@johnnyb So here is a day where I was cycling although not frequently

The interesting bits are just as the heat pumps starts up again. Flow temperature is lower for a while before it stabilises and as such you might expect a better COP during that period. However the pump isnt putting as much heat into the house as it would if it were at steady state. So there is a price to pay, the house will cool. Its analogous to running at too low a temperature to keep the house at the desired room temperature.

Let me know how homely goes as I know others who may be interested. 🙂

Posted by: @johnnyb

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I also thought that running continously with low flow temperatures was meant to be the most efficient way to run a heat pump

Running continuously will usually produce the best COP, but having setbacks where the pump is off for periods allowing the house to cool eg overnight can be less expensive in some circumstances (it is a regular somewhat contoversial talking point). For example my minimum electrical consumption is 750W, so running continuously would use 18kWh per day even when relatively mild outside. I rarely use that much because my heat pump runs for 8-10 hours per day either on Agile or Cosy. The penalty for being stingey is that parts of the house are quite cold for periods of time.

Posted by: @johnnyb

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It will be very interesting to see how the Homely controller runs the system to get maximum efficiency.  Interestingly for the duration of the trial my electricity usage for the heating is a fixed monthly price so it is in their interest to keep the usage as low as possible.

Is this the Ivie Energy Sure trial? I have expressed an interest and am waiting for details of the energy tariff. The Ivie app is not very impressive though. Unless I am missing something, it just seems to give weekly electricity costs with no kWh data and no daily data. The Octo-Aid app is far superior.

Posted by: @mike-h

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Is this the Ivie Energy Sure trial? I have expressed an interest and am waiting for details of the energy tariff. The Ivie app is not very impressive though. Unless I am missing something, it just seems to give weekly electricity costs with no kWh data and no daily data. The Octo-Aid app is far superior.

It is that trial. I ddn't think the tariff was that clear, but it is a fixed sum for the heating that doesn't change, unless you are using boost all the time or turning the heating up higher than agreed. EV charging, if you have one, is agreeing how many kWh/miles you need. Everything else is about 26p.  The allowance for the car works out at 7p/kWh but you have to agree up front how many miles you do/how many kWh you need and they give a set price for that, all subject to fair use.

The Ivie app does download my usage figures as soon as they are available and shows similar data on usage to the Octopus Watch app that I've used for a long while. The Octopus Watch app, a third party app that is designed around Agile, stopped downloading my data once I switched over, it uses the Octopus API to get data.  The Ivie asks for meter details and doesn't seem to be supplier dependant. It is supposed to give Live data, it has a section for live data on the screen, but mine doesn't show that. The trial includes the Bud in home display but that isn't connecting to my meter so isn't showing any data. I'm assuming the Ivie app is supposed to link to the Bud to get the live data. I'm going to ask what is going on when the Homely is fitted on Friday.

Posted by: @bontwoody

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Let me know how homely goes as I know others who may be interested

I will. I have read posts from a few people on here who already have homely and like it so thought it was worth trying it out, especially with a free trial.

@johnnyb

Posted by: @johnnyb

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I also thought that running continously with low flow temperatures was meant to be the most efficient way to run a heat pump. It would be interesting to see what you have found and how you are running yours @technogeek

My heat pump journey like a number of people has been a long one starting in July 2023 and I have had 2 Winters to experiment and try a number of different strategies so here is the strategy I have settled on.

The primary reasons for getting a heat pump was to remain warm in my home but reduce or zero my carbon footprint. Like the majority of people, I had the budget to install the pump but not the recommended small power station etc to make the project financially viable.

The current set up is a 12Kw Samsung heat pump plumbed in parallel with a Grant oil boiler (with a billing grade oil meter) all controlled in a bivalent configuration.
The thermostat is a Honeywell smart model which adapts the cycle run times based on the detected heat load at a fixed rate of 3 cycle times per hour.
Our comfort arrangement has a set back of 2C at night as we do not like having the house at a constant 21C 24/7. The heat pump runs between 5am and 8pm @ 21C and set back between 8pm to 5am @19C.
We have the Octopus Go EV tariff of 8.5p/Kwh off peak and at time of writing, peak rate of 27p/Kwh

I initially followed the Heat Geeks process of balancing all the radiators (important for any heating system) and then setting up the weather curve to balance the heat in to heat loss for various outside temperatures and using the thermostat at 1C above the desired set temperature as a limiter. This had the effect of running the heat pump continuously throughout the day. So far so good I hear you say.

However I personally have become more sceptical regarding the "low and slow" approach when it comes to having a set back. Having this strategy the heat pump would literally take 12+ hours to get the house back to 21C just in time for the next set back to kick in and 2 hours later, us going to bed. So the average temperature throughout the day was more like 20C, not really desirable and the point of the heating system.
This is the same as filling a bucket at 1 litre per hour but water is leaking out at 1 litre per hour, it is never going to fill up!

Furthermore we had 3 or 4 days locally in mid December were the outside temperature was a constant 6C day and night, so I took the opportunity to do direct running comparisons between the oil boiler and heat pump with the same comfort levels and schedule times.
The oil boiler came out at 8.5 litres (@63p litre) £5.35 and the heat pump (running continuously) 26Kwh (@26.72p per Kwh) £6.94.
To break even on running costs, I have a maximum of approximately 20Kwh electricity per day.

