19/01/2026
Balancing & Weather Compensation
The foundation of efficient, comfortable heat-pump heating
A heat pump only performs well when two things are right:
Water flows evenly through the system (balancing)
The heat pump alone decides flow temperature (weather compensation)
If either is wrong, no amount of tweaking will fix efficiency or comfort.
This section explains the correct order, then gives a realistic 30–60 day setup timeline.
Part 1: Balancing the heating system
Making sure heat reaches every room evenly
Balancing is the process of restricting flow to nearby emitters so distant ones receive enough heat.
This must be done before weather compensation tuning.
Step 1: Work out the order of the system
You need to know which radiators or underfloor loops are:
Closest to the heat pump
Furthest from the heat pump
You do not need drawings — use practical observation.
Ways to determine order
Trace the main flow pipe from the heat pump
Observe which radiators warm up first from cold
Assume long pipe runs, upper floors, and extensions are furthest away
Accuracy matters less than consistency.
Step 2: Start with everything fully open
Fully open all radiator lockshield valves
Fully open all TRVs
Leave the system running for at least 24 hours
This establishes a baseline.
Step 3: Protect the furthest emitters
You do not start by adjusting the furthest radiators.
Instead, you gradually restrict flow to the nearest ones.
Why
Nearby radiators steal flow
Water returns too quickly
The heat pump reduces output prematurely
Step 4: Close down the nearest radiators slowly
For the radiator closest to the heat pump:
Adjust the lockshield valve only
Close it ¼ turn
Leave everything else unchanged
Wait 24 hours
Then move to the next nearest radiator and repeat.
Do not:
Touch TRVs during balancing
Adjust more than one radiator per day
Step 5: Observe over days, not hours
After each adjustment, look for:
Distant rooms becoming warmer
Reduced temperature differences between rooms
Quieter system operation
More stable heat pump running
Heat pumps respond slowly.
Fast changes destroy cause-and-effect.
Underfloor heating balancing
If you have underfloor heating:
Each loop must be balanced
Longer loops usually need more flow
Shorter loops usually need less
Adjust:
One loop at a time
In small steps
With at least 48 hours between changes
UFH responds even more slowly than radiators.
What “balanced” feels like
All rooms broadly similar in comfort
No rooms racing ahead
No rooms lagging badly behind
No constant TRV shutting
Flow temperatures can be reduced later
Once this is achieved, stop adjusting.
Part 2: Weather compensation setup
Letting the heat pump run continuously and efficiently
Weather compensation should be the only control deciding how hot the system runs.
Step 1: Remove the thermostat from control
Set the main room thermostat high (typically around 28–30 °C).
This does not heat the house to that temperature.
It simply prevents the thermostat from:
Switching the heat pump on and off
Causing cycling
Forcing higher flow temperatures
The thermostat now acts only as a safety limit.
Step 2: Understand the curve (in plain terms)
Weather compensation links:
Outdoor temperature
→ Flow temperature
Typically defined between two outdoor points, for example:
Cold weather (e.g. −5 °C)
Mild weather (e.g. +15 °C)
The heat pump draws a straight line between them and follows it automatically.
Step 3: Start with a sensible baseline
If a design curve exists, use it.
If not, start conservatively — comfort first, optimisation later.
Let the system run continuously for at least 48–72 hours before making any changes.
Step 4: Measure indoor temperature properly
Do not tune from a single wall thermostat.
Use:
Portable digital thermometers
Multiple rooms (warm, cool, living, sleeping)
You are looking for:
Stability
Consistency
Gentle changes, not swings
Step 5: Tune the cold end first (micro-adjustments)
In colder weather, adjust the cold outdoor end of the curve first.
This adjustment has a small but powerful effect.
Method
Reduce the cold-end flow temperature slightly
Leave everything else unchanged
Wait 2–3 days
Monitor indoor temperatures
If the house drifts cool, reverse slightly.
Never chase instant results.
Step 6: Adjust the warm end later
Once cold-weather behaviour is stable:
Fine-tune mild-weather performance
Adjust the warm end slightly up or down
Again, wait several days between changes
This mainly affects spring and autumn behaviour.
What correct weather compensation feels like
Long, quiet run times
No obvious on/off cycling
Radiators warm, not hot
Stable indoor temperature
Falling electricity use over time
If it feels boring, it’s working.
Printable 30–60 Day Heat Pump Setup Timeline
Days 0–7: Stabilisation
Actions
Do nothing except bleed air
Fully open all valves
Let the building warm through
Monitor
Indoor temperatures
Noise
Any air in radiators or UFH
Days 7–21: Balancing phase
Actions
Identify system order
Adjust one lockshield per day
Balance UFH loops if present
Monitor
Room-to-room temperature differences
Distant rooms improving
Overall comfort stability
Days 21–35: Weather compensation baseline
Actions
Set room thermostat high
Confirm weather compensation is sole control
Run system continuously
Monitor
Average indoor temperature
Heat pump run time (longer is better)
Daily electricity use
Days 35–50: Cold-end tuning
Actions
Small reductions to cold-end flow temperature
One change every 2–3 days
Monitor
Indoor temperature stability
Comfort during colder periods
Any cycling behaviour
Days 50–60: Warm-end refinement
Actions
Fine-tune mild-weather performance
Make very small adjustments
Monitor
Spring/autumn comfort
Overheating in milder weather
Overall efficiency trend
Ongoing rule
One small change → wait several days → assess calmly
A heat pump rewards patience more than intervention.
Once set correctly, it becomes quiet, predictable, and cheap to run — exactly as intended.
