Heat pumps, lock-down and darkest Somerset

[Hogboon]

I'm here because I found the thread started by ProDave https://forum.buildhub.org.uk/topic/6385-lg-therma-v-mono-block-air-source-heat-pump/ to which I will add my two penn'orth in due course. I'm a woodworker but no longer compelled to hit things with a hammer to pay the bills - apart from the occasional recalcitrant tenant.

I live in a bungalow [built c. 1975] with loft conversion. The heating and h.w.  was from an oil-fired combi boiler which worked fine but the writing on the wall early last year seemed clear enough. Global warming is a fact staring all of us in the face. We are where we are because of our [8 billion of us!] collective greed, stupidity and laziness. Among other things, burning oil no longer seemed acceptable behaviour. The boiler was then about 12 years old and at some stage would inevitably need replacing. Waiting till it died, which Sod’s Law would ensure happened at the moment of greatest inconvenience, would almost as inevitably have compelled me to replace it with another oil boiler. [There’s no mains gas where I live.]

So come April 2020, with the economy stagnating under the first lock-down and people going out of work and business, it seemed to me the right moment to put my money where my mouth was, the more so as spring was well under way and the prospect of being without heating or hot water for however long it took was not something to give pause for thought.

According to the EPC [Apr 2016] the total floor area = 169 sq m and the EER = 56. “Current primary energy use per square metre of floor area = 180 kWh/sq m p.a.”

“Space heating [kWh per year] = 14,873”

“Water heating [kWh per year] = 3,534”

I canvassed the market, had a few quotes, made a decision and went for it. The work included;

Installation of an LG Therma V 9kw ASHP together with a tank that looks like it escaped from Hinkley Point [15 miles away].

Installation of 8 PV roof panels intended a] to power the heat-pump b] contribute to heating hot water and c] earn me a fortune flogging surplus generation to the grid – Octopus in my case. And that’s a laugh!

Following the installation [finished in early August] the company doing the work gave me a ‘Customer Satisfaction’ questionnaire. Among other questions, they asked; “Please rate the quality of your installation” to which I replied; “Unable to answer this. If you mean ‘technically’ I have no idea. If you mean functionally, ask me in February.” The only thing I would change now is the month which should have been January. A few years ago it got to -13ºC. This year has been nothing like that but for about the last week the daytime temperature has hovered between 5-10ºC and night time has been 2º to -2ºC.        

The system is currently configured to fire up at 08:00hrs when the internal house temperature is 15-16º. The target temperature is initially 18ºC till 10:00; then 20ºC till 15:00O then back to 18ºC till 22:00 then 12ºC overnight. At present the system struggles ever to make it to 18ºC let alone a sweaty 20º.

So I had a little test day on 2^nd January the results of which I shall add to the post started by ProDave.

[ProDave]

My first thought is the heat requirements of your house are too high for the heat pump you have.

 

heat load 14873kWh  Lets say you need the heating on half the year, that's an average of 82kWh per day heating.  That's an average, it will be a lot less in autumb and spring and a lot higher in the middle of winter.

 

Lets take a guess that the coldest winter day it will use 150kWh of heat in a day.  For a 9kW ASHP to provide that, it will need to be running over 18 hours.

 

So it is NOT going to heat up quickly like the oil boiler did, you probably need it to come on a lot earlier to stand a chance of getting the house up to temperature.

[SteamyTea]

6 minutes ago, ProDave said:

So it is NOT going to heat up quickly like the oil boiler did, you probably need it to come on a lot earlier to stand a chance of getting the house up to temperature.

 

32 minutes ago, Hogboon said:

The system is currently configured to fire up at 08:00hrs when the internal house temperature is 15-16º. The target temperature is initially 18ºC till 10:00; then 20ºC till 15:00O then back to 18ºC till 22:00 then 12ºC overnight. At present the system struggles ever to make it to 18ºC let alone a sweaty 20º.

My first thoughts, keep it on all the time, except when it is DHWing.

 

As a general aside, all this nonsense about kWh/year is of little use.  What is needed is 2 metrics, the power to keep the place warm at different temperature differences, so:

kW/K

And the power at different CoPs, so:

kW/K @ x CoP

 

 

 

[PeterW]

Chances are the oil combi was 25/27kW and you’ve replaced it with something a third of the size. That means any old ideas about the programming for heating go out of the window. Also, your losses as @SteamyTea says need to be known as at -5°C you may be losing more than you can inject. A basic system (assuming  standard rads) putting 50W/m2 into the building needs 8.45kW - it could be your losses are nearly equal that so your 9Kw ASHO will struggle to maintain the desired heating levels unless it is on for much longer periods. 
 

