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Two possible heat pump routes - how to evaluate them?

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(@lucia)
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Hello , after lurking & reading the knowledgeable folk here + researching all over the web inc Heat Geek, YouTube etc, I've organised 2 possible heat pump heat/loss surveys.

1: British Gas 

2: Octopus 

I'm what is known in the trade as a 'distress purchase' with a gas boiler on its last legs. Funds are limited so obviously installation costs matter but so do running costs. 

My home is a '70s 2/3 bedroom bungalow, 72sqm,  sw facing in the south west of England with very old cavity wall & loft insulation. I'm aiming to top up the loft insulation but can't afford to replace the cavity insulation.

It's an easy install, I think, with good outside space, a ground floor level cellar which also has cavity wall insulation (the gas combi is in there) (the bungalow is built into a hill) so no floors need lifting for pipework etc.

The garage adjoins the house & has electric, water & the CU.  But may be too far from pump unit for the boiler. The rads deffo need replacing for K2s at least but fairly sure pipes are ok.

The 3rd bedroom is now minus a (floating) wall & is part of a (24sq m) open living/dining room with ceiling to floor sliding glass doors & window at one end. And a wood burner. 

BG are coming to do the heat loss survey in 2 weeks. I understand they often fit Vaillant but don't include rads etc so will be the 'expensive option'. I reckon 5/6 new K2 rads are about a £1000 on top of the boiler/pump installation costs if they have same widths & pipework as the current P11s have . 

Octopus have my £500 but have not given me a HL survey date yet. They fit Daikins - as an all-in deal are obviously cheaper. One reason why I'm going for it now is I don't want their own home-grown Octopus Cosy HP + I'm concerned that once that is launched they will stop fitting Daikins. 

I've read people's woes with over sized pumps or bad installations, I'm shoe-string productions, a wee bit geeky, so controllability, efficiency, scop/cop (cheapest possible running costs) matter. Oh, I work from home & hate being cold. 

Qs.... What do I need to consider?

What Qs should I ask BGas & Octopus? What about the Daikin v Vaillant (I hope that's not like iPhone/Android or Apple/Microsfoft 🫣).

Will either of them share their HL reports?

What would you do if you were me? 

Forgive my long 1st post but figured it was best to spell it out. Some of the previous posts here really helped me to toe dip & learn a wee bit. Thank you. 


   
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Majordennisbloodnok
(@majordennisbloodnok)
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Just one very quick point before others start giving more expert opinions than I can...

 

Posted by: @lucia

...

Will either of them share their HL reports?

...

If you've paid for a report, you have a legal right to it. It's not sharing; it's your report. If they won't provide the report, you can require your money be returned since they haven't provided you the service you asked for.

in the real world, I haven't heard of any of these large companies refusing to share paid for heat loss reports, so I wouldn't worry overly.

 

105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and inverter
Raised beds for home-grown veg and chickens for eggs

"Semper in excretia; suus solum profundum variat"


   
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(@bontwoody)
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@lucia

I would try and ascertain your own heat loss figure before they do, to get a good comparison to ensure you dont get lumbered with an oversized unit. There are several different ways to arrive at it without doing a room by room survey. This is a good article to start. https://energy-stats.uk/what-size-heat-pump/

Be very wary of quotes that insist you need low loss header/buffer vessel, even challenge why a volumiser is needed.

I would also try and get quotes from an independent installer or two, heat geeks are a good place to start but you could also check out installers with installations that are performing well on this site http://heatpumpmonitor.org/

I understand you have some urgency, but the quote "Marry in haste, repent at leisure" is a good mantra.

House-2 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
5kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60


   
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(@lucia)
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Topic starter  

Posted by: @majordennisbloodnok

Just one very quick point before others start giving more expert opinions than I can...

 

Posted by: @lucia

...

Will either of them share their HL reports?

...

If you've paid for a report, you have a legal right to it. It's not sharing; it's your report. If they won't provide the report, you can require your money be returned since they haven't provided you the service you asked for.

in the real world, I haven't heard of any of these large companies refusing to share paid for heat loss reports, so I wouldn't worry overly.

Thanks. The British Gas survey is free and Octopus only ask for £500 to make sure you are serious. You can cancel and have a refund right up to 24 hours before installation. 

Nice to hear no one has reported issues with the reports. 

