mk1_man Posted May 12 Posted May 12 Hi all, I have used our heat pump to cool house for last three days and I have been blown away how effective it has been. We have the 7kW Vaillant with UFH. It has dropped the internal temperature on the ground floor 2 - 3 degrees which doesn't sound a lot but it has made all the difference. Just wondered who else was doing this?
JohnMo Posted May 12 Posted May 12 Was on in April for 2 weeks, then the outside temperature dropped so heating on for a week, then back to cooling for the last week. Our floor is being managed to stay below 19.4 degs currently. Blue sky all day today. It's good, CoP of around 6 to 7 mostly went running. Although first few hours we got over 8. Plus billy bonus it only generally runs when the sun's out so free running cost, powered from excess PV.
joth Posted May 12 Posted May 12 1 hour ago, mk1_man said: Hi all, I have used our heat pump to cool house for last three days and I have been blown away how effective it has been. We have the 7kW Vaillant with UFH. It has dropped the internal temperature on the ground floor 2 - 3 degrees which doesn't sound a lot but it has made all the difference. Just wondered who else was doing this? What emitters is that with, and where? I've been doing this with UFH (GF) and fan coil (upstairs), I've never found the UFH cooling especially useful, but if you have UFH upstairs then perhaps it is more useful. Our FCUs work a charm though. (Or did, until motor on one failed.... ebay special was not so special, sigh)
Bramco Posted May 12 Posted May 12 We set the heating pump on cooling last year but in the height of the summer. At this time of year though, the roof lights and patio sliding doors give enough draght to keep things ok. Having said that, when we used cooling it was very effective. Cool slab underfoot in the morning.
Michael_S Posted May 12 Posted May 12 How low flow temp are people risking with regards to the condensation risk? Has anyone tried home made 'fan tails' by putting the fans to blow onto the radiators?
JohnMo Posted May 12 Posted May 12 22 minutes ago, Michael_S said: How low flow temp are people risking with regards to the condensation risk? My target flow temperature is 12.5 degs. But pipes are in 100mm concrete. Floor temp is closer to 19.5, so never see any issues. Now on year two doing cooling. Typical heat pump cycling Red line is flow temperature, green is return. Purple line is outside temp.
Michael_S Posted May 12 Posted May 12 2 hours ago, JohnMo said: My target flow temperature is 12.5 degs. But pipes are in 100mm concrete. Floor temp is closer to 19.5, so never see any issues. Now on year two doing cooling. Typical heat pump cycling Red line is flow temperature, green is return. Purple line is outside temp. So you don't have any pipes anywhere indoors in voids anywhere that could see condensation? I read somewhere that anything below 18C was risky for (unseen) condensation leading to damp/rot problems down the line.
JohnMo Posted May 13 Posted May 13 8 hours ago, Michael_S said: So you don't have any pipes anywhere indoors in voids anywhere that could see condensation? I read somewhere that anything below 18C was risky for (unseen) condensation leading to damp/rot problems down the line. Be careful what you read always check yourself. Yes I have pipes inside and an uninsulated UFH manifold. No voids though. But nothing runs below dew point and that's the important bit, so are always dry. Read this currently running thread also 1
joth Posted May 13 Posted May 13 13 hours ago, Michael_S said: How low flow temp are people risking with regards to the condensation risk? Has anyone tried home made 'fan tails' by putting the fans to blow onto the radiators? My system low limit is calculated dynamically based on indoor temp and RHI, using https://www.loxone.com/enen/kb/dewpoint-calculator/ However in practice I could hard code it at 13deg and be about the same result. 1
jack Posted May 13 Posted May 13 18 hours ago, mk1_man said: Just wondered who else was doing this? We moved in at the end of 2015 and I think I started doing underfloor cooling two or three years later. As I've written elsewhere on BH (and you've experienced yourself), it works insanely well. I suspect one of the biggest factors in how well this works in individual circumstances is floor makeup. We have a polished concrete screed, on top of a nominally 100 mm structural slab with embedded UFH pipes. That's a great combination for storing a lot of coolth and transferring it efficiently. The one carpeted room downstairs is, unsurprisingly, noticeably warmer than the rest of the space. 14 hours ago, Michael_S said: How low flow temp are people risking with regards to the condensation risk? I've tried everything from 14 - 17 °C flow temp over the years and all have worked fine. I'd have to check, but I think I just left it at 15 or 16 °C after the last time I changed it a few years back. In terms of condensation, the only exposed and unsulated pipes in our system are the manifold pipework and connectors. We get a breath of condensation on the metal parts of those, but never enough for it to drip. As @JohnMo says, running the cooling while the sun's out means free cooling if you have PV.
