ASHP winter additional heating ideas?

[ashthekid]

Hi,

 

I have recently now moved into my home which is a newly converted old property which is now a very well insulated home (recently rated A on EPC) totalling 385sqm. We have 16kw air source heat pump providing underfloor heating upstairs and downstairs as well as hot water. We have no gas whatsoever in our village but I have 11 solar PV panels to support the setup with a myEddi diverter to use any unused PV generation straight into the hot water cylinder(size 400 litre). On 3 phase electric supply.

 

We moved in Jan, admittedly during an unusual freezing cold snap but our first months bill was £850 using 2500 kWh(average 80 kWh per day). (Solar PV was not up and running during this month)

Feb was £700 @ 2100 kWh (average 75 kWh per day)

March was £540 @ 1650 kWh (average 55 kWh per day)

April was £400 @ 1300 kWh (average 43 kWh per day)

 

My question is, what can I do in addition to my heating during those winter months when costs are dramatically higher?

Is it worth me getting a battery and storing any unused generation to be used during the winter? (side NOTE: I have no idea what I waste)

Should I get a couple of little gas heaters for the larger rooms?

Should I consider an additional small electric boiler that may run more efficiently during the winter to service my UFH and hot water needs compared to the ASHP?

 

 

Edited May 23, 2023 by ashthekid

[Conor]

You're four months consumption is greater than  my entire year, also an A rated house of similar size (but new). Think we need to know more about the ASHP setup and how it's being operated. How much insualtion under the ground floor? I'm assuming the heatloss is higher than the EPC says (they are far from accurate). Was there any other analysis done?

 

Off the bat you can look in to off-peak tariffs, we run our ASHP 90% of the time on low rate, a third cheaper than peak (10p vs 30p). Check the flow temp you ave for heating. Other main question, is the house warm enough and what do you have the room stats set at?

[Dave Jones]

what was the air test result for the house ?

 

your heat is disappearing somewhere, either insulation, cold bridging or poor air tightness. combo of all 3 ?

Edited May 23, 2023 by Dave Jones

[ashthekid]

I'm not sure of the air test result but the specialist plumbing/ASHP company did forecast £450 spend per month with all of the heat loss calculations.

 

We do have a large 100sqm open space double height ceiling room with vaulted roof and one wall being totally double glazed glass and bifold. The whole property's 1st floor is vaulted ceilings with no loft space. Natural stone floor throughout.

It gets insanely hot upstairs during sunny days.

 

I also just recently last week has the broken smart meter fixed. Turns out it was never commissioned. i'm hoping that helps me identify exactly what and when is sucking the consumption.

[JohnMo]

How are you running the heat pump

 

For UFH what is your flow temp and heating regime. How many zone and how are operating?

 

Same for DHW ?

[mattman]

As above, I would look at finding out the cause of your large energy and heat requirement.  I would also get on to a low electricity tariff asap if you're not already.  The heat pump during the winter months needs to be on all the time to be most efficient and we have found a low priced tariff all during the day and night seems to work well - as an example we are on the Octopus Tracker tariff which hovers around 17 to 18p a kwh, all day any time of the day - during the winter months it was about 20 to 24p.  Since March we haven't needed the heating on at all - just heating our water - which bearly costs anything - about 50p a day for around 3kwh a day or less.  During the minus temp winter months for all space heating and hot water we used more energy, on average 25 to 30kwh per day.  We are a smaller house than you, at 264sqm, a new masonry built self-build, reasonably air-tight with a 2.5 air tightness score, electric only, no gas, and a smaller 8.5kw ashp, ufh on the ground floor only, no heating upstairs apart from two towel rails, very open plan with a double height entrance area, so not a like for like comparison but I can share what we have done to achieve the lowest costs with our heat pump usage in our own situation (we did a lot of trial and error testing during the very cold winter months, not long after it was installed, and every time I made a change in a setting on the heat pump I found we had to wait 24 hours to see the result - after a few weeks of LOTS of trial and error with the heat pump I managed to significantly reduce our energy usage while at the same time maintaining an adequate constant room temperature):

 

I have found best results with our heat pump is to have it on as low a flow temperature as possible, in the winter months when you require space heating: keep all ufh zones on (I recommend not turning some zones off, as this makes the zones which are on work harder - we trialled turning some zones off and it ended up costing us more and the whole place was colder too - we don't have any heating upstairs so I can't comment on whether or not to turn some of the zones off upstairs but it might be worth trialling possibly turning off some or all of the zones upstairs and see what difference in energy usage and room temp this makes - unfortunately it's the wrong time of year to test as the temperatures outside are quite mild), schedule your hot water heating to once or twice a day (we schedule ours to come on an hour before morning showers and an hour before evening bath/showers as we have small children), and make sure the max temperature in the cylinder is around 50° or ideally below with a max temp drop of round 4 to 6°, and most importantly make sure the immersion does not come on at any time apart from once a week for the Legionella cycle where it has to heat the cylinder to 60°.    Hope this helps.

