Ecodan COP thoughts

[Keno]

4 hours ago, J1mbo said:

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.

 

Thats definitely worth a try, Im going to try it over the weekend. Thanks

[puntloos]

As a small aside, everybody in this thread seems to have 200L cylinders, are you all small families? I'm told for a 5BR house 200 is smallish?

 

Also, how long is your coolant run (with split it's coolant, not water)

[Luke1]

11 hours ago, puntloos said:

As a small aside, everybody in this thread seems to have 200L cylinders, are you all small families? I'm told for a 5BR house 200 is smallish?

 

Also, how long is your coolant run (with split it's coolant, not water)

 

I've a 3 bedroom house with 1 bathroom and 1 ensuite with a 200L tank.

We run the tank at 48C and after 2 average length showers and some use of hot water in the day for washing up, the top of the tank drops by 4-6C and the mid probe can drop down to 35C suggesting we are running out of DHW by the end of the day. 

I only heat the tank at night on E7, and therefore I'd suggest a 200L tank is only just big enough for 2 people at 48C, however if it was continually topped up in the day then it would probably be sufficient / if the water was stored at a higher temperature.

 

Also I thought a split ASHP uses refrigerant between the units?

[epsilonGreedy]

19 minutes ago, Luke1 said:

I only heat the tank at night on E7, and therefore I'd suggest a 200L tank is only just big enough for 2 people at 48C, however if it was continually topped up in the day then it would probably be sufficient / if the water was stored at a higher temperature.

 

 

48C - I am correct in thinking that the E7 electricity powers an ASHP which then heats your DHW tank?

 

In my case I am leaning towards DHW heating via immersion element which would allow a tank temp of 60c. This would effectively double the energy capacity of a 200l tank and the only downside is higher tank loss say 1.5kWh per day rather than 0.75 = 0.75 x 365 x £0.10 = £27 per year = more than I expected.

[J1mbo]

What ASHP are you looking at? Many will deliver DHW at over 60 degrees anyway

[Luke1]

1 hour ago, epsilonGreedy said:

 

48C - I am correct in thinking that the E7 electricity powers an ASHP which then heats your DHW tank?

 

 

Yes correct. If in the future I need more hot water then I'll increase the tank storage temperature. The ASHP should be able to do 55C or so.

Hopefully I am still achieving a COP of around 2.5 with the ASHP. Only downside is the heating demand is not fulfilled whilst the DHW is being heated and it has to catch up in the morning. (Trying to time this so that this also happens in E7 hours is tricky)

[joth]

4 minutes ago, Luke1 said:

Hopefully I am still achieving a COP of around 2.5 with the ASHP. Only downside is the heating demand is not fulfilled whilst the DHW is being heated and it has to catch up in the morning. (Trying to time this so that this also happens in E7 hours is tricky)

Interesting. What size ASHP is this? (Sorry if we're repeating this thread).

I have 8.5kW ecodan and it can heat my 300L UVC from 25 to 45ºC in half an hour. (Caveat: temp measured at the mid-point so it probably has a bit more heat up top prior to that recharge).

I'm squeezing all our heating+DHW into the octopus Go 4 hour cheap rate. It's a push but the main thing was running heating first then DHW for the final 30mins, otherwise you loose about 20mins of time while the system cools back down from DHW to heating temps.

 

[I only run the ASHP at 45º for DHW because solar divert and or a make-up ASHP "boost" mode tops it up to 55+ most days]

[SteamyTea]

9 minutes ago, Luke1 said:

Trying to time this so that this also happens in E7 hours is tricky

Can't you use a suitably sized buffer tank to do this.

Only needs to be able to store a similar useable amount of kWhs as you use in DHW.

[epsilonGreedy]

2 minutes ago, joth said:

[I only run the ASHP at 45º for DHW because solar divert and or a make-up ASHP "boost" mode tops it up to 55+ most days]

 

 

How does PV production drop off in the winter?

 

In my planning approximations I am assuming PV production varies from zilch to very little 165 days of the year.

[Luke1]

3 minutes ago, joth said:

Interesting. What size ASHP is this? (Sorry if we're repeating this thread).

I have 8.5kW ecodan and it can heat my 300L UVC from 25 to 45ºC in half an hour. (Caveat: temp measured at the mid-point so it probably has a bit more heat up top prior to that recharge).

I'm squeezing all our heating+DHW into the octopus Go 4 hour cheap rate. It's a push but the main thing was running heating first then DHW for the final 30mins, otherwise you loose about 20mins of time while the system cools back down from DHW to heating temps.

