Radiators Are Still Hot When The Heating is Off, Why?

Central Heating Turned Off But Radiators Still Hot, Why?

When most people think of heating problems, they think of inadequate heat or heaters that do not work.  What if you cannot turn your heat off?  We sometimes get questions from people with radiators that produce heat, even when the heating is off.  No one wants to be too hot or resort to having the windows open or even the air conditioner on just because the radiators won’t turn off.

Radiators have two common but completely different ways of getting the hot water or steam that makes them hot. Depending on what type of heating system you have, the radiator can stay hot for different reasons.

1) Malfunctioning Check Valve

Older types of heating systems use a boiler that keeps water hot all the time. Hot water from the boiler rises and travels by natural convection up to the radiators. When your home’s heat is turned on, a pump starts and draws water up from the boiler and pumps it to the radiators.

When the house reaches the desired temperature, or the heat is turned off, the pump stops running. To keep natural convection from allowing hot water to circulate to the radiators when the pump is off on, there is a check valve. A spring or weight keeps the check valve closed and stops the natural convection from occurring.

Once the pump is activated, it can overcome the resistance of the weight or spring and allow hot water or steam up to the radiators. If the check valve fails because of a broken spring or some debris, your radiators will be hot from the natural convection, even if the heat is not “on.”

2) Diverter Problems

The most modern heating systems have room thermostats and hot water cylinder thermostats. Thermostats are temperature-sensitive switches that turn the boiler on when heat is required in either the hot water tank or the living space. Either the room thermostat or the water cylinder thermostat calls for heat when the boiler turns on.

The diverter valve then directs the hot water to the radiator or the water cylinder as needed. What happens when both of the thermostats call for heat at the same time? The diverter goes into a ‘mid position’, which allows the hot water to flow to both the water tank and the radiators.

When a diverter fails or gets blocked with debris, hot water intended for the hot water circuit can get into the radiator circuit. Then the radiators will be hot even though the heat is turned off.

You do not have to live with constantly hot radiators. Your radiator service person will perform a drain-down and replace the faulty component.

If you are experiencing this specific issue with your radiators. We are capable and prepared to repair, maintain, and install any parts or equipment your heating system needs.

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