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Air Source Heat Pumps (ASHPs)
Last Post by ectoplasmosis 12 months ago
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 JWilliams89
(@jwilliams89)
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Joined: 2 years ago
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Topic starter 12/10/2024 9:10 am  

Currently running our arotherm plus 5kw in manual mode for the heating, with the heat curve set at .45. Room temp mod is set to inactive. I'm aware that the controller ignores the desired temp set, and modulates to the heat curve, in manual mode however my question is what happens in time control mode? Does it work the same as manual mode and just modulate to the heat curve or is it trying to use the controller thermometer even though room temp mod is set to inactive? What happens in the setback period? I'd have liked it if there was a way to adjust the heat curve downwards in any setback period however it doesn't seem that that is possible, and I'm concerned it's running off room temp and therefore running less efficiently. I'm basically trying to work out if there is a way to run the ASHP very efficiently, whilst also adjusting the temps down slightly at night as we are finding our daytime temp of around 19c is too hot at night.

 

Am I right in thinking that the way to set up fully weather comp mode is by putting the controller into room temp mod inactive mode?

 

Lastly, any thoughts on the myvaillant app? We currently don't have it as I was happy to use the controller, however I wasn't aware before we got it how many movements through the menu I'd have to take just to turn things on and off! I'm also wondering if the app would be useful for monitoring useage etc.



   
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 Judith
(@judith)
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Posts: 401
12/10/2024 10:48 am  

I can’t answer your questions on the inactive mode since we’re not using at present (using expanded because we still have solar gain) but I can answer you can’t set WC coefficient dynamically but I can’t see why you would need to .

The app is very much worth getting you can scroll through days, consumption per hour, COP, room temp, outside temp and download full data set for a separate analysis from it. We been very pleased with daily COP of 6 usually and although early on Friday ~9am when it was recovering from set back and OAT was 2C the COP for the day was 3 by the end of the day’s temp profile the daily COP was 5. So it will definitely give you the information you need to optimise. 
But it’s a pig to install correctly we needed Vaillant support (and we’re technically minded).

 


2kW + Growatt & 4kW +Sunnyboy PV on south-facing roof Solar thermal. 9.5kWh Givenergy battery with AC3. MVHR. Vaillant 7kW ASHP (very pleased with it) open system operating on WC


   
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 JWilliams89
(@jwilliams89)
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Posts: 42
Topic starter 12/10/2024 12:24 pm  

@judith Sorted out the first issue with folk on the Vaillant fb page, it was a misunderstanding on my part.

 

Re the app - how do you find the data on cop etc stacks up against the data on the sensocomfort? Our hp is currently running at very low flow temps, around 24c, yet the scop recording is dropping from 4.25 to 3.8. The install is good, so I'm a bit concerned theres something going on in the background I need to adjust. One reason for getting the app would be to confirm that these numbers are correct.



   
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 GunboatDiplomat
(@gunboatdiplomat)
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Joined: 1 year ago
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12/10/2024 12:52 pm  

The way I read the sensocomfort manual is the flow temperature on the curve only apply at a target indoor temp of 20. If you adjust this up or down the curve 'shifts about 5C for every 1C difference in the desires indoor tem.'. So in the day at 20C might be low 40C flow at an outside of 0C and with a 18C setback might be 30C flow at 0C outside.

I found https://energy-stats.uk/vaillant-arotherm-weather-curve-information/ which seems to back up the way I understand the manual.

Now I don't have a heat pump so this is what I understand with my system boiler & the sensocomfort controls. I'm pretty sure the behaviour is the same irrespective of heat source.



   
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 JWilliams89
(@jwilliams89)
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Topic starter 12/10/2024 1:06 pm  

@gunboatdiplomat I found this useful for quickly working out diff flow rates.

 

https://heatcurve.psimonkey.org.uk/



   
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 Judith
(@judith)
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Joined: 2 years ago
Posts: 401
12/10/2024 4:09 pm  

The app and sensocomfort align for instantaneous readings but the app gives you the pattern over time and allows you to see heating and dhw independently. You might have the dhw set to keep refreshing the cylinder temperature for example and hence see cop variations which don’t make sense. We’re on timed for dhw.

I've not seen any difference in values between the two. You’ll need the sensocomfort to change the settings the app doesn’t do that much.


2kW + Growatt & 4kW +Sunnyboy PV on south-facing roof Solar thermal. 9.5kWh Givenergy battery with AC3. MVHR. Vaillant 7kW ASHP (very pleased with it) open system operating on WC


   
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 ectoplasmosis
(@ectoplasmosis)
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Joined: 1 year ago
Posts: 21
14/10/2024 11:13 am  

Posted by: @jwilliams89
↑

@gunboatdiplomat I found this useful for quickly working out diff flow rates.

 

https://heatcurve.psimonkey.org.uk/

 

This is great! Where did you find it?

 



   
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 JWilliams89
(@jwilliams89)
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Joined: 2 years ago
Posts: 42
Topic starter 14/10/2024 11:36 am  

@ectoplasmosis Someone sent it to me on a post on FB. although interestingly the values are slightly different to those on the page on energy stats. Still a nice quick tool.



   
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 ectoplasmosis
(@ectoplasmosis)
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14/10/2024 12:55 pm  

@jwilliams89 The reason for asking is that the tables on the Energy Stats website are incorrect, and in a way so is the Vaillant manual.

The actual heat curve equation is:

TFlow = a * (HC * (Tset - Tout))b + Tset

a = 2.55
b = 0.78



   
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 JWilliams89
(@jwilliams89)
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Joined: 2 years ago
Posts: 42
Topic starter 14/10/2024 1:09 pm  

@ectoplasmosis So are you saying the page I posted is more correct?

 



   
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 ectoplasmosis
(@ectoplasmosis)
Trusted Member Member
Joined: 1 year ago
Posts: 21
14/10/2024 1:24 pm  

@jwilliams89 Yes, it is accurate. You can verify it by modifying your desired temperature and checking the new target flow temp on the controller.



   
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 JWilliams89
(@jwilliams89)
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Joined: 2 years ago
Posts: 42
Topic starter 14/10/2024 1:37 pm  

@ectoplasmosis I did wonder. I was noticing this was more similar to the readings I was actually seeing.



   
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