How to Balance Your Radiators

If some rooms in your house are boiling while others stay chilly, or if the radiators furthest from your boiler take forever to warm up, your heating system likely needs balancing.

Balancing is the process of adjusting the radiator valves so that hot water is distributed evenly across the entire system.

Tools You Will Need

• Radiator bleed key (to ensure no air is trapped first).

• Lock-shield valve key or an adjustable spanner.

• Digital thermometer (a clip-on pipe thermometer or an infrared laser thermometer is best).

• Screwdriver (to remove plastic valve caps).

• A notepad and pen.

Step 1: Bleed Your Radiators

Before balancing, you must ensure there is no air trapped in the system.

1. Turn the heating on and identify cold spots at the top of radiators.

2. Turn the heating off and let the system cool slightly.

3. Use your bleed key to release any air until water starts to drip out.

4. Check your boiler pressure afterwards; you may need to top it up using the filling loop.

Step 2: Open All Valves

You need a "clean slate" for the system.

1. Manual/TRV Valves: Turn the main control knob (the one you usually touch) to the highest setting on every radiator.

2. Lock-shield Valves: Remove the plastic cap from the valve at the other end of the radiator. Use a spanner or key to turn it anti-clockwise until it is fully open.

Step 3: Map Your System

1. Turn the heating back on.

2. Walk through the house and note down the order in which the radiators heat up.

3. The ones closest to the boiler will usually get hot first. You will be "throttling" these later to force water toward the furthest ones.

Step 4: The Balancing Act

Turn the heating off and let the radiators cool down completely. Once cool, turn the heating back on to begin the adjustments.

Go to the first radiator that got hot (closest to the boiler):

1. Identify the Intake: Check which pipe gets hot first.

2. The Lock-shield Adjustment: Close the Lock-shield valve completely (clockwise), then open it by just a quarter turn.

3. Measure the Temperature: * Take a reading of the pipe leading into the valve.

   • Take a reading of the pipe leading out of the Lock-shield valve.

   • The Goal: You want a temperature difference (Delta T) of exactly $12^\circ\text{C}$ (or $20^\circ\text{F}$) between the two pipes.

4. If the difference is less than $12^\circ\text{C}$, close the lock-shield slightly. If it’s more, open it slightly. Wait a few minutes between adjustments for the temperature to stabilise.

Step 5: Repeat Throughout the House

Move to the next radiator on your list.

• Radiators in the middle of the system might require the lock-shield to be open about halfway.

• Radiators at the very end of the system (furthest from the boiler) will likely need the lock-shield valve fully open to receive enough flow.

Summary Table for Adjustments

Radiator Location	Lock-shield Position (Approx)	Goal
Closest to Boiler	$1/4$ Turn Open	Restrict flow to "push" water further.
Middle of System	$1/2$ to $3/4$ Turn Open	Moderate flow.
Furthest Away	Fully Open	Maximise flow to the coldest area.

Final Checks

Once all radiators are balanced, your home should heat up at a uniform rate. If you find one room is still cold, open that radiator's lock-shield by another $1/8$ of a turn and check it again after an hour.