Posted by: @mike-patrick

Many on this site quote their achieved COP ratings and I wonder how. Do some makes provide the heat output figure or is it more complicated than that?

My installation has a Sontex heat meter wired into it and I think the numbers I eventually see (after a trip through some cloud services) come from that.

If you don't have a heat meter, then Open Energy Monitors's EmonCMS (that @batalto mentions above) can estimate COP with fewer sensors and the simulated Carnot COP formula, but it is an estimate.

In one way, it doesn't matter what COP anyone else gets, or whether it matches what's in the data book for your pump. I think most people start off using it as a useful tool for optimising a setup, taking into account many variables, but some do seem to lose track of it: maybe COPs are the new environmentally-acceptable Miles Per Gallon to compare on enthusiast forums?

What really matters is whether you can afford the power consumed and whether the heat output is sufficient for you.

Posted by: @mjr

Posted by: @mike-patrick

Many on this site quote their achieved COP ratings and I wonder how. Do some makes provide the heat output figure or is it more complicated than that?

My installation has a Sontex heat meter wired into it and I think the numbers I eventually see (after a trip through some cloud services) come from that.

If you don't have a heat meter, then Open Energy Monitors's EmonCMS (that @batalto mentions above) can estimate COP with fewer sensors and the simulated Carnot COP formula, but it is an estimate.

In one way, it doesn't matter what COP anyone else gets, or whether it matches what's in the data book for your pump. I think most people start off using it as a useful tool for optimising a setup, taking into account many variables, but some do seem to lose track of it: maybe COPs are the new environmentally-acceptable Miles Per Gallon to compare on enthusiast forums?

What really matters is whether you can afford the power consumed and whether the heat output is sufficient for you.

Agree.  Power consumed is all that really matters.  Just like petrol consumed in your car.   

If you know how much water is in your CH system you could measure how much energy is consumed to raise it from X to Y degrees and compare that with the amount of energy theoretically required.  The flow temps are available from your control panel.  You'd have to make some corrections for heat loss so I'm not sure how accurate it would be. Doing it for DHW would be easier. 

Posted by: @mjr

...

In one way, it doesn't matter what COP anyone else gets, or whether it matches what's in the data book for your pump. I think most people start off using it as a useful tool for optimising a setup, taking into account many variables, but some do seem to lose track of it: maybe COPs are the new environmentally-acceptable Miles Per Gallon to compare on enthusiast forums?

What really matters is whether you can afford the power consumed and whether the heat output is sufficient for you.

Yes-ish.

I got a heat pump rather than a replacement boiler primarily as a lower burden on the world's resources whilst keeping us warm. That's also why I got the solar PV. The latter means I can "afford" a rather lower efficiency in the heat pump than otherwise, but anything I can do to increase the heat pump's efficiency will still reduce the amount of energy I pull from the grid and, therefore, the carbon emissions I'm responsible for. As a result, I'd say I don't care much about what anyone else's COP is other than providing a benchmark. I do, however, care very much about what my COP is compared with what it has been, because that's a useful measure of how well the heat pump is being managed and maintained, and a useful early warning if things may need to be changed.

Posted by: @majordennisbloodnok

anything I can do to increase the heat pump's efficiency will still reduce the amount of energy I pull from the grid and, therefore, the carbon emissions I'm responsible for. 

Yes-ish, back at you! 🙂 I could achieve better efficiency by not allowing the pump to shut off or cycle on sunny afternoons and thereby avoiding the less-efficient startup phase, but we don't really need even the 3ish kW minimum output then, so it would be a waste of energy.

Posted by: @mjr

Posted by: @majordennisbloodnok

anything I can do to increase the heat pump's efficiency will still reduce the amount of energy I pull from the grid and, therefore, the carbon emissions I'm responsible for. 

Yes-ish, back at you! 🙂 I could achieve better efficiency by not allowing the pump to shut off or cycle on sunny afternoons and thereby avoiding the less-efficient startup phase, but we don't really need even the 3ish kW minimum output then, so it would be a waste of energy.

