Ecodan COP thoughts

[Keno]

Hi all, we have an Ecodan A2W heatpump (spilt not monobloc) with the pre plumbed cylinder all in one unit. I have the DHW set at 48C. The cold water storage tank is out in the shed, so the water coming into the hot cylinder will be quiet cold in the winter. The immersion is powered off on the unit, so thats not affecting it. I do one manual legionnaires heat to 60c once per month.

 

My average cop for winter ufh is 3.45 with downstairs stats set at 21C, upstairs we dont need the heat. I found the best setting for our need was to set flow temp at 28C. So Im happy with this COP.

 

However we are getting a DHW cop of 1.83 in the winter months with 2.1 in high summer.

 

Does this sound low, its hard to tell without other realworld users thoughts?

[joth]

Sorry really dumb question but how are you calculating the COP?

I have an ecodan 8.5kW, the MELCloud gives a very vague bar chart of energy consumed and delivered per month, but I can't see how to extract actual numbers from it to get a ratio

 

(Yes my cooling usage was through the roof this summer, working on that)

[Radian]

14 minutes ago, joth said:

I have an ecodan 8.5kW, the MELCloud gives a very vague bar chart of energy consumed and delivered per month, but I can't see how to extract actual numbers from it to get a ratio

Long shot... have you ever right-clicked the web page for those stats and selected "View page source" or similar? Maybe just images pushed from server but if there's some <script> stuff...

[Keno]

On the front of the hydrobox on the ftc5 screen it breaks out consumed and delivered energy in kWh per month or year 

 

Thx very much for posting that. 

 

BTW Im looking for A2W real world DHW cop, doesnt have to be an Ecodan.  

Edited December 6, 2021 by Keno

[SteamyTea]

Does the DHW CoP vary, month by month, during the non heating season?

What are the flow and return temperatures when heating water?

What size is the cylinder?

[epsilonGreedy]

30 minutes ago, joth said:

 

(Yes my cooling usage was through the roof this summer, working on that)

 

 

You have a fascinating flip from heating to cooling and two shoulder months when you require both.

 

Does the house have a very low heat capacity or are the human occupants sensitive to temperature variation either side of a desired temp?

[Keno]

3 minutes ago, SteamyTea said:

Does the DHW CoP vary, month by month, during the non heating season?

What are the flow and return temperatures when heating water?

What size is the cylinder?

Yes the cop varies month by month but not by much, around 1.85 in march climbing to 2.1 in july and august. Then slowly back down to 1.75 - 1.85 in winter.

 

Ill post the flow and return in a while when she kicks on.

 

Cylinder is 200l.

 

There is only 2 of us in the house.

[SteamyTea]

4 minutes ago, Keno said:

Cylinder is 200l.

You may only be putting in a handful of kWhs, so may not enough time for the HP to get into its stride.

Especially if the flow temp is high.

Does it cycle rapidly when heating the water?

Edited December 6, 2021 by SteamyTea

[Keno]

10 minutes ago, SteamyTea said:

You may only be putting in a handful of kWhs, so may not enough time for the HP to get into its stride.

Especially if the flow temp is high.

Does it cycle rapidly when heating the water?

This time of year we use 3-4kWh per day on DHW.

I have the setting on economy for dhw so it takes prob 30-60 minutes depending on how much water she is heating and the temp outside.

From what I remember I dont think the flow gets that hot when using economy setting, but will know more later when it heats and Ill post.

Edited December 6, 2021 by Keno

[SteamyTea]

6 minutes ago, Keno said:

This time of year we use 3-4kWh per day on DHW.

Yes, not many. What power is the heat pump?

Edited December 6, 2021 by SteamyTea

[Keno]

8KW

[joth]

55 minutes ago, epsilonGreedy said:

Does the house have a very low heat capacity or are the human occupants sensitive to temperature variation either side of a desired temp?

One bedroom easily overheats. It  has a FCU for cooling, but it is woefully undersized for the ASHP so results in a lot of short-cycling so low COP. Once we're through this heating season, I'm looking to install a buffer tank to fix it. Probably makes sense to post on the relevant linked conversation ?   

[joth]

1 hour ago, Radian said:

Long shot... have you ever right-clicked the web page for those stats and selected "View page source" or similar? Maybe just images pushed from server but if there's some <script> stuff...

I thought about it a few times,  but hadn't got around to trying

 

It's not obvious in the page source (just the pixel height of the bar chart elements) but reloading the report with Network logging on makes it easy to find. (I'd previously used that trick to discover restful commands to turn it from heating to cooling mode and back, meaning in principle I can automate switching the unit over at the start/end of cooling season)

 

That spat out some JSON numbers for consumed and delivered DHW figures for this year, by month.

