Meter readings - air source heat pump

samsam89

Hi - looking for some advice if possible.

Moved into a brand new house May 2019 and after a couple of months a meter read request arrived as builder had switched the energy over. I submitted the reading and began paying approx £50 per month on a fixed British Gas tariff (3 bed house, detached, 2 adults/2 kids, energy efficient bulbs and appliances etc). We have an air source heat pump and underfloor heating downstairs. 

I hadn’t submitted any meter readings throughout this year. (pandemic fever must have got me and I just completely forgot - should have done!). At the end of October British Gas randomly increased the direct debit to £150 without notice so I got in touch to which the rep told me that as it was ahead of winter they assume increased usage. I submitted a meter reading to discover we are £667 in debit with them.

Clearly we’ve been underpaying which I understand but I’m struggling to get my head around how we’re using so much energy. I’ve taken meter readings since 02/11 and we have used an average of just over 16kwh per day over the last 23 days. Is this excessive or about right for the above scenario?

After scouting about on MSE I inspected our heating curve which I believe had been set way too high by the installer. It was heating the water for the heating to 40+ degrees and I remember the heat pump going full blast a lot of the time. Since I adjusted the curve down (On 2nd November) the heat pump is barely making a noise and isn’t on nearly as much.

Our whole set up seems odd and we were never given a full handover for the unit. We also cannot get hold of the original installer to try and assist.

Any thoughts on heat pump setup or billing situation and usage are most welcome before we fork out for someone to come and assess the whole thing.

Cheers.

matelodave

Let us know what make and model so we've got a vague idea of what you've got.

Ideally try an run it at around 35 degrees, mine is weather compensated and runs at between 30 and 40 degrees depending on the temperature  outside. The temperature indoors it kept at around 19-20 degrees during the day but only sets the temperature back to 17 degrees overnight. Letting the house get to cold means it can take hours (if not days to get back up to temperature).
If you run a heat pump on and off like a conventional boiler is less efficient than letting it run at lower temperatures for longer.

Likewise don't have your hot water too hot - we have ours at 45 degrees with a boost to 60 for half a hour on Saturday mornings we also only heat the water for a couple of hours a day as we get sufficient hot water for all our daily needs.

During the summer ours uses around 2kwh for producing hot water but at this time of the year the consumption can ramp up to quite alarming levels - I guess the most we've used in a day is around 60kwh. We are on the cheapest single rate leccy tariff I can find (Neon Reef at 12.25/kwh and 13.5p/day)

We are all electric and our total annual consumption is around 7200kwh/year of which about 3500kwh is for heating/hotwater

samsam89

matelodave said:

Let us know what make and model so we've got a vague idea of what you've got.

Ideally try an run it at around 35 degrees, mine is weather compensated and runs at between 30 and 40 degrees depending on the temperature  outside. The temperature indoors it kept at around 19-20 degrees during the day but only sets the temperature back to 17 degrees overnight. Letting the house get to cold means it can take hours (if not days to get back up to temperature).
If you run a heat pump on and off like a conventional boiler is less efficient than letting it run at lower temperatures for longer.

Likewise don't have your hot water too hot - we have ours at 45 degrees with a boost to 60 for half a hour on Saturday mornings we also only heat the water for a couple of hours a day as we get sufficient hot water for all our daily needs.

During the summer ours uses around 2kwh for producing hot water but at this time of the year the consumption can ramp up to quite alarming levels - I guess the most we've used in a day is around 60kwh. We are on the cheapest single rate leccy tariff I can find (Neon Reef at 12.25/kwh and 13.5p/day)

We are all electric and our total annual consumption is around 7200kwh/year of which about 3500kwh is for heating/hotwater

Thanks for the reply. We’re running with a Nibe F2040 heat pump and a Nibe VVM320 indoor module.

We have an open plan living/dining room with no thermostat. The only thermostat we have is in our whole house is in the entrance hall right in front of our front door. 

The thermostat is wirelessly linked to the control unit which is next to the manifold In my cupboard under stairs. Every time it drops below a certain temp, the thermostat asks the manifold to heat the floor. I wonder if this is what’s costing a lot? If it’s only asking for heat at certain points then it won’t be as efficient as you mentioned? I have no idea how to change it so that it’s a constant same temperature all the time.

Im also concerned that the thermostat is in the completely wrong place of if it’s even suitable for an underfloor system.

matelodave

It's not ever so easy to see what is going on - your manifold has four actuators but what is controlling them, do they all open at the same time under control of the single room stat. Do you have radiators upstairs, if so what controls them or have they just got TRV's. 

Look at page 22 of the NIBE manual and it shows the energy consumption profile which is very similar to what happens with ours, lots of energy between November and March (about 70% of our annual consumption) and only 30% in the summer). I have ten years worth of both monthly and weekly meter readings)It did take me our first winter with quite a bit of tweaking to optimise the controls.