After this trial in December I now run the heat pump a little hotter at the expense of the COP figure which now heats the house back to 21C in approximately 4 - 6 hours but I literally set the thermostat to the desired room temperature and let the thermostat cycle the heat pump on and off 3 times an hour, allowing the thermostat to adjust each cycle time length accordingly. My electricity consumption is now 18Kwh for an OAT of 6C.

After various discussions on this thread it seems the Samsung controller is no different in its behaviour and capabilities.

"Homely" manages to achieve its objects because it communicates directly with the Samsung controller "brain" via the ModBus interface. This interface enables Homely to dynamically change the Field Settings within the Samsung pump thus constantly changing the weather curve, flow temperature etc as it sees fit. This enables Homely to drive the heat pump harder when it needs to heat the house back up (with possible cheap electricity) and then reduce the flow temperature to run it cheaply when electricity is expensive.
You cannot do that with the standard thermostats which only allow fixed Field Settings.

Sadly though with the cost of electricity I currently run my oil boiler when the OAT is less than 5C. Even with my COP at a respectable 3.8 when it is cold (SCOP of 4.25) it is cheaper to heat my building with a litre of oil. I cannot see the situation improving for a least another 10 years either in this country!

Posted by: @technogeek

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Sadly though with the cost of electricity I currently run my oil boiler when the OAT is less than 5C. Even with my COP at a respectable 3.8 when it is cold (SCOP of 4.25) it is cheaper to heat my building with a litre of oil.

We totally relate to this. Running costs at temperatures below 3C on an ASHP are much, much higher than oil (and probably gas). 

Posted by: @editor

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Posted by: @technogeek

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Sadly though with the cost of electricity I currently run my oil boiler when the OAT is less than 5C. Even with my COP at a respectable 3.8 when it is cold (SCOP of 4.25) it is cheaper to heat my building with a litre of oil.

We totally relate to this. Running costs at temperatures below 3C on an ASHP are much, much higher than oil (and probably gas). 

In fairness that is well understood and why its costs over a season/SCOP that commonly get quoted and compared not costs at any particular temperature. 

At 7-10C (more normal temperatures, at least in the south of the UK), the coats of a tolerably well installed ASHP are (or at least should be) quite a bit cheaper than gas.

Ovo are currently offering 15p/kWh for all the leccy used for an ASHP, provided you have a suitable model (basically Mitsubishi, Viessmann, Vaillant at present).  If that's not cheaper than both oil and gas then the installation is not compliant with the rules of the BUS grant, which require a SCOP of 2.8 minimum. I can see however that, if you only heat a small proportion of a relatively poorly insulated property (eg a room or two) for a small proportion of the time (eg a few hours in the evening), with oil/gas then this calculation might not apply.  The OvO tarrif is also no use if you don't have one of the compatible models!

@jamespa 

Posted by: @jamespa

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In fairness that is well understood and why its costs over a season/SCOP that commonly get quoted and compared not costs at any particular temperature. 

At 7-10C (more normal temperatures, at least in the south of the UK), the coats of a tolerably well installed ASHP are (or at least should be) quite a bit cheaper than gas.

To be fair the couple of days trial at 6C was only a single test for me to verify my own calculated figures for various settings but it was an eye opener to potential running costs.

I have calculated a financial budget based on my own 5 year average of 1162 litres of oil per year and the current cost of oil in my tank ( as you only buy in bulk once a year unlike gas so cannot use current market prices). I have been keeping a running total of electricity consumed by the heat pump ( April to March) and as it stands I have burnt through 70% of the budget. It would be a lot more if the oil boiler was disabled and we have at least another 2 months of winter to go! 😀

My budget is based on 63p litre of oil however at the time of writing oil is now averaging 58p per litre (BoilerJuice).

During the 7 - 10C OAT range the heat pump is cheaper to run by approximately 18%  but I am sceptical about all these claims that you save money over the year. This may have been true for the very old non-condensing boilers but I would challenge these claims for more modern high efficiency condensing boilers (which I and majority of the population now have) with which at best you would financially break even.

For me to completely abandon my oil boiler and financially break even each year I have calculated I should not pay anymore than 18p/Kwh. If you have either a heat pump or an EV you can get a tariff to suit but if like me, you have both then you are sadly no better off I reckon.

Until the electricity market and infrastructure are sorted out in this country ( which maybe 10+ years) I think successive Governments are going to have a very hard sell to get people off of fossil fuel boilers. Most people do not have the budget for just a heat pump but over the last 2 years I have been becoming aware that at present you need the addition of a small home power station to make the heat pump financially viable. My view is having a great COP / SCOP is all very well but if you are cold in your house in the process then the heating system is not doing its job?

