Glyn Hudson Profile picture
Aug 18, 2022 17 tweets 7 min read Read on X
Following on from my air source heat pump installation thread, this thread will document the performance of the system #ASHP🧵🤓 Image
HP is a 5kW Samsung Gen 6 with 150L DHW tank and 7x upgraded radiators in a 200yr old 2 bed end-terrace house with sold stone construction, max heat loss at -3 degC ambient is estimated to be between 3.3kW-4.2kW, 28mm pipework to 3-port, mostly 22mm primary with 15mm drop to rads ImageImage
The monitoring system is a @Openenergymon Level 3 setup with class 2 MID approved heat and electricity meters (Sontex 749 M-BUSand Estron SDM120 Modbus), data logging and graphing is done using Emoncms guide.openenergymonitor.org/applications/h… Image
The ASHP has now been installed for almost 2 weeks, it's been a heatwave, so no heating required! My DHW has been heated from solar PV divert, however the last couple of days have been dull so DHW needed a topup...
This evening the ASHP heated my DHW tank from 20 degC to 55 degC with a COP of 4.2, it still feels like witchcraft how a meagre 1.25kWh of electricity results in 5.3kWh worth of piping hot water! Image
I had planned to limit DHW temp to 45 degC to maximise COP, however I was pleasantly surprised how it managed to go from 45 degC tank (50 degC flow) to 55 degC tank (60 degC flow) with a respectable COP of 3.6, so not need to limit max temp, at least not at this time of year Image
I also had an airtightness test done which indicated the house was not as leaky as I though which should mean max heatloss is closer to 3.3kW rather than 4.2kW, the 5kW ASHP I fitted is the lowest output ASHP widely available
In terms of noise, I've found the outdoor unit to be quieter than expected, I can't tell if it's running without going outside, the rubber dampers and flexi connections on the wall-mount must be doing their job, no noticeable vibrations, however... ImageImage
I've found the pump Grundfos UPM3 PWM located in cupboard next to bedroom to be louder than expected during DHW cycle, setting 70% inverter limit (FSV 4051) reduces pump speed from 23l/min to 17l/min during DHW which makes pump almost inaudible, no noticeable performance diff Image
I've noticed the Samsung display reports about 10% less heat energy delivered than the class 2 MID heat meter, maybe the Samsung calculation is assuming I'm using glycol? @JeremyClimas Image
I was expecting the opposite, i.e Samsung to be reading slightly higher since there will be some heat loss between the outdoor unit (where Samsung reading is calculated) and indoors where the heat meter is located, the flow rates and temperature readings from each system match
Coldest night of the year so far last night, ambient dropped to 5.4°C, indoor averaged 21.5°C, ASHP averaged 4.8 COP for heating in the evening and 4.37 COP including DHW cycle top-up overnight and some heating this morning 👍 ImageImage
It still feels like witchcraft how 1.5kWh of electricity results in over 7kWh of heat 😁 #magic
Ran a test this evening to see how hot the ASHP is able to heat DHW without using an immersion, I stopped the test when middle of tank hit 56C with a flow temp of 64C which is close to max for my R32 ASHP, ambient was 9C and overall COP of 3.3... Image
Therefore, maybe using an immersion for legionella is not always required since apparently 90% of any potential legionella is killed within 2hrs at 50C so 56C should be pretty safe, COP of 3.3 is not great but much better than COP of 1 from an immersion!
Now the outside temperature has dropped a bit the ASHP is running for a bit longer, in last 24hrs: average outdoor 12C, average indoor 20C, 18kWh of heat delivered using 3.6kWh of electricity, overall COP of 4.9 for central heating and DHW, or COP of 5.5 for just central heating Image

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More from @glynhudson

Dec 10, 2022
Coldest day of the year today, -2.2C overnight and freezing most of the day, heat pump kept our house cosy 19C-21C during the day, 17C overnight, including hot water for 1x bath and 2x showers it used 17.6kW electricity which resulted in 60kWh of heat, COP=3.4 🧵
Even in sub-zero temperatures a flowT of 35C with just radiators was sufficient to maintain 20C-21C indoorT, radiators are large but not ridiculously so, here's a video of the design and install process
The average SCOP since the unit was installed is in Aug is 4.35, data from independent revenue grade meters logged by @Openenergymon, checkout heatpumpmonitor.org for live data from lots of different ASHPs
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