Question 1

How do you balance a central heating system?

Accepted Answer

By **adjusting the flow through each radiator** so they all heat at a similar rate — because water takes the path of least resistance, which means radiators nearest the pump get too much and distant ones get too little.

**The symptom that indicates it.** Some radiators hot, others lukewarm or cold, **with no air in them** — if bleeding fixes it, the problem was air, not balance. Typically the radiators furthest from the boiler underperform, and upstairs may run hotter than downstairs.

**The two valves on a radiator, which are different things:**

**The wheel head or thermostatic valve (TRV)** at one end controls the room temperature and is the one you adjust daily.

**The lockshield valve** at the other end — usually with a plastic cap — is the balancing valve. **It is set once and left alone**, which is why it has a cap rather than a handle.

**How balancing is actually done:**

**Open every lockshield fully** and run the system until all radiators are as hot as they will get.

**Turn the system off and let it cool.**

**Close all lockshields**, then open the one on the radiator **nearest the boiler** by a quarter turn, the next by slightly more, and so on — the furthest radiator's lockshield stays fully open.

**Restart and measure the temperature difference** across each radiator, at the pipes either side, using a clip-on thermometer or an infrared one. **You are aiming for a consistent drop across each radiator** — commonly around 11°C on a conventional system, and larger on a heat pump.

**Adjust and repeat**, working from the nearest outward, since each change affects the others.

**Why it matters beyond comfort.** A balanced system returns cooler water to the boiler, which is what allows a **condensing boiler to actually condense** — and an unbalanced system can prevent it, costing efficiency continuously. For a **heat pump this is far more important**, because performance depends heavily on running at low flow temperatures.

**If balancing does not fix it:** check pump speed, sludge in the system requiring a power flush, an undersized pump, or a radiator that is simply too small for the room.

Question 2

What does a thermostatic radiator valve do, and where should the thermostat go?

Accepted Answer

They control heat in different ways, and getting the relationship between them wrong is a common cause of a house that is simultaneously too hot and too cold. A thermostatic radiator valve (TRV)

Question 3

Why is my radiator cold at the top but warm at the bottom?

Accepted Answer

Cold at the top with warmth at the bottom is the classic sign of trapped air. Air rises to the highest point in the radiator and displaces water, so the upper section cannot heat. Bleeding it

Question 4

Why is one room in my house always colder than the others?

Accepted Answer

Because heat loss and heat delivery are not distributed evenly around a house, and one room is usually losing more, receiving less, or both. Working through the possibilities in order saves a lot of

Question 5

What is a power flush, and does a heating system need one?

Accepted Answer

A cleaning process that circulates water and chemicals at high flow through a central heating system to remove magnetite sludge — and it is genuinely useful in specific circumstances and routinely

Question 6

Why does a heat pump need bigger radiators?

Accepted Answer

Because a heat pump produces water at a much lower temperature than a gas boiler, and a radiator's output depends heavily on how much hotter it is than the room. The temperature difference. A gas

Question 7

Why does my shower run hot and cold?

Accepted Answer

Usually a pressure or flow imbalance, and the specific pattern of when it happens identifies the cause. If it goes cold when another tap or the toilet is used, the shower is losing cold water

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