 


   
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(@lucia)
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Posted by: @bontwoody

@lucia

I would try and ascertain your own heat loss figure before they do, to get a good comparison to ensure you dont get lumbered with an oversized unit. There are several different ways to arrive at it without doing a room by room survey. This is a good article to start. https://energy-stats.uk/what-size-heat-pump/

Be very wary of quotes that insist you need low loss header/buffer vessel, even challenge why a volumiser is needed.

I would also try and get quotes from an independent installer or two, heat geeks are a good place to start but you could also check out installers with installations that are performing well on this site http://heatpumpmonitor.org/

I understand you have some urgency, but the quote "Marry in haste, repent at leisure" is a good mantra.

Thank you - I will read the article - it will be good to be very prepared on that score but me and maths eek. 🤦🏻‍♀️

I stalked all Matt Drummer's posts on the Open Energy Monitor community about his journey with an over-sized Daikin installed by Octopus - he ultimately got it changed from a 9 to an 8kw and has it running well now. But it is something that worries me.

I gather that many installers over-size to stop complaints.

Unfortunately I can't afford a Heat Geek survey or independent fitters. They will charge more and plus I have no local recommendations. Whereas Octopus have a fairly good reputation and British Gas are ok according to YouTube reviews. I only added BG because Vaillant seem so popular although not sure about after service. 

Why do fitters insist on buffers? My understanding is they are an impediment to flow/efficiency but I'm only learning so that idea may be way off. 

 


   
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(@jamespa)
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Posted by: @lucia

Why do fitters insist on buffers? My understanding is they are an impediment to flow/efficiency but I'm only learning so that idea may be way off. 

 

In most cases you are correct, they reduce efficiency.  However fitters think they reduce call outs and in some circumstances they are correct.  From the POV of a fitter that matters more than efficiency.  Also there is an element of inertia, heat pumps and their understanding have moved on so buffers are less likely to be necessary than was formerly the case, or than was formerly thought to be the case, however not all fitters have moved on.

 

There are in fact very few circumstances in a domestic environment where a buffer/llh is required.  There are rather more where a volumiser (2 port buffer, as opposed to 4 port) is a good idea.  Volumisers, fitted in the return, do not cause an efficiency penalty, but the distinction isn't always drawn.  It's currently a bit of a mess tbh.

This isn't unique to heat pumps btw.  Condensing gas boilers have, for decades, been left by installers set up in a way that means they don't condense, resulting in reduced efficiency.  Many still are set up that way.  This behaviour also reduces call outs at the expense of efficiency (and, in at least some cases, comfort because a heating system run at a lower, but sufficient, flow temperature will generally be more comfortable than one run at an unnecessarily high flow temperature)

 

However I don't think it's entirely fair to blame installers for this, the general public very likely doesn't care so long as they are warm and can have their daily 10 min shower at 15l/min, and doesn't have to think about heating or have any understanding thereof (judging by behaviours I witness this is definitely the case).

 

Perhaps, in the fullness of time, we will come to the view that the complaints many on these forums make about lost efficiency are just noise generated by early adopters who of course care (and understand) more than the general public.  I hope not but I fear so, lowest common denominator behaviour is frequently where the 'market' takes us.

This post was modified 4 weeks ago 9 times by JamesPa

   
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(@bontwoody)
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@lucia 

The heat geek cheatsheet on the article only requires rudimental maths and will give you an idea. Using previous energy usage is very advantageous as a basis for calculating future use if you can manage it.

House-2 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
5kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60


   
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(@lucia)
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Posted by: @jamespa

Perhaps, in the fullness of time, we will come to the view that the complaints many on these forums make about lost efficiency are just noise generated by early adopters who of course care (and understand) more than the general public.  I hope not but I fear so, lowest common denominator behaviour is frequently where the 'market' takes us.

This is why I've booked into the Octopus deal now before they launch their 'mass market' Cosy heat pump. I would have liked a Vaillant but suspect it's out of my reach financially but a Daikin is preferable to the next generation of 'high temperature' heat pumps.

Even Daikin are pushing their high temp version and when you search on their site it asks you if it's for a 'new build' or 'renovation'. The Altherma monoblocs are now apparently for 'new builds'....  🤦🏻‍♀️

The heat pump manufacturer's websites are notable for their lack of information and patronising, 'don't worry your pretty little head' tone..

Lowest common denominator - you are absolutely right and to hell with efficiency it seems. 


