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Heat Pumps - Yes/no Or Maybe...?


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#31 IronmanG

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Posted 31 October 2021 - 11:56 AM

Being ignorant as I am. How do you get more energy out than what you put in. Electric heaters are regarded as 99.9 % efficient as all the energy they use is turned into heat.
In the table previously posted it says 2.7kW electric creates 8kW of heat?I do have food poisoning at the moment so I could be missing something obvious

Attached File  Screenshot_20211031-114946_Samsung Internet.jpg   40.59K   0 downloadsAttached File  Screenshot_20211031-114946_Samsung Internet.jpg   40.59K   0 downloads

#32 PoolGuy

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Posted 31 October 2021 - 01:12 PM

As Mab has posted the same question on the other channel, it’s amusing to see the direction that it’s going over there http://mk1-forum.net...=33225&start=10



#33 Homersimpson

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Posted 31 October 2021 - 04:05 PM

 

£70,000 in grants for a heat pump - but it still saved us NOTHING... and it's so chilly our daughter keeps her coat on indoors

The Roche family now question their decision to have the heating system installed in their detached four-bedroom home, situated in the village of North Luffenham in Rutland:-

https://www.thisismo...ed-NOTHING.html

They've obviously had the wrong system installed...

 

The system in the article is a different type of system (although similar principles) as it uses a loop of pipe buried in the ground to extract heat from the ground rather than from the outside air as the more common systems (air to water heat pumps).

 

With this system (assuming the pipes have been buried at the correct depth) it has the advantage that its less affected during colder weather as the ground stays at a fairly constant temperature and hence you don't get the reduction in performance to the same level in the depth of winter.

 

The thing that these systems really suffer from is people thinking they will save a shed load of money.  If we look at a simple example a heat pump with a COP of 2.5 for a heat ouput of 10kWh would use 4kWh of electricity.

 

At present the average electricity cost is in the order of 15p per kWh unit so the heatpump above would cost 60p to run for 1 hour.

 

A gas boiler for the same load would have an efficency (assuming its fairly modern) in the order of 90% and therefore to produce 10kWh of heat you would need around 11kWh or gas.

 

at present the average gas cost is in the order of 3.5p per kWh unit so the gas boiler above would cost around 38.5p to run.

 

As the price of gas increases and in theory electricity become cheaper (I doubt that will happen but we can hope!) then a heatpump will become more viable at the moment it just isn't for a direct replacement.

 

They do have their place and one of the main advantages for housing developers is it removes the need to install a gas supply which depending on the point of connection and any reinforcement required could cost millions on a large development.



#34 Homersimpson

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Posted 31 October 2021 - 04:10 PM

Being ignorant as I am. How do you get more energy out than what you put in. Electric heaters are regarded as 99.9 % efficient as all the energy they use is turned into heat.
In the table previously posted it says 2.7kW electric creates 8kW of heat?I do have food poisoning at the moment so I could be missing something obvious

attachicon.gif Screenshot_20211031-114946_Samsung Internet.jpgattachicon.gif Screenshot_20211031-114946_Samsung Internet.jpg

This is the commone misunderstanding with these units, they are called heat pumps because that is what they do, they move heat energy from outside to inside and as part of the process (the vapour compression cycle) they increase its temperature.

 

You have to think of it as using 2.7kW of energy to move and reprocess 8kW of energy that already existed but was just outside you house before.

 

The technology is sound and well proven and has been in use in almost everyones home for decades in the form of a fridge and freezer.  They do exactly the same, extract heat energy from inside the fridge and as part of the process increase is temperature and dispose of it at the rear of the fridge/freezer.

 

They do work and they can work well but there is so much misunderstanding and misinformation about them that people are understandably sceptical about them.

 

I would like to think I have a pretty good understanding of how they work and what the system should do and I am still sticking with my gas boiler at the moment as its financially a better option for me.



#35 IronmanG

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Posted 31 October 2021 - 06:46 PM

Being bed ridden I've done some reading.
Ye they just move the heat.
It seems underfloor heating would be the best bet with heat pumps as they have a very large surface area as opposed to rads?

#36 Homersimpson

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Posted 31 October 2021 - 07:41 PM

Being bed ridden I've done some reading.
Ye they just move the heat.
It seems underfloor heating would be the best bet with heat pumps as they have a very large surface area as opposed to rads?

The answer is, it depends, if you have an existing building then hacking the floor up to install underfloor heating makes it a non starter and if you want your heating to be responsive (i.e. to increase the temperature quickly) then underfloor heating isn't generally the best idea as it has a very low thermal inertia and takes a long time to increase temperature, it also takes a long time to decrease.



#37 IronmanG

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Posted 31 October 2021 - 08:16 PM

And therein lies the problem. The dwelling needs to be purpose built around that system to make the best use of it?
Retrospective installation cant be a realistic use of funds. Even if the final result does end up at the upper spectrum of efficiency, the sheer cost involved makes it as you say a non starter

The grants that are available surely would be better put into double or triple glazing and insulation. Currently there is no direct replacement for a gas boiler?