My controls are different (its a Daikin and the controller is much cruder that yours) and I've also got a programmable stat for each room which adjusts the room temp and controls the appropriate manifold actuators and heating unit. Although it's underfloor it's an overlay system rather than buried so a bit more responsive but with low flow temperatures (between 30-40c).
It still takes several hours for any adjustment to have any real effect on the room temperatures so we don't actually turn it off, just down by 2-3 degrees (our first winter we turned it down when we went away for a couple of weeks and it took two days to reheat the place)
 We do have the advantage that we are at home all day so aren't heating an empty house. If we do go away we set up a holiday mode on the thermostats which reduces the temp to around 12 degrees but then turns it back up at least 24 hours before we return

Bear in mind that underfloor heating and a heat pump will be very slow to respond to adjustments so you need to give it a couple of days to settle down between tweaks to see what the effect is and it's important that you only adjust one parameter at a time to see what happens. Page 22 of your manual suggests that just one degree  cost you 5% in energy.

I'd advise that you set up a spreadsheet with the settings that you've already got (so you can revert if you totally cods it up) and then note down what adjustments you make and what the effect was (take note of your meter readings and even the outside temperatures) - if you don't record what you've done you wont know whether it made it better or worse. I've also got an energy monitor which monitors our consumption so I can get a graphical indication of the consumption of ours which show when its running.

Make sure that you limit or even disable the backup or boost heater and keep the flow temperatures as low as you feel is comfortable - heatpumps wont go any hotter than 50-55 degrees so if you increase the temperature above that then an immersion heater will kick in. Lastly make sure you are on a decent tariff, if the unit is running most of the time and heating during the day and not much overnight then I don't reckon that an E7 tariff is appropriate. Our unit only uses about 2kwh a day to heat the hot water tank in the summer - probably more in the winter but doesn't use enough overnight to justify E7.

samsam89

matelodave said:

It's not ever so easy to see what is going on - your manifold has four actuators but what is controlling them, do they all open at the same time under control of the single room stat. Do you have radiators upstairs, if so what controls them or have they just got TRV's. 

Look at page 22 of the NIBE manual and it shows the energy consumption profile which is very similar to what happens with ours, lots of energy between November and March (about 70% of our annual consumption) and only 30% in the summer). I have ten years worth of both monthly and weekly meter readings)It did take me our first winter with quite a bit of tweaking to optimise the controls.

My controls are different (its a Daikin and the controller is much cruder that yours) and I've also got a programmable stat for each room which adjusts the room temp and controls the appropriate manifold actuators and heating unit. Although it's underfloor it's an overlay system rather than buried so a bit more responsive but with low flow temperatures (between 30-40c).
It still takes several hours for any adjustment to have any real effect on the room temperatures so we don't actually turn it off, just down by 2-3 degrees (our first winter we turned it down when we went away for a couple of weeks and it took two days to reheat the place)
 We do have the advantage that we are at home all day so aren't heating an empty house. If we do go away we set up a holiday mode on the thermostats which reduces the temp to around 12 degrees but then turns it back up at least 24 hours before we return

Bear in mind that underfloor heating and a heat pump will be very slow to respond to adjustments so you need to give it a couple of days to settle down between tweaks to see what the effect is and it's important that you only adjust one parameter at a time to see what happens. Page 22 of your manual suggests that just one degree  cost you 5% in energy.

I'd advise that you set up a spreadsheet with the settings that you've already got (so you can revert if you totally cods it up) and then note down what adjustments you make and what the effect was (take note of your meter readings and even the outside temperatures) - if you don't record what you've done you wont know whether it made it better or worse. I've also got an energy monitor which monitors our consumption so I can get a graphical indication of the consumption of ours which show when its running.

Make sure that you limit or even disable the backup or boost heater and keep the flow temperatures as low as you feel is comfortable - heatpumps wont go any hotter than 50-55 degrees so if you increase the temperature above that then an immersion heater will kick in. Lastly make sure you are on a decent tariff, if the unit is running most of the time and heating during the day and not much overnight then I don't reckon that an E7 tariff is appropriate. Our unit only uses about 2kwh a day to heat the hot water tank in the summer - probably more in the winter but doesn't use enough overnight to justify E7.

It’s the one thermostat that controls all of the actuators at the manifold for all zones. Yes we have TRVs on the radiators upstairs. Upstairs we’ve never had an issue and the radiators have always been lukewarm/not hot, but sufficient for bedrooms.

Interestingly I turned the curve down to 31c at the start of the month when I realised that it was heating to 40+ degrees so that should provide a corresponding saving. But I suppose it will take time for that to filter through.

I was always under the impression that underfloor heating should always be on, but it seems ours just stops and starts based on the thermostat which is where I feel our energy consumption is coming from.

What’s frustrating is that it’s a lot of guess work and I’m in no way fully understanding of the whole system!

Talldave

Putting the thermostat by the front door is a bit bonkers, as is having 4 zones all controlled by the one thermostat.  It's frustrating, you have an excellent infrastructure with rubbish (cheap to fit) controls.  You might want your living room(s) at 21 during the day and 18 or 19 at night; correspondingly you might want the bedrooms at 18 during the day and 20 at night.  You can't do that because the only control you have is "temperature by the front door".  It's a typical cack-handed, cheapskate British approach!!