There is a common misconception that ASHP reduce the amount of heat energy needed for a house - people install them, try and run them on the same programmed times as their old boilers that were 3 times the size. Basic physics of thermodynamics says that cannot work. 

[SteamyTea]

53 minutes ago, PeterW said:

There is a common misconception that ASHP reduce the amount of heat energy needed for a house

Yes, not sure how to get that message across, maybe a pointer to Zoot's thread, can that be retitled 'How to make your ASHP fail'.

[Gone West]

I think it's a great shame that, it seems, a lot of people are 'conned' into thinking it's a straightforward process to replace a gas or oil fired boiler with an ASHP. This is only relatively easy if it's being fitted to a modern reasonably well insulated house with underfloor heating. Fitting an ASHP into an old house essentially means replacing the whole central heating system and the DHW storage system. I think the government should not be advertising ASHPs as a panacea for home owners heating requirements and government CO2 reduction targets.

[SteamyTea]

4 minutes ago, PeterStarck said:

This is only relatively easy if it's being fitted to a modern reasonably well insulated house with underfloor heating.

Not even that. Small ASHPs are reasonably priced, a 30 kW one isn't.

In some ways, people that consider swapping should do some research  they should start with a basic energy course.

I tried to get funding for one a decade ago, was told there was no interest because it had numbers in it.

[joth]

47 minutes ago, PeterStarck said:

I think the government should not be advertising ASHPs as a panacea for home owners heating requirements and government CO2 reduction targets.

I'm finding this causes additional harm throughout the system. The government's messaging that it's easy to retrofit an ASHP (and solar PV) encourages so many people undertaking major renovations ("lifestyle" driven; giant knock thoughs and bifolds and UFH are the norm around here) to think "I'lll get all the core work done, then see what money I have left over for sustainability measures at the end". 

And only when they get the ASHP installer in they discover (if they are lucky!) all the errors they made from the very start of the project, in underspecifying UF insulation, draft proofing, window/bifold selection etc etc which makes ASHP that much harder. With the cruel irony that had they put those other measures in from the start, switching to a sustainable heat source is so much less useful anyway as the heat demand already is that much lower anyway.

 

43 minutes ago, SteamyTea said:

I tried to get funding for one a decade ago, was told there was no interest because it had numbers in it.

Sad but true. The angle I've been trying to push in local groups is to stress the desirability of many of the fabric first measures. E.g.:

- drastically increasing under-floor insulation means you can run the UFH at a much lower temperature, which means you can choose that really expensive and fragile real wood or cashmere carpet floor finishes.

- installing MVHR means you can breath fresh clean COVID free filtered air all year round, solve humidity/mould issues, and improve sound proofing keep those car/plane/neighbour noises away

- ASHP can be used in cooling mode, meaning you can have beautiful cool aircon when all your neighbours are sweltering

 

Like the iPhone, these things need to be considered aspirational and then they'll get more pre-renovation design time attention. A crash course in thermodynamic physicals is not sexy enough for most.

 

 

 

 

[Rich123]

Hi, ok to size the heat pump you need the heat loss for the rooms .

Generally heat pumps are under sized if compared to traditional , I would say 9 kW should be ok.

My concern is the system it’s connected to. Is this radiators ?

I’ve checked the heat pump and I assume they have installed the high temp version ?

As a previous post I would leave the heating on longer , allow 3 hours pre heat so on at 5 to get to temp by 8 Am .

Also check your hot water settings , you should have heating priority 

Heating requires 2 elements

1. to meet the heat loss

2. to meet the fabric absorption - the admittance of the structure.

So a masonary building needs a lot more heat to warm up than a timber frame due to the fabric response.

 

Therefore if you have masonary then the problem will be worse timber frame in general.

Edited January 6, 2021 by Rich123
Edited

[Temp]

If I ever decide to switch from oil to ashp I'm first going to log how long the burner on the oil boiler runs for in January to get an idea of how many kWH a day are being used in cold weather. Cross check it against oil consumption. Not just going to rely on someones calculations of energy loss based on a quick look around.

 

 

[Rich123]

One way to check would be to measure the radiators to establish the heat output.

I would then reduce the flow temperature in winter to see the minimum to heat the house , then calculate the heat output from the radiators at the reduced temperature. That will be the actual heat required.

Heat pumps generally are required to run longer as they don’t have the output to meet the heat up load - its a difficult job to size them correctly and I have always had a few discussions with the suppliers and installers on this subject.

I haven’t been involved in retro fit , only new builds where the options are better.

in general for an old house allow 100w/ m2 - New build around 45 W / m2 , however these are calculated loads and in reality you can get away with less but then it’s a bit of guessing unless you can model it using expensive software, and even then I wouldn’t use the figures as they would be low.

