Air Source Heat Pumps Do Not Work

[SteamyTea]

22 minutes ago, Ferdinand said:

What would a GSHP area be for that - say 30kWh a day in winter?

About 10m of trench for every kW

 

So 300m long

 

Trenches can not be tightly packed, so say a 2 m gap between them. and they are about 1 m wide, that area becomes ~ 1000m²

Or about the same as PV (ish).

This is not surprising as GSHP are really solar powered, just that the ground is buffering the annual solar input.

Edited November 6, 2020 by SteamyTea

[Nick Laslett]

2 hours ago, PeterW said:

I’ll counter those, and provide a bit of insight .. 

 

Just to reinforce PeterW’s advice. I downloaded LoopCAD and did my UFH design. This software does a lot more than pipe loops. I also completed Jeremy Harris Heat Loss spreadsheet. The heat loss calculations from both tools agreed with each other. I also downloaded the Stroma SAP tool. This was easy to complete having already gather all the data for the other tools. There is also a very good MVHR spreadsheet here somewhere, that I also found very useful. (I will add link late)

[joth]

(sorry too long a post for me to pick through it all right now)

 

3 hours ago, PeterW said:

On your point on RHI addressing the issue, that is completely incorrect. It has made it worse, as don’t forget, the worse the losses, the more the customer gets paid .. and no-one is going to “buy” a system that has no return on investment when it is supposed to be an incentive scheme to change

 

I don't understand how you can say I'm completely incorrect. My statement was that the intention of RHI is to increase the number of trained suppliers. This is literally word-for-word relaying what my friend that used to work at BEIS when it was setup told me. Same as Solar PV RHI, they set it up to increase the network of trained professionals, not to make the systems cheaper per-se.

I did not claim that this policy is actually working. It's too soon to call, incentives like this will take many years to work through, but right now the evidence is very thin that it's working.  Certainly I had incredible trouble finding an installer, and numerous friends/neighbours/acquaintances have asked me for advice simply because they don't understand the technology, can't find info on it, and get the run around if they try and talk to suppliers. And GHG has added acute pressure that makes this even worse, not better at all.

 

Beyond all that, people pointing out their own DIY installed worked out fine is not evidence that it's a scalable solution for the majority of the country to do it. It's once you get out of early adopter and into mass-market that the problems and misinformation highlighted by the OP really starts to get peddled about.

Edited November 6, 2020 by joth

[Thedreamer]

2 hours ago, joe90 said:

I don’t think the majority of people instal wood stoves on a financial basis, I know we didn’t. We just love an open fire, goes with our “cottage” style, happen to have plenty of wood available fir free locally (neighbour is a tree surgeon ?). I would not consider one if I lived in a city/town because of the pollution but here in the middle of nowhere!!!! (I also drive a diesel ?).

 

I'm anti stove in cities and towns. 

 

In the right circumstances and locations, stoves can work. 

 

2 hours ago, Ferdinand said:

 

I think my error margins are so large that the extra (or not) 5-20% mass of the moisture is De minimis. ?

 

(And with a single bound he was free).

 

I would put the overall error bars at +/-50% or so, but it is still a useful indication of scale - which is what I intended.

 

F

 

I would say the timber is a bit less than that, prehaps 7.5kgs, sometimes we don't go through all of that just a few logs.

 

My stove a Charnwood C4, is mid range UK built stove. There will be models that are more efficient but having the stove centrally place means it heats the entire house. Last night we took it 23c with half a trug and then in the morning the house was 21.5c.

 

2 hours ago, SteamyTea said:

Of dry timber, not sure if the FC table is for that.

And just for a giggle, work out the area of land needed, with PV on it, to supply the same energy at the same time of year.

 

On the PV, during the day the sheer amount of solar gains from the south facing glazing provides heat. This is my free 'sun' energy. Overheating wasn't an issue in the summer, as generally a hot day here would be 20c compared to 30c down south. Lots of cross ventilation to ensure a breeze can be captured from any direction.

 

[Nick Laslett]

13 hours ago, Nick Laslett said:

Just to reinforce PeterW’s advice. I downloaded LoopCAD and did my UFH design. This software does a lot more than pipe loops. I also completed Jeremy Harris Heat Loss spreadsheet. The heat loss calculations from both tools agreed with each other. I also downloaded the Stroma SAP tool. This was easy to complete having already gather all the data for the other tools. There is also a very good MVHR spreadsheet here somewhere, that I also found very useful. (I will add link later)

 

I thought I could edit posts, seems not. (Ah, I see Edit function has a time limit.)

 

Link for the MVHR Sizing Spreadsheet, posted by Triassic

 

 

File is in .ODS format, but first online convertor Google found, did the trick to convert it to Excel.

MVHR_Sizing.ods

Edited November 7, 2020 by Nick Laslett

[SteamyTea]

  

1 hour ago, joe90 said:

well I have just dug the manual out fir mine and can confirm only one water  temp programable , so I am glad I have a buffer with a stat set to 35 and a blending valve down to 24.