That said, all heating systems work by stopping and starting based on a thermostat!  The trick with UFH, as @matelodave says, is never to let it cool down too much, because it takes an age to get back up to temperature.  Using a thermostat intended for use with UFH with optimum start helps.

If it was my place and I was planning on being around for some time, I'd rip out the thermostat and put in wired stats for every zone actuator, connected to a hub that supports tablet/phone control.  I'd go wired because it removes all battery life/wireless comms problems (which are the only kind I have with my Heatmiser setup).  Sadly that would have best been done when the house was being built.  You could go for wireless stats but you'll be forever chasing flat batteries (which always fail when its cold!) unless you learn to religiously replace them every "n" months - once you've found out what "n" is !!

matelodave

Mine are all wireless stats and I dont have problem with either the batteries of lost/random connections. I just swap the batteries when the clocks back in October although they will last about two years- it's just easier to sort it out on a schedule rather than waiting till they've gone flat and you haven't any spares . My system is now ten years old so a wifi control system wasn't available. However as I had the system installed I had quite a lot of input on how it all works and spent a lot of effort in understanding how to operate it.

I would relocate the thermostat to somewhere like the lounge and set the programming to say 19 or 20 degrees for when the room is actually in use (you actually dont need it quite as hot because the whole room is warm from the floor up and then set it back to around 16 or 17 for the times that its not in use (say overnight or during the day) That way it wont get stone cold and it will only have to raise the temp 2-3 degrees to comfort levels. You can then juggle with the timings to try and optimise it.
Looking at the operating info for your Flomasta thermostat (looks like Screwfix) you can programme up to six different temps a day during the week and have a different prog on Sat & Sun if you want so you've got a fair amount of flexibility. 

As I said, don't do lots of changes all at once and keep a record of what you've changed and how it affected everything. My stats also have optimum start which anticipates when to bring the heating on so although I might have it set to say 19 degrees at 0700 the relevant stat might turn the heating on at 0630. We do have different temps at different times in each room and if it's everso cold then the system does sometimes run all night if it needs to, it's not often though so dont get hung up about one day with a high consumption.

It took me most of the first winter we had it to get it sorted out and apart from a few minor tweaks we now just leave it to get on with it.

TBH ours is probably a bit of overkill but we can have the bedrooms and bathroom turned down during the day and just boost it a bit when we get up and go to bed. The study is only turned up during the day and then down in the evening and overnight. The lounge is on all day as that's the main room and the kitchen is just turned up in the morning and evening but nowhere gets very cold and the hall is set to 17 degrees.

samsam89

Thanks both for your replies - pleased I’m not going mad.

So exploring your replies, could I potentially purchase a nest thermostat for and have it installed to control the main living/kitchen/dining area (which makes up two of the zones) and then use a room sensor to link to it for the entrance hallway and downstairs cloak??

matelodave

You could but you'd need to work out how to wire it all up.

TBH I wouldn't bother with a Nest etc, they are a nice toy but in your case with the very slow response in underfloor heating there's no advantage in being able to turn it on just before you get home. 

Just shift the thermostat from the hall to a place thats more representative of the temperatures that you want and adust the times and temps to suit your lifestyle

Do you know if the room stat initiates the heating unit, starts the pump and operates the actuators.  Does upstairs have a zone or stat or do the rads just get warm when the stat calls for heat or even stay luke warm for most of the time

As I said, I know how my system is wired and configured - each stat has a receiver channel which operates the manifold controller which not only drives the appropriate actuators (four for the lounge) but enables the heatpump and circulating pump. So just one room can initiate the whole sequence.

You'd need someone who knows what they are doing to ensure that multiple stats can control the various functions and zone without interfering with each other and you might need a controller to enable the manifold actuators to be independently controlled

I'm not saying that it cant be done but I'd suggest that the cost and complexity may be significantly higher than any savings you hope to make. I'd also doubt that having a clever stat on one or two zones would really make a lot of difference to the running cost or the comfort level - just my opinion you understand but I reckon you'll get a lot more out of tweaking and adjusting what you've got than just adding another layer of expensive complexity.

samsam89

OK - I'll have to give that a think then. I do want to change the stat so I can control the open plan area and downstairs hallway and cloak but sounds like nest isn't necessarily the best way to do it.

The rads are fed hot water heated from the boiler much the same as the underfloor is (from what I can gather) - except they don't rely on the thermostat downstairs and aren't connected to it at all. They have TRV's fitted so regulate their own temperature based on the temperature within the rooms. I have to say the rads work really well and are more often than not at that warm but not hot stage. It maintains the bedroom temperatures really nicely. I suppose it doesn't have the ability to stop heating totally in the daytime like a thermostat which I guess could be a downside - though my understanding is that if the flow temperature is there from the boiler to the underfloor throughout the day, then there's no harm in it?

As far as I'm aware the heat pump isn't activated when the thermostat calls for heat but I've never actually thought about it or observed. The stat itself is horrible looking and very cheap. I just feel like upgrading to something a bit more purpose fit to an underfloor system would be beneficial...

matelodave

I'm guessing then that the stat just operates the u/f actuators and the heating unit just circulates hot water whilst it's on, if so then you could control each actuator with it's own stat, you just need to either sort out the wiring