Confused on price ASHP

[mk1_man]

Apologies, I should have said 150m2 underfloor on the ground floor,  also have 100m2 1st floor but we never have heating on that apart from bathrooms

 

[MikeSharp01]

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12 minutes ago, mk1_man said:

Apologies, I should have said 150m2 underfloor on the ground floor,  also have 100m2 1st floor but we never have heating on that apart from bathrooms

 

 

It is somewhat about volume / surface area because you could have a 156m on the ground floor with 50m ceiling height and 100m 1st floor - extreme I know but I guess you see the point. Pretty sure it won't make difference though will it.

[SteamyTea]

2 hours ago, MikeSharp01 said:

It is somewhat about volume / surface area

Plan is important as well, you could have 1 metre wide and 150 metres long.

 

https://www.dummies.com/article/academics-the-arts/math/calculus/how-to-use-differentiation-to-calculate-the-maximum-volume-of-a-box-192226/

Edited March 13 by SteamyTea

[sharpener]

3 hours ago, mk1_man said:

Apologies, I should have said 150m2 underfloor on the ground floor,  also have 100m2 1st floor but we never have heating on that apart from bathrooms

 

 

Unless you have substantial insultation in the ceiling/first floor you will find a lot of heat makes its way up to the first floor whether you "heat" it or not.

[Surfiejim]

On 13/03/2024 at 09:35, mk1_man said:

I am finding that the MCS route to market is a complete rip off, more akin to ambulance chasers.  I am doing a self build with the intention of installing a heat pump at some stage so all main flow and returns are 28mm copper to tank and underfloor manifolds. The mains cable and 2 wire control cable is already run, I have an existing 250l twin coil cylinder that they have confirmed is suitable for heat pump so they have agreed not to swap etc.  They have said that my install should be really simple and take no longer than a day possibly two.  The quote is £13,250 of which I can claim £7,500 back.  This is for a 12kw Vaillant which retails around £5700 and I am sure they pay much less.  The only additional materials is a few valves, possibly antifreeze valves and a couple of meters of copper, interface, rubber feet etc.  Say that amounts to an additional £1000 that would take a total of £6700 in goods.

 

How on earth do they justify £6.5k for possibly two days work !   All of the companies appear to be the same.  I obtained a few quotes last year before government increased grant to £7.5k,  the difference I had to pay hasn't changed, it appears companies are able to just pocket an additional £2.5k in their pockets. 

 

How on earth does the government expect people to migrate from gas boilers to heat pumps with this closed shop racket going on !

 

I feel that these grant harvesters are conmen too and I'm not sold on ASHP's. I have therefore asked my sapps guy if I can go to gas. Yes he said. So I phoned around today and I've had my eyes opened. LPG is cheap and pretty clean for now but down the line they expect Biopropane and Dimethyl ether to be available for off mains gas systems. All new systems are either hydrogen ready or fully able to take Net Zero alternatives. I think I can get an underground bulk tank, boiler and install for a lot less than the ASHP even after the grant. 

[SteamyTea]

47 minutes ago, Surfiejim said:

down the line they expect Biopropane and Dimethyl ether to be available for off mains gas systems

Do they.

50 minutes ago, Surfiejim said:

hydrogen ready

This government has dropped hydrogen as an alternative. While governments do change, physics does not.

51 minutes ago, Surfiejim said:

Net Zero alternatives

No idea what that is.  Is it like BP and Shell saying they are going to become Net Zero companies.

53 minutes ago, Surfiejim said:

I'm not sold on ASHP's

Apart from the selling practices, what do you dislike about them?

[JohnMo]

1 hour ago, Surfiejim said:

I think I can get an underground bulk tank, boiler and install for a lot less than the ASHP even after the grant.

My boiler in 2020 cost a £1000 in a pre COVID sale, around £400 off. In 2023 I swopped over to ASHP all self funded.  The asap cost £1300, some other bits and pieces added to that cost, but not much. Running costs are cheaper than gas overall for me and I get summer cooling. Win win

[JamesPa]

3 hours ago, Surfiejim said:

I feel that these grant harvesters are conmen too and I'm not sold on ASHP's. I have therefore asked my sapps guy if I can go to gas. Yes he said. So I phoned around today and I've had my eyes opened. LPG is cheap and pretty clean for now but down the line they expect Biopropane and Dimethyl ether to be available for off mains gas systems. All new systems are either hydrogen ready or fully able to take Net Zero alternatives. I think I can get an underground bulk tank, boiler and install for a lot less than the ASHP even after the grant. 

Sadly all greenwash.

 

It is of course your choice, but please don't be fooled into thinking that it is, or may become green.  It isn't and won't.  But every person they successfully convince with their lies is another customer for the fossil fuel industry retained for 15 years, which is a win for them.

