Posted by: @heacol

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@gunboatdiplomat The £2-3000.00 extra cost could very easily be eaten up in a few months, Last year I repaired a system with an average winter spend of £2300.00 per month and cold, this year the same property averaged just over £600.00 and was warm, the repair cost £4500.00.

My advice is, do not compromise when it comes to heat pump design and installation, you will be sorry.

If the cost to repair the system was £4500, then it was not just a matter of changing a few radiators. Your example is therefore not what is being discussed in this thread.

 

@gunboatdiplomat Heatpump monitor is definitely worth keeping an eye on for possible efficiencies. The data is so useful and particularly when you read the notes on property type and so on.

Posted by: @jamespa

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Some people simply don't have the luxury of indefinite capital funds and are forced daily to sacrifice 'running cost' to save on capital that they simply don't have.  That's why people rent, get a mortgage, put off doing insulation, take out loans and why there may well be a market for 'rented' heat pumps.  So long as they are clear on the tradeoffs you would surely agree it's their choice not yours.  Of course it's equally your choice whether to quote or not.

But there's a wider social benefit that's not being accounted for in this view. We need, as a society, for everyone to be better insulated, efficiently heated by electricity etc., The 'individualist, market forces' take is part of our climate change problem is it not?

I think efficiency standards should be imposed from the start. What are we talking about here? A few extra rads? Cost-wise to a supplier, that's naff all. Building regs imo need to catch up (but pigs will fly I realise this.)

@lucia For what it is worth: Our Daikin ASHP monobloc is an EDL08E2V3 8 kW model; and 8 out of 10 radiators were replaced. The heat loss I was told is 6.5 kWh and the installer informed me they work to MCS guidelines and based the heat output on using 50 degrees C. I actually started dropping this on the day the system was commissioned as it was very mild anyway. (This was previous to having a Homely smart controller fitted as they were not then available as an integrated option)

I wound the system down to 35 degrees C and since Homely ‘took over’, the system rarely exceeds 40 degrees C. In milder weather, I note that the flow is ~ 30 - 32 degrees C. I have observed consumption when the system has throttled back to be typically ~400 - 500 W. During the OAT -7 or -8 degrees last winter (early December and parts of January 2024), consumption rose to ~1.5 - 2.0 kW. occasionally. The COP at this time was ~ 3.0 - 3.5 but during milder weather, I see a COP of ~4 - 4.5 or so.

I haven’t tried observing the modulation capabilities of the Daikin pump but am pleased with whatever the system is accomplishing for me. I imagine that the Daikin is a true 8 kW unit and not a throttled 10 - 12 - or more kW unit. The larger radiators fitted in very easily as the sizes were matched to the old radiators in the main - just an increase in depth so very few pipework changes were required. Regards, Toodles.

Posted by: @jamespa

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Posted by: @jamespa

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Some people simply don't have the luxury of indefinite capital funds and are forced daily to sacrifice 'running cost' to save on capital that they simply don't have.  That's why people rent, get a mortgage, put off doing insulation, take out loans and why there may well be a market for 'rented' heat pumps.  So long as they are clear on the tradeoffs you would surely agree it's their choice not yours.  Of course it's equally your choice whether to quote or not.

 

 

But there's a wider social benefit that's not being accounted for in this view. We need, as a society, for everyone to be better insulated, efficiently heated by electricity etc., The 'individualist, market forces' take is part of our climate change problem is it not?

I think efficiency standards should be imposed from the start. What are we talking about here? A few extra rads? Cost-wise to a supplier, that's naff all. Building regs imo need to catch up (but pigs will fly I realise this.)

In principle I entirely agree.  However unless it's mandated by government, suppliers aren't going to provide extra services free of charge and as a consumer if you can't afford it you can't afford it, and compelling you to pay as a condition of getting a heat pump simply means you will opt for a gas boiler instead.  Also there is disruption associated with radiator swaps and in some cases people may be happy to pay a bit more in the long term to avoid the disruption, particularly if it involves redecoration or K3s (which many hate).  So long as they are fitting a heat pump I can't see that there is any material harm in allowing it them to choose the trade off between capital and running cost.

So I would wholeheartedly agree with some financial support (perhaps in the form of a loan repaid from the running cost savings) to bridge the cost difference between a radiator upgrade to reduce ft from 55 to 45,  but I can't support compulsion because it simply may not suit everyone.

 

 

 

Posted by: @lucia

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@JamesPa

They should be told the capital and running cost difference and allowed to choose their own trade off.  Some will prefer to pay a bit more in running cost for a saving in capital cost and less disruption (a factor frequently ignored), others will take the opposite approach.

 

I see your point and agree to a degree but the point here is:

a) I'm not being given that choice and

b) the capital cost is the fixed/same whatever you have with Octopus.

I'm not disagreeing with you, ideally you should be given the choice (and informed of the implications) and, if the price is the same, then it comes down to disruption etc. but it should still be your choice.

Personally I'm fed up with heat pump installers telling me what trade offs I should make.  It shouldn't be their choice, it should be mine and, so long as I'm well informed, (hopefully by them) I should be able to make it and installers should respect that, just as I respect their right not to quote.

 

Posted by: @gunboatdiplomat

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@heacol £2300/month? Yikes, that is shocking example.

