You have spent countless hours/days/months/years tinkering with your system to get it working right for you. 3. You are using 1 anecdotal example, which is your own, to base a general conclusion that is being suggested as suitable for all and everyone. 4. You have some very particular views on indoor temperatures such as your view on bedroom temperatures for example. Your system, because it utilises the self-balancing effect, actually manages to self-regulate independently of the controls in your system - that is what these systems are known for. But, it requires a significant amount of pre-planning and integrated design, and if being applied in a retrofit situation, a hugely costly upgrade process. Your graphs therefore don't reflect the nature of the heapump and it's controls but this thermodynamic behaviour which is independent of it, but nevertheless impacts the behaviour of the system as a whole. This is a great solution if you have the low heat loads required and all areas of the house have similar heat demand (e.g. there's no area where there is a significantly higher demand), as a basis to allow it to work. These are highly significant caveats to what you are proposing and I believe people reading posts on this forum need to be aware of this and that there are so many other factors involved, such as floor coverings etc. I'm not saying anywhere that your approach is wrong, I'm suggesting that other approaches may be more suitable for other people considering designing their own system, and whether you accept this or not, is neither here nor there as it's something that good designers and installers of systems are utilising more and more from their vast experience of putting these system in.

Just to add - yes, but if the weather compensation is calling for heat and the heatpump sees an increase in return temperature, it will increase the flow temperature to maintain target Dt, which is one reason why a buffer, for example is less efficient when there's too much distortion. Just seeing an increase in return temperature is not enough - the heat pump needs additional feedback. This is another reason why room influence is useful in circumstances where there is additional heat input into rooms. Hence your description of the heat pump modulating down when it sees a higher return temperature, is not necessarily, nor universally, correct. It depends on controls.

Can you explain what you mean by this?

Yes, if there are significant heating inputs that are not measured by weather compensation alone, and/or if the occupant want some control in rooms such as bedroom. In our house, for example, we can have the triple glazing on the north face still covered in ice while the upstairs has already been heated to 23C by the sun. In this instance, even if the MW-AT delta T is such that the radiators then don't theoretically add heat into that space, it seems a bit silly not to modulate the heatpump using room temp feedback as the home heat load has reduced. In ours this is easily by 50%. The idea around room influence is that an internal thermostat provides input to the heatpump to modulate. This can also be achieved using TRVs on radiators without modulating the heatpump, or with electronic mixers. Most manufacturers will provide 1 or 2 of these room stats but companies like Stiebel Eltron can build a system with up to 6 and it also provides the ability to weight system control input between weather compensation and room. Nobody here is saying that a heatpump installed with open loop and weather compensation isn't the simplest solution. It's just that get a heating system to work for its occupants may NOT be that simple, especially in highly insulated homes. Room influence does not make the system more complex. It can infact make it simpler for both the occupant and the installer. Room influence does not necessarily shut down flow and therefore reduce system open volume, except for at the extremes. Zoning, using relay type controls is a different matter as this does reduced system open volume and therefore the system becomes more complex. For me the issue here is the understanding of controls, what they, do and how they work, and then when to implement them - but that's a headache for the whole industry right now which is still learning. But most good decent installers will go for open loop with some room influence baked into the system in current designs.