markharro Posted February 18, 2023 Share Posted February 18, 2023 Just trying to agree a quote with installer and I want to check I am not missing anything in terms of the overall spec I am getting for the money. Can anyone provide a tick list of what I should be checking are included in the price? thanks Link to comment Share on other sites More sharing options...
JohnMo Posted February 18, 2023 Share Posted February 18, 2023 More details are you zoning, if how much, one floor more? System volume, flow rate? PV not much to do with ASHP install. Big ASHP that needs 3 phase, are you insulated and draft free, or just a massive house? Link to comment Share on other sites More sharing options...
markharro Posted February 18, 2023 Author Share Posted February 18, 2023 UFH just to ground floor. Don't really understand zones - I know there are separate pipe runs back to a manifold. No idea about volume or flow rate. Its not that we "need" 3 phase - its simply that we have it in case of relevance. Pump will be 5kw. Yes we are building a passive house Link to comment Share on other sites More sharing options...
JohnMo Posted February 18, 2023 Share Posted February 18, 2023 Zones are areas with a thermostat and or timer. If you run on single zone one thermostat puts the whole UFH off or on, multiple thermostats shuts down or starts up small areas. This will choice affects the need for a buffer or volumiser which will be one of your ticks or otherwise. Best efficiency is from a single zone system run on weather compensation. It also the cheapest to install, as one thermostat and no actuators on the manifold. Can you get a 3 phase 5kW ASHP? Link to comment Share on other sites More sharing options...
markharro Posted February 18, 2023 Author Share Posted February 18, 2023 Ah I see thanks - as far as I can tell from contact with the installer he is planning multiple thermostats. I will ask him about this. Link to comment Share on other sites More sharing options...
JohnMo Posted February 18, 2023 Share Posted February 18, 2023 Our house started with lots of thermostats, slowly over the past year removed them. With a thick screed, and low flow temps they just don't work well, the hysterisis is too large, so temps would overshoot then under shoot. If you have 50mm screed you may be ok. Link to comment Share on other sites More sharing options...
ReedRichards Posted February 18, 2023 Share Posted February 18, 2023 6 hours ago, JohnMo said: Best efficiency is from a single zone system run on weather compensation. It also the cheapest to install, as one thermostat and no actuators on the manifold. That's if you want your rooms at a constant temperature 24/7 and you are prepared to spend as much time as it takes adjusting flow rates to achieve this. 1 Link to comment Share on other sites More sharing options...
JohnMo Posted February 19, 2023 Share Posted February 19, 2023 11 hours ago, ReedRichards said: That's if you want your rooms at a constant temperature 24/7 Just incorrect, my gas boiler has 3 temperature ranges you can⁶ set and program, all change the flow temp in relation to the heating curve. Plus if you don't have that feature you use your thermostat to have programmed set backs. Link to comment Share on other sites More sharing options...
ReedRichards Posted February 19, 2023 Share Posted February 19, 2023 12 minutes ago, JohnMo said: Just incorrect, my gas boiler has 3 temperature ranges you can⁶ set and program, all change the flow temp in relation to the heating curve. Plus if you don't have that feature you use your thermostat to have programmed set backs. That's excellent but a lot of heat pumps, mine included, cannot do "temperature ranges"; I'm not even sure what that means. My heat pump has a single programmed weather compensation "curve" (actually a straight line). There is a control feature that allows me to shift this up or down by + or - 5 degrees in one degree steps but this is a manual control feature which cannot be programmed. So if you go with @JohnMo's recommendation, make sure you have a heat pump that is sophisticated enough to do give you the control you actually want. I have two zones, one for the bathrooms and one for the rest of the house. I did this so I can heat the towel rails in summer in order to dry the towels. Each zone has a thermostat; I have only radiators. All the radiators have TRVs but only a few rooms, like the bedroom, are set to less than the max setting. I use a night time set back and gradually increase the main zone temperature during the day; something I have been doing since I got my first programmable room thermostat in 1998. I keep reading that having more than one zone is "bad" for efficiency but I have yet to convince myself that this is true for my particular heat pump. As best as I can tell it has a series of stepped target output powers. The step it aims for is higher the colder it is outside. It ramps itself up to that step and holds the power to see what happens. When the house is at temperature, or near to, it holds that power until (I imagine) the return water gets too hot and which point it stops and starts again 20 minutes after the start of the previous cycle. So it runs in 20 minute cycles nearly all the time except when it is working hard and the cycles coalesce. Given this actual mode of operation I find it hard to convince myself that having two zones is bad for efficiency. Link to comment Share on other sites More sharing options...
dpmiller Posted February 19, 2023 Share Posted February 19, 2023 1 hour ago, ReedRichards said: When the house is at temperature, or near to, it holds that power until (I imagine) the return water gets too hot and which point it stops and starts again 20 minutes after the start of the previous cycle so it's not modulating? Link to comment Share on other sites More sharing options...
ReedRichards Posted February 19, 2023 Share Posted February 19, 2023 Yes, most certainly it's modulating but the modulations appear to be quantised. They go up in steps rather than across the full range of minimum to maximum, although these steps seem to be reached by slowly increasing the power over a few minutes. Link to comment Share on other sites More sharing options...
IanR Posted February 19, 2023 Share Posted February 19, 2023 (edited) On 18/02/2023 at 13:54, markharro said: Ah I see thanks - as far as I can tell from contact with the installer he is planning multiple thermostats. I will ask him about this. There's not one solution that works for all houses, you need to give some thought to how your house will react to dynamic factors, especially solar gain. While you can set up an UFH system to work off a single thermostat and manually set flow rates to stabilise temps room-to-room at roughly what you want them to be, if your house benefits from, say, solar gain, that's going to mess up all your manual settings and some rooms will then overheat and depending on where the thermostat is it may switch the heating off where other rooms are not at their target temperature. A multi-zone setup with electronically controlled actuators really works for me. For heating days where there's only enough solar gain to heat the rooms directly receiving it, then the UFH is shut down to those rooms and just heat the rooms on the North-East and North-West side of the house. A PassivHaus that can maximise its solar gain easily compensates for the loss of a couple of tenths of COP that a buffer/volumiser may incur. Edited February 19, 2023 by IanR Link to comment Share on other sites More sharing options...
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