Posted by: @squeakysim

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Posted by: @allyfish

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Mine was designed for 50degC max but runs quite happily at 42degC max.

This is something I need to remember, because we can actually drop the flow temp straight away because most of the rooms temps have been designed 3 degrees higher than what the thermostat would be set at! Therefore if we do manage to get it designed to 45C flow, then the actual flow temp at the outside design temp should be closer to 40C which will be amazing!

The lowest LWT is often dictated by heating the coldest room to the desired temperature. A room by room heat loss calculation should determine the heat emitter output to balance each room for the lowest LWT.

Posted by: @squeakysim

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I just had a quick look and it doesn't appear they have an option that includes both heat pump and solar pv input which is what we'd be wanting. You'd think they must have that option too!

Are you looking for the Sunamp thermino hpPV-VT? I think the combination of heat pump and PV diverter is only available for the Vaillant Arotherm Plus compatible heat-battery. Looking at the manuals, one connects both a permanent electricity supply (presumably to run the internal gubbins of the battery) as well as a variable supply (e.g. the output of an Eddi). Alternatively I guess that it is possible to wire up standard heat-pump compatible battery using the Electric override switch (a volt-free contact).

Posted by: @robl

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Attached to help is our COP versus heatpump flow temperature - the graph shows all the datapoints available for January DHW.  We had a mean COP of 2.7 heating the DHW. 

What monitoing system did you use to get this data?

One thing I'm not actually that clear about is how a heat pump heats the DHW, is it only heated to the the temp of the heating or does it get heated fully to whatever the DHW temp is set to? The graph seems to suggest you have water going into the tank at 30C, is that right?

@squeakysim 

The monitoring is all my own 😎   Two off +/-0.1C temperature sensors, each in copper "pockets", and a flow meter, and a little embedded processor with a display.  It counts pulses from an MID certified elec meter, so includes pumps etc in the COP.  We have plain water, no glycol to take into account, which makes it simpler.  Piccy of the "pockets" below, before a load of insulation was wrapped around them.  

The water going in is 10C or so I guess, but the tank doesn't normally get emptied every day, and then it's recharged during the "Go" cheapskate time.  Also, there's 9C between the heatpump out and the DHW water temp itself 😫 , as the coil in the tank is a bit undersized.  There's another, larger, coil in the tank, so I might be seriesing them up in future. 

@robl if you have the time, would you perhaps mind explaining exactly how you do the maths?

I've just finished installing my own ASHP. I have temperature monitoring F+R. I have flow rate. I have electrical power input (CT clamp on the ASHP). All fed into home assistant.  Got the all the raw data I need, just need to code what to do with it. The bit I'm puzzling over is the best way to process the data and run the statistics . What I mean is specific details , getting from samples every 30 seconds of 

output power = (FlowT - ReturnT) * flow rate * heat capacity.

input power = electrically metered number

to a data set that is  sampled and statistically evaluated appropriately and gives a meaningful COP.

also do you include data where output goes negative - When the compressor stops but the pump carries on so DT goes -ve  - either low output and/or defrosting.

@iancalderbank 

The code is entirely running in a loop; it measures flow rates, temperatures, then electicity meter pulses, then does it again.  The flows and elec meters use timers, with variable aborts if something takes too long.  If the heatpump is active, the loop takes perhaps 5 seconds, if it's fully in standby it might take 60 minutes - most of the time is taken up waiting for the elec meter to pulse measuring standby energy.  If there's a state change (ie off to on), it hurries the loop up. 

The raw data must be taken over a long enough period that it looks stable.  So the code counts 5 on and off pulses to get a nice stable flow rate, in litres/minute.  

After the data is gathered, thermal power is calculated:

@squeakysim We had Octopus Energy visit and advise us last March / April; a plumber and an electrician both spent three hours carrying out a very thorough survey and I was impressed with their methodology and keenness to ‘get it right’ for us. Unfortunately, in those early days of OE carrying out installations, several aspects of our intended installation were not ‘within their scope’ (Wall hanging the Monobloc, fitting the DHW in the loft and a few other minor things) were not compliant with their then working practices and they told us that we might have to wait some time before such aspects were incorporated in their normal H&S controlled training etc. After some months and some further investigations, OE wrote to say that reluctantly, our installation would fall outside of their remit and wish us well in our endeavours. I was very impressed with their efforts and had felt that had they been able to do the work, we would have had a very good system indeed. The peculiarities of our requirements have since been met by A.N. Other company and we are very pleased with our Daikin based system. OE did do their best to accommodate our unusual requirements and I learnt a great deal from them for which I am eternally grateful - it is a great shame they were unable to carry out our installation at that time. Regards, Toodles

@toodles thanks for the info!

How did the quotes compare between them?

@squeakysim  Due to the inability to come to a final plan for installation, OE did not provide a quote; I did write and thank them for all their efforts though and kept in touch with the plumber for a little while too.

I then contacted a total of 19 MCS registered companies about my proposed ASHP installation; by this time, I knew more or less what I wanted. Out of 19 companies, 5 replied but one who ‘quoted’ without even visiting to survey later rescinded with a ‘Woops, we don’t install in your area - sorry!’ A company in Warminster (who I would like to have had carry out the installation) replied that they were now so busy that they were no longer able to venture as far as Berkshire. From the 4 remaining, 3 carried out surveys to a greater or lesser degree of thoroughness and a fourth never made it to the appointment we had agreed.

Our Daikin system is now fully working and the ASHP is for space heating with the DHW being handled by the Sunamp Thermino unit which has been ‘shoe-horned’ into the airing cupboard sideways on. Eddi talks to the grid and PV whilst it can see the Powerwall but may need a third CT Clamp to monitor the status of all aspects properly though it does a fairly good job with the 2 CT clamps. Regards, Toodles

Thanks for sharing this info- I’ve been reading it with interest since I’ll be getting a quote from them as soon as they’re operating in my area which is in about a month or so hopefully.

You are most welcome, I think you will be making a very good decision to invite OE to carry out a survey - if it is as thorough as the one they carried out for us, I think you should be confident that there will be no ‘surprises’ after the installation and you will have all the information laid out before you to enable you to make a well-informed decision. Good Luck with your project! Regards, Toodles.

I return to my attempt to actually get heat pump installed (brief history; OE did a survey last year, declined to quote, accepted a quote from elsewhere - they didn’t turn up, successful Section 75 claim on my credit card).

OEs online quote is £6000 after the increased grant. Earlier this year I had a heat pump ready unvented hot water tank installed so called the OE heat pump team first. They didn’t sound too bothered, unlike British Gas where it was a flat no to using it. They would want to install their own. 

Should have a visit from their team within the week.