Carpe Diem Posted February 6 Share Posted February 6 Hi, Wondering if I can gain some insights from the community on my setup.... I have attached the proposal the company I used supplied for installing the UFH and Hot Water system in my house. We have been in since November and found that we are using c.40kWh per day on electricity from the grid. We only have electricity. I have a few concerns..... The company were great when they were doing the install, but afterwards I have not been impressed with the service. They came back and reinstalled all the PV units (not the panels) because they said they were installed wrong. This was after they signed it off. I was told I would get a new sign off, but this has not happened and I have chased. I have a couple of minor leaks on the system and it didnt seem to be setup correctly as they did not do a formal handover. They have come out (not addressed the leaks as yet) or done the handover, but they did change it so that the unit is set on Curve with a tank temperature of 50c. It took a week to heat the house up. When I felt the hot water return pipe from on the boiler it was always luke warm. Hot water also seems to take around 2 to 3 minutes to arrive when the tap is turned on. The house is c.450sqm. My concerns are: 1. Have they under specified the heating supply / tank? Its only a 300L system and we have a lot of underfloor heating to fill.... is it simply too small. The home automation company think that for a property of this size, they would normally have 2 tanks - one just for UFH and one for hot water. 2. We can only have hot water or UFH. So if the tank is being heated by a shower, the UFH demand exists from the home automation system, but the valve does not switch to prioritise the UFH. This in itself is dine, as we would expect the shower (for example) to get the hot water and the UFH to wait. But the home automation system does not know this (its Loxone) so it think it takes longer than it actually to heat up, which messes with its brain... which makes it think it make take 3 hours to heat a room instead of 2.5hrs, but somebody was showering for 30mins. Not a major issue, but do you just live with this? 3. Is the 40kWh excessive? That is literally just the energy for the Heat Pump and MVHR units. Thanks in advance! Bill Report_Redacted.pdf Link to comment Share on other sites More sharing options...
JohnMo Posted February 6 Share Posted February 6 What is your floor make up? How are you operating your DHW heating - always on on, one or two heating periods per day and what temperature do you heat too? 1 hour ago, Carpe Diem said: took a week to heat the house up Was that a new build, first heat period? 1 hour ago, Carpe Diem said: concerns are: 1. Have they under specified the heating supply / tank? Its only a 300L system and we have a lot of underfloor heating to fill.... is it simply too small. The home automation company think that for a property of this size, they would normally have 2 tanks - one just for UFH and one for hot water. Do you mean 300L DHW cylinder? If so that is nothing to do with the UFH as that is a separate system. The Two tanks are DHW and a buffer, you will not need a buffer, unless you have a out 10 zones (thermostats) 1 hour ago, Carpe Diem said: We can only have hot water or UFH You heat one or the other not both at the same time that is normal. You have a priority hot water system. Your shower water will come from the cylinder not your UFH system - confused? What do you have automated and why? Link to comment Share on other sites More sharing options...
Conor Posted February 6 Share Posted February 6 (edited) It takes a long time to dry out a house. And a lot of energy. Do you have your final air tightness test result and have your PH certification? However, I do think the heatpump is undersized. We're 315m², same assumed heat load of 15W/m², and have a 9kW heatpump. We used 20kWh on the worst winter days, including working from home, washing machine etc etc. The pump they've installed will mean it needs to be on 24x7 in the coldest weather and not much room left for hot water. How many people are in the house and so you use much hot water? Other than that, we really need to know the timings schedule, control scheme etc. The time it takes for hot water to arrive at the tap is purely a function of the length of pipe, diameter and flow rate. A large pipe over long distance will take longer to flow than a small pipe over a short distance. How involved in the build wee you? Do you know the type of plumbing system, diameter of pipe and the route the pipes running ? Sounds like we're talking a good 30m+ run for your hot water pipe. Edited February 6 by Conor Link to comment Share on other sites More sharing options...
