Set up the heating curve

A systematic guide to finding the right heating curve for your system. Follow the steps and use the decision tree for troubleshooting.

Preparation

Before you start adjusting the heating curve, make sure these prerequisites are met:

  1. Open all thermostats fully – Don't close off any rooms. Thermostats should be set to maximum (usually 5 or the highest setting).
  2. Note current settings – Write down the heat pump's current curve and offset so you can revert if needed.
  3. Choose the right season – Fine-tuning is ideally done during the heating season when the temperature is below +10°C.
  4. Be patient – Plan to wait at least 24 hours between each adjustment.

Step 1: Choose a starting point

If you've never adjusted the curve before, start with values based on your system. See the reference tables for recommended starting values.

Rule of thumb

  • Underfloor heating (concrete slab): Curve 1-2
  • Underfloor heating (wooden joists): Curve 3-4
  • Radiators (new/well-insulated): Curve 4-5
  • Radiators (older house): Curve 5-6.5

Step 2: Evaluate

Wait at least 24 hours and then note how the temperature feels in the house:

  • Is it generally too warm, too cold, or just right?
  • Is the problem worse at certain outdoor temperatures?
  • How warm are the radiators/floor?

Step 3: Adjust

Based on your evaluation, make one change at a time:

How do you experience the indoor temperature?

Adjustments in practice

What does the slope do?

Increase the slope when:

  • It's comfortable in mild weather but too cold when it's really cold outside
  • The supply temperature doesn't rise enough at low outdoor temperatures

Decrease the slope when:

  • It's too warm when it's really cold outside but fine in milder weather
  • The system overreacts to temperature swings

What does the offset do?

Increase the offset when:

  • It's generally too cold at all outdoor temperatures
  • The whole house needs to be warmer

Decrease the offset when:

  • It's generally too warm at all outdoor temperatures
  • Thermostats start throttling everywhere

Golden rules

1

One change at a time

Never change both the curve and offset simultaneously. Otherwise you won't know which change had the effect.

2

Wait 24 hours

The house has thermal mass. It takes time before a change reaches full effect.

3

Small steps

Adjust by a maximum of 0.5-1 units on the curve or 1-2 degrees on the offset per round.

4

Thermostats at maximum

During calibration, all thermostats should be set to maximum so they don't mask the curve's effect.

Frequently asked questions

Can I adjust when it's warm outside?

It's possible but harder. At temperatures above +10°C, the supply temperature is often so low that differences are hard to detect. It's best to wait until the heating season.

How do I know the curve is correct?

When the thermostats are nearly fully open all the time and the temperature is even throughout the house – then you've likely found the right curve.

Should I turn off hot water production during calibration?

No, that's not necessary. The heat pump prioritizes automatically and it doesn't affect the heating curve itself.