There are several different reasons why a single radiator or multiple radiators may not be getting completely hot. Also, the way a radiator is cold/hot can give some clues as to why this is happening. Feeling the radiator itself can give us some clues, for example:
The radiator is cold at the top but getting hot at the bottom
The radiator is hot at the top but cold in the center/bottom of the radiator
The radiator is cold all over
We’ll break down the possible reasons behind each scenario. Sometimes there can be multiple different problems that can cause the same symptoms.
1. The Radiator is cold at the top but getting hot at the bottom
Possible Cause: This is usually down to air being trapped inside the radiator. The air accumulates at top of the radiator preventing the hot water of the heating to circulate fully around the radiator.
The fix: Bleed the radiator. Ensure the heating system is turned off. Bleeding the radiator is done by finding the bleed nipple and using a radiator key (most modern bleed nipples will take a flat-headed screwdriver). Slowly open the nipple until you can hear a hiss, this means that air will be leaving the radiator under pressure. As soon as the water starts running out of the radiator this means the radiator is fully bled. It is good to keep a cloth underneath while bleeding to catch any water that comes out. After this is done, you may need to top the pressure back up depending on what type of heating system you have.
2. The Radiator is hot at the top but cold in the center/bottom of the radiator
Possible Cause: A build-up of sludge inside the radiator is causing poor circulation through the radiator. This is usually caused by poor heating system maintenance and a lack of inhibitor in the system.
The Fix: A full system flush is recommended when a radiator has built up with sludge/debris is identified. This is because it is likely to have large amounts of sludge floating around the heating system. It is likely that over time it has deposited the bulk of the sludge into the affected radiators.
3. The Radiator is cold all over
Possible Cause: Radiator valves are closed or stuck
The Fix: Make sure both valves on each side of the radiator are open. Sometimes the pin on the TRV (Thermostatic Radiator Valve) can get stuck in the off position. This can be caused by a faulty pin or faulty TRV head. Remove the TRV head, use some pliers to gently pull the pin upwards. Wait a minute and see if the heat starts flowing into the radiator. If this is the case it is likely a new TRV is needed.
Possible Cause: Blockage or airlock to the radiator
The Fix: Turn off other radiators that are getting hot to help divert the force of the pump to the radiator with blockage. This may help shift the blockage. Some blockages may require more force and may require a full power flush of the heating system to completely remove blockages.
This is not an exhaustive list of possible reasons why your radiators may be cold, if these don’t help solve your problems then it would be best to get a professional who can diagnose and fix it.
If you would like further information feel free to get in touch with us at DPJ Plumbing, Heating and Gas contact page. We are based in Rugeley and work in the surrounding areas; Cannock, Lichfield, Stafford, Stone, Uttoxeter, etc