Posted by: @ecoste

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@sheriff-fatman Thank you. Like you I am not chasing a particular COP, I am using COP to demonstrate the poor efficiency and hence the high cost. I have tried Havenwise but I found that their control reduced the COP and did not work well with the 12kWHr of battery storage that I have. The "maximum demand from the heat pump"  approach tended to fully drain my batteries in just over a couple of hours.

I currently have a COP of 1.3 for water heating across the 2 months since installation. I checked the initial power draw for water heating yesterday, it was 6.5kW. 

Do you have a problem with the Mitsubishi Energy Data updates, mine are very intermittent, sometimes 3 days between updates and sometimes one per day, but never more than one per day?

Thank you for the offer of more stats, I'll come back to you. I have a visit from my installer tomorrow.

I don't have any obvious issues with the MELCloud data updates, other than the fact that energy usage stats are only available on the following day each time (so anything for 29th currently reports as zero).  The hourly reports are updated to within the minute, but only show temperature data, rather than energy usage.  Of all the available reports, I find the Operation Mode one the most useful in terms of getting a snapshot of what's going on over the previous 24 hours, or 7 days.

I've got similar battery storage to you (2 x 5.3kWh Sunsynk batteries for now, with a 3rd one due to be added soon).  I've seen how quickly they can drain in the colder weather but, now that the heat pump is consuming over 20kWh per day, they are going to get depleted at some stage regardless of the profile in which the energy is used.  The PV generation is variable at this time of year, but I'm typically getting to the early evening at the moment before I'm on grid power for the rest of the day and the 3rd battery will assist with that.

I hope your visit from the installer provides you with some answers, but happy to provide more comparative info if otherwise.  From a hardware perspective, our systems seem to be very similar overall.

Posted by: @sheriff-fatman

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Posted by: @ecoste

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@dgclimatecontrol I am on an Octopus Intelligent Go Tariff, so I tend to heat my water when that starts and then heat the house for the remaining duration of the low cost time. There is very little temperature drop (2C max) in the water by next morning when I need it.

There is an immersion heater but I am not aware of any other back up heaters, where would they be located?

I have the same 10kW R290 heat pump as you, installed in June, and currently being run via Havenwise on the same Intelligent Go Tariff.  I see similar power draws to yours by the heat pump, but for limited periods of time and with an overall COP of around 3.0 at present.  For the last week, which has included the first sustained cold weather, Havenwise shows a CoP of 2.3 for DHW and 2.9 for heating.  MelCloud shows that over the last 7 days, the pump has spent 29.1% of its time doing heating, 3.7% doing DHW, 63.2% of its time in stop mode, 3.6% in Freeze Stat (which I believe kicks in below 5C OAT) and 0.3% of time running a fortnightly Legionella cycle.  To date, I've equated the relatively low CoP figure with the fact that it runs harder for shorter periods of time, hence spends a lot of the time sitting idle (and the experience living in the house is that the heat provided is constant and comfortable in all rooms, so it's doing exactly as I'd hoped from that perspective).

Having just done some analysis on the costs over the last month, I've calculated the cost of the heat pump energy draw as £8.39 for DHW and £34.03 for Heating from 28th Sep to 27th Oct, which compares to a gas bill of £117 for the same period last year, so I'm getting the expected overall cost efficiencies from the system, despite the reported CoP not being as high as many people report from their systems.

The peak power draw, as with your system, occurs when the once daily DHW cycle kicks in during the cheap rate period and, like you, I see usage spikes at times showing upto 5kW power draw for brief periods attributable to the heat pump, and usually as it starts either a heating or DHW cycle.  Total energy consumption for the past week, per Havenwise reporting from the MELCloud data, has been 21.6kWh for DHW and 134.2kWh for heating, neither of which looks excessive to me compared to circa 400kWh of gas consumption on last year's gas bill for the same period (based on a monthly consumption of just under 1,600kWh on that bill).

Ultimately, I'm more interested in cost savings than SCoP chasing, and I've attributed the low CoP scores (admittedly nowhere near those you have calculated on your system) with short periods of harder running that Havenwise has chosen to use as the optimal mode of operation, and this seems to be being delivered so far.

It might be worth you signing up to Havenwise for their free 30-day trial, to see whether this gives you any additional insight on performance.  There's no obligation to continue after this but the app will provide you with a weekly summary of CoP for both DHW and Heating during this time, using the MELCloud data.

Happy to provide more info on my stats, if this will assist.

