Hello, I'm an expert in heating systems and I'm here to help you troubleshoot the issue with your downstairs radiators being cold. Let's dive into the possible causes and solutions for this common problem.

Step 1: Air in the System
The first thing to consider is that there might be air trapped in the system. Air can accumulate in the radiators over time, especially if the heating system hasn't been used for a while. This can prevent the hot water from circulating properly and cause the radiators to feel cold. To fix this, you'll need to bleed the radiators. This involves releasing the trapped air by opening the bleed valve, which is usually located at the top of the radiator. You'll know you've done it correctly when water starts to flow out instead of air.

Step 2: Central Heating Pump Issues
As you've mentioned, the issue could be related to the central heating pump. If the pump is not working correctly, it won't circulate the hot water throughout the system effectively. This can result in some radiators, particularly those on the lower floors, being cold. You've suggested increasing the pressure setting on the pump, which can indeed help. The correct pressure for most systems is around 1 to 1.5 bar. If the pressure is too low, the pump may not push the water around the system with enough force.

Step 3: Insufficient Circulation
Another potential cause is insufficient circulation of the heating water. This can happen if the radiator valves are not fully open or if there's a blockage in the pipes. Make sure all the valves on the radiators are open and check for any signs of blockages. If you suspect a blockage, you may need to call a professional to inspect and clear it.

Step 4: Zone Valves or TRVs
If your system has zone valves or thermostatic radiator valves (TRVs), they could be set incorrectly. Zone valves control which areas of the house are heated, and if the ones for the downstairs radiators are closed, those radiators won't get hot. Similarly, TRVs control the temperature of individual radiators, and if they're set too low, the radiators won't heat up properly.

Step 5: Sludge Build-up
Over time, a sludge can build up in the central heating system, which can restrict the flow of water and heat. This is more common in older systems that haven't been serviced regularly. If you suspect sludge is the issue, a power flush of the system may be necessary to remove it.

Step 6: Boiler Issues
Lastly, the problem could be with the boiler itself. If the boiler is not firing up or is not heating the water to the correct temperature, none of the radiators will get hot. Check the boiler's pressure and make sure it's set to the correct level. If the boiler is old or has not been serviced in a while, it may be time for a service or even a replacement.

In conclusion, there are several potential reasons why your downstairs radiators might be cold. It's important to check each of these areas to identify the cause and then take the appropriate action to fix it. If you're unsure or if the problem persists after trying these steps, it's best to consult with a professional heating engineer.

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Radiators Are Hot Upstairs, but Cold Downstairs. Cause: This is most likely caused by a problem with your central heating pump and can often happen when your heating has been switched off for a few months (e.g. over summer). ... Try increasing the pressure setting on the pump.read more >>