Heating schedule
It's been a few months since the ASHP was installed and so far no issues - it's only doing hot water.
Now the autumn is coming I'm expecting the heating to actually come on every now and then. So the question is, how should I best set my system.
Currently it's set to 21 during the day with set back to 17 overnight. I've seen a tonne of things saying that you should just leave an ASHP on all day rather than set back. Does anyone have any specific feedback on this? What kind of power use would be expected if leaving it on Vs set back? It's a 12kw Midea unit
Hi Batalto,
The easy answer is 'how long is a piece of string'.
Any potential energy reduction, achieved by lowering the indoor temperature setpoint overnight, is dependent upon many variables.
1) The heat loss due to the difference between the indoor temperature and the outdoor temperature.
2) The thermal mass of the building, which will dictate how quickly it will cool down and heat up due to (1) above.
3) The variation in efficiency of the ASHP at differing outside air temperature.
4) How the system responds to the selected weather compensation curve if enabled.
5) When and for how long the indoor temperature setpoint is lowered.
Lowering the temperature setpoint does not immediately lower the indoor temperature, which would probably take many hours to fall from 21C to 17C. It should therefore be remembered that raising the setpoint will not immediately increase the indoor temperature, which could take several hours to get back to the desired value.
I'm doing a similar thing. I just can't bring myself to heat the house or parts of it while I'm not there. Also, I want it to be warm when I'm getting up and dressed but not when I'm asleep. I don't have any comparative figures; leaving it on all the time could be better. At the moment the heating occasionally comes on for an hour or so but not longer.
Hi Kev,
From calculations that I have carried out, it may be possible to reduce energy consumption by about 5% by lowering the setpoint overnight. Of course at this time of year energy consumption for heating is virtually nothing, so 5% of virtually nothing is not a great deal.
Since your heating system is running for approximately 1 hour per day, it would be more efficient to make that 1 hour when the outside air temperature is at its peak value for the day. Even better, if you have a solar PV system, would be to heat your home when your solar PV can power your ASHP.
As you are aware at this time of year the heating demand is quite low, so if you were to run your heat pump continually at its lowest continuous operating parameters, its output heat energy would exceed the heat demand, and the indoor temperature would increase, until the heat loss was equal to the heat energy produced by the heat pump. The indoor temperature would therefore increase during the warmer daytime hours and fall during the night. The heat pump is therefore switched on and off to keep the indoor temperature around the desired setpoint.
As we go into Winter and the heat demand increases, there will be a point where the heat demand exceeds the minimum output of the heat pump, so if left on it would run continuously, but at the lowest output temperature that is required to meet the heat demand.
If the heat demand for a home throughout a 24 hour period is 120 kWh, giving an average heat demand of 5 kWh per hour. If the heat pump is now switched off for 4 hours, then it needs to provide the 120 kWh of heat energy during 20 hours of running time, so the average heat output would now need to be 6 kWh per hour. Running ASHP's at higher outputs uses more electrical energy and therefore reduces efficiency. This is particularly bad if the heat pump is switched off during the day and has to work harder during the night.
I think I'm going to have to do some trials when it gets colder. I'm in the process of getting the full MMSP monitoring package so that should help track usage.
If my ASHP is controlled by a wireless room thermostat (and it currently is) then it will tell the ASHP that there is a heat demand when the room temp drops below the level I have set. The water pumps will start up so the ASHP will detect the return water temperature and the weather compensation will tell it what the output temperature should be. So it will just heat the water to that temperature and pump it round until the room thermostat tells it to stop. I don't know how it decides to heat at high or low power (it definitely varies though; I can hear the difference). Is it the difference between output and return temps or does it also use the internal temperature? (I know this sort of thing was discussed on another thread).
Interesting stuff.
- 26 Forums
- 2,208 Topics
- 48.7 K Posts
- 288 Online
- 5,868 Members
Join Us!
Podcast Picks
Latest Posts
-
RE: Heat loss calculations and how they work in conjunction with heat pump sizing
Thanks and apologies if I was a bit lazy...I have not p...
By Batpred , 6 hours ago
-
RE: Havenwise App Help & Forum Support – Get the Most from Your Heat Pump
@plasfron Hi there! Yes your Mitsubishi heat pump needs...
By HCas , 9 hours ago
-
RE: Aira Heat Pump: Stylish Scandinavian Heating
The recent ZeroDisrupt discussions reminded me to take ...
By Mars , 9 hours ago
-
RE: What is the Heat Geek Guarantee?
@colinc, that’s a very fair and well-balanced comment, ...
By Mars , 9 hours ago
-
@toodles Thanks. I will assume they have made som...
By Papahuhu , 10 hours ago
-
RE: Are We Sleepwalking Into Another Race to the Bottom?
Oh come on, that's a ridiculous argument by an installe...
By JamesPa , 10 hours ago
-
RE: Say hello and introduce yourself
I've seen photos of other people placing the tank in a ...
By Transparent , 11 hours ago
-
RE: PV Panels on roof in Conservation Area
@colinc Do your own due diligence re reviews etc but...
By Morgan , 12 hours ago
-
RE: Heat Pump Installers: Competence, Illusion and the Hard Truth Homeowners Must Face
So true, possibly with the exception of people you woul...
By JamesPa , 12 hours ago
-
RE: Isolating the system for a planned power cut
I hadn't realised your reason for a 100mA trip was due ...
By Transparent , 12 hours ago
-
RE: Midea ASHP – how to set weather compensation
Some things worth mentioning: (1) the Headroom Heat P...
By cathodeRay , 13 hours ago
-
RE: Heating Turned Off but Radiators Still Warm
@9jwr9 I didn't get an answer at the time and there has...
By Pipcart , 13 hours ago
-
RE: Battery storage to run Heat Pump.
@majordennisbloodnok I’m not sure you will be able to r...
By Toodles , 13 hours ago
-
RE: Renewables & Heat Pumps in the News
You've completely missed the point. Old, unpatched so...
By Majordennisbloodnok , 14 hours ago
-
RE: Ecodan Energy Monitoring Pack
@batpred that’s an idea yes. Will look into it
By Carpenterstation , 14 hours ago
-
-
PUHZ SW120Y & EHSC-VM2D - Buffer tank to Volumiser
Eventually I was able to find someone here in the Algar...
By DavidAlgarve , 15 hours ago
-
RE: Anyone still weathering it out with Agile?
We are still on agile and it works ok'ish to charge the...
By Batpred , 15 hours ago
-
RE: New Fogstar 15.5kWh upright solution
Ah... now I can see a photo,and that changes the advice...
By Transparent , 17 hours ago