Carpe Diem Posted February 6 Author Share Posted February 6 Firstly, thanks for the replies.... answering them one after another... The floor sits on a raft... minimum 100mm MOT, them 100mm of XPS Ratherm Insulation, then 175mm concrete, then another 100mm insulation and the final c.70mm of screed with the pipes at 250mm centres in most places. Yes, it was a new build, first heating period. There is only one tank, the 300L DHW cyclinder. There is a splitter valve that comes out of the cyclinder and diverts the water to the UFH circuit, or the hot water circuit. My understanding was that the underfloor draws the water from the tank, which then makes the tank cold as cold water from the UFH circuit mixes which then makes the tank cold, so when that drops below a temperature, it turns off the UFH, fills the tank and repeats. Is that wrong? The house is fully automated via Loxone. We have switches/sensor in every room that act as the thermostats, humidity sensors etc. They tell the pumps when to come on and which valves to open. We have 4 manifolds -> left and right of the house on each floor. I have attached the airtightness test result. 0.59. There is 3 people usually in the house, no excessive use, couple of showers etc. The heating kicks in every time it drops below the room temp, which varies from 19.5C in some rooms to 21.5C in others. That is set from 7 till 10:30, 7 days a week, then it drops to Eco mode -2.5C below the comfort settings. Hot water I think is just permanent to keep the tank at the set temp. I was involved in the plumbing to the extent I know how it is done. We use Multipipe 16mm pipe to each room that runs of a central return flow system that is on 32mm pipe. Boiler is at one end of the house, so to the longest point it will be c.25m both ways, 50m in total that will run through the 32mm pipe, and then be called off to the 16mm when the tap/shower is open. @Conor - How did you work this out? "However, I do think the heatpump is undersized. We're 315m², same assumed heat load of 15W/m², and have a 9kW heatpump. We used 20kWh on the worst winter days, including working from home, washing machine etc etc. The pump they've installed will mean it needs to be on 24x7 in the coldest weather and not much room left for hot water." I feared it was too small and not able to handle the load. Thanks Bill Airtightness Test 24.07.2023_Redacted.pdf Link to comment Share on other sites More sharing options...
jack Posted February 6 Share Posted February 6 1 hour ago, Conor said: We're 315m², same assumed heat load of 15W/m², and have a 9kW heatpump. We used 20kWh on the worst winter days, including working from home, washing machine etc etc. We're 290 m2 and our 5 kW Panasonic has been fine for 8 years. It does run a lot of the time when it's very cold, but no issues heating DHW as as needed. Link to comment Share on other sites More sharing options...
Iceverge Posted February 6 Share Posted February 6 What country are you in and how hot do you keep the house? We are in Ireland and use 9kWh / day (2adults+3kids) for DHW with an immersion and avoid 18kWh per day of direct electric at peak winter for heating our passive house. House is generally about 20⁰ This translates into about 2kWh/person per day of DHW and 0.1kWh/m2 per day space heating. For your three people the equivalent would be 6kWh DHW and 45kWh of Space heating demand in direct electric so 51kWh total. You should be at least aiming for a COP of 3 with the ASHP so I would expect your actual usage at the meter to be more like 17kWh not 40kWh as you have reported. The heat pump isn't working properly. Can you get a schematic of the install? Link to comment Share on other sites More sharing options...
Andehh Posted February 6 Share Posted February 6 (edited) I'm not hearing any alarm bells ring from a quick read. We're at about 240sqm non passive/2.5 air tight, but still well Insulated... Yet inefficient home (bungalow, high ceilings, lots of glass etc) with a 12 kw ASHP. We run dish washer and washing machine daily and average about 35kwh during mild winter up to 50kwh during very cold spells. System will run luke warm all day during these periods. That's normal. DHW priority over heating is normal, 300L is your hot water not UFH, second tank would be UFH buffer which is optional but for big homes not required. We don't have one. Your 40kwh seems reasonable enough to me. Wouldn't worry about it. Edited February 6 by Andehh Link to comment Share on other sites More sharing options...
