Posted by: @editor

Posted by: @heacol

Here is a picture from one of my customenrs controllers, taken today, the external temperature is 3 Deg C and the house is 21 Deg C. The system is piped and controlled exactly as I have described above. COP of 7.4.

@heacol, that is the highest COP I have ever seen registered from any user in the UK. Is this a Panasonic air to water unit and what is the model because that is extremely impressive indeed.

Mars, this is not exceptional, it is normal. Yours could be similar to this if you listened to me. I thought I would post some evidence as I could clearly see I was being ignored.

Posted by: @heacol

Posted by: @editor

Posted by: @heacol

Here is a picture from one of my customenrs controllers, taken today, the external temperature is 3 Deg C and the house is 21 Deg C. The system is piped and controlled exactly as I have described above. COP of 7.4.

@heacol, that is the highest COP I have ever seen registered from any user in the UK. Is this a Panasonic air to water unit and what is the model because that is extremely impressive indeed.

Mars, this is not exceptional, it is normal. Yours could be similar to this if you listened to me. I thought I would post some evidence as I could clearly see I was being ignored.

@heacool

You aren't being ignored.  It's very difficult having found a installer, which isn't easy in itself, it's very difficult to then argue with said installer and demand he installs as per your design and not his.  Surely the installer simply walks away.  I moved in here to my present address that had no CH in February.  It was absolutely freezing.  We could not have gone through that again for a full winter.  So we have what we have even if the system will require changes to make it better in the future.  So, no, you aren't being ignored.  It is what it is.

@heacol, I struggle to see how our heat pump could run at a COP of over 7 as the pump’s badge states a maximum of 4.76. 

Maybe you can correct me, but most (if not all) off-the-shelf heat pumps will deliver maximum COPs in the 4s. What are the ratings for the Panasonic heat pump you’ve used in this installation? Is it marketed at delivering COPs in excess of 7?

@editor I decided to do a bit of maths here as this claim also bothers me. So here we go and hopefully I haven't messed this up somehow.

COP = [1/ eff] = 7.4

solving for eff we get eff = 0.135135

3 degrees is 276.15 Kelvin so we can now solve the unknown flow temperature using the formula       1 - [ 276.15 / x ] = 0.135135

Solving for x we get the unknow flow temperature as 319 kelvin, or 46.55 degrees centigrade

So the claim is that 3 degrees ambient at 46.5 degrees flow is working on a COP at 7.4. This isn't impossible, the maximum theoretical COP for 3 degrees and 21 degrees is 16.3 [294.15 / (294.15 / 276.15) = 16.3]

Posted by: @batalto

@editor I decided to do a bit of maths here as this claim also bothers me. So here we go and hopefully I haven't messed this up somehow.

COP = [1/ eff] = 7.4

solving for eff we get eff = 0.135135

3 degrees is 276.15 Kelvin so we can now solve the unknown flow temperature using the formula       1 - [ 276.15 / x ] = 0.135135

Solving for x we get the unknow flow temperature as 319 kelvin, or 46.55 degrees centigrade

So the claim is that 3 degrees ambient at 46.5 degrees flow is working on a COP at 7.4. This isn't impossible, the maximum theoretical COP for 3 degrees and 21 degrees is 16.3 [294.15 / (294.15 / 276.15) = 16.3]

 

Batalto,

I'm afraid I find your maths very confusing. If you look at the table for your heat pump, that you provided, you will see that the manufacturer states that the anticipated COP value at an outdoor temperature of 3C and water flow temperature of 46.55C would be in the region of 3.

To consistently produce a COP value of 7.4, would require the water flow temperature to be in the region of 25C.

@derek-m its not my heat pump, so I wanted to see what was possible using just raw physics. Like I said, its theoretically possible to get that COP, but it seems very high without low flow temperatures. Ultimately heat pumps are limited in their efficiency by the refrigerant they use and its ability to boil under a certain pressure/temperature. If Heacol can achieve those COPs then he is 100% doing something right and we should all be listening. But I would very much like to know all the details of a system before I believe a claim of 7.4 COP at 3 degrees ambient.

@heacol, it's not about ignoring your experience or insights. What you have to take into consideration is that you are a professional and this is what you do for a living. Most heat pump installations in the UK have a buffer tank, so saying that we should bypass the buffer tank is a huge deal and it's daunting to most homeowners in the UK, us included. It's not something that can be DIYed in a morning because the pipework on our system is complex. 

@batalto 

As an Instrumentation and Control Systems Engineer, my career has been spent ensuring that the correct information is being supplied to the control systems and operators.

Based on the data supplied by ASHP manufacturers, for an ASHP to produce a COP of 7.4 would require a water flow temperature of 30C at an ambient air temperature of approximately 15C. For each kW of electrical energy used the heat pump would need to extract 6 kW of energy from the outside air, which becomes more and more difficult at low ambient air temperatures.

It is the laws of Physics and Thermodynamics, energy cannot be created or destroyed, it can only be changed in form.

@editor Hi, The figure you see in the plate is a figure based on lab test results and bears no resemblance to real life performance figgures what spo ever, you unit will get a COP of arround 115 in the summer and arround 2 at the peak of whinter. The COP figures do not take de-frost in to account and if you fun your system flat out like you do, all the time this will sunstantually reduce your COP, I have seen daily avsrage COP levels on Mitsubushi units below 1.

Here is the spwcf for the 12 Kw unit installed.

@batalto, thanks for the doing maths, which is not my strongest point. 

Heat pump manufacturers must provide data that shows the pump's performance at different temperatures and flow rates. I'm sure you can achieve high COPs with low flow rates (as you've stated). So it comes down to insulation. If my house is passivhaus standard, I can get away with 25C flow rate. But most houses are not that well insulated so we need to run at 35-45C. Brendon says there's nothing special about the house in Glasgow that he installed the system in, so I don't see how you'd get away with a really flow rate. 

I've also not seen any heat pumps on the UK market that make a COP claim of 7 at 3C ambient. If this COP can simply be achieved with any heat pump by simply bypassing the buffer tank and disabling all thermostats and TRVs, then the UK installation industry has a lot to answer for because they will have installed hundreds of thousands of heat pumps incorrectly. 

@derek-m You are wrong, there are a lot more peramiters involved than you think, the inverter system running at low load is increadably efficient as the collector can be up to 6 times larger than at peak. All measurements are done at peak. In addition,the inverter it'self can reduce efficiency by up to 60 % from most efficient point to worst (just like an engine as it goes up the rev rainge).

The manufacturers do not give you this data, I have spent many years working it out in rela life scenarios to get the best possible output and performance for my customers.

@batalto Not as simple as that, you have left out most of the variables.