[DavidO]

On 06/01/2021 at 08:21, ProDave said:

My first thought is the heat requirements of your house are too high for the heat pump you have.

Completely agree with this and other posts suggesting the same/similar. So.....given that you are where you are, spent your money, and presumably don’t want to rip out your brand new ASHP and start again, the first and most practical question is can you do anything about the heat requirements of your house? You don’t mention anything about existing insulation/airtightness in your opening post, but that’s surely got to be the place to start?
First seal any obvious drafts. Second investigate/seal less obvious sources of air leakage (almost certainly lots in a 1970s build...... service pipes/wiring which enter through external walls/floors/ceilings....suspended floors, particularly timber, which have almost certainly shrunk/sagged, and all the points at which they meet the walls. Third, can you improve insulation of the external shell? Look at the ceilings first, floors second, and walls/windows third, depending on what you find. The more you can do to narrow the gap between your heat requirements and the capacity of your ASHP (at sensible cost) the more comfortable you are going to feel.

[Hogboon]

My thanks to all for your replies. I thinlk I explained somewhere that I am a retired 'hammer man' so my starting point, as outlined in my first post, was to stop burning fossil fuel, and reduce my carbon footprint as much as possible. The ramifications of this were not explained at all by any of those I consulted - and you're damned right Joth; "a crash course in thermodynamic physicals is not sexy enough" - not by a long way. 

 

So, as DavidO says, I am where I am. It was retro fit and rads not underfloor etc. But I am not utterly averse to the notion of 'ripping out my brand new ASHP and starting again' - although that remains one option. I did not install the ASHP to save money but to reduce my carbon footprint. [Although by the time one works out all the implications of the retro-fit there will probably be precious little in it.] But one thing from Rich123 and others seems apparent; I am not giving the ASHP enough time to do its job, especially when I confess to the cavalier attitude I have to the 'intelligent' thermostat which, in spite of my telling it to come on at say 08:00 would often come on way earlier until I discovered that rather than coming on when told to, it was assuming what I really meant was that was the time at which I wanted my target of 18ºC to be effecive. Instant gratification etc. But I discovered that I could stop it second-guessing in this fashion [by turning OFF the 'true radiant' option on my t'stat] so that 'on' meant 'on' only at the time set not 1½ - 2hrs earlier. In view of what has been said above by Rich123 and others I shall allow the thermostat to revert to its earlier 'bad' behaviour.

 

My thinking was [and remains] that PV panels don't work in the dark; therefore the ASHP should only be operational in good daylight hours in order that the PV panels can have some chance of contributing to the power consumed. I could not [and still can't] see the point of getting rid of the carbon footprint generated by burning cheap oil only to replace it with another courtesy of expensive juice from the grid.

 

   

[AliG]

Sadly @Hogboon PV panels generate virtually zero electricity, even during the day in the winter. The sun is considerably lower in the sky, the days are shorter and there tends to be more cloud. Thus trying to supply an ASHP from PV is difficult. You will get a small percentage of your usage.

 

It seems like the main issue is that your heating is not on for a long enough period of time.  Think of it this way. Say your house needs 100kWh of heat on a cold day. Basically it is losing 4kWh per hour. Thus if you have the heating on all the time it will use 100kWh over the day to stay at 20C. If you have it on for half the day it will still need to put 100kWh into the building to get back to 20C and stay there, but you will be at the limits of what the ASHP can provide over that length of time. So you would not save much on heating, but your house would be much more uncomfortable. There is a chance that your ASHP can't provide enough heat input for when the temperature is very cold, but it sounds more like you are losing so much heat overnight that the ASHP can't put it back into the house in the morning. Because you are not actually getting the house up to temperature then you are not getting as much heat as you would like into the house so it probably will increase your bills to run the heating all the time. This though is due to it being warmer, not due to running it too much.

 

No one has mentioned that a 9kW ASHP is usually the heat output in optimum conditions. Often if you are running the water hotter than ideal or if the outside temperature drops below a certain lever they cannot put out their maximum output. This might be exacerbating things in the current cold snap.

 

I would guess that you need around 100-120kWh a day when the temperature is at zero outside. If you ran the heating all day it could provide this, but trying to do it over 14 hours is pushing it. I would set your thermostat at 20C and leave the heating running and see how much electricity you use in a day. If the house is too warm during the night for you at that temp then I would cut it to 19C during the night, maybe 18C. The problem with cutting the night time temperature 2C below the daytime temperature would be that the heating would stay off most of the night and then struggle to get back to temperature.

