Central Heating not working properly

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Lancashire
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United Kingdom
Hi

The radiators in my house are only getting warm at the top. Bled all of the radiators and therefore don't think that its air in the system. Hot water is working fine. Boiler starts up for about 3-5 minutes and then shuts down. Pump is working fine. Thermostat is at the max. Think it might be a circulation problem but all of the radiators are warm at the top. Its a sealed system with 2 2 port valves for hot water and central heating. Could it be anything overheating and shutting down? i.e 2 port valve. Any ideas?
 
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It definitely sounds like a circulation problem. Your rads are only hot at the top due to the lack of water flow. Your boiler keeps shutting down due to the fact it cannot get rid of the heat quick enough. Is your pump in your boiler or seperate?
 
The pump is separate.

I have moved the pump from setting 2 to 3 to see if that works and closed off all of the radiators downstairs.

When the central heating and hot water are on at the same time the boiler doesn't shut down, but only heats the hot water. Radiators are still only luke warm.
 
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Can you hear the CH valve working when you turn the room stat up and down?

Is the valve lever loose when the stat is turned up and stiff when the stat is turned down?
 
If your heating honeywell valve has a lump on the metal case top, its a removable head, undo the screw and remove the casing. See if the syncro motor moves, if your unable too, isolate the electrics, remove the valve head completely and manually open the valve via the center spline using pliers.

If the rads then get hot, should notice pretty much straight away via the pipework heating up on the CH Flow, then its your valve head/motor.
 
do the pipes supplying the cylinder cool down when (a) the cylinder has reached its temperature as indicated by the cylinder stat clicking or (b) when, using your programmer, you set CH on and HW off?
 
just checked the valve again. The lever is loose when on and stiff when off. The room stat turns the boiler off immediately when on low, but doesn't turn it on immediately when turned to high, but comes on eventually after around ten minutes.

Have removed the honeywell valve head and, and the centre spline operates smoothly. Hot water flows in the immediate pipework but only lasts for 3-5 minutes, before the CH switches off.

In terms of the cylinder, the hot water operates normally.
 
In terms of the cylinder, the hot water operates normally.
do you mean that the hot supply to the cylinder shuts off as I described?

This is important. If the flow is able to go through the cylinder, it will do that, instead of going round the radiators.
 
that's good. When the cylinder pipes cool down, do the radiator pipes warm up?
 
just checked the valve again. The lever is loose when on and stiff when off.
That means the motorized valve is opening and closing.

The boiler is lit via a microswitch in the valve.

If you have a multimeter you can check the voltages on the valve's grey and orange wires. It's best to wait until the system has cooled down so the boiler thermostat does not work while carrying out the tests.

Turn HW OFF and CH ON at programmer

Measure between each wire and blue with the room stat turned down. One will read 204Vac (usually grey), the other 0Vac (usually orange).

Leave the meter connected to the one reading 0Vac and turn the room stat to max. You should hear the valve operate (lever will go loose) and the boiler should light. The meter should now read 240Vac.

If there is 240Vac on the wire but the boiler is not lighting, make sure the boiler thermostat is set to max. If it is, the problem is in the boiler.

If the boiler lights, wait until the boiler goes out and check the voltage on the same wire. If it is 240Vac, then it is the boiler's own thermostat which is turning it off.

If it is 0Vac, check that the lever is still loose. If it is, there is a problem with the microswitch in the actuator. Replace it.

If the lever is not loose, check the voltage between valve brown and blue.

If 240Vac, there is a fault in the valve motor. Replace it.

If 0Vac, either the room stat is faulty or the room is up to temperature.
 

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