Carpe Diem Posted February 6 Author Share Posted February 6 1 hour ago, Iceverge said: What country are you in and how hot do you keep the house? We are in Ireland and use 9kWh / day (2adults+3kids) for DHW with an immersion and avoid 18kWh per day of direct electric at peak winter for heating our passive house. House is generally about 20⁰ This translates into about 2kWh/person per day of DHW and 0.1kWh/m2 per day space heating. For your three people the equivalent would be 6kWh DHW and 45kWh of Space heating demand in direct electric so 51kWh total. You should be at least aiming for a COP of 3 with the ASHP so I would expect your actual usage at the meter to be more like 17kWh not 40kWh as you have reported. The heat pump isn't working properly. Can you get a schematic of the install? Im in Cheshire, UK. The house is really well insulated too. 200mm of EPS insulation on all the walls and c.300mm to 500mm of insulation on the flat roof. I thought 40kWH per day was high considering that is not any of the lighting or plug circuit, its literally just the ASHP and MVHR units. We are a little warmer, c.21C average throughout. We have two Zehnder Q350s running that say Consumption is 131w to 175W, so 350W max total. So .35kWH x 24 = 8.4kWh. So c.32kWh being used by the ASHP. That also exclude anything I generate from the PV panels on the roof - granted int he winter it is low, but I figure it balances out some of the MVH. How can I go about demonstrating this to the installing and progressing it so that they address it? Technically, I am unsure of what to say... because they have been pretty despondent. Link to comment Share on other sites More sharing options...
Iceverge Posted February 6 Share Posted February 6 With 200mm of EPS I'm assuming masonry construction of some sort. That does mean some drying out time but I wouldn't expect it to be as high as you say. The power demand for the MVHR seems high too. Perhaps you are over ventilating. The smart home gubbins are a bit redundant in a passivhaus I always think. Can you show us any pictures of your install and any schematics? I wonder if your system is cycling lots or else trying to run at a very high flow temperature, perhaps asking for additional heat from an immersion or defrosting regularly. ASHPs work most efficiently being able to heat things "just enough" over a very long period. Link to comment Share on other sites More sharing options...
Carpe Diem Posted February 6 Author Share Posted February 6 Sure, I will get some more specific details of the install and setup. The construciton is a thermo block and external insulation. The slab has been down near 18 months and roof has been on for c.12 months - so relatively dry. I figure its more a case of too much water around the system and not enough power so its over working and emptying itself and its stuck in a cycle of the constant demand.... just a hunch. The Q350 I found two sites, one saying max consumption 131 and another 175W, but I guess that is on boost - which ours never is. The automation is more for lighting control, security etc - the heating part of it should just be in the background. The sensors are more for humity checking to boost MVHR (not configured yet) Link to comment Share on other sites More sharing options...
MPH243 Posted February 6 Share Posted February 6 Have you got the Zehnder comfo control app it will show actual usage, my Zehnder Q450 uses about 40w, I tried it on boost and was 75w then I changed to Max ventilation 167w. This is mine the supply and exhaust need tweaking when I get around to it. Our house is 260sq m and a bit better than building regs. Link to comment Share on other sites More sharing options...
IanR Posted February 6 Share Posted February 6 2 hours ago, Carpe Diem said: My understanding was that the underfloor draws the water from the tank, which then makes the tank cold as cold water from the UFH circuit mixes which then makes the tank cold, so when that drops below a temperature, it turns off the UFH, fills the tank and repeats. Is that wrong? Your description sounds like you have a thermal store, not a UVC, but your quote in the OP is stating a UVC, so fingers crossed that's what is installed and you are misunderstanding how your UFH is working. A thermal store is not appropriate for a ASHP installation. If you only have a single tank, and that is a UVC, then when "on", your UFH is fed directly from your ASHP and the UVC is not playing any part of your space heating. There maybe a minor issue that Loxone can shut down your UFH zones (as they come up to temp) and leave insufficient volume of water open to the ASHP while there is still a call for heat and cause the ASHP to short cycle, but that's not causing you to use excessive electricity. Your ASHP has been correctly sized and the 300l UVC @ 50°C is sufficient for 3 people occupancy. With the size of house though, could it have a higher occupancy (with a future owner) and maybe a 500l tank would have been more appropriate? 7 hours ago, Carpe Diem said: 3. Is the 40kWh excessive? That is literally just the energy for the Heat Pump and MVHR units. 32kWh / day for heating and hot water does seem a bit excessive, if that's the average from November to now. If however that was just for a few days when it was averaging around 0°C, then it's in the right ball-park. If it's an average then maybe you have an electrical resistance heater in your ASHP and your settings are causing that to come on to support the compressor and it's driving down your overall COP. Do you know if the ASHP has an electrical resistance heater? If so, can you disable it? The HP is more than capable of covering your hot water and space heating requirements without it, given enough time. When you say your space heating is set to be on "7 till 10:30", I assume that is 7am to 10.30 pm? Your house is similar size and performance to my own (and also controlled by Loxone) and I'd expect it to loose around 1°C per day with no heating on, so your 21.5°C for 15.5 hours and 19.5°C for the rest is effectively switching it off from 10.30pm to 7am, as it's unlikely to be dropping to 19.5°C. That should be fine on all but the coldest day as there should be enough headroom on the ASHP to put sufficient energy into the house in a 15 hour period (minus the couple of hours it maybe doing hot water). In short, there's nothing particularly wrong with your set up (accept it could on occasion cause short-cycling), so if you are using excessive electricity I'd look to disabling the internal resistance heater on the ASHP, if you have one. Link to comment Share on other sites More sharing options...