 

1. HotWater: [0.03, 41.129, 74.68999999999998, 61.456, 41.15999999999999, 41.328, 45.029, 20.189999999999994,…]

1. ProducedHotWater: [0, 5.39, 192.41999999999996, 184.10899999999998, 148.61900000000003, 165.85999999999996,…]

	consumed	delivered	COP
Feb	0.03	0	0.00
Mar	41.129	5.39	0.13
Apr	74.69	192.42	2.58
May	61.456	184.109	3.00
Jun	41.16	148.619	3.61
Jul	41.328	165.86	4.01
Aug	45.029	182.04	4.04
Sep	20.19	86.418	4.28
Oct	26.348	93.619	3.55
Nov	25.089	69.9	2.79
Dec	2.21	7.28	3.29

 

 

December is suspiciously high, but maybe just data error as we're only a few days into it.

But ranging from 4 in summer to 2.8 in Nov seems healthy.

 

EDIT: I'm a bit suspicious though of why the overall demand dropped so much from Sept onwards. We have PV divert in addition to this, but do run the ASHP to heat DHW when the sun is strong too. Give me a grim feeling that when running in Cooling mode, it actually spends a bunch of time chilling then reheating the cylinder. GOD DAMN IT I bet that's the damn Honeywell VA4073A they installed getting stuck in the mid position ?  

 

 

 

 

Edited December 6, 2021 by joth

[J1mbo]

1 hour ago, Keno said:

BTW Im looking for A2W real world DHW cop, doesnt have to be an Ecodan.  

 

I don't yet have a full year and have changed strategy a few times... but it's data nevertheless:

 

[Radian]

19 minutes ago, joth said:

reloading the report with Network logging on makes it easy to find

Nice one!

[SteamyTea]

46 minutes ago, Keno said:

8KW

Or kW even.

 

If it is trying to deliver most of that 8 kW to satisfy the 3 to 4 kWh/day, it should only run for about half an hour in total.

[Keno]

Thx folks for the replys, so I timed the cycle tonight, it took 40 minutes after a shower was taken, with the outside temp of 2c. The flow temp seems to keep 5C above the temp of the water and the highest it got to was 51C flow the return was about 5c less at all times when it finished at 48C in the cylinder.

 

Thanks j1MBO for the numbers, your COP seems 2x better than mine, although you seem to use twice the kWh that we use.

 

Maybe Im just being picky but my ufh cop seems bang on, DHW Im still not convinced is normal.

 

 

 

[Stones]

We have an 8.3kW Ecodan, FTC5 controller and 300litre preplumb cylinder.

 

Heating CoP ranges between 3.4 and 4.1, yearly average 3.6.

 

DHW CoP ranges between 2.1 and 2.5, yearly average 2.3  Economy setting, DHW heated to/ stored 48/49C

[Keno]

27 minutes ago, Stones said:

We have an 8.3kW Ecodan, FTC5 controller and 300litre preplumb cylinder.

 

Heating CoP ranges between 3.4 and 4.1, yearly average 3.6.

 

DHW CoP ranges between 2.1 and 2.5, yearly average 2.3  Economy setting, DHW heated to/ stored 48/49C

Thats great info , Thanks, very similar to my setup and my ufh cop but your well ahead of my DHW cop.

[Stones]

I know of another Ecodan install locally who is only getting DHW performance the same as you @Keno 

 

8.3 kW Ecodan, FTC5, and preplumb cylinder. Only difference to between my set up and that one:

 

They have a smaller cylinder (200 litre), cylinder is located in unheated outbuilding and some of the pipework is uninsulated.

 

[Keno]

11 minutes ago, Stones said:

I know of another Ecodan install locally who is only getting DHW performance the same as you @Keno 

 

8.3 kW Ecodan, FTC5, and preplumb cylinder. Only difference to between my set up and that one:

 

They have a smaller cylinder (200 litre), cylinder is located in unheated outbuilding and some of the pipework is uninsulated.

 

 

Interesting, my cylinder unit is inside and all pipe work lagged.

 

Just curious Stones, do you have a cold water storage tank inside that maybe gaining heat from the house ambient air?

 

My cold water tank is outside and its always very cold coming into the house.

Edited December 6, 2021 by Keno

[Stones]

No, mains fed. 

 

What size cylinder do you have?

[Keno]

200l

[Stones]

I wonder if it's as simple as that, larger volume to heat, longer and more efficient run and hence CoP.

[J1mbo]

The way the heat programme runs sounds the same as the eco DHW mode on the Vaillant. Having colder incoming water would surely increase the COP as the average output temperature would be lower.

 

Could it be the way that the controller is reporting things that is the issue? As in if it’s reporting energy consumer and environmental yield, then adding the two would provide the total energy transferred. If you’re prepared to run the DHW right down to cold then heat it all you could easily do the maths to check.