 

[I only run the ASHP at 45º for DHW because solar divert and or a make-up ASHP "boost" mode tops it up to 55+ most days]

I have an 8kW Nibe with a 200l UVC. 

Looking at last nights log at an ambient temp of 5C:

Charging circuit:

2:40 - 33C

4:00 - 41C 

The system then switches over to do heating for 30 mins and then switches back to DHW at 4:30

4:30 - 41C

6:15 - 48C

 

The top of the tank is as follows:

2:40 - 42C

4:00 - 42C

6:15 - 48C

 

In the summer it was much quicker to heat the tank.

I'm just wondering whether I should give the DHW full priority over heating to save the changeover time during E7 hours.

 

That said, the flow temp at night for heating is around 40C so it wouldn't have had to wait for long to switch over I suspect. 

 

It seems your ecodan is much quicker to heat the DHW, but then I guess it also depends on your ambient temp and the frequency your HP is working at. 

Mine seems to work at 66Hz. Its generally never got higher than 80Hz, expect for one occasion where it hit 110Hz however this may be an anomaly. So its either operating at 83% or 60% of peak??

Does anyone know where you can find the maximum frequency stats for heat pumps? 

[john0wingnut]

4 minutes ago, Luke1 said:

I have an 8kW Nibe with a 200l UVC. 

Looking at last nights log at an ambient temp of 5C:

Charging circuit:

2:40 - 33C

4:00 - 41C 

The system then switches over to do heating for 30 mins and then switches back to DHW at 4:30

4:30 - 41C

6:15 - 48C

 

The top of the tank is as follows:

2:40 - 42C

4:00 - 42C

6:15 - 48C

 

In the summer it was much quicker to heat the tank.

I'm just wondering whether I should give the DHW full priority over heating to save the changeover time during E7 hours.

 

That said, the flow temp at night for heating is around 40C so it wouldn't have had to wait for long to switch over I suspect. 

 

It seems your ecodan is much quicker to heat the DHW, but then I guess it also depends on your ambient temp and the frequency your HP is working at. 

Mine seems to work at 66Hz. Its generally never got higher than 80Hz, expect for one occasion where it hit 110Hz however this may be an anomaly. So its either operating at 83% or 60% of peak??

Does anyone know where you can find the maximum frequency stats for heat pumps? 

 

I have a NIBE. Are you using the the SMO 20? If so it alternates between 30 mins hot water and 30mins heating, when there is demand for both, so in your example where it starts heating the tank, its likely done it on 30 min cycles from 2:40, which could explain why its taken longer.

 

John

[Luke1]

8 minutes ago, john0wingnut said:

 

I have a NIBE. Are you using the the SMO 20? If so it alternates between 30 mins hot water and 30mins heating, when there is demand for both, so in your example where it starts heating the tank, its likely done it on 30 min cycles from 2:40, which could explain why its taken longer.

 

John

 

Yes the SMO20 controller.

I've fiddled with the priority and it is currently set at 90mins DHW and 30mins heating.

 

Generally very happy with the unit and controller (It seems a lot more straightforward to adjust settings than some of the other systems people talk about on here). 

How long have you had your unit and is it performing as expected? Don't tend to see many reviews on them here.

[john0wingnut]

8 minutes ago, Luke1 said:

 

Yes the SMO20 controller.

I've fiddled with the priority and it is currently set at 90mins DHW and 30mins heating.

 

Generally very happy with the unit and controller (It seems a lot more straightforward to adjust settings than some of the other systems people talk about on here). 

How long have you had your unit and is it performing as expected? Don't tend to see many reviews on them here.

I have got the F2040 12Kw version. Ive had it about 4 years

 

I have recently started playing with settings myself, having read a few ASHP efficiency threads on here. 

 

I have my DWH set to 45 degrees from 10pm through to 4pm (next day), then have it from 4pm-10pm at 50 degrees, as this is when we all normally shower, but sometimes, my Wife will shower in the morning or mid morning. Seems to be working well.

 

In terms of heating, I have just removed the weather compensation curve and set it at a flat heating curve of 30 degrees. The tech doc shows decent COP at 35 degrees. I have a 100l buffer, and with these settings its currently working well. I have also changed the minimum charge pump speed to 15%, down from 30% and also the degree minute settings from -60DM to -100DM

 

 

[Luke1]

25 minutes ago, john0wingnut said:

 

In terms of heating, I have just removed the weather compensation curve and set it at a flat heating curve of 30 degrees. The tech doc shows decent COP at 35 degrees. I have a 100l buffer, and with these settings its currently working well. I have also changed the minimum charge pump speed to 15%, down from 30% and also the degree minute settings from -60DM to -100DM

 

 

That's interesting, whats your thinking behind the charge pump speed? I notice that 30% is only during 'wait' mode whilst the heat pump itself is not running. 

