Hi,
Although I’ve had a heat pump of nearly two years for a whole variety of reasons I‘m only now digging into the why my lifetime COP is only 2.36! I’m gathering information but am struggling to know what to expected and what/how to optimise, so I’d really appraicfte you help and expertise!
So, our environment is:
- Well insulated 2y old detached house
- Samsung Gen6 AE120RXYDEG
- Pre-plumbed system provided by Joule, UHF downstairs, radiators upstairs
- Heating runs as single zone
- Wilo para pumps on ASHP - Joule advocate running all the pumps at maximum speed
I don’t have any of the design documentation for the system - I’m chasing the developer for it with little success so far!
I’ve just installed monitoring using ESPHome Samsung HVAC Integration and so can finally look at the system in some detail. I also forward the data from Homeassistant to emoncms: Dashboard (ignore Friday 24/1 14:00 - Saturday 25/1 12:00)
What do I see:
- UFH performs better than rads, maintains good difference between flow and return
- When the rads are heating up, performance is OK, but as the they get warmer the difference between flow and return narrows to only 1-2 degrees
- DWH COP is terrible usually less than 2, but lower priority at the moment
- Primary and secondary pumps on ASHp are fixed speed, typically pushing around 24l/m
- Monitoring shows that compressor frequency and fan speed are reduced as the system approaches target flow
- PWM signal also reduces significantly to 40% or less
Key variables:
- WL 2011/2012: -2 to 15
- WL1/WL1 (2021,2022,2031,2032): 35-45
- FSV 2091/2902 set to 3 (joule default is 1)
I don’t know if these settings are remotely close to being optimal!
So key questions:
- Delta T: I’m becoming fixed on the low delta T when the radiators are warm. I read conflicting views on whether this is an important factor in the efficiency of the system, what do you recommend? I’m not sure if I can achieve a different delta T for HFW and Rads, but if I can should I?
- PWM pump or not: Should I replace the primary pump with a PWM pump? Would that allow the system to use Water Law/Weather compensation more efficiently?
- Balancing radiators: I’ve currently balanced the rads to have roughly the same return temp. I read in some places that it is best to have maximum flow through the radiators Including keeping all TRVs fully open. What is recommendation?
Any help gratefully received!