mk1_man Posted May 13 Author Posted May 13 whilst cooling my flow goes as low as 12.5 degrees however return is circa 15 so somewhere in the middle. I haven't noticed any condensation anywhere Really impressed how well it works and am sure will be even more impressed once I get my solar installed if the G99 ever comes back! 1
Conor Posted May 13 Posted May 13 Condensation for short periods of time in a hot summer isn't going to do any damage to a building. It'll dry up as soon as you stop active cooling. It's only going to form on exposed pipes and manifolds anyway. 1
IGP Posted May 13 Posted May 13 I haven’t got an ASHP yet (hopefully later in the year) but I’m planning for having cooling, but it will be have to be high wall fan coils (of which I can’t find many examples). My plan in my head is to run the chilled water pipes (insulated of course) through the loft, and drop them down through the ceiling within trunking for each bedroom, and have a condensate pump for each fan coil pushing the condensate back up into the loft and the condensate to join the existing MVHR condensate line there. Im thinking it will also need to be a separate zone as we don’t want chilled water going to the rads (it’s all rads). Has anyone else done something similar? Is this stupid? What about the water in the cooling zone for the heating season? Or should I forget it and go classic mini-split air conditioning?
JoeBano Posted May 13 Posted May 13 You could swap the radiators for fan coil units? I swapped mine beginning of last summer worked a treat. Not insulated the pipework, 16c is my flow temperature not had any issues. I’ve got myson Ivector units, think they are brilliant, lowered my heat flow temperature to 32c @ -2. My bedrooms suffer room overheating in the late evening, they kept the bedrooms at 20c on the hottest days last year.
MikeSharp01 Posted May 13 Posted May 13 On 12/05/2025 at 16:51, JohnMo said: It's good, CoP of around 6 to 7 mostly went running. Although first few hours we got over 8. Plus billy bonus it only generally runs when the sun's out so free running cost, powered from excess PV. The ASHP we are looking at says the COPs up to 5.56 is that the limit should I be looking for one that get up to 8 or is the quote from the manufacturer based on some output value?
JohnMo Posted May 13 Posted May 13 54 minutes ago, MikeSharp01 said: The ASHP we are looking at says the COPs up to 5.56 is that the limit should I be looking for one that get up to 8 or is the quote from the manufacturer based on some output value? You may need to get a proper look at the performance data table, for heating and cooling. Headline figures are just an average based on prescribed outside temperature and flow temperature. If I was buying again, I would get a Panasonic, everything I have seen, or read say they are good.
MikeSharp01 Posted May 13 Posted May 13 3 minutes ago, JohnMo said: You may need to get a proper look at the performance data table, for heating and cooling. Headline figures are just an average based on prescribed outside temperature and flow temperature. If I was buying again, I would get a Panasonic, everything I have seen, or read say they are good. The one we are looking at has a Panasonic DC Inverter Compressor - which is the real heart of the machine I guess.
JohnMo Posted May 13 Posted May 13 1 hour ago, MikeSharp01 said: The one we are looking at has a Panasonic DC Inverter Compressor - which is the real heart of the machine I guess. The control algorithm is the bit that matters as much as anything. Read the instructions well or post details
MikeSharp01 Posted May 13 Posted May 13 11 minutes ago, JohnMo said: Read the instructions well or post details Will do, when they finally tie down the spec, as things stand it keeps coming and going from their web site, something to do with MCS certification.
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