Heating controls and radiators: questions answered

A Y-plan uses one three-port mid-position valve to send heat from a regular or system boiler to the radiators, the hot water cylinder or both. It is controlled by a programmer, a room thermostat and a cylinder thermostat. It is common in UK homes with a hot water cylinder.

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An S-plan uses two separate two-port zone valves, one for heating and one for hot water, each opened by its own thermostat. When either valve opens, a switch inside it tells the boiler to fire. It is popular because each zone works independently.

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Look at the motorised valves near the hot water cylinder. One valve with three pipes is usually a Y-plan. Two valves, each on a single pipe, is usually an S-plan. If you are unsure, take a photo before your engineer visits, but do not open the valve covers.

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Check the programmer has hot water switched on and the cylinder thermostat is not turned down. If both are set correctly, the cause can be a stuck motorised valve, a valve motor fault or a wiring issue. A heating engineer can test the controls and valve safely.

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Make sure the programmer is calling for heating, the room thermostat is set above the room temperature and its batteries are not flat. Check radiator valves are open. If the boiler still does not respond, a zone valve or controls fault is likely, which an engineer can trace.

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On a zone valve system, a valve's internal switch can stick, telling the boiler there is still demand. A faulty programmer or thermostat can do the same. Check settings first. If the boiler keeps running with everything off, switch it off and call a heating engineer to test the controls.

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It is the dial strapped to the hot water cylinder. When the stored water reaches the set temperature it tells the controls to stop heating it. A setting around 60°C is common so stored water stays hot enough to control bacteria. Your installer can confirm the right setting.

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The programmer is the timer. It decides when heating and, on cylinder systems, hot water are allowed to run. A twin-channel programmer controls each separately, a single-channel one only times one service. A room thermostat then decides whether the house needs heat within those times.

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Wireless stats commonly fail because of flat batteries or a lost link to their receiver. Replace the batteries and check the receiver near the boiler shows power and a connection. The manufacturer's guide explains re-pairing. If it still will not call for heat, ask an engineer to check it.

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Check the Hive receiver by the boiler has lights showing and is connected to the hub and thermostat, and that the boiler itself has power and normal pressure. Hive's own app and support guide cover pairing. If the receiver is calling but the boiler does nothing, book a heating engineer.

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Yes. If the programmer or room thermostat is not sending a signal, the boiler will sit idle even though it has power, gas and pressure. Check times, modes and batteries first. An engineer can prove whether the boiler or the controls are at fault by testing the wiring safely.

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Yes. A combi can run two heating zones, for example upstairs and downstairs, using two zone valves and separate thermostats or a smart system that controls both. It needs correct wiring so the boiler fires when either zone calls. A heating engineer can design and fit it.

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A TRV senses room temperature and reduces flow to that radiator when the room reaches the set number. Higher numbers allow a warmer room. If a radiator will not heat with the TRV fully open, its pin may be stuck, which an engineer can free or replace.

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A smart thermostat lets you control heating from an app and schedule it room by room or zone. Most work with standard combi and system boilers, but wiring and boiler communication options vary. A heating engineer can confirm compatibility and fit it safely.

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It is the valve at one end of a radiator, usually under a plastic cap, used to set the flow during balancing. It is normally left alone once set. The other valve is the one you use to control the radiator.

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A motorised valve opens or closes heating or hot water routes. A heating engineer can test the motor and switch. Replacing a motorised valve head is a job for a heating engineer. Have your boiler make and model to hand when you call, as it helps the engineer plan the visit.

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The cylinder may not be heating fully, from a thermostat set too low, a valve or programmer fault, or an immersion that is off. Check the programmer and cylinder stat. If correct, an engineer can test the controls. An engineer can also check the cylinder thermostat and immersion heater safely.

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Often not, because the stat cannot send a heating demand. Replace the batteries and set the temperature above the room reading to test. If the settings look right and the problem continues, a heating engineer can test the controls safely.

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Check it has power, the clock and mode are set, and the heating channel is on. If it shows a call but the boiler does nothing, ask an engineer to test the wiring and boiler. If the settings look right and the problem continues, a heating engineer can test the controls safely.

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Check the programmer clock and schedule, including after power cuts or clock changes. Smart controls may need app or hub checks. If the settings look right and the problem continues, a heating engineer can test the controls safely. If you are unsure about any step, call a Gas Safe registered engineer.

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