Agree entirely. I'm not after the heat pump running at its most efficient, I'm after the most efficient use of the energy at my disposal. There is a difference, as you point out.

Here’s some food for thought.

How many distribution pumps do you have connected to your heat pump system at the moment and do you know how much power they consume?

I’ve just tallied ours up, and it’s a frightening amount in kW usage and running costs. I’ll post some figures tomorrow, and this doesn’t make it into COP calculations.

i think its hilarious that our industry worries about cop when all that matters is run cost. The pumps are there to do a job, they would be there if you had a boiler too. The boiler lads dont take any electrical consumption into consideration when talking about efficiency and despite what you are told neither do the heat pumps. The cop your machine measures is just for the compressor, no pumps, valves, controls nothing else is measured. Get over it. its so bloody dull. 

all i care about is what it costs and am i warm, now lets move on. 

@editor We have two pumps that use ~35w each. The idle power consumption of the unit is also substantial I think. However, the "energy consumed" figure my Mitsubishi Ecodan reports slightly over-estimates compared with the actual meter in the garage (which the pumps run off as well I believe). The COP therefore is probably slightly higher in reality than reported in my heat pump's figures.

It is quite frustrating that this isn't just measured as standard.

@grahamh, and therein lies the biggest issue for me with the ASHP industry. Running costs don't correlate with the heat they produce (and the manufacture's promise to produce), especially in poorly designed systems, because the heat pump industry does not want to take ownership of its incompetence. 

I'll use us an example. When water flow through the system drops below 28 litres per minute our air source heat pumps goes full berserker mode with alarms. So what did our installers do when we complained, they came and put in a bigger Grundfos distribution pump that runs at 190 watts per hour. Bish, bosh, bang. Problem solved. This is in addition to two other distribution pumps in the heating system already. That makes three. If they all run at 190 watts per hour that's 570 watts per hour. 

When we wanted to run the system bivalently last winter on HVO, we were getting more flow dramas and errors. Solution. Add another distribution pump. That takes the tally to four: 760 watts per hour – 18kWh per day – approx. 547kWh per month, which costs £200 per month. 

There's nothing hilarious about that Graham – the heat pump installer base seeps with incompetence. Most installers are literally slapping heat pumps in and hoping for the best. There's no thought, design or planning. Just do the job, get paid, move on. If things go wrong, they compound expensive running costs by "remedying" the issue by adding more things to the system that make it even more expensive to run and no one factors that it in and even raises it. It's a dishonest practice.

And to be clear, all these distribution pumps were not factored into our running costs and these additional pumps would not be required with a boiler because it doesn't care about flow, but they are very much a part of our running costs because they are costing a lot of money to keep running. 

@editor - well spoken

@batalto - can you by any chance let me have the email address for MSmartHome Tech Support, or point me to where I can find it (google hasn't been my friend). I want to suggest they add an option to download data as a csv file, and (not sure how this one will be received) suggest they make a browser based version that can be accessed using a browser on a PC (or any other browser capable device for that matter), reason being I am not getting very far with my python attempts to access the Midea server.

Posted by: @grahamh

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i think its hilarious that our industry worries about cop when all that matters is run cost.

On the subject of COP, I have to disagree because it should matter greatly. Each and every MCS-accredited heat pump in the UK has a published COP for different flow temperatures. This is the benchmark for homeowners to know that if I buy product X it'll deliver x-amount of heat and it'll use x-amount of power. This helps to understand running costs. 

If I'm sold a heat pump that can deliver a COP of 4 at 45C flow to deliver 21C in the house, that's what I'd expect. If the system is installed poorly and must run at 50C or higher to deliver the required 21C I've been mis-sold the equipment and I'm paying a lot more than I should for running costs. That lowers COP, so COP does matter. It's a metric that should hold the installer base accountable for the quality of their installations.  

So far, from hundreds of emails and messages I've received over the past three years, no one's heat pump comes in even close to delivering on the published COP figures from manufactures which the MCS has on record, and everyone's running costs are higher than what they've been sold.