Edited May 23, 2023 by mattman

[Marvin]

Hi @ashthekid

 

 

2 hours ago, ashthekid said:

We do have a large 100sqm open space double height ceiling room with vaulted roof and one wall being totally double glazed glass and bifold. I cannot remember the figures but the higher the ceiling the hotter the air above your head  needs to be to be warm enough where your standing....

 

However £450 over 12 months is what £5.6k?   We are not using the ASHP for heating at all now, and won't until about October. I'm sitting here eating lunch and its 23.7°C and my wife had had the cooler on!

 

We only have 100m2 with 5.12kW PV (16 panels) ASHP, 205litre hot water pump, and a PV diverter and we are using about 3000kWh a year for the heating.

 

We noticed that in the winter months although there is a reduction in the PV electricity generation to about a quarter of the summer production its usually produced in bunches of days. 

 

We also noticed that the hot water tank temperature drops quite quickly in the winter months, although our tank is super insulated and is in the thermal envelope with an air temperature no lower than 19°C 24 hours a day.   We put it down to temperature migration along the pipes connected to the central heating (not on 24 hours a day).

 

In the winter we have the water temperature quite low, with a boost every month over 60°C remembering that the closer the ASHP water output temperature is to the outside air temperature, the more efficient.

 

Setting up a relay on the tank thermostat which is using the PV excess diverter means you can heat the tank up from the excess solar and after that divert it to a night storage heater. This can store heat for about 24 hours.

 

However to achieve the same sort of ratio of PV panels to floor surface as us would mean you would need about 60 PV panels (assuming that they have about the same assumed output per panel of about 320W) 

 

Best of luck.

 

M

 

 

 

[Wil]

Hi Ashthekid,

 

I’m in a similar situation with horrendous winter bills and then almost nothing in the warmer months with solar taking care of almost all HW. Sadly I’m also collecting the RHI, so can’t make any changes in the first 7 years.

 

When I can I’ve been looking at a WBS with backboiler to take the strain off the ASHPs for the winter months to take advantage of my free wood supply. Relatively complex to integrate the two systems however and probably needs me to replace the buffer tank with a thermal store to take the heat loads. 

 

We’re due to start a renovation shortly so will be trying to hit our air tightness issues and improve insulation in floors and sloped roof wherever possible.

 

 

[joth]

Does your ASHP have any kind of monitoring or logging support?

What you want to know is how much energy it pushed out each day and how many kWh it consumed, rather than how much money you poured into electricity in total in the day.

 

This will then give a first clue if the house is leaking energy, if the ASHP is poorly setup, or if it is in fact some else entirely. (Or combo of all three).

 

Most MCS installs had the option of advanced monitoring package, you could ask the installer about adding this as it's not performing to your expectations 

 

 

 

 

Edited May 23, 2023 by joth

[Lofty718]

What is the COP of the heat pump? bills seem ridiculously high

 

also is it running on weather compensation? sounds like a bad install

[ProDave]

What is your monthly energy use now, now that the heating is off?  In the absence of any other metering, that will give an indication how much of your usage is heating and how much is other stuff.

 

Even in winter the other stuff uses more than the ASHP.

 

Only when you know WHAT is using all the energy can you look into making it use less.

[Dave Jones]

20 hours ago, ashthekid said:

I'm not sure of the air test result but the specialist plumbing/ASHP company did forecast £450 spend per month with all of the heat loss calculations.

 

We do have a large 100sqm open space double height ceiling room with vaulted roof and one wall being totally double glazed glass and bifold. The whole property's 1st floor is vaulted ceilings with no loft space. Natural stone floor throughout.

It gets insanely hot upstairs during sunny days.

 

I also just recently last week has the broken smart meter fixed. Turns out it was never commissioned. i'm hoping that helps me identify exactly what and when is sucking the consumption.

 

you need to find out. You also need to determine the U values of your walls, floors and ceiling.

 

It may be you have zero floor insulation for example. 

 

Once you have the results of your air test and know your insulation levels you will know exactly where the pound notes are disappearing.

[ashthekid]

Thank you all for your replies.

 

I'm still averaging 30 kWh per day even with all UFH set to low temps so I know it's not pulling anything in any of the zones.

Within the ASHP settings (it's a Hitachi Yutaki S split system as the outdoor unit is 35m away) I attach some of my settings screenshots - would be interested if anything flags up for anyone when looking. 

