BadgerBadger Posted March 21 Share Posted March 21 I'm trying to finalise our UFH and ASHP strategy ready to start buying bits and getting it installed. But keep going round in circles... Background is we have a large but well-insulated house with usual MVHR etc. My heat loss modelling is showing losses of 170W/K, giving a total heating demand of 4000W at -3C. We're planning UFH in screed on the ground floor, with no heating upstairs. Planning on an 8.5kW Ecodan ASHP. Had some UFH designs back and we're looking at about 15 loops. Trying to get away from zoning, but this might be another leap of faith for my wife. Things seem to have the potential to get complicated very quickly! With buffers, two manifolds, extra pumps etc, but I get the feeling much of it is specified to cover all bases without a true understanding of what is actually needed. I'm really keen to keep things as simple as possible. I came across this article which highlights how hugely dependent the final COP was on system was setup, and examples with buffers etc. are significantly worse. https://renewableheatinghub.co.uk/how-to-correctly-install-heat-pumps-so-that-they-work-properly-and-efficiently So, can I go super simple? Put my 15 loops on a single manifold, no buffers and just let the ASHP pumps do all the circulation. I recognise that maybe the ASHP integrated pump can't achieve the same flow rates as external pump (I think the 8.5kW Ecodan can do ~11l/s to ~24l/min) but given we're at very low flow temps maybe that's OK? I guess I'm trying to work out which sums I can do to show if it is/isn't a problem, and likewise justify the inclusion of additional items. Link to comment Share on other sites More sharing options...
Jenki Posted March 21 Share Posted March 21 (edited) Yes you can go simple, but more information is needed as 15 loops just for ground floor sounds like a massive house. My 89sqM has 4 off 90M loops at 150 centres, I didn't have the guts to go to 200or even 300mm centres. NB my UFH is in 120mm concrete slab Edited March 21 by Jenki More info Link to comment Share on other sites More sharing options...
BadgerBadger Posted March 21 Author Share Posted March 21 Thanks Jenki - Ground floor UFH area is approx. 160m2, with total house of 260m2. Bit skewed as we have a large single-storey volume! The routing to reach the plant room isn't very efficient, so am trying to improve that. Link to comment Share on other sites More sharing options...
Jenki Posted March 21 Share Posted March 21 3 minutes ago, BadgerBadger said: Thanks Jenki - Ground floor UFH area is approx. 160m2, with total house of 260m2. Bit skewed as we have a large single-storey volume! The routing to reach the plant room isn't very efficient, so am trying to improve that. 160m and you've got fifteen loops???? Id start there. My loops span rooms. I've got 4 loops, and 8 rooms / areas . 1 loop does bathroom and a bedroom, another a bedroom, Utility and hallway. I don't have zones, but I do have a buffer that I piped on to the return so acts to increase volume. Also my ASHP is a Samsung so I needed a pump. Link to comment Share on other sites More sharing options...
JohnMo Posted March 21 Share Posted March 21 8.5kW is a big heat pump for 4kW duty. A lot of loops - We are 192m2 with 7 loops. Our heat load is slightly lower but not much and we are on 300mm centres. With 15 loops you may struggle to get enough flow out the heat pump circulation pump, you have to do the calcs. If the calcs work then no issues. You need to do a pressure drop calculation for the pipe between the UFH and heat pump, plus your longest UFH loop, that will tell you where you sit on the pump curve and your max flow available. We a bigger heat pump, you could just charge the floor (like a storage heater) use a 0.1 hysterisis thermostat so you don't under or over shoot temperature set point too much. We just run the heat pump at 35 degs and do most the heating on E7. Messed with WC but didn't see much advantage in a low energy house. The shorter run times actually use less electricity. Link to comment Share on other sites More sharing options...
MR10 Posted March 21 Share Posted March 21 4 minutes ago, BadgerBadger said: The routing to reach the plant room isn't very efficient, so am trying to improve that. Can you install your UFH manifold in a more central location to optimise the loops and routings? Link to comment Share on other sites More sharing options...