My comment on £2-3000 buying a lot of electricity really should have been caveated on the system being well designed. The proposed SCOP from octopus was 3.6 @ 50C, the proposed minimum SCOP from heat geek was 3.8 @ 45C. The running cost difference I calculate is about £90 a year assuming those could be achieved. Obviously if they couldn't be achieved (and I had serious doubts on the 9kW Daikin octopus proposed) that capital saving could be quickly eaten up.

Please do not believe any SCOP figures, they are calculated laboratory figures and bear absolutely no resemblance to real life whatsoever. If you have a buffer tank or any form of system separation, your SCOP WILL be closer to the average value of 2.8, shown by every trial government has dome over the last 15 years unless your installer is exceptionally talented. I have tried and my installations were not much better, whatever I did. There are verifiable reasons, but it is exceptionally complicated. It took 2 days for me to explain it to the head of design at BG.

Generally, the difference between a 45Deg C design and a 50 Deg Desing will be a 40-70% increase in the electricity bill. It is not as simple as most make it out to be.

 

Posted by: @derek-m

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Posted by: @heacol

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@gunboatdiplomat The £2-3000.00 extra cost could very easily be eaten up in a few months, Last year I repaired a system with an average winter spend of £2300.00 per month and cold, this year the same property averaged just over £600.00 and was warm, the repair cost £4500.00.

My advice is, do not compromise when it comes to heat pump design and installation, you will be sorry.

If the cost to repair the system was £4500, then it was not just a matter of changing a few radiators. Your example is therefore not what is being discussed in this thread.

 

You are correct, the house was 100% under floor heating so no emitter changes, just redesigned and modified for correct operation.  For the customer, the repair was very cheap, he paid it back in savings over 2.5 months. He regrets not taking our original quotation which was £1200.00 more expensive than the one he took, but ended up costing him over £15000.00 more.

 

Posted by: @heacol

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Generally, the difference between a 45Deg C design and a 50 Deg Desing will be a 40-70% increase in the electricity bill. It is not as simple as most make it out to be.

If this is the case we need to see the evidence and understand the reasons, as it's completely at odds with the manufacturer data.

And if it is the case then it implies that a small error in a WC curves will have a similarly devastating impact (1C error = 8-18 percent degradation in performance)

Finally if going from 50 to 45 saves 40-70%, can I save another 40-70% by going from 45-40.

Whilst absolute SCOP figures might not be accurate, you would expect the comparative figures to be closer.

What evidence do you have for your assertions please and what is the physical explanation?   This is clearly of massive importance if what you assert is true!

@JamesPa Do you tell your surgeon where to cut? I think not, however when things go wrong, and if they did listen to you, they would still get the blame and hold liability, you would not. If you do not believe the expert and do not like what you hear, try another and take your chances, usually you get what you pay for. If the installation is not perfect, there is always a trade-off.

I have walked away from many customers who think they know better, sometimes the job is not worth the hassle.

Posted by: @jamespa

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Posted by: @heacol

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Generally, the difference between a 45Deg C design and a 50 Deg Desing will be a 40-70% increase in the electricity bill. It is not as simple as most make it out to be.

 

If this is the case we need to see the evidence and understand the reasons as it's completely at odds with the manufacturer data.

And if it is the case then it implies that a small error in a WC curves will have a similarly devastating impact (1C error = 8-18 percent degradation in performance)

Finally if going from 50 to 45 saves 40-70%, can I save another 40-70% by going from 45-40.

Whilst absolute SCOP figures might not be accurate, you would expect the comparative figures to be closer.

What evidence do you have for your assertions please and what is the physical explanation?   This is clearly of massive importance if what you assert is true.

 

 

 

I will give you a clue and only 1 of many reasons, for every 1 Degree you move the flow temperature up from source (outside temperature), you add between 2.5 and 3% to the electricity bill. This is compounded and not linier as you assumed, hence the significant increase at higher temperatures.  

Heat pumps are exceptionally complex machines. Whether you believe my 30 years of experience is of little consequence to me, there are papers I have written, published here that show the complexity of heat pump and system design. Obtaining good performance with a heat pump is not simple, there are many thousands of variables that change continually in real time, to consider, however if relatively simple rules are followed, there is a good chance, with good equipment that does most of the work for you (not many available), a high level of performance and comfort can be achieved. If you compromise, you WILL pay the price.

 

Posted by: @toodles

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For what it is worth: Our Daikin ASHP monobloc is an EDL08E2V3 8 kW model; and 8 out of 10 radiators were replaced. The heat loss I was told is 6.5 kWh and the installer informed me they work to MCS guidelines and based the heat output on using 50 degrees C

Thank you @toodles That's really helpful. I reckon my heat loss is around 6-6.5kw too but I have to admit I'm only basing this on previous gas bills and heat geek's quick calc so far. Not very scientific. 

The 8kw Daikin is the only one of the 3 (4, 6 or 8kw) not software throttled. There's a couple of Daikin 8kws on heatpump monitor getting really good cop/scops 

British Gas seem to permit 45º design temps - there's a guy on YouTube who shares his entire BG/Vaillant fitting process including showing the heat loss survey spec sheets and costing. He's had his system designed for 45º and he's happy with it. 

Octopus are daft because these ASHP YouTube channels are getting really big visitor numbers and lots of questions about efficiency/economy. It was this channel (Upturned Fork) that made me ask BG to quote.