 

My solar PV(11x panels of 360w each) is generating an average of 15-24 kWh per day at the moment - peaking at 24.8 on yesterday.

I generated:

Feb 169 kWh (ave 6 per day). --  OVO usage 70 per day

March 212 kWh (ave 6.8 per day) --  OVO usage 55 per day

April 407 kWh (ave 13.5 per day)  --  OVO usage 43 per day

May so far(upto today 25th) 405 kWh (ave 16.2 per day)  --  OVO usage is 703 so far (ave 29 per day)

[ashthekid]

@Dave Jones I have OTT insulation in general in the floor, walls and roof. It was a 200 yr old property that we essentially built a newbuild timber frame inside. We have 100mm in the floor, 125mm in the walls (including 25mm on top of studwork to stop any cold bridging) and then 250mm within the roof in the large open space rooms, 150mm in other rooms. 11x velux windows all triple glazed, 10x small softwood framed windows with double glaze, then large double glazed bifolds 8 metre wide and matching double glazed windows above. I know there is heat loss through these windows.

[JohnMo]

Not sure what I am reading from the screen shots.

 

Can you confirm

The cylinder looks to at 49?

Your radiators 46 to 47?

 

Is this correct?

 

 

[Conor]

If you heating flow temp is 45+ then you need to lower it. Ours runs at 32-35c. You'll gain a whack of efficiency by doing this.

[Mungo]

Agree with Conor in lowering the heating flow temp.

We also live in a converted granary with as ASHP and UFH, and average around 6-8 kWh per day.

[Dave Jones]

13 hours ago, ashthekid said:

@Dave Jones I have OTT insulation in general in the floor, walls and roof. It was a 200 yr old property that we essentially built a newbuild timber frame inside. We have 100mm in the floor, 125mm in the walls (including 25mm on top of studwork to stop any cold bridging) and then 250mm within the roof in the large open space rooms, 150mm in other rooms. 11x velux windows all triple glazed, 10x small softwood framed windows with double glaze, then large double glazed bifolds 8 metre wide and matching double glazed windows above. I know there is heat loss through these windows.

Air test result ?

[SteamyTea]

You say the floor is traditional stone, is there any insulation under it?

You say the upstairs gets hot in the spring, how much insulation is up there.

You may be better off heating your hot water with the heat pump when the sun is out. But if your PV is supplying your needs, not much in it.

 

As for space heating in the winter, not much you can do, a direct electric boiler will cost you more. Your HP will almost certainly have a direct heater built in. That may be on permanently. Turn it off.

 

Can you get some thermal energy data directly off the heat pump, that should show you how much energy the house is using.

 

[ashthekid]

@SteamyTea floor is made up of 400mm concrete, 100mm celotex, then the UFH within approx 60mm of screed, then the stone floor tile of approx 15mm. 
 

I would say upstairs has more than adequate insulation: 150-250mm of celotex. Then 15mm Soundbloc plasterboard everywhere too. 
 

@Dave Jones I don’t have an air test result. As far as I’m aware I didn’t need one. I had a ventilation test as part of BC requirements. Where would it be exactly? I’ll try and find it if it exists. 
 

@Conor @Mungo I’ll definitely lower the flow temp from 45 down to 40 and see what difference that makes over a few days although at the moment I have all the UFH set to Standby 12 degrees so practically off. 
 

@JohnMo No radiators, 100% UFH plus a few towel rads in the bathrooms but they are duel fuel and currently switched to * and off electrically. 
yes the cylinder is set to 49. Too high?

I looked just now and it said the cyclinder temp was 54 but I assume that’s mainly from the solar energy we gained through the myEddi diverter today. 

 

[JohnMo]

If your UFH is running at 45 your CoP will not be much better than 3, if your running the UFH for short periods then CoP will drop from that.

 

Running at 35 your CoP jumps to 4, so you use 33% less electric. 

 

UFH runs better if you run for a long periods at the lowest possible temperature.

 

You need to drop the temperature on the heat pump controller, not the mixer on the UFH manifold as such.

[Dave Jones]

On 26/05/2023 at 12:41, Dave Jones said:

Air test result ?

 

your pissing heat out the building somewhere. arent you curious where ?

[JohnMo]

Or just running everything too hot, for too short a period, therefore getting a rubbish CoP. Basically trying to run like a gas boiler.

[DanDee]

38 minutes ago, JohnMo said:

Or just running everything too hot, for too short a period, therefore getting a rubbish CoP. Basically trying to run like a gas boiler.

This one runs like a boiler, best SCOP vs everyone on weather compensation.

 

https://emoncms.org/ecodantest2/app/view?name=My+Heatpump

[JohnMo]

So what do you mean when you say runs like a boiler. From what I can see you seem to run at 2t degrees or on DHW.