rhymecheat

Yes, yes it does. Indeed there is. I don’t know how long a cycle would be but I’ve monitored the sensors for about an hour straight and never saw a difference of more than 1C, always with the return higher than the leaving

It’s a polypipe. It’s got a mixing valve set at 35C and gauges for in/out water temperature.

I’ve checked with a FLIR camera and it seems to match the sensors. Yes, there is a buffer tank, it’s a Cordivari 29W 26L

The confusing part to me is that most of the day the UFH is on and it says on the manifold that return temp is about 8C lower than incoming water temp so the UFH must be dissipating heat at a good rate. Most of the day. This is the only loop in operation so I don’t get why the heatpump still reads a return so high. Atm heatpump flow is between 27 and 32l/m (is oscillates).

it’s the EPRA14DV3 on this brochure: https://www.daikin.co.uk/content/dam/dauk/document-library/Brochures/Heating/Heating Installer brochures/Daikin Altherma 3 H HT_767.pdf Heatpump installation was done by one company and house upgrade by another. The property was massively extended so all both companies had to work with was the drawings regarding calculations. Both plumber responsible for the build and the heatpump engineer were in contacting regarding what the UFH should look like but ultimately plumber installed it. Heatpump engineer however, was fully in charge of the rads. With the old boiler, total consumption for last year was 14890kwh if that helps.

I didn’t but it was the only one with a design my wife approved (insert massive eye roll). I think over 30kwh/day is wrong as with a COP of over 3 at 45C and 8C outdoor, that would seem like a massive amount of heat. But then the return temperature always stays high which tells me the heat is not leaving the loop or too much heat is being produced

Sadly no as the thermal output is only displayed when glycol is not in the system, which it is.

Brochure claims a COP of 4.86 at 7C outside and 35C leaving. And 3.70 at 7C outside and 45C leaving. so setting it at 35C should be better than 45. When I set it to 45 however, the cost goes up considerably.

Yes good point. I’m running it at a constant 35C but setting the thermostats to go down during the night. During the night the thermostat is set to go from 20 to 18. At this stage the leaving temp from the heatpump can go too as low as 25C (but not lower). But, in the morning when I come down it read 17.3 and in the evening when I go up it’s never above 19.3.

Floor is amtico on a 40mm insulation I believe. Not sure about perimeter insulation. I’ve used the FLIR on the pipes. Right now leaving temperature is at 35C. Inlet at 36C

I believe the indoor unit for the heatpump measures this from pipe in/pipe out

I’m hypothesising. I’m asking here to be corrected or validated. If I see two things that are strange I can’t help but think they’re related to the same issue. More probable then there being two separate issues. The unit is a Daikin Altherma 3 H HT. indoor unit is the etbx16ef6v (the wall mounted one). House just got fully renovated and properly insulated. Used a FLIR camera to look for week spots and couldn’t find any obvious ones. the heatpump is new and is replacing a 35 year old boiler that couldn’t even heat the house to 16C in the winter. All the pipes have been replaced, all the rads replaced for bigger low temperature ones. Downstairs is UFH and it seems to be the only area that never reaches desired temperature (max I can get with 35C is about 19.3C over a period of about 6/7 hours). I could increase the leaving temperature but then the costs become even higher. yes, analysis was done but I have no access to it unfortunately.

Yes. When the rads come on, it has no issue achieving 40C. It has no issue achieving 55 if needed either. What I find weird is that it never seems to maintain a temperature for longer than a minute before dropping drastically. This is why I think it’s consuming so much power in the first place. How do I go about comparing the heat loss? I’m just looking at the warnings in the manual regarding the delta T. I can’t really correlate the high power with the low delta T, I’m just noticing that the power usage is abnormally high and that return and flow temperature are always close together which I didn’t think they should be. That I don’t really know but I can try and confirm.

Correct! Indeed. Manual states that any pump limitation will compromise the ability to achieve delta T so I’m not sure but I still have it a shot. It also states a minimum of 25l/min is required at all times but when I checked, it was at about 30l/min. Now, there are 3 pumps in the system: the heatpump one, a pump to send water to the system, and a pump for the UFH manifold pump. When I reduce the heatpump speed (have options for 90, 80, 70 or 60% limitation) I can get it down to almost 20l/min. Still, the return temp is as high as leaving. However, I don’t fully understand what reducing the other pumps would do to the system. Currently, these other 2 pumps are Grundfos set at speed 3 (the UFH manifold pump can also do constant pressure instead). I don’t know if reducing these other pumps would reduce the heatpump speed or just fail to move all the water the heatpump is dishing.

Hello there, Ive recently installed a Daikin Altherma 3 H HT and have noticed that it never seems to reach the configured delta T. The heat pump main zone is configured for UFH which the manual claims should follow a delta T of between 3-10C. Leaving water temperature is set to 35C and it seems to be able to heat the property to about 19C when outside is 8C. However, from the sensor readings it seems that inlet temperature is often the same (occasionally, even higher) as the leaving temperature. This tells me the heatpump is working for nothing as no heat is leaving the loop. Because of this the heat pump seems to runs almost continuously costing energy in the the lower 30s kWh/day which is costing me a fortune… The UFH manifold shows a delta of about 8C (35C in, 28C out). Why do I not see this same drop on the heat pump? By the way, the second zone is comprised of large radiators and it’s configured for 40C (there’s a mixing valve on the UFH preventing it getting too high temp water). Any help with debugging this issue would be much appreciated.