JohnMo Posted March 21 Share Posted March 21 1 minute ago, Jenki said: 1 loop does bathroom and a bedroom, another a bedroom, Utility and hallway. I don't have zones I do something similar, one loop does bathroom, hall and kitchen diner., nothing in utility except all the loops travelling through it. Again no zones, or actuators on manifold. 1 Link to comment Share on other sites More sharing options...
Jenki Posted March 21 Share Posted March 21 (edited) 7 minutes ago, JohnMo said: Messed with WC but didn't see much advantage in a low energy house. The shorter run times actually use less electricity. @JohnMo, I want to look at this, as I'm not sure what I'm gaining with weather comp. When it's really windy eg last night, but not cold 6deg the heatpump was still trying to heat the house this AM. So this thread has prompted me to do just that I think I'll just change the parameters for weather comp so the temp range is 35deg to 35 Deg. Edited March 21 by Jenki Typos Link to comment Share on other sites More sharing options...
ProDave Posted March 21 Share Posted March 21 I have a "conventional" UFH setup. a normal UFH manifold with a temperature blending valve and circulating pump. There are only 5 pipe loops on 2 zones downstairs. I have yet to find an issue with this setup. Beware that many heat pumps require quite a high flow rate and their own internal pump on it's own may not be able to achieve that (mine could not) so I would not be in a rush to ditch the manifold circulation pump. Arguably with the ASHP setting the flow temperature for heating you might say the temperature blending valve could be omitted but what about when the ASHP switches from DHW to heating and that slug of 55 degree water in the system would get sent round your UFH loops. All my loops are on 200mm pipe spacing and cover up to 8 square metres, so your 15 loops for 150 square metres sounds reasonable. I would be looking for no more than a 6kW ASHP for your heating load. Link to comment Share on other sites More sharing options...
SteamyTea Posted March 21 Share Posted March 21 45 minutes ago, BadgerBadger said: Bit skewed as we have a large single-storey volume I am not sure how that affects the heat losses, as long as the exposed areas are correct, and the air changes taken into account. It may change the spacing of the UFH pipework, but the room by room heat losses should show that. Link to comment Share on other sites More sharing options...
BadgerBadger Posted March 21 Author Share Posted March 21 27 minutes ago, JohnMo said: 8.5kW is a big heat pump for 4kW duty. A lot of loops - We are 192m2 with 7 loops. Our heat load is slightly lower but not much and we are on 300mm centres. With 15 loops you may struggle to get enough flow out the heat pump circulation pump, you have to do the calcs. If the calcs work then no issues. You need to do a pressure drop calculation for the pipe between the UFH and heat pump, plus your longest UFH loop, that will tell you where you sit on the pump curve and your max flow available. 22 minutes ago, MR10 said: Can you install your UFH manifold in a more central location to optimise the loops and routings? With a bit of improvement in routing/manifold position we can save a couple of loops (about to start my LoopCAD trial) but really there's so many because I arbitrarily picked 150mm centres! This was purely on the basis of "it will let me run a lower flow temp, and therefore that must be better" but this is really what I want to work through and see if it's actually the case. If that choice stops me using the heat pump directly, then I'll likely end up with a more efficient system by increasing the centres. More reading to do I think! The heatpump sizing, and to an extent the spacing, is also mitigating things if I've got my sums wrong and the house doesn't perform as well in practice. Plus faster re-heat times on the DHW with the more powerful pump. Link to comment Share on other sites More sharing options...
SteamyTea Posted March 21 Share Posted March 21 Also the length of pipework can make a difference to how many loops you can get out of a reel. You don't want joints or lots of offcuts that are too short to be useful. Link to comment Share on other sites More sharing options...
BadgerBadger Posted March 21 Author Share Posted March 21 3 minutes ago, SteamyTea said: I am not sure how that affects the heat losses, as long as the exposed areas are correct, and the air changes taken into account. It may change the spacing of the UFH pipework, but the room by room heat losses should show that. I only meant skewed by that our "downstairs only" UFH area is more than half the floor of the house. Not envisaging any trouble and will simply adjust the flow rates accordingly to account for different losses, but if we did end up zoning anything this vaulted space would be the obvious candidate as it's quite thermally separate from the rest. Link to comment Share on other sites More sharing options...
