Different temperatures in different rooms
Your central heating system should distribute heat evenly around your home. Radiators heat up in turn, which means those nearest the boiler will often be warmer.
The system can sometimes become unbalanced with radiators working at different temperatures, resulting in some rooms becoming much too warm, and others feeling cooler. If this is the case, it’s likely that your heating system may need balancing.
How to balance radiators
By partially closing the lockshield valve on the hotter radiators you can allow more hot water to flow to the other radiators which will help distribute the heat around the system. This may need to be repeated on several radiators.
You can gradually adjust the lockshield valves on every radiator until you feel the system is balanced. A good rule of thumb is to reduce the flow in the warmest rooms and increase it in the coldest, and then make slight adjustments bit by bit.
Cold radiators in different zones
Check your zone timer or thermostat
In order to rule out a problem with your timer or thermostat, check the controls in the zone where the radiators aren’t working.
Your manufacturer's manual will provide details on the correct settings.
Cold radiators upstairs
If you find that the radiators on the upper floors of your home are cold, it’s likely that there’s a problem with the feed and the expansion cistern. This will be the small cistern, usually in the loft.
In order to check what’s causing the problem, follow the steps below:
Locate the cistern.
Ensure there’s enough water within the cistern to enable the ballcock to float. But be careful not to fill it completely.
You should now notice that the radiators start heating up normally. If for any reason heat doesn’t return to the upper floors of your home, contact your local heating engineer.
Cold radiators downstairs
If you find that the radiators on the lower floors of your home are cold it is likely that there’s a problem with your pump.
In order to repair or replace a faulty pump, contact your local heating engineer.
One radiator is cold but the others are hot
If you find that one radiator within your home stays cold, ensure that the valves located on the sides of the radiator are open.
If the valves are open but the radiator is still cold it’s possible that the valves are blocked.
If you have an open-vent system (a conventional central heating system which is unpressurised and tank fed), you can use a heating system sludge remover that can be bought at most DIY stores. Be sure to follow the manufacturer’s instructions.
You can flush the system yourself by:
Adding the liquid to the feed and expansion tank.
After a few days you'll need to empty and refill the system.
If you have a pressurised system it may need a powerflush. Seek expert advice.