   
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(@lucia)
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Posted by: @bontwoody

@lucia 

The heat geek cheatsheet on the article only requires rudimental maths and will give you an idea. Using previous energy usage is very advantageous as a basis for calculating future use if you can manage it.

You are talking to the woman who read Beano comics in her grammar school maths lessons.

You have inspired me to hunt for ancient gas bills with annual consumption and I am reading the heat geek cheat sheet and other bits. 

Over on OpenEnergy Monitor - the last bastion of real geeks (she says with respect and a little jealousy for their IT skills) - there's several clear examples of over-sized heat pumps. So even if I only have a very rough estimation it will help me when the assessments are done. Thank you. 

 


   
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(@jamespa)
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Posted by: @lucia

Posted by: @jamespa

Perhaps, in the fullness of time, we will come to the view that the complaints many on these forums make about lost efficiency are just noise generated by early adopters who of course care (and understand) more than the general public.  I hope not but I fear so, lowest common denominator behaviour is frequently where the 'market' takes us.

This is why I've booked into the Octopus deal now before they launch their 'mass market' Cosy heat pump. I would have liked a Vaillant but suspect it's out of my reach financially but a Daikin is preferable to the next generation of 'high temperature' heat pumps.

Even Daikin are pushing their high temp version and when you search on their site it asks you if it's for a 'new build' or 'renovation'. The Altherma monoblocs are now apparently for 'new builds'....  🤦🏻‍♀️

The heat pump manufacturer's websites are notable for their lack of information and patronising, 'don't worry your pretty little head' tone..

Lowest common denominator - you are absolutely right and to hell with efficiency it seems. 

Nothing wrong in my view with high temperature heat pumps provided you don't run them at high temperature, at least for the space heating.

In reality most manufacturers will move to propane as a refrigerant (R290) which gives the ability to run at 70 by default.  As they do so they will likely update other features (eg appearance and noise levels) which matter.  

Incidentally Vaillant heat pumps are 'high temperature!'

There is a separate thread on this forum about quality of tech support which might interest you given your comment about 'patronising' (which I agree with).

System design generally matters more than choice of pump.  One thing to watch on choice of pump however is oversizing/turndown ratio.  The unit really needs to be capable of turn down to  half the actual peak load (at oat 7-10 and ft corresponding to that oat) because that is where it will spend most of its time!  Daikin range rate their heat pumps in the firmware, which of course clobbers turndown ratio if you happen to need a lower rated pump in any particular range rated series.  Others also do this, so Daikin aren't alone. 

This post was modified 4 weeks ago by JamesPa

   
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Mars
 Mars
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@lucia I’d proceed with the BG quotation. @heacol, who is driving the movement to get rid of buffers in heat pump installations, is now Head of Domestic Heat Pump Design, Net Zero British Gas. I’d be very curious to see how your survey goes and what’s proposed.

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From Zero to Heat Pump Hero: https://amzn.to/4bWkPFb

Follow our sustainability journey at My Home Farm: https://myhomefarm.co.uk


   
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Mars
 Mars
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Posted by: @lucia

Why do fitters insist on buffers? My understanding is they are an impediment to flow/efficiency but I'm only learning so that idea may be way off. 

In the past, buffer tanks played an important role in the heating industry. They emerged as a solution to address the inefficiencies of early on-off fossil fuel boilers. These boilers needed to run at high temperatures, above 80°C, to avoid corrosion in their heat exchangers. Operating at such temperatures was suitable for the technology of that era, and using a buffer tank to blend the heat down was beneficial. Furthermore, these systems required a low flow rate, unlike modern systems with multiple circuits demanding higher flow rates. Buffer tanks helped manage these differing needs effectively.

There is a growing misconception that buffer tanks are essential for heat pumps to "smooth out the load." In reality, the impact of buffer tanks on load management is minimal. For example, a 100-liter buffer tank can only store 1.17 kW of energy when the temperature is 10°C higher than needed. If the system's load is 10 kW, this provides just about 7 minutes of buffer time, which is insignificant. Additionally, raising the temperature by 10°C can increase energy costs by up to 25%.

Buy Bodge Buster – Homeowner Air Source Heat Pump Installation Guide: https://amzn.to/3NVndlU
From Zero to Heat Pump Hero: https://amzn.to/4bWkPFb

Follow our sustainability journey at My Home Farm: https://myhomefarm.co.uk


   
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