dpmiller Posted February 7 Share Posted February 7 not sure if you're worried about the cost or the consumption, but an E7 tarrif might help /we've just received the last quarter's bill and for our 260m2 non-passiv it's an average of 30kWh/ day total consumption. On a cooler day a full half of that is for heat into the slab during the E7 period. Link to comment Share on other sites More sharing options...
Carpe Diem Posted February 7 Author Share Posted February 7 Hopefully, this is all relevant. I have uploaded a video of the setup I have here.... https://youtu.be/UFWexaN-h6o (it will be available from 12:00 today, still uploading whilst writing) And a video of the Loxone interface here..... https://youtube.com/shorts/4K4lUXrkWxI I have also attached some images for reference. In the video, you can see the heat pump is running for UFH. This is because the Master Ensuite has a call for heat, minimal as the valve is 5% open as can be seen in the other video. The valve is open because the temp 21.7c in the room, and it should be 21.5c. There is a variance of .5c, so in this instance it is calling for heat upto 22c then would stop. Every other room is fine. I have adjusted the temp control from 21.5c to 21c in the image IMG_5342.png, which automatically falls outside of the .5c variance and the valve automatically went to 0% open and the UFH call was stopped. Just thought that would explain the system and how it works. I have also attached images from the Mitsubishi Ecodan MEL Cloud software for past 24 hours. This shows the hourly temperate both internally, and externally (which I presume it gets from the ASHP unit itself). You can see that yesterday, 67.9% of the the time it was calling for heat..... which seems crazy. It wasnt that cold, but a tiny 5% open on a single valve seems to make the heat pump kick in full power and run continuously rather than just taking some hot water from the tank. Does this help? Link to comment Share on other sites More sharing options...
Lofty718 Posted February 7 Share Posted February 7 I'm rather suprised that in a new build passivhaus the installers would of put in UFH pipes at 250mm centres Link to comment Share on other sites More sharing options...
Carpe Diem Posted February 7 Author Share Posted February 7 @MPH243 Is that via the Lan C module? It would seem that without the Lan C module installed, you get nothing out of the system other than going to the interface and looking at all the settings. TBH, I have been disappointed that this isn't standard, or wasn't specified when commissioning. My system does not have that. Zehnder have said to install the Option Box which seem to allow control but no output. @IanR Thanks for the reply.... good to see another Loxone user. What information do you get from your heating into Loxone? Yes, the kwh is average from 11th Nov to 5th Feb. I will ask the question, as I am not sure about the internal resistance heating. Maybe the video helps? Link to comment Share on other sites More sharing options...
JohnMo Posted February 7 Share Posted February 7 6 minutes ago, Lofty718 said: I'm rather suprised that in a new build passivhaus the installers would of put in UFH pipes at 250mm centres Why - are they too wide or too narrow a spacing? Link to comment Share on other sites More sharing options...
Lofty718 Posted February 7 Share Posted February 7 Just now, JohnMo said: Why - are they too wide or too narrow a spacing? Narrow, not a huge deal but with 100mm spacings you can probably run 2c lower flow temperature A lot of heat pump installers strive for a 100mm spacing when speccing ufh Link to comment Share on other sites More sharing options...