SteamyTea Posted March 21 Share Posted March 21 Just now, BadgerBadger said: I only meant skewed by that our "downstairs only" UFH area is more than half the floor of the house. Right. Link to comment Share on other sites More sharing options...
JohnMo Posted March 21 Share Posted March 21 1 hour ago, Jenki said: @JohnMo, I want to look at this, as I'm not sure what I'm gaining with weather comp. When it's really windy eg last night, but not cold 6deg the heatpump was still trying to heat the house this AM. So this thread has prompted me to do just that I think I'll just change the parameters for weather comp so the temp range is 35deg to 35 Deg. What actually happens to the house UFH is a little different to what you may expect, the floor settles to about 23/24 over the day, following heating it up overnight (I leave the UFH pump stays on 24/7 to distribute the heat evenly), i trip the ASHP off via thermostat. When the heat pump starts against a 24 Deg floor, it's trying to managing a dT of 5/6, so the output temp of ASHP is actually pegged at 30, with lots of concrete to soak the heat away, the temperature takes hours to rise, a sub zero day it gets to about 33 by the time the house is up to temperature. Repeat the next day. The heat pump doesn't modulate just runs at a high sustained load but at a low flow temp. In theory on a 7 deg day I should get an average CoP of 5. Whether I do, not sure, I just look at the most cost effective way. Doing most of it overnight at 13p kWh is as cheap as gas even with a CoP of 2. 2 Link to comment Share on other sites More sharing options...
Trojan Posted March 22 Share Posted March 22 Similar to you badger I'm looking at installing a simple ashp single zone UFH system (although in a much higher heat loss area). This is a performance table I've been looking at to get an idea (they also have performance tables for their different systems and floor coverings, this ones fairly low profile with ceramic tiles - highest output). 4kW at 120m2 works out at 33W/m2. Looking at that 8 loops at 150mm centres would be more than sufficient and you could probably even get away with 6 or 7 at 225 centres while maintaining output at 35 degree flow temps. Looking into calculating flowrates a lot of google sources say 2-3 litres per minute or loop length/40. I watched a video of urban plumbers though where he calculates it by flow rate(l/s) = heat output(kw)/delta T(K) x 4.2 (specific heat capacity of water). Annoyingly his came out at 2.5lpm with a delta t of 7 so I don't know if it's just coincidence that he's in the range everyone else seems to use. If the formula is roughly correct though you'd only need 8 litres per minute (or 1 l/m per loop) for a delta t of 7, and the lower the output required (warmer days), the further that required flowrate falls. I've switched up the formula as I know the range the heat pump wants to operate (7-14l l/m) which would give you a delta T closer to 4 or 5 depending on output needed and flow supplied. I'd also urge you to go for the 5kw ecodan as it will modulate down to sub 2kw in warmer temps. Take everything I say with a pinch of salt though, I've not actually done it yet so it might turn out I'm talking complete pish. 1 Link to comment Share on other sites More sharing options...
Dave Jones Posted March 23 Share Posted March 23 100mm pipe centres for low flow temp and max efficiency. obviously zoning will drop efficiency a fair bit. Link to comment Share on other sites More sharing options...
BadgerBadger Posted March 25 Author Share Posted March 25 Does anyone know is Ecodan's have an integral circulation pump, or do they rely on an external pump in the system to move water through? I'd found the min/max flow rates in the manual (8.5kW Ecodan, ~11l/s to ~24l/min) so had assumed they did. But struggling to find any more information on pressure/pump curves etc. so doubting my assumptions, and wondering if its the flow rate requirements to be matched with an external pump? Link to comment Share on other sites More sharing options...
Trojan Posted March 25 Share Posted March 25 8 minutes ago, BadgerBadger said: Does anyone know is Ecodan's have an integral circulation pump, or do they rely on an external pump in the system to move water through? I'd found the min/max flow rates in the manual (8.5kW Ecodan, ~11l/s to ~24l/min) so had assumed they did. But struggling to find any more information on pressure/pump curves etc. so doubting my assumptions, and wondering if its the flow rate requirements to be matched with an external pump? Probably depends on the model but the ones I was looking at are outdoor unit only with no pump. PUZ-WM50VHA. That's the one you should be looking at as well IMO Link to comment Share on other sites More sharing options...
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