How To Set Your Weather Compensation Heat Curve - Vaillant Arotherm Plus Heat Pump

In this video we walk through the basic steps to get your weather compensation curve correct for your home.

All weather compensation systems, regardless of make work by adjusting the flow temperature of the water in the radiators or under floor heating based on the outside temperature.

You need hotter water in the heating system when it is -3C outside than when it is 10C outside. Hotter water in the heating system equals more heat output from the radiators or under floor heating.

A weather compensation system uses an outdoor temperature sensor to monitor what the latest external temperature is and the system is constantly adjusting the flow temperature of the water in your rads/ufh in response.

The key to weather compensation is finding the curve setting that matches the heat loss of the house.

Too high a curve setting and you’ll put too much heat into rooms, which wastes energy.
Too low a curve setting and the rooms won’t get up to your desired temperature.
Where you need to be is akin to a Goldilocks setting – not too hot, not too cold, but just right.

Once you find the right place on the curve you should get to a situation where there is just enough heat is being put into the house to match the heat lost to the outside. This improves efficiency, running costs and comfort.
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My system :
Vaillant Arotherm Plus 7kW
200L UniStor Cylinder
45L Buffer tank
140sqM Detached 1997 built house
10mm copper microbore pipework downstairs
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[UpsideDownFork]

I should have mentioned that to set the correct heat curve with underfloor heating, you will need to temporarily set your heatmiser/other room stats to max so that they don't interfere with the Vaillant controller.
You can bring the room stats back into action once you are on the right curve.
Otherwise it's like pressing the accelerator and the brake at the same time in a car.

[MT-zntc]

I've been gradually reducing my WC over the last few weeks and I think this cold period has really brought home the efficiency of our system. I've been in touch with our UFH installer (we've kept in touch intermittently since he fitted it 27 months since) and he commented that it was over-delivering on what he was expecting. Flow temperature was 31degreesC when it was minus 2 outside (it cost us about £4.00 in electricity that day).
Today is much warmer and have COP snapshot of 5.3 (combined CH and DHW) and the WC is sitting at 2.50. This is in a 1975 125sqm bungalow with moderate insulation.
It was a leap of faith to get a heat pump but it has worked out well for us. I have sympathy for those who have had poor installs. I also think there should be better education out there as I'm aware of some who still attempt to run them on/off like gas or oil boilers, then cry when they're costing a fortune.

[crm.]

Nice overview. I have our curve setting at 0.55. When I first got our ASHP, I found a formula for plotting the heat curves and had fun plotting the curves at various values.

[alexhgft]

The same is also valid for a boiler. I'm using a viessmann boiler with weather compensation on a fairly well insulated house with mechanical ventilation and heat recovery, trying to keep the heat curve at 0.4 and a target temperature of 20 degrees. It is still cycling a fair bit when the temperature outside is a bit higher because the boiler can only modulate down to 2 kW.

[MrJons]

Thanks for the video, Ive tried this out, we have a 184year old terrace house solid walls, 300mm insulation in the loft, 2 bedrooms with internal wall insulation, 7 year old windows with trickle vents, warm flat roof in kitchen and downstairs bathroom. We have a Vaillant ecofit pure 825 on gas CH, Which I’ve range rated down to 5kw an external temperature sensor with a senso home thermostat, I basically copied what you’ve done and notice its warmer and the desired matches the current temperature now.

[indymind]

Great video.

Just had a Mitsubishi Ecodan fitted and really impressed. The heating COP is around 4.5.

Looks like the Vailent system is easier. I can set up the temperature at both the higher and lower points. So far, I have found the 6KW unit runs better by leaving it to sort itself out.

[garycoppinger]

Thanks for vid
I’ve slightly copied your tactics and got a heating score of 5.4 👍🏻
Had vailant 7kwh now just over 1 month

And very happy comfort miles better 👍🏻

[danielbarton]

Good stuff. That will no doubt help a lot of people, the extensive menus can be a little intimidating to some.

[vinp]

Someting that does not make sense to me is that when in room temo mode inactive its meant to just be a thermostat with no influence, how ever on the weekly planner you have different ranges through the day, so how does that influence full weather conp? Thanks

[toniilievski]

Does the weekly schedule work with the weather comp ?

[FB-kgfn]

Having had our vaillant system for over 3 years I'm only just beginning to poke around in the settings! If were trying to establish the heat curve using weather compensation only (room mod inactive), do i need to turn on all radiators including in the rooms we don't use, i.e. unused bedrooms, conservatory etc or can we leave them with the thermostat rigjt down on anti frost setting?

[philippehebert]

Hello from France and great content..thank-you!....my current room temp mod was set to Expanded...can you please elaborate why this setting needs to be set to Inactive? 2nd question, i see the heating curve settings are now available in the My Vaillant app...when i change the setting in the app to .65 and hit save, it defaults back to .60? using the controller like you are, and changing to .65, the change remains in the controller but the change is not visible in the app??

[derekpaisley]

Another good video. Can I ask when its zero or -2 outside what's the COP showing on the controller, disregarding the HW.

[h.e.verheijden]

I have a Daikin and I have weather compensation curve on my screen. Thee are two set points +15C and -9C with there flow tempertures. I can’t translate your numbers to my curve set points. Any idea???

[KavanOBrien]

Is it only me that finds the heat pump world somewhat amusing = it’s like a mission impossible film, can you get a good installer? Will you have the installation with no extra things that is not needed and make it less efficient ? Will you be sold the correct Kw heat pump ? Will the system work well and not cost a fortune to run ? Can you sort the temperature right in each room or in fact the whole house ? Obviously the song for this new film = The Impossible Dream = Andy Williams .

[martinsykes]

Hi, I’m pleased I watched this video. I’ve had my vaillant aerothern heat pump for 3 years. I occasionally go into the settings to have a look around without changing anything. After watching the video I went into the settings, the target flow temp was 0 degrees. Heat curve set to 1, room temp mod was set to expanded. My current temperature and desired temperature are usually the same very occasionally been 0.5 degrees different. In the winter my heating is set to 18-19 degrees which for me is comfortable, domestic hot water set to 50 degrees. Should I still be changing the heat curve and other settings. I would be very grateful for any advice

[brp]

Useful info, although I do wonder if people would be better off starting with a fixed temperature to get the curve dialled in, before playing about with different timings?🤔
Surely, when using timed temperature, you need a higher WC to catch up from the cooler periods, and the temptation is to then use the ASHP in a boileresque fashion.

[guillettoaparicio]

I’ve finally found on the internet the problem with my heat pump.
Last year I’ve put 20 degrees and thermostat marked 23 degrees. I thought that it was because my house was very well isolated. Nevertheless electric bill was too high!
So I decided to go the temperature down, to 18 degrees, and my thermostat shows right now 20.5C.
Until now, I didn’t know why this gap. I’ve just learnt the problem!

One more thing! I’ve seen you enable a heat program with differences of two degrees or more oil the heating. What if I have a floor heating system? I’ve heard floor heating systems must be on all the time.

Thanks for the video and I hope you can reply to me ;)

[alloyd]

Hi. I followed your video and set my system to.0.7 from 1.20 and the settings you suggest. Two days ago.. Heating seems to be working well.. but my hot water performance has reduced drastically - insufficient for a decent shower. Previously, for the last year no issues.
Any advice?? Please 😢

[mrblobby]

Hi, i’m trying to follow your video but my room temp is 3 degrees higher than desired? I was told to ignore my room temp as my controller is in a cupboard with my buffer tank. Room temp mod is set to inactive? Thanks