@technogeek 

The majority of the population probably do have condensing boilers but, sadly, the majority are set up not to condense (flow temperature too high).  That said I believe that modern condensing boilers, even if not actually condensing, can have an efficiency of 95%

Heating oil is 10kWh/l you are currently paying 5.8p/kWh.  Thats just a smidgen below typical gas price.  You would need a COP of just under 3 to get that from the OVO tariff.  That should be easily achievable, but I grant is not always achieved because heat pumps like boilers, are too often badly set up it seems.  It also assumes that your house demand doesn't increase materially as a result of the change, which it might if you previously heated only a small proportion for a small time which some of course do.

Whatever the numbers, which vary from person to person and house to house, your basic point is that electricity costs are too high (or too high relative to gas/oil) and, that being the case, governments are going to have a hard sell getting people off fossil fuels.  With this I would wholeheartedly agree, and its clear that action needs to be taken. 

Energy prices are largely political so its do-able, but the challenge is a chicken and egg one.  Whilst most people are dependent on gas for their heating, shifting policy costs that currently fall on electricity to gas is a political minefield, and subsidising electricity difficult.  Obviously as more move to electric it becomes easier.  It possibly also becomes easier as the more frequent occurrence of severe weather events finally convinces people that climate change will negatively affect them, not just others.

Any technology change tends to start with early adopters (the current phase of heat pumps) who debug it for the next wave, after which it starts to accelerate as the new technology becomes more the norm.  This process is probably inevitable and pretty much universal, but its also the case that it can stall or reverse if the conditions aren't right (which is where government determination/political will comes in).

Personally I think its a complete myth to expect that doing something about climate change is going to be pain free.  That ship sailed ~50 years ago, when the fossil companies already knew the damage that was being done but chose to hide it until it was too late.  We are, unfortunately, now in the position where either we can suffer pain, or we can inflict even more pain on our children and grandchildren.  I personally think it will probably be a combination of the two, the key question ultimately being whether the pain we inflict on our ourselves but particularly our children, grandchildren and others, causes complete societal breakdown or not.  Some rich people appear to be betting on the less optimistic outcome whilst making the underlying problem even worse!

Posted by: @bontwoody

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Let me know how homely goes as I know others who may be interested.

There's not much to report back yet as the Homely has only been in 2 weeks, the temperature 'Node' battery was flat in less than 10 days and the WC on the Samung controller was still on for the first week so Homely wasn't contoling the flow temperature. It is set so the max water leaving temperature is 35 with a minimum of 25, but it seems to go for 35 most of the time, which means the floor gets quite warm and the temperature can overshoot quite easily. I do think that 35 is more efficient, but without a monitoring system that is hard to tell. The deltaT is around 4 most of the time with the flow temperature higher and the heat pump is running less.

I think it is now starting to learn how the house heats up and isn't overshooting the set temperature much.  The main thing I'm trying to work out at the moment is how to get a lower temperature during the day as it seems to keep the temperature the same 24/7 where as we like it 21 or slightly over in the evening then cooler the rest of the time.  It does do a good job of keeping the temperature consistant, but I would like it to drop overnight.

It doesn't seem to have improved the COP or reduced the electric use yet, but it is only now that I think it is understanding the house so it may get better over the next few weeks.  I registered as a Homely installer so I could access some of the data and it is saying my COP is over 4 for heating and over 3 for DHW and the average a little under 4.  It does have a disclaimer saying 'These values are indicative estimates based on data reported by the heat pump etc. etc. so I don't know how accurate they are, but I assume it shows the system is running reasonably well. I would like to get a simple monitor to record the electric used so I can see how much electricity is used by the heating.  At the moment the Samsung controller shows I am using between 60 and 100 kWh per week, but I have no way of checking how accurate that is.  I know when I had the legionella cycle switched on the first week the DHW didn't get up to 60° so I got an error message after it had been running for the set 8 hours. The contoller was showing electric use for that day as if the immersion heater was running at 3kW for 8 hours but the immersion heater thermostat had switched off once it had reached its set point, I guess in less than an hour. When I checked my usage on the Octopus app it hadn't been running for 8 hours so the contoller is assuming the electric use not measuring it.

I had an email discussion with the installers about removing the extra bits I shouldn't need, the second pump, 2 port valve, auto bypass valve, and changing the buffer tank from 4 ports to 2. He said he spoken to Samsung to make sure he can remove/change the buffer without affecting the warrenty, he had told me SAmsung insist they fit a buffer tank but Samsung have plumbing/wiring layouts that don't include a buffer tank on the paperwork he sent to me before they started work.  He said he is going to change his buffer at home first, as he can do it himself and test it without sending his guy to mine to change it. He has also said he will change my pump to a PWM pump, once the busy start to the year has died down a little.  It does seem like I am making progress with that, although if the figures on the Homely graphs are anywhere near right then it is actually performing OK as it is.

@johnnyb

Well that all sounds like progress. I’m guessing that the COP figures are calculated from the internal sensors on the unit so should be viewed as approximate. 

The old no buffer will invalid the warranty is pedalled a lot but as you say you have seen diagrams that exclude it and I visited a good ECO4 grant installation with a gen 6 that didn’t have one. I suppose if he is going to test it on his first that’s fair enough. 

The PWM pump is a definite win. 😁

Please keep me updated as Homely beds in.