Keystone COPs? I'm ...
 
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Keystone COPs? I'm not getting the efficiencies I expected on my Ecodan.

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(@gotaashp)
Estimable Member Member
441 kWhs
Joined: 1 year ago
Posts: 79
Topic starter  

Hi all. A new member here, and a new Ecodan owner as of a few weeks ago.

Having done a fair bit of reasearch in to all things heat pump, I was fairly convinced I'd be seeing COPs of 3.5-4 or more at ambient temps of circa 8 degrees C - not so. I've yet to see a 3 in the number, and I'm sure you'd see less cycles at the Tour de France.

Having read some threads here, that does not seem that uncommon where the Ecodan is concerned?


   
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(@davew)
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302 kWhs
Joined: 1 year ago
Posts: 42
 

@gotaashp

You may already have read the "How to run this efficiently with zero understanding" forum(and the excellent contribution from some very knowledegable people) but you have the same concerns that i have had.

I was struggling to see cop's of even 2 but have now got to around 2.5-2.7 and having to accept that's as good as it will get.

I managed to get through to Mitsubishi support last week and he concluded that in winter time under 3 was to be expected in my circumstances, he also confirmed that he supported Auto mode over weather compensation.(I have more issues with cycling in weather comp)

Just check your thermistors are correctly placed where they should be and insulated.

 

 

 

 


   
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(@gotaashp)
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441 kWhs
Joined: 1 year ago
Posts: 79
Topic starter  

@DaveW

Yeah I have read it (along with quite a few others). In fact I just posted on your thread (awaiting moderation).

I'm also seeing better performance in room temp mode. Out of interest, what were your 'circumstances' that lead Mitsubishi support to the conclusion that you would likely not achieve 3 or above in winter?


   
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 mjr
(@mjr)
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Posts: 304
 

I don't recognise the complaint in the opening post. Our system still has unresolved installation problems (some uninsulated pipe outside!) yet achieves COP of 3.6 at about 6°c ambient outdoors. Here's yesterday:

image

It's important to remember that people are more likely to post on forums like this when something is wrong and either their performance goes through the floor (as mine did after a firmware update) or bills go through the roof.

The Ecodan "black box" of auto-adaptation mode can be a source of problems (I think matching the "interval" setting to the home is as important as getting the WC curve vaguely correct) in addition to all the normal heat pump incompetent installer problems, such as the primary control in a cupboard or barn and "traditional" on/off thermostats used to run it at a fixed max design flow. Problems in the mirror may appear larger than reality...


   
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(@gotaashp)
Estimable Member Member
441 kWhs
Joined: 1 year ago
Posts: 79
Topic starter  

Posted by: @mjr

It's important to remember that people are more likely to post on forums like this when something is wrong and either their performance goes through the floor (as mine did after a firmware update) or bills go through the roof.

I'm sorry if my original post come over that way. It was not my intention. I'm very happy with my installation and how it's performing, I joined here as I'd like to understand more what makes it 'tick' so that I may be able to get the absolute maximum efficiency from it. It's apparent there are a fair few very knowledgeable members here to learn from.


   
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(@scrchngwsl)
Estimable Member Member
1401 kWhs
Joined: 2 years ago
Posts: 88
 

I haven't been tracking outdoor temp vs COP for that long, but so far I've been getting ~3.75-ish at 8C outdoor temp:

image

The above is the average daily outdoor temp on the x-axis, and the COP according to MELCloud on the y-axis.

ASHP: Mitsubishi Ecodan 8.5kW
PV: 5.2kWp
Battery: 8.2kWh


   
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(@sunandair)
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Or is it “Good COP bad COP”?

there’s something of a deception when looking at COP alone IMO. 

when we first powered up our heat pump we were using an on/off thermostat and had no screen data on kw consumption or production.

after some changes we discovered we were operating at a COP of 1.49  - full speed pumps, low DT etc.

we are now 5 days into a settled Auto Adaptive mode. 

The BAD COP in my mind is the apparent deception of 24 hour operation even with a night time set back…..

BAD COP - with a 19c setback at night, 4c outside, we were getting a COP of 3.17 with 24kwh consumption.

GOOD COP -However by selecting a setback of 17c we damaged our COP to 3.4 but only used 16kwh. Basically switching off the HP until about 4am.

We have since also lowered our daytime room temp to 19c and got the COP to 3.73 for the last 24 hours. 6c outside using 15kwh.

Im sure the COP police 👮‍♀️ might be able to shed some light…

 

 


   
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 mjr
(@mjr)
Prominent Member Member
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Joined: 2 years ago
Posts: 304
 

COP is useful because you can work it out in the short term and optimising it should, all else being equal, reduce the amount of kWh used. It's a handy target for quick fixes over a day or two.

Of course, the problem is that all else is never equal. Not least, the weather keeps changing!


   
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(@sunandair)
Prominent Member Member
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Posts: 345
 

@mjr Put like that we do expect a lot….

- A constant room temperature when all the other parameters are constantly changing 😂😂👍


   
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(@scrchngwsl)
Estimable Member Member
1401 kWhs
Joined: 2 years ago
Posts: 88
 

Posted by: @sunandair

Or is it “Good COP bad COP”?

there’s something of a deception when looking at COP alone IMO. 

when we first powered up our heat pump we were using an on/off thermostat and had no screen data on kw consumption or production.

after some changes we discovered we were operating at a COP of 1.49  - full speed pumps, low DT etc.

we are now 5 days into a settled Auto Adaptive mode. 

The BAD COP in my mind is the apparent deception of 24 hour operation even with a night time set back…..

BAD COP - with a 19c setback at night, 4c outside, we were getting a COP of 3.17 with 24kwh consumption.

GOOD COP -However by selecting a setback of 17c we damaged our COP to 3.4 but only used 16kwh. Basically switching off the HP until about 4am.

We have since also lowered our daytime room temp to 19c and got the COP to 3.73 for the last 24 hours. 6c outside using 15kwh.

Im sure the COP police 👮‍♀️ might be able to shed some light…

Maybe I'm misunderstanding, but what do you mean by "damaged our COP" here? You say it's gone up from 3.17 to 3.4?

 

ASHP: Mitsubishi Ecodan 8.5kW
PV: 5.2kWp
Battery: 8.2kWh


   
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(@sunandair)
Prominent Member Member
2538 kWhs
Joined: 1 year ago
Posts: 345
 

@scrchngwsl well spotted you’re absolutely right. I must have read .17 as bigger than .4 

So possibly a lower setback, may also favour a Good COP? the question rolls on…


   
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(@scrchngwsl)
Estimable Member Member
1401 kWhs
Joined: 2 years ago
Posts: 88
 

@sunandair A priori, a lower setback ought to improve the COP because the flow temperatures can be reduced to correspond to the lower heat demand. Lower flow temp = better COP.

ASHP: Mitsubishi Ecodan 8.5kW
PV: 5.2kWp
Battery: 8.2kWh


   
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