That is quite interesting.  I wonder if a heatpump cannot vary the temperature, a buffer tank and temperature blending valve should always be fitted, regardless of the system size.

 

[joe90]

19 minutes ago, SteamyTea said:

I wonder if a heatpump cannot vary the temperature,

some appear to be able too, even Jeremy struggled with his controller and we have the same unit and controller (so I stand no chance ?).

[SteamyTea]

10 minutes ago, joe90 said:

some appear to be able too,

It may just be a function of how the refrigerant gas works best.  As long as the lowest temperature is high enough to do the job, then the rest can be sorted with airflow though the heat exchanger and temperature differences between fluid flow and return flow.

They may be more efficient as well.

[CharlieKLP]

Sorry to bump this, do ASHP work in older properties with not the best insulation or not do you think?

 

I have a property that has some clay walls with damp and limecrete so they need to breathe. Are they stuck with an oil powered boiler?

[SteamyTea]

2 minutes ago, CharlieKLP said:

Sorry to bump this, do ASHP work in older properties with not the best insulation or not do you think?

Comes down to sizing an ASHP correctly, just as you would with any heating system.

Then it is down to installation costs and running costs.

The first part has to be done first, then the other parts can be established.

 

Limecrete is not really breathable like an airbrick, it is more a case of letting moisture wick though to the outside, where it evaporates.  Depending on the mix, it is not inherently different from concrete mixes.

Getting the kg.s^-1.m².kPa^-1 numbers is challenging though, why there is so much 'mystic' around lime.

It is a short hop from the above units to kg⋅m²⋅s⁻² which is a unit of energy, and as we know, if you increase energy levels in a solid, the temperature rises.

A pascal is kg⋅m⁻¹⋅s⁻²

[Adsibob]

On 04/11/2020 at 13:46, ProDave said:

Perhaps it is time for the law to state clearly that someone designing a heating system should warrant that it will work in all normal weather conditions for the house and it's location.

The law already says that. All goods must be fit for purpose. So as long as the supplier of the ASHP knows that the purpose you will use it for is to heat your home, there is an implied term in the contract that it is fit for that purpose. Ergo, always get the supplier to survey the house the ASHP is going to be fitted in. See https://www.legislation.gov.uk/ukpga/2015/15/section/10/enacted

 

[Spacey73]

My neighbours spent or were conned into buying £52k worth of heat pump ground source for underfloor heating and radiators in a very leaky old cob farmhouse. It’s so expensive that they have only turned it on twice allegedly.

 

They poo poo’d my idea of putting in the 2 x heat pumps which run 5 x air conditioners in an 80’s built bungalow.

 

Its been a month since they were installed and I’ve set the 1,900 square foot building to 20 deg C. It is so damn energy efficient and we have no radiators at all or awful copper piping running all over the place.

 

Oncr the bungalow got up to temperature the power used settled down and is powered by the one set of solar panels dedicated to the hot water and heating….not even connected to the grid. 12 x 390w ground mount panels seems to be holding up nicely so far.

 

So I think air conditioning is the way for leaky buildings (I have. Positive air pressure system as well to sort out damp and have constant fresh air coming in). I’m not convinced on Heat Pumps when you use radiators unless in very midterm houses.

[Dave Jones]

On 23/06/2022 at 22:06, CharlieKLP said:

Sorry to bump this, do ASHP work in older properties with not the best insulation or not do you think?

 

I have a property that has some clay walls with damp and limecrete so they need to breathe. Are they stuck with an oil powered boiler?

 

oh it will certainly work BUT will cost 4 or 5 times more to run than a gas combi to achieve the same result.

 

if you havent got a super insulated, air tight box then your pissing in the wind. literally.

[Radian]

2 hours ago, Spacey73 said:

Oncr the bungalow got up to temperature the power used settled down and is powered by the one set of solar panels dedicated to the hot water and heating….not even connected to the grid. 12 x 390w ground mount panels seems to be holding up nicely so far.

That sounds great but I suspect you'll be having to plug it in sometime in the next month assuming you're not within 30^o of the tropics. The A/C units I've bought are supposed to be scop 5 with a heat output of 3.5kW so 1.4kW electric in at full blast. I don't expect to have the PV to power that beyond the end of this month.

 

Air-water ASHP cop figures seem to be slowly catching up with air-to-air but I still like the immediate 'on demand' kind of heating for my application.

[Spacey73]

I might have to do a sneaky economy 7 charge from 01:00 to 06:00 at £0.14 (compared to day rate of £0.46 now) for Nov Dec jan, but maybe not.

 

34kwh of battery and 14kwh of Sunamp hw storage, 34 x PV panels at circa 380w all facing perfect south and I can adjust Deg of panels really easily as ground mounted single rail design. Car has its own 9 x 540w supply on car port.

 

Will be interesting to see how this goes.