Posted by: @hydros

@derek-m 

The cycling is only occurring at outside temperatures above about 8C so probably nothing to worry about. COP for yesterday was 3.18, not bad but I was hoping for a little better. Not sure what else I can do to improve this?

Regarding thermostat. It is a remote thermostat that the installer fitted, which gets interfered with by something in the house, so this needs replacing with a different model. I like the idea of a smart version to be able to see some stats on the house temperature but from the experience over the last week, I think it's something that will mostly be forgotten above once weather compensation curve is fully optimised, so a basic wired version is probably sufficient. 

Hi Hydros,

You don't actually need a thermostat in your system, in fact it would be better to remove the thermostat altogether, and move your Daikin controller into the main living area and set it for Leaving Water Temperature Modulation.

One way to improve the COP for DHW production would be to reduce the setpoint to the lowest acceptable level, thereby reducing how hard the heat pump has to work. Another way to improve the COP is to schedule DHW production when the outside air temperature is warmest, often mid to late afternoon.

It is my understanding that the sanitisation cycle is only required once per week, and needs to raise the water temperature above 60C for approximately 10 minutes. Again, if this were to be performed mid to late afternoon, in place of a normal heating cycle, this should help to improve the overall COP values.

@heat-pump-newbie electricity usage is about the same for a comparable day, but heat output is higher, so that's a win. But I've noticed the compressor cycling has gone up at the lower running temperature on days like today when it only needs to run at 26-28C, this isn't good for wear & tear on the compressor.

This has reminded me of the SuperHomes report from Ireland where they advocated a minimum output temperature for radiator circuits, controlled by a thermostat to reduce the cycling. The final report is Superhomes 2.0 D4.4 Best Practice Guide for ASHP Retrofit Final.indd (lit.ie) and the section 3.4 (page19) about radiator performance during low heat demand is making for an interesting read. I first read this months ago but had other things to sort with the original installer back then.

@derek-m if you haven't read this report I'd be really interested to hear your opinion.

@kev-m was going to try this approach of controlling the house with a thermostat last week, I think I read on another thread so it'll be interesting to hear the results of that trial.

@derek-m forgot to add - agreed on scheduling the time of the hot water run, I did find that improved things. I've already got mine setup for late afternoon. I might secretly drop the tank temperature a degree or two and see if it gets noticed. 🙂

Posted by: @hydros

@heat-pump-newbie electricity usage is about the same for a comparable day, but heat output is higher, so that's a win. But I've noticed the compressor cycling has gone up at the lower running temperature on days like today when it only needs to run at 26-28C, this isn't good for wear & tear on the compressor.

This has reminded me of the SuperHomes report from Ireland where they advocated a minimum output temperature for radiator circuits, controlled by a thermostat to reduce the cycling. The final report is Superhomes 2.0 D4.4 Best Practice Guide for ASHP Retrofit Final.indd (lit.ie) and the section 3.4 (page19) about radiator performance during low heat demand is making for an interesting read. I first read this months ago but had other things to sort with the original installer back then.

@derek-m if you haven't read this report I'd be really interested to hear your opinion.

@kev-m was going to try this approach of controlling the house with a thermostat last week, I think I read on another thread so it'll be interesting to hear the results of that trial.

I'll post some interim results soon.  Some interesting results re cycling as well as energy consumption. 

I have posted a link to the report, it's just not showing as one. I'll insert it properly here as I can't edit my original post.

Hi to all, first of all wish you all the best for this holidays, I am new here, from Croatia and I found this forum gives a lot of answers really, good job!! I will ask later a detailed question but for now...i have more or less similar problem.

Heat pump going on of pretty often when the cycle is running. 

On which percentage should be set the room influence??

Goran

@rocky11, welcome to the forums. When you're ready, please start a new thread detailing your system and what's going wrong with it.

Where is the auto bypass installed in the system?  Is it close to the ASHP end of the circuit as implied by the diagram?

@saenergy 

Auto bypass? Diagram?  Really difficult whilst not knowing what make etc of system you have.

@morgan, I think this was a question directed at @hydros so that @saenergy can help.

Hi @hydros 

I have read through the full report and although it is now several years old, much of it is still relevant.

There are however a few areas where it does appear to be contradictory, in one section highlighting the problem of compressor cycling and the need for continuous consistent operation, and then another section would be advocating on - off operation in preference to continuous operation.

One thing that is abundantly clear is that there is no 'one solution fits all situations', and that careful design, correct installation and optimal configuration and commissioning are all required to produce a system that operates with the best efficiency.

Posted by: @hydros

I have posted a link to the report, it's just not showing as one. I'll insert it properly here as I can't edit my original post.

LIT.IE "https://lit.ie/getmedia/db76033d-396d-4a27-adbd-2a9e1767e50c/Superhomes-FINAL.pdf"

@hydros,

Reduction in COP due to excessive cycling sounds a feasible theory but if the quality of the data analysis in the attachment is similar to that of the arguments and written text I don't believe any of the results. I'm not sure what they have proven, other than the manufacturer's stated COP isn't being achieved in a single ASHP installation.  I'm not even sure the data supports their theory that the reduction in COP is due to cycling; COP seems to stay constant as cycling increases. 

I'll publish my own results soon. 🙂