Ecodan - are these COP figures correct?

shinytop

I don't know.  I'm not sure what 'prohibitive mode' is though.  Can you explain?

I just switch the thermostats down and the heating stays off

dllive

shinytop said:

I don't know.  I'm not sure what 'prohibitive mode' is though.  Can you explain?

I just switch the thermostats down and the heating stays off

I think they call it Prohibitive mode. I basically change the icon to 'pause', which is the same. I think.

dllive

Ive just found this in the pdf handbook https://library.mitsubishielectric.co.uk/pdf/download_full/2387


Perhaps I need to actually Stop it rather than Prohibit it. 

shinytop

Maybe.  I can't see how prohibiting would be any different to what I'm doing but I don't know.   

dllive

shinytop said:

Maybe.  I can't see how prohibiting would be any different to what I'm doing but I don't know.   

Yes, thats what I thought. 

Ive looked all through the Ecodan settings and cant find a Stop button. I only have Start/Prohibit/Schedule.

As it happens, Mitsubishi are sending an engineer out next week (for free!). I must say, they are responsive with their emails. 

Im going to write a short list of questions to ask the engineer. If theres any specific questions you have Im happy to ask him for you.

shinytop

That's good of you to offer; I'll let you know.  

dllive

Hi guys,

An update:

The Mitsubishi engineer was here. Very helpful chap (he was here for about 4 hours!).

He said the strainer filter was partially blocked. This improved the flow from 6 litres to 23 litres. The Delta T has changed from 18 degrees to 4 degrees. He also insulated the pocket where the DMW sensor is, because even though it looks like I had the DHW set to 45 degrees, it may have actually been up to 10 degrees more. Now he's insulated the pocket it should give a more accurate reading.

He said the above should certainly help improve things.

I must say, the above is lost on me. does it make sense? He showed me how to clean the filter. It will be interesting to gauge how the next few week go.

shinytop

dllive said:

Hi guys,

An update:

The Mitsubishi engineer was here. Very helpful chap (he was here for about 4 hours!).

He said the strainer filter was partially blocked. This improved the flow from 6 litres to 23 litres. The Delta T has changed from 18 degrees to 4 degrees. He also insulated the pocket where the DMW sensor is, because even though it looks like I had the DHW set to 45 degrees, it may have actually been up to 10 degrees more. Now he's insulated the pocket it should give a more accurate reading.

He said the above should certainly help improve things.

I must say, the above is lost on me. does it make sense? He showed me how to clean the filter. It will be interesting to gauge how the next few week go.

Yes it does. Your ASHP needs a minimum flow rate (it's litres per minute) of about 12.  If the flow rate was only 6 then this would indeed make the delta T (in this case the temperature differential between water leaving from and returning to the ASHP) very high. Your radiators tend to be a temperature that is around the average so they will probably end up cooler than they should be You'll almost certainly get warmer radiators and better efficiency now. 4 degrees delta T is spot on.

It's really important to install the temp sensors properly.  If it's not insulated properly it will read low so the water will end up hotter than you've set it. You should just about be able to hold your hand under 45 degrees indefinitely whereas 55 can scald.

dllive

shinytop said:

dllive said:

Hi guys,

An update:

The Mitsubishi engineer was here. Very helpful chap (he was here for about 4 hours!).

He said the strainer filter was partially blocked. This improved the flow from 6 litres to 23 litres. The Delta T has changed from 18 degrees to 4 degrees. He also insulated the pocket where the DMW sensor is, because even though it looks like I had the DHW set to 45 degrees, it may have actually been up to 10 degrees more. Now he's insulated the pocket it should give a more accurate reading.

He said the above should certainly help improve things.

I must say, the above is lost on me. does it make sense? He showed me how to clean the filter. It will be interesting to gauge how the next few week go.

Yes it does. Your ASHP needs a minimum flow rate (it's litres per minute) of about 12.  If the flow rate was only 6 then this would indeed make the delta T (in this case the temperature differential between water leaving from and returning to the ASHP) very high. Your radiators tend to be a temperature that is around the average so they will probably end up cooler than they should be You'll almost certainly get warmer radiators and better efficiency now. 4 degrees delta T is spot on.

It's really important to install the temp sensors properly.  If it's not insulated properly it will read low so the water will end up hotter than you've set it. You should just about be able to hold your hand under 45 degrees indefinitely whereas 55 can scald.

Thanks for putting that in laymans terms @shinytop . 

He said that - if the flow rate had dropped any further - I would have got 'LF errors'.

So Im pleased I took action and the engineer came out. Ill give it a few weeks and post an update.  

dllive

Hi guys,
Just thought Id reignite this thread.


Ive just checked the air source heat pump stats, and its still showing a high consumption for doing nothing than heating the cylinder for 30 minutes every 2 days.

These are the last 2 logs Ive taken:

1 September 2022

Consumed: 85kwh (13 for DHW; 71 for heating); Delivered: 46kwh (46 for DHW; 0 for heating)

Immersion: 0

Heat pump meter reading: 13751kwh

DHW COP: 3.5

Heating COP: 0

Overall COP = 0.5

Meter reading: 49245kwh

KWh used TWO weeks: 69

_________________________

15 September 2022

Consumed: 37kwh (5 for DHW; 31 for heating); Delivered: 20kwh (20 for DHW; 0 for heating)

Immersion: 0

Heat pump meter reading: 13764kwh

DHW COP: 4

Heating COP: 4

Overall COP = 0.5

Meter reading: 49294

KWh used TWO weeks: 49

So why has it consumed 31kwh for heating when it has delivered 0 (because I have the heating turned off) ?

And why does it shows its consumed 85kwh but the Heat pump meter reading shows the systems used 13kwh? (13764 - 13751 = 13)?

Very odd. Im probably missing something obvious.

Thanks