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Weather Compensation Cost not efficiency?

 
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Air Source Heat Pumps (ASHPs)
Last Post by jeegnesh 2 years ago
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 jeegnesh
(@jeegnesh)
Estimable Member Member
Joined: 2 years ago
Posts: 100
Topic starter 24/10/2024 11:00 am   [#1795]

So I have been reading about how you should run weather compensation as its better for the heat pump and its more efficient, obviously I am a new convert and my mind is trained into hitting temperatures then just pure off/setback mode.

Now I totally get the efficiency part but I would also like to know the cost element, will I be using more of my kw to run in WC mode?

Also nighttime we would want a slightly lower temp, I get the diff should be kept only to 2/3c which is fine, but how does that work if you are not using temperature?

Advise appreciated.


13.6kw Solar, 40kw Battery, 10kw Heat Pump and EV Cars


   
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 jeegnesh
(@jeegnesh)
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Joined: 2 years ago
Posts: 100
Topic starter 24/10/2024 11:38 am  

Also what would a 10kw aroTHERM plus modulate down to at most?

I switched to WC, my heat timers are still in place but little confused now if and how it would use that in WC mode


13.6kw Solar, 40kw Battery, 10kw Heat Pump and EV Cars


   
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bontwoody
 bontwoody
(@bontwoody)
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Joined: 4 years ago
Posts: 1009
24/10/2024 1:32 pm  

@jeegnesh

Hi

Running in WC mode just means that you will be using the lowest flow temperature that is suitable for heating your house given the outside temperature, as such the heat pump pump will be running most efficiently.

Another way of putting that is you will get the most heat out for the least electricity in, so to answer your question it will be cheaper to run that way.

You may find running without timers best, but dependent on your electricity tariff and house properties you might find the odd timer useful.


House-3 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
5kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60


   
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Majordennisbloodnok
 Majordennisbloodnok
(@majordennisbloodnok)
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Joined: 4 years ago
Posts: 1763
24/10/2024 1:43 pm  

Posted by: @jeegnesh
↑

So I have been reading about how you should run weather compensation as its better for the heat pump and its more efficient, obviously I am a new convert and my mind is trained into hitting temperatures then just pure off/setback mode.

Now I totally get the efficiency part but I would also like to know the cost element, will I be using more of my kw to run in WC mode?

Also nighttime we would want a slightly lower temp, I get the diff should be kept only to 2/3c which is fine, but how does that work if you are not using temperature?

Advise appreciated.

An analogy works well here.

Imagine a long straight urban road with lots of traffic light junctions. Imagine too that the urban planners have been sensible for once and set the traffic light phasing so that if a car goes along the road at the 30mph speed limit it will reach each set of traffic lights as they turn green. Some people will still stop at the first red traffic lights and then, when they turn green, accelerate off like a drag racer, speed to the next lights and then find they have to stop again 'cos they're red. Some others will stick to the speed limit and sail on through all the lights at a constant 30mph.

Not only is the efficiency of the stop/start drivers far worse than the others, the stopping and starting uses far more fuel overall. Same thing with weather compensation; it's using the lowest amount of energy it can to maintain a constant temperature in the house and over the course of a day/week/month/year that equates to far less energy used than any other heating strategy except in circumstances where you're away from the house for multiple days (in which case, turn the heating off altogether or put it in holiday mode).

 


105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and SPH5000 inverter
1 x Myenergi Zappi
1 x VW ID3
Raised beds for home-grown veg and chickens for eggs

"Semper in excretia; sumus solum profundum variat"


   
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 jeegnesh
(@jeegnesh)
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Joined: 2 years ago
Posts: 100
Topic starter 24/10/2024 2:04 pm  

Thanks for that.

The only thing I cannot figure out is that I am in timed mode, pretty sure its ignoring that as I had a set temp of 20.5 and it heated over that, it essentially says it is heating right now using literally nothing kw's so I don't care.

But what relevance does the times actually play now, or is it purely just looking at times as ON or setback and during setback the heating curve is automatically reduced?


13.6kw Solar, 40kw Battery, 10kw Heat Pump and EV Cars


   
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bontwoody
 bontwoody
(@bontwoody)
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Joined: 4 years ago
Posts: 1009
24/10/2024 2:16 pm  

@jeegnesh With my Samsung, I can set my internal thermostat (in lounge) to different temperatures. So for instance, my heating is set to 21C between 3am and 5.30am (cheap rate) then 17C till 8am when it raises to 21C again until 6pm when it raises to 22C and then back to 17C at 10pm.

If the room temperature hits this then the heat pump turns off. But all the time it is running its flow temperature is governed by the WC curve.


House-3 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
5kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60


   
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 jeegnesh
(@jeegnesh)
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Joined: 2 years ago
Posts: 100
Topic starter 24/10/2024 3:25 pm  

so this is on Valiant aroTHERM and my settings has the the room temp mod now set to inactive, so essentially no thermostat, hence my question what the timer is for


13.6kw Solar, 40kw Battery, 10kw Heat Pump and EV Cars


   
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bontwoody
 bontwoody
(@bontwoody)
Noble Member Contributor
Joined: 4 years ago
Posts: 1009
24/10/2024 5:01 pm  

@jeegnesh sorry, i dont have much knowlwdge of how arotherms work, im sure someone else will be able to help.


House-3 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
5kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60


   
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 ectoplasmosis
(@ectoplasmosis)
Eminent Member Member
Joined: 2 years ago
Posts: 26
24/10/2024 5:17 pm  

@jeegnesh Check your 'setback temp' setting. This will dictate the desired set point temperature that your Vaillant will target outside of your normal 'scheduled' heating times. It will not stop heating between your scheduled periods, it will just target your chosen setback temperature.



   
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 jeegnesh
(@jeegnesh)
Estimable Member Member
Joined: 2 years ago
Posts: 100
Topic starter 24/10/2024 7:20 pm  

Ok so during a timed period it will work to hit the design temperature via flow rate regardless of internal temperature and non timed hours run heat curve minus something to run at a lower temp. Is what I’m getting. Soon find out as setback starts in an hour. 


13.6kw Solar, 40kw Battery, 10kw Heat Pump and EV Cars


   
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 ectoplasmosis
(@ectoplasmosis)
Eminent Member Member
Joined: 2 years ago
Posts: 26
24/10/2024 8:40 pm  

@jeegnesh Almost. 

Your heat pump has no idea about your ‘design temp’, which is just the result of a theoretical calculation used to specify your heating system. 

When using a schedule, during the ‘on’ periods your Vaillant, depending on the type of room temp modulation setting you’ve chosen (load compensation), will be heating your house at a flow temperature dictated by the outdoor temp sensor and the weather compensation curve value that’s been set in the controller. 

During the ‘off’ periods, the heat pump will be doing the exact same thing, but will be shifting the curve accordingly to attempt to achieve the lower ‘setback’ temp set in the controller. 



   
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 jeegnesh
(@jeegnesh)
Estimable Member Member
Joined: 2 years ago
Posts: 100
Topic starter 24/10/2024 9:14 pm  

Got it. Thank you. 

and now Valliant seem to have made my energy data disappear have to wait till it loads back to see what’s been happening. 

damn I wish the openenrgymonitor wasn’t so extensive and expensive to install. 


13.6kw Solar, 40kw Battery, 10kw Heat Pump and EV Cars


   
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