 

I've currently left my DM at -60, it seems to cycle 20-30mins on and 30mins off during the day, which apparently seems reasonable. 

 

I currently have WC enabled and I also have a room thermometer connected. It reduces the calculated flow temperature as the room temperature increases. Even though its not recommended for UFH due to slow reaction times it does seem to be working ok at keeping a steady temperature with a low ish flow temp.

 

Sorry Ecodan people this has gone off topic!

[joth]

2 hours ago, Luke1 said:

I have an 8kW Nibe with a 200l UVC. 

Looking at last nights log at an ambient temp of 5C:

Charging circuit:

2:40 - 33C

4:00 - 41C 

The system then switches over to do heating for 30 mins and then switches back to DHW at 4:30

4:30 - 41C

6:15 - 48C

 

The top of the tank is as follows:

2:40 - 42C

4:00 - 42C

6:15 - 48C

 

In the summer it was much quicker to heat the tank.

I'm just wondering whether I should give the DHW full priority over heating to save the changeover time during E7 hours.

 

That said, the flow temp at night for heating is around 40C so it wouldn't have had to wait for long to switch over I suspect. 

 

It seems your ecodan is much quicker to heat the DHW, but then I guess it also depends on your ambient temp and the frequency your HP is working at. 

Mine seems to work at 66Hz. Its generally never got higher than 80Hz, expect for one occasion where it hit 110Hz however this may be an anomaly. So its either operating at 83% or 60% of peak??

Does anyone know where you can find the maximum frequency stats for heat pumps? 

That does seem slow. It should only take 3.5kWh to heat the entire 200L by 15ºC, so a 8kW pump should be able to do it in under 30mins.

 

I looked at my data again, I'm nearer 22ºC rise which is about 7.7kWh demand so I'm doing very well to get that in 45mins with a 8.5kW heat pump. However as mentioned this is a mid-point temp measurement so the actual volume heated is likely a bit less. I guess I should empty the tank sometime for a real test.

 

[Luke1]

3 minutes ago, joth said:

That does seem slow. It should only take 3.5kWh to heat the entire 200L by 15ºC, so a 8kW pump should be able to do it in under 30mins.

 

I looked at my data again, I'm nearer 22ºC rise which is about 7.7kWh demand so I'm doing very well to get that in 45mins with a 8.5kW heat pump. However as mentioned this is a mid-point temp measurement so the actual volume heated is likely a bit less. I guess I should empty the tank sometime for a real test.

 

I'll monitor it over the next few days. Perhaps I'll set the heating to be off so that it doesn't switch over and I can then get a better idea of the times just for DHW

 

I'll upload some graphs to a new thread when I've done this. 

 

[john0wingnut]

2 hours ago, Luke1 said:

I'll monitor it over the next few days. Perhaps I'll set the heating to be off so that it doesn't switch over and I can then get a better idea of the times just for DHW

 

I'll upload some graphs to a new thread when I've done this. 

 

Luke

 

Have you got both the Bt6 and Bt7 temp sensors fitted, so hot water top and hot water charging?

 

John

[Luke1]

Yes both sensors are installed. I assume the hot water charging sensor is half way up the tank however I haven’t actually looked at it. 
I think this is the sensor the system uses when the temperature falls past a set point to re heat the tank. 

[Keno]

On 08/12/2021 at 23:13, puntloos said:

As a small aside, everybody in this thread seems to have 200L cylinders, are you all small families? I'm told for a 5BR house 200 is smallish?

 

Also, how long is your coolant run (with split it's coolant, not water)

 

Only 2 of us, however we can get 2 good full showers out of it and then it only takes 30-45min to come back up to 48c, so if there were 2 more people in the house I dont think it would be an issue unless the 4 people shower at the exact same time every day.

 

Our refrigerant line run is about 3m (10') from compressor to hydrobox.

[Gorslad]

How man kw should I be using per day? 4 bedroom detached house with Ecodan with radiators, 2 adults only

I have set the water to 40 degrees via the MELCloud 

I looked at Gary’s helpful video of the compensation curve which mine is not set, here are 2 images that I have just taken a photo of