 

[pdf27]

1 hour ago, Hogboon said:

My thinking was [and remains] that PV panels don't work in the dark; therefore the ASHP should only be operational in good daylight hours in order that the PV panels can have some chance of contributing to the power consumed. I could not [and still can't] see the point of getting rid of the carbon footprint generated by burning cheap oil only to replace it with another courtesy of expensive juice from the grid.   

Things aren't quite so clear cut.

If you're exporting to the grid, you are meaning that fuel isn't being burned as a result - importing means that additional fuel is being burned. 90% of the time the difference comes out in the wash - it's gas plant with a reasonably fixed efficiency which is being turned up and down, so using the electrons provided by your own PV doesn't make much of a difference.

What does have an effect is if a particularly dirty fuel (i.e. coal) is on the grid - mostly in winter at the moment:

Not the easiest graph to read, but it's pretty clear from the middle chart that coal is mostly on during the day. So that means at this time of year (when admittedly you won't get much from your solar) you're better off running it at night. Octopus agile pricing is actually a pretty good proxy for how clean energy is - burning fuel costs money, so if it's cheap it's probably green too.

I'd just run it whenever need to in order to stay comfortable, and not worry about it.

[Rich123]

Hi , just read your response, if I could get the manual I’d have another look for you . 
But these are a few items 

1. The thermostat as you described is optimised start. This calculates the pre heat required to get the temperature to the required level by the occupancy set time. This is an essential element. It may also have economy off which is the same thing in reverse.

2. Ensure that you have set the unit to heating priority. I would actually try turning off the hot water for a day just to see if it responds better.

With a standard domestic boiler and cylinder , the heat load required is actually relatively low. Recovery heat up of the cylinders is around 

half an hour with a 28 kW boiler. So with a 9 kW heat pump that is potentially 2 hours.

Heat pumps also ice at low temperatures , therefore there is a defrost cycle. From the very sketchy info on the LG I think it has an electric heater but I’m not sure if that is totally compensating for the defrost.

I also see that the system is weather compensated , this changes the supply temperature based on external temperature , this may be adjustable and if you can change the curve it may help as at 5 degrees the supply temperature could be around 65 C .

Edited January 7, 2021 by Rich123
Added

[Hogboon]

Morning all - and to coin a phrase "Well! Well! Well!" ProDave would appear to be psychic! His first thought that "... the heat requirements of your house are too high for the heat pump you have" seem to have been spot on. The installation company rep confessed that they had installed the wrong size pump! The original calculations suggested a 7kw whereas it should have been a 14kw! My uninformed increase of pump size to 9kw, while seemingly a step in the right direction, still fell way short of the mark. So within the next week or so they are to fit a 14kw heatpump. As this 9kw almost does the trick I assume a 14kw should cope easily?

 

A word of explanation won't be amiss even though I have named no names. The installer is a privately owned company who specialise in heat pumps. Until recently i.e. within the last few days! they sub-contracted out the EPC and heat calculationss to a fully qualified third party who it seems f.u.b.a.b. [b.a.b. = beyond all belief]. Mine were not the only calculations he got wrong; there are two other installations that are apparently similarly afflicted. The installation company is now doing all its own calculations 'in house'. Hey ho.

 

For what it's worth, having turned back ON the 'True Radiant' option on my thermostat, the heatpump was thashing away more-or-less all night long. Come the appointed hour [08:00] the temp was 17.5º [as opposed to the 18º demanded]. Temp outside most of last night was about -2ºC according to a rather unreliable trail camera I have set up to record hedge hogs; it is  now around 8ºC according to an equally unreliable cheap stick-on thermometer and the heatpump is chassing the target temp of 20ºC demanded from 10:00 til 15:00.   

 

Thanks for all the help and I will report back once the new heatpump is up and running.

 

[Rich123]

28 minutes ago, Hogboon said:

Morning all - and to coin a phrase "Well! Well! Well!" ProDave would appear to be psychic! His first thought that "... the heat requirements of your house are too high for the heat pump you have" seem to have been spot on. The installation company rep confessed that they had installed the wrong size pump! The original calculations suggested a 7kw whereas it should have been a 14kw! My uninformed increase of pump size to 9kw, while seemingly a step in the right direction, still fell way short of the mark. So within the next week or so they are to fit a 14kw heatpump. As this 9kw almost does the trick I assume a 14kw should cope easily?

 

A word of explanation won't be amiss even though I have named no names. The installer is a privately owned company who specialise in heat pumps. Until recently i.e. within the last few days! they sub-contracted out the EPC and heat calculationss to a fully qualified third party who it seems f.u.b.a.b. [b.a.b. = beyond all belief]. Mine were not the only calculations he got wrong; there are two other installations that are apparently similarly afflicted. The installation company is now doing all its own calculations 'in house'. Hey ho.