 

Are you using Havenwise for Hot Water? I have seen it uses the "boost now" maximum power, highest speed and lowest efficiency method of re-heat so the CoP hit is expected

I run mine on the Eco DHW mode & controller schedule - so 32Hz maximum for longer (allowed up to 120min run time) and CoP is around 4.1

Heating can be tweaked with the controller max/min flow temperature and Thermo Diff setting to reduce cycling

Posted by: @f1p

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Are you using Havenwise for Hot Water? I have seen it uses the "boost now" maximum power, highest speed and lowest efficiency method of re-heat so the CoP hit is expected

I run mine on the Eco DHW mode & controller schedule - so 32Hz maximum for longer (allowed up to 120min run time) and CoP is around 4.1

 

Heating can be tweaked with the controller max/min flow temperature and Thermo Diff setting to reduce cycling

Yes, I use Havenwise for hot water, which is currently set as a 50C requirement at 6am with a 'top up' to 40C at 4pm if required.  By coincidence of timing to this thread, I've adjusted the early morning requirement from 55C in the last couple of days and the DHW CoP has, albeit on a very limited sample, gone above 3 since doing so.  I believe that avenwise's algorithm logic is to heat the water during the overnight cheap rate, which makes sense, albeit I'm reliant on their assessment as to why doing so quickly at a higher flow rate is better than a slower process.  Presumably, part of this is to enable more time for the system to switch to heating mode, if needed.  It may also be something that is specific to this newer type of R290 heat pump, which is advertised as being able to achieve flow temperatures of 75C, so has a wider range of operation when needed than the equivalent R32 models, based on a recall of the reading I did at the time of installation, which resulted in me requesting the R290 Ecodan model instead of the R32 one initially proposed.

Ultimately, the test I care about as a homeowner is cost of running & comfort inside the home, rather than an overall CoP score, but I'm interested in these numbers as a secondary matter and looking for small tweaks such as the DHW one above (which no-one in the house has noticed has happened since it was changed) are bits of fine-tuning that my natural geeky curiosity will always look to make.

More generally, I've switched Havenwise's heating mode in the last week or so from their 'Option 1' heating mode (which is tariff-focused and tries to minimise peak use) to the 'Option 2' version, which is more of a 'low and slow' mode, less focused on tariff.  This is due to the Havenwise system not knowing my true costs of electricity due to the impact of the PV system and batteries, so it can only work with the Octopus off-peak and peak rates in its calculations.  My expectation is that this should potentially improve the CoP score relative to Option 1, albeit the change coincided with a drop in temperature, so it's an unfair comparison at present as the heating requirement has increased since it was switched.  I'll monitor this over time to see if the reality matches the expectation.

Ultimately, if I only ever continue to achieve a CoP of 3.0, but the system provides the heat required and saves money vs the alternative options then it will have done what I'd hoped.  The house itself, and the system design (with the heat pump feeding from ground level to a 1st floor cylinder in the middle of the house via the loft) will each provide constraints to the achievable CoP.  Some system designs did suggest that a better option would have been to go through the 1st floor floorboards, for example, rather than the loft, but this would have been at a much higher installation cost and with a significantly more disruptive installation process.  Ultimately, there's a trade-off between 'perfect efficiency' and cost to be considered in any installation.  I'm pretty sure I'd be looking at a higher CoP and improved efficiency if I'd gone with the Stiebel Eltron system I was quoted for with a floorboard level access rather than the loft.  I doubt that doing so would ultimately ever pay back the additional £7k+ of installation cost above the £2,850 net cost I paid for the 10kW Ecodan solution, and if that was the only quote I'd have received, I suspect I'd still be living in a house with a gas boiler.

@sheriff-fatman 

Your post is quite long, but i think the answer to this:

"albeit I'm reliant on their assessment as to why doing so quickly at a higher flow rate is better than a slower process."

Is that it's the only option you can do via MELCloud, you can't trigger an Eco on demand boost without some tricks (such as powering off the system and turning it back on, or going into holiday mode and back out)

I'm now interested to see what Octopus Energy will allow in terms of smart control, now they have started to offer MELCloud direct integration as a "device", similar to Daikin and their own heat pumps

Posted by: @f1p

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@sheriff-fatman 

Your post is quite long, but i think the answer to this:

"albeit I'm reliant on their assessment as to why doing so quickly at a higher flow rate is better than a slower process."