Carpe Diem Posted February 7 Author Share Posted February 7 The spec supplied said 200mm centres, but I thought the installer had said that the spec from pipe supplier wasnt based on a passivhaus house, with the slab insulation we had so he advised on making it wider. The span in the pic is 3m wide and I think 24 loops. Link to comment Share on other sites More sharing options...
JohnMo Posted February 7 Share Posted February 7 1 minute ago, Lofty718 said: Narrow, not a huge deal but with 100mm spacings you can probably run 2c lower flow temperature A lot of heat pump installers strive for a 100mm spacing when speccing ufh When you get to low outputs (less than about 20W/m2) it make almost no difference to flow temp. We have 300mm spacing in a non-Passivhaus (around 600m pipe in a 195m2 slab), it was -5 last night and doing a batch charge our flow temp didn't go above 33 the house is at 20 degs and garden room is at 21. If I set my flow temp at or below 28 deg, it means my heating is effectively off, as there is 8 deg restart hysteresis from set point to restart after a heating cycle, so the house floor would have to drop to 20 degs to allow the heat pump to start, that just never happens, as that is below the house temp. Practically gets in the way, unless you want to install a buffer to draw heat from, but the heat runs hotter to charge the buffer. Never understood, why anyone needs 100mm pipe spacing unless the house leaks heat like seize. Installer may strive to get 100mm spacing but to what gain in a low heating requirement house or Passivhaus. Link to comment Share on other sites More sharing options...
Carpe Diem Posted February 7 Author Share Posted February 7 @JohnMo I did originally have the controller set on flow temp, but the installing company then change it to compensation curve. I am not sure what the best setting is to have - flow, or curve. The Tank temp is set at 50c, and currently shows the tank being at 44.5c. When it was set to Flow temp, it was set at 38c. Link to comment Share on other sites More sharing options...
JohnMo Posted February 7 Share Posted February 7 If you are running a weather comp curve, you just need to actively make sure on different temp days you are not running too hot or cold and make tweeks to the curve to fine tune. You really shouldn't be bouncing off thermostats ever. If you do your flow temp is too high. Our house isn't passive, possibly about 50% more heat demand due to form factor and some massive windows, our house will stay very stable down to zero degs just running the ASHP at around 30 and mixing down to 28 degs. So 38 was possibly way to high. For context the 8 degs possibly represents about 3-400W extra power while the heat pump is running, compared to 30 flow temp. Link to comment Share on other sites More sharing options...
Carpe Diem Posted February 7 Author Share Posted February 7 It looks like the comp curve is set + or - X degrees based on the temp from outside. I dont really want to be messing/adjusting the temp frequently, id rather have it automatic.... which I am guessing that based on the outside temp reading it is automatic, if the curve is set correctly. However, I am not sure what the curve +- is of..... is the room temp? When you say, shouldnt be bounding off the thermostat, do you mean the rooms should not hit the max temp? If so, then in theory they wont (give or take the +-0.5c variance. Or, I can change it back to flow temp? and if so, what temp would you recommend. It just seems wrong that if there is a tiny demand in one room, that the ASHP is running as though it is heating the whole house, when it should just be a small amount. Link to comment Share on other sites More sharing options...
Conor Posted February 7 Share Posted February 7 (edited) 18 minutes ago, Carpe Diem said: It just seems wrong that if there is a tiny demand in one room, that the ASHP is running as though it is heating the whole house, when it should just be a small amount. Which is why you run systems like this as a single zone (or zone per floor) rather than individual room stats. You probably don't want to hear this, but might be best ditching all the room stats and luxone stuff, and running it simpler. We've three floors, separated into two zones, runs on a manual timer (with one stat set to 21c, only in mild weather does it hit this) for 18hours a day on weather comp. I never need to think about it and I never notice when it's running or not. Edited February 7 by Conor Link to comment Share on other sites More sharing options...
JohnMo Posted February 7 Share Posted February 7 The thing with a passivhaus the heating demand is very low, therefore the floor surface temp only needs to be about 2 or 3 degrees above room temperature. Correctly setup the system should self regulate. The floor output is a factor of area and dT between the floor surface temperature and room temperature. So if your room temp is 21 and the floor is 23. Once room hits 22 the floor output is halved, so it looks after without any outside influencers. Solar gain who cares the floor output drops to zero without any intervention. Link to comment Share on other sites More sharing options...
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