 

For what it's worth, having turned back ON the 'True Radiant' option on my thermostat, the heatpump was thashing away more-or-less all night long. Come the appointed hour [08:00] the temp was 17.5º [as opposed to the 18º demanded]. Temp outside most of last night was about -2ºC according to a rather unreliable trail camera I have set up to record hedge hogs; it is  now around 8ºC according to an equally unreliable cheap stick-on thermometer and the heatpump is chassing the target temp of 20ºC demanded from 10:00 til 15:00.   

 

Thanks for all the help and I will report back once the new heatpump is up and running.

 

That’s great and it’s good that they have been honest and are rectifying it , 14 kW will be fine I’m sure .

Also ask them to commission it and let you have a certificate with all of the settings on .

[George]

I've got a 16kW Samsung ASHP and if anything I think it is oversized. The house heats up within a few hours so it doesn't run it continuously, which I believed was the most efficient way in winter. COP seems pretty good at 2.89 during the latest cold weather inc defrost cycles.

 

However, previously we had an one room oil rayburn and log burners so have nothing to compare it to.

 

When installed we did insulate and it was a complete new CH so rads are sized correctly. We also kept the 2No wood burners as supplementary heating - which when working from means I'm not using electricity to heat the office. 

[larry]

16 hours ago, pdf27 said:

Things aren't quite so clear cut.

If you're exporting to the grid, you are meaning that fuel isn't being burned as a result - importing means that additional fuel is being burned. 90% of the time the difference comes out in the wash - it's gas plant with a reasonably fixed efficiency which is being turned up and down, so using the electrons provided by your own PV doesn't make much of a difference.

What does have an effect is if a particularly dirty fuel (i.e. coal) is on the grid - mostly in winter at the moment:

Not the easiest graph to read, but it's pretty clear from the middle chart that coal is mostly on during the day. So that means at this time of year (when admittedly you won't get much from your solar) you're better off running it at night. Octopus agile pricing is actually a pretty good proxy for how clean energy is - burning fuel costs money, so if it's cheap it's probably green too.

I'd just run it whenever need to in order to stay comfortable, and not worry about it.

I very much recommend the free NG ESO app (at least on Android) which shows the above data as well as regional differences and makes future forecasts for carbon intensity/kWh. 

Burning coal is indeed the real stimulus of carbon output it seems! 

[Ferdinand]

The other part of the equation is to reduce the heat needed by the house - which is insulation, airtightness and all the rest.

 

Let me point you in a couple of diections:

 

1 - One of your members built a heat-modelling spreadsheet which is straightforward to use to build a heat model of your house. See this thread:

2 - I have this piece on my blog on the site had 10 steps to reduce your energy bills - simple but relevant, and really the same thing as reduction.

 

3 - Remember that the biggest impact on energy bills is to get into a regime of regular switches.

 

4 - And don't forget tariffs such as Economy 7 and Economy 10.

 

They help as you are helping balance the network.

[joth]

1 hour ago, Hogboon said:

The installer is a privately owned company who specialise in heat pumps. Until recently i.e. within the last few days! they sub-contracted out the EPC and heat calculationss to a fully qualified third party who it seems f.u.b.a.b

Is the installer MCS registered? If so, they should have done (or requested) room-by-room heat loss calcs, in order to specify controls and emitters on a room by room basis. A whole house EPC is not sufficient. If this is the case then they both FUed.

(If not MCS then they can do whatever they want within statury limits, but it sounds promising that they're carrying the can for it)

 

 

Edit: opps just read again and noticed you said "and heat calcs" so sounds like they were trying to do it right ? 

 

Btw to link to @Ferdinand post - do ask the installer for a copy of the room by room calcs. This can act as a good starting point to figure out where energy savings can be made, saves some time redoing it all yourself

Edited January 8, 2021 by joth

[dangti6]

I know nothing about ASHP, but hello and welcome from a fellow Somerset member ?

[Ferdinand]

Further note:

Do I calculate correctly that your 1 year guarantee (if it is) still has another 3 months to run? And that they are acknowledging that by offering the replacement.

[SteamyTea]

17 hours ago, pdf27 said:

What does have an effect is if a particularly dirty fuel (i.e. coal) is on the grid - mostly in winter at the moment:

Coal seems to have been replaced with wind now.

At 12:18 08/01/2021Coal was supplying 3.1 GW, wind 3.38 GW (6.7% and 7.6% respectively).