Edited March 14 by JamesPa

[mk1_man]

Just had my quote from Alto Energy, 11.2kw Mitsubishi Ecodan, new 250 litre cylinder with 28mm 3m2 coil, all of the required bits and pieces £1500 once BUS grant removed.  They operate what I feel is a unique and sensible approach, they do the heat calcs, mcs certification, commissioning etc but let the home owner / self builder either use their own plumber or install themselves if you are hands on build.  All you need to do is attend their training course which can be done in physical classroom or via teams. Post install you still get the 5 or 7 year warranty. 

 

heat loss calculated so far at 8kw, not sure why 11.2kw heat pump being specified, do mcs add 20% or so wiggle room?  My preference is to have a more suitable sized heat pump for majority of the time and if the rare occasions it drops to around -2 or less then we simply have a slightly colder house or wear a jumper.

Edited March 15 by mk1_man

[Dave Jones]

On 03/03/2024 at 16:47, JamesPa said:

Not sure what you are 'calling bs' on.  MCS is required for pd, see the post referred to here  

 

if you can find any ambiguity in the source texts quoted in the post, please say.  I would be delighted to be proved wrong but, sadly, can't see that will happen.

 

 

 

maybe blind but cant see where it says that anywhere.

[JohnMo]

20 minutes ago, mk1_man said:

do mcs add 20% or so wiggle room

No - but is the output of the heat pump a your design outdoor temperature?

[SteamyTea]

10 minutes ago, JohnMo said:

No - but is the output of the heat pump a your design outdoor temperature

I just had a quick look at the Ecodan R32 spec sheet, and it seems they name the models after the power output at -7°C.

 

It was a quick look though.

[JohnMo]

36 minutes ago, mk1_man said:

heat loss calculated so far at 8kw, not sure why 11.2kw

 

4 minutes ago, SteamyTea said:

I just had a quick look at the Ecodan R32 spec sheet, and it seems they name the models after the power output at -7°C.

 

It was a quick look though.

A quick look and the next size down is 8.5kW, so by the time you have allowed for DHW heating, it would be too small.

[SteamyTea]

10 minutes ago, JohnMo said:

quick look and the next size down is 8.5kW, so by the time you have allowed for DHW heating, it would be too

Yes, good point.

 

I noticed that there is a data handbook that you can ask for.

 

[mk1_man]

Hi, I am still somewhat confused as to why the heat pump has to be bigger to support hot water. With the diverter it is either space heating or hot water but not at same time.  With our current boiler setup system turns itself off for quite a bit of the day once slab (85 - 90mm) is heated up, and there is never demand for heat between 22:00 - 04:00 as heat loss appears minimal i.e. temps drop form around 21 - 19   so doesn't that leave plenty of time for heat pump to heat the dhw?

 

My concern about a more powerful pump is that for 95% or higher time it is over sized so not efficient.  I would prefer to just add a jumper or except a slightly colder house when temps drop below zero etc, it appears mcs don't allow / permit this approach?

[JamesPa]

1 hour ago, Dave Jones said:

 

maybe blind but cant see where it says that anywhere.

 

It's there in plain text.

 

 The Town and Country Planning (General Permitted Development) Order 2015 clause G1 ( which is the section dealing with heat pumps)

 

https://www.legislation.gov.uk/uksi/2015/596/schedule/2/part/14/crossheading/class-g-installation-or-alteration-etc-of-air-source-heat-pumps-on-domestic-premises/made

 

says (my italics)

 

G.1  Development is not permitted by Class G unless the air source heat pump complies with the MCS Planning Standards or equivalent standards.

 

The MCS Planning Standards are defined in MCS 020 as follows:

 

 

That very clearly includes that it shall be installed to MCS standards by an MCS contractor.

 

There are no recognised equivalent standards and, it seems to me that to be equivalent, it would need to include something like clauses (a) and (b) not just clause (c).  Thus MCS becomes compulsory to benefit from PD rights.

 

The key is the definition of 'the MCS Planning Standards '

[JamesPa]

20 minutes ago, mk1_man said:

Hi, I am still somewhat confused as to why the heat pump has to be bigger to support hot water. With the diverter it is either space heating or hot water but not at same time.  With our current boiler setup system turns itself off for quite a bit of the day once slab (85 - 90mm) is heated up, and there is never demand for heat between 22:00 - 04:00 as heat loss appears minimal i.e. temps drop form around 21 - 19   so doesn't that leave plenty of time for heat pump to heat the dhw?

 

My concern about a more powerful pump is that for 95% or higher time it is over sized so not efficient.  I would prefer to just add a jumper or except a slightly colder house when temps drop below zero etc, it appears mcs don't allow / permit this approach?

The argument is that while it's heating hot water it's not heating the house so the house fabric is cooling.  The energy lost from the fabric must be replaced during the hours it is heating the house hence it must be larger.

 

Personally I think this is probably over engineering, although I haven't done the numbers to prove It.  It is true that the house cooks while it is heating hot water and the energy lost from the fabric must be replaced, however because it is cooler for a while the total energy required by the house is reduced.  So the extra needed is in part (but I grant not fully) offset by the fact a bit less energy is lost from the house.