Is that it's the only option you can do via MELCloud, you can't trigger an Eco on demand boost without some tricks (such as powering off the system and turning it back on, or going into holiday mode and back out)

 

I'm now interested to see what Octopus Energy will allow in terms of smart control, now they have started to offer MELCloud direct integration as a "device", similar to Daikin and their own heat pumps

Using Havenwise replaces the need to do anything directly with MELCloud, in terms of operating the system.  If you opt for Havenwise control, the MELCloud heating settings are switched to a 29C room temperature so that they don't interfere with the Havenwise control, and similarly, hot water scheduling is controlled by Havenwise through the MELCloud settings.

There are options within Havenwise to boost either heating or hot water at any time, if needed, but all the control is done through their app, which then results in the necessary changes being made in MELCloud.

I only use the MELCloud app to access the reports currently, which leave a lot to be desired in terms of functionality, but are better than nothing.

@sheriff-fatman Yes, i understand from the user perspective you no longer need to interact with the front-end interface of MELCloud

But for Havenwise to operate, it depends entirely on the MELCloud "service" being available to perform commands and collect data

Posted by: @f1p

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@sheriff-fatman Yes, i understand from the user perspective you no longer need to interact with the front-end interface of MELCloud

But for Havenwise to operate, it depends entirely on the MELCloud "service" being available to perform commands and collect data

Totally agree that any system is reliant on the ability it provides a user, either directly or via a 3rd party, to interact with it.  A significant factor in choosing the Ecodan system was its compatibility with Havenwise, whereas other manufacturers were in the 'coming later' category.

You'd think that it should be relatively straightforward for the system manufacturers to measure 'simple' stats such as energy in and out, and much of their promotional material is aimed at telling us how efficiently they operate, which is reliant on them knowing these figures.  Their willingness to share this data in the form of easily accessible stats leaves a lot to be desired and, judging from various threads on this forum, it's something that seems to be a common frustration across most of the main manufacturers.

Admittedly, I'm someone who wants to get under the skin of the numbers more than a typical user would, and we're within a online community heavily skewed towards that type of person, many of whom have chosen to purchase additional hardware to enable accurate monitoring of their systems, when the expectation is that it should be something that is relatively easy for a user to access and monitor, should they wish.

For clarity, I'd separate accessing usage data from the ability to perform various operational commands as two separate things.  It takes a certain degree of confidence, and knowledge, to want to go into the heat pump settings and tinker with things such as weather compensation and I can imagine that there's a very wide scope for the broader spectrum of customers to 'do more harm than good' if they've got free access to the system settings but are expecting it to be operated in the same way as a gas boiler system, so I can appreciate why many functions are hidden behind installer-level access rights.

@jamespa Time for an update. My installer has been to visit and has confirmed that the heat pump is faulty. He has contacted Mitsubishi. They have required payment before they will investigate and have explained that they are very busy and it will be some time in December before they can investigate. Current status now that the temperature has dropped to 5C, the heat pump is running at a flow temperature of 30C, it is continuously running and providing 2.3kW of heat for 2.6kW of electricity. A COP of 0.9, is this a record?

Posted by: @ecoste

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@jamespa Time for an update. My installer has been to visit and has confirmed that the heat pump is faulty. He has contacted Mitsubishi. They have required payment before they will investigate and have explained that they are very busy and it will be some time in December before they can investigate. Current status now that the temperature has dropped to 5C, the heat pump is running at a flow temperature of 30C, it is continuously running and providing 2.3kW of heat for 2.6kW of electricity. A COP of 0.9, is this a record?

Thats bad but at least there is an acceptance that its faulty.  I might be tempted to tot up the excess electricity and expect the installer/mitsubishi to cough up if they are delaying until mid december. 

I dont see how its going to work this week though assuming your house loss is anything like 10kW.  Its going to need 8-10kW input which the electricity feed wont be capable of, and anyway will surely fry it.  

@ecoste If a compressor fault under warranty they'll send out a new unit foc, unless your installer deals direct this will be on an account with the wholesaler.

@jamespa That is an acceptance by the installer, the problem is with Mitsubishi, it is their unit that is faulty. They have required payment to investigate and are so under resourced that it will be a long time until they can attend. Is this an indication that they have a lot of faulty units?

Posted by: @ecoste

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@jamespa That is an acceptance by the installer, the problem is with Mitsubishi, it is their unit that is faulty. They have required payment to investigate and are so under resourced that it will be a long time until they can attend. Is this an indication that they have a lot of faulty units?

Don't know answer to final question. 

Your contract presumably is with installer so it's his problem to solve if Mitsubishi take an unreasonable time.  At this time of year I would say mid Dec is unreasonable, particularly if the local plumbers merchant has the units in stock!