#38 IronmanG

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Posted 31 October 2021 - 08:18 PM

I like this guy. Watched a few of his videos and he is simply no sh*t

https://youtu.be/pFl8jcLOiP8

#39 Homersimpson

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Posted 31 October 2021 - 08:50 PM

And therein lies the problem. The dwelling needs to be purpose built around that system to make the best use of it?
Retrospective installation cant be a realistic use of funds. Even if the final result does end up at the upper spectrum of efficiency, the sheer cost involved makes it as you say a non starter

The grants that are available surely would be better put into double or triple glazing and insulation. Currently there is no direct replacement for a gas boiler?

You can fit to an existing building, you just need to make sure the radiators are sized for the required heat output at the lower flow temperature and that the heat pump is sized correctly for the load it needs to serve.



#40 sonscar

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Posted 01 November 2021 - 09:40 AM

Before putting expensive heat in you need to fit the most efficient expensive insulation.In my humble opinion heat pumps need to be considered as a "holistic all embracing" approach.The sheer cost to lots of people is not achievable.Same as buying electric cars,a lot have no money spare.I agree something is done but I do not think this is the whole answer.
When they turn off the aeroplanes,tie up all the container ships and cancel Antarctic cruises along with stopping advertisers brainwashing us into buying tat we did not even know we needed(heat pumps?)we are in danger of penalising the masses to appease the few,wasn't it always this way.Just my limited fixed income pensioners view,others will differ.Steve..

#41 Ethel

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Posted 01 November 2021 - 09:48 AM

Better insulation, less heat required from any source.

 

The other factor to heat loss is time. If your heating doesn't have enough over capacity to warm your home quickly for when you get in or get up, you'll have to run it for longer which will mean an increased average temperature and more overall energy loss.

 

It'd be interesting to see a comparison with  solar panels & some updated form of the storage heater. You'd get a return for the investment in the summer when a heat pump would be largely idle. Higher temperatures would be more easily achieved and we'd have a storage buffer to take power from the grid at the most efficient time if we needed an external boost.

 

 

 

....

 

A litre of water could store about 0.1KWH worth, You'd need around 100KWH a day as a ball park figure, so you'd just need somewhere to stash 33, well wrapped up, Mini fuel tanks.



#42 IronmanG

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Posted 01 November 2021 - 11:12 AM

Before putting expensive heat in you need to fit the most efficient expensive insulation.In my humble opinion heat pumps need to be considered as a "holistic all embracing" approach.The sheer cost to lots of people is not achievable.Same as buying electric cars,a lot have no money spare.I agree something is done but I do not think this is the whole answer.
When they turn off the aeroplanes,tie up all the container ships and cancel Antarctic cruises along with stopping advertisers brainwashing us into buying tat we did not even know we needed(heat pumps?)we are in danger of penalising the masses to appease the few,wasn't it always this way.Just my limited fixed income pensioners view,others will differ.Steve..


Agreed

#43 mab01uk

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Posted 01 November 2021 - 02:39 PM

When they turn off the aeroplanes,tie up all the container ships and cancel Antarctic cruises along with stopping advertisers brainwashing us into buying tat we did not even know we needed(heat pumps?)we are in danger of penalising the masses to appease the few,wasn't it always this way.Just my limited fixed income pensioners view,others will differ.Steve..

 

What climate change emergency?

"President Joe Biden will generate an estimated 2.2 million pounds of carbon during his trip to Europe to speak on the perils of climate change.
The gigantic carbon footprint is comprised of 2.16 million pounds of carbon dioxide generated by the four large planes that comprise his airborne entourage on the trip to Italy and Scotland, where the president will speak at the COP26 summit on climate change in Glasgow, with the remainder emitted by Biden's specially imported fleet of cars.....including the Beast which has a 5-litre diesel engine and gets about 8 mpg."


Edited by mab01uk, 01 November 2021 - 02:39 PM.


#44 PoolGuy

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Posted 01 November 2021 - 03:43 PM

Yes, that’s just one of the reasons that I struggle to give a ****.



#45 finch661

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Posted 17 November 2021 - 12:52 PM

I had a heat pump installed last year, and have had it running for about a year now.  Mine is an air to water, so uses the previous radiators.  Up here, we have no gas, so the option was sticking with existing oil (price varies so much), or storage heaters.  We replaced our old oil boiler (which was burning 3-4L of oil an hour) with a 9kW panasonic unit (going into a 6 bed 1960's build).  One thing i should note, is that i have been doing up my house, and as i went round each room, i installed between 100-125mm of kingspan in each outer wall. This was key, as the water flow is only 40degC.  We just leave the temp at 21degC through the day, and down to 18 during the night.  Its strange that its always on, but means the house never really has a chance to cool down, unlike the old oil system.  We have gone from 2 tanks of oil (2400L) per year (which at the current prices is £1400) down to about £550 up to today.  

 

Big thing is making sur that your house is well insulated, and the system is designed for your house (we were given heal calcs for each room, and basically whether the system would work for our house). As with anything, a poorly installed system will not work, which i think is where a lot of the issues are arising.  If we had a gas supply up here, i would have stuck with gas.

 

overall i am happy with our system.

We ended up getting the no interest loan to pay for it, and we get the RHI payments each year for 7 years


Edited by finch661, 17 November 2021 - 12:52 PM.





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