 

This matters only on the coldest days, which happen a few times a year. Personally I'd put on a jumper or turn on the immersion if the problem actually occurred which quite likely it wouldn't.

Edited March 15 by JamesPa

[PhilT]

32 minutes ago, mk1_man said:

My concern about a more powerful pump is that for 95% or higher time it is over sized so not efficient.  I would prefer to just add a jumper or except a slightly colder house when temps drop below zero etc, it appears mcs don't allow / permit this approach?

how would you operate? If it's anything like JohnMo, using the slab as a night storage heater to utilise cheap rates, then you would need a pump that is much more powerful than the design steady state continuous heat loss/energy input of 8kW at -2degC

 

[JohnMo]

47 minutes ago, mk1_man said:

somewhat confused as to why the heat pump has to be bigger to support hot water

In simple terms

To get the grant the heat pump has to be capable of heating the house and got water at the lowest design temperature.

 

So using easy number 3 kW heat demand, AND requiring 2 hours for DHW heating, that leaves 22 hours for heating.

 

3 x 24, is 72kWh. You now need to put 72kWh into the house in 22 hours.

 

72 divided by 22 is 3.3 kW.

 

Now add your numbers to those and see what you come out with.

[JohnMo]

5 minutes ago, PhilT said:

If it's anything like JohnMo, using the slab as a night storage heater to utilise cheap rates,

My heat demand is around 3.5kW at -7. The heat output is 6kW at -7. On that temperature day the heat runs for around 12 -14 hours. On an 8 degree day it runs for a few hours.

 

If you installed an 8.5kW heat pump with a demand of 8kW, your heat pump would have to run at nearly full load 24/7 to cope. If you want to batch charge the floor oversized is ok, in fact it has to be oversized.

[SteamyTea]

MCS uses a standard convention, which I think is that the system must be able to deliver enough energy 99% of the time.

 

I had a look at the Central England Temperature (CET) records for 1900 to 2000 and 1990 to 2020, which are the longest running instrument recordings, so considered the gold standard.

 

Without getting into silly decimal places of percentages, between 1900 and 2000, the lowest 1% was from -3°C downwards, 1990 to 2020, it was -2°C and below, so 1°C higher.

Looking at the point I turn my heating on, outside air temperature (OAT) of 9°C, 1900 to 2000 is 53% of the time, and between 1990 and 2020, 49% of the time.

 

 

It is a similar story with overheating, just not so frequent.

1900 to 2000, >=24°C is 0.02%, 1990 to 2020 0.1%.

 

The mean temperatures during those dates (actually the median temperature as the MET Office reads twice a day) is 9.5°C and 10.2°C.

 

So if you design your house with way to much glazing 'because you love natural light', you really need to think about paying for cooling.

 

 

 

[JamesPa]

23 minutes ago, JohnMo said:

To get the grant the heat pump has to be capable of heating the house and got water at the lowest design temperature.

Ok, I admit that I had forgotten that the grant rules prohibit the use of jumpers.  As you say if you have a good slab and want to take advantage of night time rates that's also a reason to oversize.

 

[mk1_man]

Thanks all and I appreciate the feedback.  My issue is that I currently heat house and hot water with a 19kw system boiler (Viessmann) that majority of time modulates down between 10% & 30% so outputting around 1.9 - 5.7 kW    The heating also runs infrequently apart from the 04:00 - 08:00 start time each day. My rooms are between 20.5° & 22°   I just can't get my head around the fact the mcs figures are saying that I need to input 8kW or so 24 x 7 

 

Maybe I am worrying too much, just need to clarify what the minimum output is for an 11.2 Ecodan so as not to be cycling all of the time. 

Edited March 15 by mk1_man

[JohnMo]

38 minutes ago, mk1_man said:

My issue is that I currently heat house and hot water with a 19kw system boiler (Viessmann) that majority of time modulates down between 10% & 30% so outputting around 1.9 - 5.7 kW 

If that's the case there looks to be something not right with the heat loss calculation - rubbish in - rubbish out

[Gary68]

My heat loss was calculated at 7.7kW and they installed a 8.5kW Ecodan, it works well at the -2C design temp it has to run 24/7 to keep the house at 21C but works right down to the -7C temps we saw this winter with no noticeable impact to internal temp.

 

I believe this is because the MCS heat loss survey is probably conservative so we have a bigger buffer (no pun intended) in the heat loss than calculated.

 

The bigger issue with Ecodan's is that if you have the Mitsubishi preplumbed cylinder then they come with an awful LLH and a whole host of pumps and to maintain warranty they have to be filled with glycol.

 

The other issue with Ecodan is that the primary pump is not located within the outside unit, its installed internally within the house so depending on the location can cause a noise nuisance, especially at night.  The Ecodan also cannot modulate the flow rate itself to maintain delta T.

 

In saying all that its run flawlessly for 5 years, has a reasonable COP of 3.5.

 

Would I buy one again, no, I would give Vaillant or Daikin a go if I had to change.

Edited March 15 by Gary68