SteamyTea Posted June 18, 2017 Share Posted June 18, 2017 As we have had a few sunny days recently and pretty close to the longest hours of daylight, has anyone suffered increased overheating? Decent temperature data is always welcome, but a general response is also useful. Link to comment Share on other sites More sharing options...
ProDave Posted June 19, 2017 Share Posted June 19, 2017 When we had our summer (about a month ago, all 3 days of it) the house remained comfortably cool inside. I would love some thermal gain right now. Link to comment Share on other sites More sharing options...
SteamyTea Posted June 19, 2017 Author Share Posted June 19, 2017 Thanks Dave I have not heard any mention recently of overheating problems, I think it is because the sun is high in the sky and sets in the north west at the moment. Air temperatures down here have not been exceptionally high, around 22°C, but the sea is not fully up to temperature yet. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted June 19, 2017 Share Posted June 19, 2017 (edited) From just random observations, the house temperature has reached about 23.5 deg C, cooling back to around 21 deg C overnight. The MVHR is on bypass a fair bit of the time, and was running in active cooling mode during the later part of the day. The slab seems to be sitting at around 19 deg C, and has been cooled a couple of times - the slab cooling comes on when the house exceeds 22.5 deg C. I'll have the data for June at the end of the month, as the logger records data in monthly chunks to a USB stick now. I need to look at adding a way to pull the data out mid-month to look at it, perhaps. The outside temperature peaked at 31 deg C yesterday afternoon. Edited June 19, 2017 by JSHarris Link to comment Share on other sites More sharing options...
ragg987 Posted June 19, 2017 Share Posted June 19, 2017 These few days we have been hitting above 26C by late afternoon - we have quite a lot of west-facing glass. I have just switched on our cool slab so hopefully that will help. Timed to run during the day so we use generated PV to drive the cooling. At present we are trying to keep windows shut in daytime and open through the night. Link to comment Share on other sites More sharing options...
SteamyTea Posted June 19, 2017 Author Share Posted June 19, 2017 1 minute ago, ragg987 said: I have just switched on our cool slab Can you monitor the extra energy used. 26°C sound comfortable to me, but then I grew up in the Far East and the West Indies. Link to comment Share on other sites More sharing options...
gravelld Posted June 19, 2017 Share Posted June 19, 2017 Is there a definition of overheating? I would consider our house over heated in the past few days. During nights temps don't go much under 24C. I've seen one thermometer read 28C in late afternoon which appears to be the hottest point. Our house is complete crap btw. Mostly cavity, all filled but only about 60mm. Old school 8mm 2G windows. One solid wall gable and some 1G here and there. Poor air tightness. My plan to fix it: - More external insulation (to stop heat getting in) - Fix the air tightness when insulating - Mechanical ventilation - More shading according to the sun's position - use software to calculate and plan this - Any other ideas people? I noticed just how much a difference even a small overhang can make. Most of our gables have none, but one section that does - the window is completely shaded from 11-2. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted June 19, 2017 Share Posted June 19, 2017 Our slab cooling uses a pretty constant 500W or so when on, and has been on for around 4 hours a day during the hot days, so around 2kWh/day, perhaps. That's input power and energy to the ASHP, and seems to equate to a bit over 7 kWh of effective cooling energy, or around 1.8 kW of cooling power. In addition, the MVHR heat pump has been running for around the same time, and that delivers an output power of around 1.5 kW in cooling mode, and uses about 400W, so around 1.6 kWh input energy, and perhaps 6 kWh output energy (bearing in mind that this is really outward heat transfer power and energy for both). We have been generating over 40 kWh/day recently, so the cooling is effectively free, in terms of energy cost. We are just coming up to 20 MWh of generated energy in total, with a total consumption of just over 7 MWh, over a longer period (the electricity supply went in before the house was erected). Link to comment Share on other sites More sharing options...
ragg987 Posted June 19, 2017 Share Posted June 19, 2017 40 minutes ago, SteamyTea said: Can you monitor the extra energy used. I will report back on energy generated by the ASHP for cooling. I am unable to monitor consumption, I am expecting no overall extra power consumption and that the PV generates what we need. Prior to switching on cooling, I relied only on PV to heat DHW. Now that cooling competes for that generated power, I have put the ASHP to heat DHW as well as cooling of slab. Should consume no more energy in total, but does mean ASHP is back in duty. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted June 19, 2017 Share Posted June 19, 2017 (edited) I doubt that the ASHP will be using more than a small percentage of your PV generated output in practice, so rather than have the ASHP switching from heating to cooling mode, with the inherent power loss that creates for every switch over, I'd just leave the DHW running from the excess PV. What's the output rating of your ASHP in cooling mode? Ours is rated for a lower output when cooling than when heating, and rarely uses more than around 500W of input power in cooling mode. Right now the PV is generating nearly 6 kW and the cooling has yet to come on, but when it does that will still leave more than 5 kW of spare generation capacity for DHW, and the Sunamp PV can only use 2.8 kW of that, so we will still be exporting a fair bit (enough to charge my car). Edited June 19, 2017 by JSHarris Link to comment Share on other sites More sharing options...
