Water takes the easiest path, so without adjustment most of your boiler’s output goes round the shortest circuit. Balancing sets each radiator’s lockshield so every one takes its correct share, measured by temperature drop rather than by feel.
The symptom
One end of the house is warm and the other is not. The radiators near the boiler get hot quickly; the ones at the far end never quite do. The room thermostat is usually in the warm end, so the boiler shuts off early and the cold rooms stay cold.
Almost everybody concludes the boiler is too small. It very rarely is.
A cold far room with an already oversized boiler is the classic scenario. Fitting a bigger boiler changes nothing, because the problem was never a shortage of heat – it was distribution. Balancing costs a fraction of a boiler and it is the first thing to try.
Why it happens
A heating system is a set of parallel circuits sharing one pump, and water takes the path of least resistance. The radiator nearest the boiler has the shortest, widest route, so it takes a disproportionate share of the flow. The radiator at the far end of a long circuit, with more pipe and more bends between it and the pump, receives very little.
The two valves on each radiator do different jobs, and this is where people go wrong:
| Valve | Purpose | Adjusted by |
|---|---|---|
| Control valve – TRV or hand wheel | Regulates room temperature, opening and closing as the room warms | The occupant, day to day |
| Lockshield – usually under a plain cap | Sets how much flow that radiator can ever take. This is the balancing valve | The installer, once, then left |
Two mistakes account for most unbalanced systems: somebody opened all the lockshields fully because a radiator seemed cold, or somebody tried to balance using the TRVs – which cannot work, because TRVs open and close on their own.
How we do it
- Start from a known stateAll lockshields closed, counting the turns each takes, then opened a small equal amount as a starting point. All TRVs fully open so nothing closes during the process.
- Run the system to temperatureBalancing a cold system tells you nothing.
- Measure each radiatorFlow and return pipe temperatures with a clamp or infrared thermometer, and the difference between them.
- Adjust to a target dropStarting with the radiator nearest the boiler, which needs restricting most, and working outward.
- IterateAdjusting one radiator changes the others, because they share a pump. Two or three passes is normal, and it is why this takes a couple of hours rather than twenty minutes.
- Record the settingsTurns open for every lockshield, written down and left with you. Invaluable next time a radiator comes off for decorating.
The principle: a radiator with too much flow shows a small temperature drop, because water passes through too fast to give up its heat. One with too little shows a large drop. The target is a similar drop across every radiator, which means each is taking its proportionate share.
What balancing will and will not fix
Will fix
- Far radiators that never get properly hot while near ones roast.
- One consistently cold room in an otherwise warm house.
- Upstairs too hot and downstairs too cold, or the reverse.
- A system that takes a very long time to heat the whole house.
- A boiler that short-cycles because the near radiators satisfy quickly.
Will not fix
- A radiator cold at the bottom – that is sludge. See radiators cold at the bottom.
- A radiator cold at the top – that is air. Bleed it.
- A seized TRV, which needs replacing – see thermostatic radiator valves.
- A radiator genuinely too small for the room, which is a sizing problem.
- A failing pump.
- A room with very high heat loss, where the answer is fabric or a larger emitter.
So the sequence is: bleed, check the valves, confirm it is not sludge, then balance. Balancing a system full of magnetite is the right job in the wrong order.
Why it is so rarely included
Honestly: because it takes time, it is invisible, and nobody sees it on a quote. A competitively priced boiler installation has to find its margin somewhere, and two hours of methodical measurement at the end of a long day is the easiest thing to omit. The house gets warm, and the customer does not know what they did not get.
It is worth asking about explicitly when you get quotes – whether commissioning includes balancing and how it will be done. The answer tells you a good deal about the rest of the work.
It is also worth having done on an existing system that has never had it. No parts, a couple of hours, and on a system that has never been balanced the difference is frequently striking. The fuller explanation is in balancing a heating system.
One room always cold? Balancing needs no parts and it is the first thing to try before anybody suggests a bigger boiler.
Questions we get asked about this
What does balancing actually do?
It sets each radiator’s lockshield so every radiator takes its correct share of the flow, measured by the temperature drop across it. Without it, most of the flow goes round the shortest circuit.
Which valve gets adjusted?
The lockshield – the one under the plain cap. TRVs open and close on their own, so they cannot be used for balancing, and adjusting them is a common mistake.
How long does it take?
A couple of hours on an average house, because adjusting one radiator changes the others and it needs two or three passes.
Should it be part of a new boiler installation?
It should be part of proper commissioning, and it is the item most commonly omitted from a competitively priced quote. Worth asking about explicitly.
I took a radiator off to decorate and now the house is cold.
You almost certainly reopened the lockshield further than it was, which pulled flow away from the rest of the system. It needs rebalancing – and next time, count the turns.
Can I do it myself?
Yes, with an infrared or clamp thermometer and patience. Write the settings down when you finish.
What happens when you call
Call and describe it
You speak to an engineer, not a call centre. Most jobs can be narrowed down on the phone.
We look at it properly
A real diagnosis before a price, and a straight answer if it is not worth doing.
A written quote
Itemised, so you can see what you are paying for.
The job, and the paperwork
Certificates where the work needs them, and what will need attention next.
Where we do this work
Across Norwich and the whole of Norfolk. If you are on the edge of the county, call and ask — we will tell you honestly whether we are the right people.
- Norwich
- Wymondham
- Dereham
- Attleborough
- Aylsham
- North Walsham
- Cromer
- Diss
- Loddon
- Long Stratton
- Watton
- King's Lynn
Need this doing?
Call and describe the problem — you will speak to an engineer, not a call centre. Written quotes, no estimates over the phone.