Ferdinand Posted June 19, 2017 Share Posted June 19, 2017 Ours - OK but not passive and 2G - has been tricky to cool down overnight. Yesterday the house was at 26C for the afternoon (I dislike above 23C and ideally to be at 20C), and I couldn't get it below 24.5C overnight with windows open. At present the air is still and balmy. Last week it was coping as it was windier. As we are gas / ufh and no ASHP/MVHR I am stuck as to what to do. One thing I did notice was that out landing rooflights. when exposed to the morning sun, were like radiators. Perhaps need to look into external roof films, and evaluate just how robust they are. And we have an unprotected Southern Facade, so I may need to look at a veranda. Ferdinand Link to comment Share on other sites More sharing options...
Bitpipe Posted June 19, 2017 Share Posted June 19, 2017 We're pretty warm also - east shading is working well but more exposed on the west. Basement is nice and cool though.... Link to comment Share on other sites More sharing options...
jack Posted June 19, 2017 Share Posted June 19, 2017 We're at 25.5 downstairs and 26.5 upstairs. Far too warm. Part of this is the eastern facade getting a long period of morning sun, and not having any shading on half of the windows. I'm looking at setting up some temporary shading just to keep the sun out for the next few weeks. Also looking at buying some fans for bedrooms at the moment, as getting to sleep is starting to become uncomfortable. I've also realised in the last week that something seems to be wrong with the MVHR summer bypass mode. It works fine if you switch it on manually, but the automatic setting doesn't seem to be working. Need to contact the supplier for input! Link to comment Share on other sites More sharing options...
ragg987 Posted June 19, 2017 Share Posted June 19, 2017 (edited) 1 hour ago, JSHarris said: I doubt that the ASHP will be using more than a small percentage of your PV generated output in practice, so rather than have the ASHP switching from heating to cooling mode, with the inherent power loss that creates for every switch over, I'd just leave the DHW running from the excess PV. We have 4kWp array, on a really good day we can generate 24kWh. Our DHW consumption is relatively high, we have 6 people to cater for. In reality, my heating / cooling strategy (still in infancy, will fine tune) is a bit more subtle. DHW on a timer starts at 10:30 set point 42C. By then we should have had about 5kWh PV to immersion. If sufficient DHW then it will not come on at all. Cooling on a timer starts 10:40. So if no DHW load will come on straight away, else is delayed until DHW is satisfied. Any excess PV goes to topping up the DHW - we do not seem to export unless we are away and not using DHW and power. We also try and run washing / dishwashing from early afternoon to even out the load as best as we can. Cooling load can be relatively high - the unit reports current of 4A (single phase so about 1kW). Cooling capacity is approx 7kW, 10% lower than heating capacity. Edited June 19, 2017 by ragg987 corected PV Link to comment Share on other sites More sharing options...
billt Posted June 19, 2017 Share Posted June 19, 2017 Our old house is on 3 floors with distinct zones. Bottom floor is built into a bank with thick stone walls and small windows, max temp was 22, middle floor has thick stone walls and small windows, max temp 24, top floor single brick walls with 70mm internal insulation and largish S facing windows max 25. Maximum outside temperature 29. For the last few days curtains/blinds and windows have been closed during the day and opened when the outside temperature has dropped. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted June 19, 2017 Share Posted June 19, 2017 Something odd is going on today, as it's hotter outside, yet cooler inside, so much so that the slab cooling hasn't come on yet. It's 32.1 deg C outside, from the sensor standing off from the sheltered North wall (the hottest I've seen so far this year) yet it's only 22.2 deg downstairs and 22.6 deg C upstairs. The MVHR cooling has just come on (it comes on at 22.5 deg C upstairs), but I suspect that the slab cooling may not come on at all today (it comes on at 22.5 deg downstairs). We're currently generating just over 6 kW, and consuming around 3 kW, with my car on a slow charge. I'm tempted to pull the USB stick from the logger and see what all the data looks like. Link to comment Share on other sites More sharing options...
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