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The room stat is not the problem., Because it moves the valve to mid position. The problem is the actuator head. Two actions are required to obtain CH only. The valve has to move from mid position to CH position. Secondly the valve has to trip a microswitch to light the boiler. If valve moves to...

A simple way to assess your problem. Can you indentify the CH only position. With CH only selected, does the valve move to the CH only position. If yes, the problem is most likely the micro switch so nothing comes out of the orange wire to fire the boiler. If No, then either there is no power...

Screw threads are a bit of a mine field, especially for pipes. For example the British Standard Pipe thread, refers to the bore size of the pipe and not the size of the thread. In addition to the diameter of a thread, the form of the thread needs to be considered along with the pitch of threads...

Hi David Those pressures would indicate the expansion vessel is working as it should. When charging a vessel the water pressure must be zero, but the water must be open to atmosphere. If the vessel had water in the air space, then it would need to be discharged out of the system as the air...

Hi David. You need to understand how the expansion vessel works. When first installed, it is charged with air to approx 1bar. This means there is no water in the vessel and note there will be a rubber diaphragm separating the water from the air. Now when the water gets heated, it expands and...

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You can by pass the room stat, but I don't see how it will help you. I understand you get heating but not on its own. To get heating with hot water means the valve has moved from HW only to mid position so the stat and the motor are not the problem. The problem is lack of power to drive the...

I only have limited experience on a halstead boiler, but this is my understaning. There are two circuits for the heated water. The circuits are separated by the diverter valve. The valve allows water to be pumped round the radiators for central heating. For hot water, it is a case of cold mains...

I've been following your problem with interest and wondered if the root cause had been found. I thought the pump solenoid seemed the most likely, but that has already been changed.

The problem may be more related to the gear teeth on the motor and quadrant. Constant use causes burrs to be formed at the edges and may cause fouling. Also you can lift the head off the spindle and test to see if valve turns easily using finger and thumb. If stiff try silicone lubricant

You can prevent the head being warm if you select HW which will allow valve to return to HW position and then switch off.. Motor no longer energised.. If rads get warm with only HW then valve must be sticky and not fully returning to the rest position (HW)

There are two requirements to get CH. First the valve has to driven to the correct position and secondly power has to be supplied through the room stat is and valve head to light boiler. When room stat is satisfied power to light boiler is cut, but valve position remains. This means the motor is...

Depends what is meant by ' replaced the ball valve' . Some years ago I replaced the rubber valve disc only to find the leak had not been fixed. The disc which is moved by the floating ball is pushed against a plastic nozzle and l found this nozzle had a groove worn in it on the sealing face.

The Y plan is based on the use of a 3 port mid position valve. The valve is supplied with water from the boiler using the pump. There are three positions the valve can be in. Hot Water only or Central Heating only or with the valve in mid position both HW and CH get the water shared. The valve...

Don't expect your problem to be cured. The air valve on the expansion vessel has leaked. The air that escapes gets replaced with water. The volume of air for compression gets reduced. When this reduced volume of air gets compressed, it's pressure rises far higher than 3bar and opens the PDF It's...

You're not supposed to use the lever while boiler is in operation. The lever is used during refilling of the system it holds the valve in mid position so water can get to both sides and prevent air locks. When you select HW and CH, from cold the valve goes to the mid position. But this is not a...

Have looked at your problem. To me it would appear there is nothing wrong with programmer or the room stat. The problem is the 3port mid position valve. It could just be stiff and too much resistance for the motor to drive the valve over the second half. Test by removing the head from the...

Relative has similar system, with one radiator furthest away from boiler not getting hot. It was easier for water to go back to boiler via by pass valve, rather than radiator. Problem solved by slightly closing this valve and restricting the flow through it.

The increase in pressure is related to the size of the vessel and the " air charged ". These dictate the volume of air that is available to be compressed. A large system holding more water would need a larger vessel with larger volume. Initially before any water is pressurised the 'air' side...

A faulty microswitch is highly likely. There are two in 3port mid position valve. Both have dual functions No 1 supplies power to drive motor to mid position.The swich cuts off the power breaking the contacts but makes a second set of contacts, which provides power to drive the motor/valve from...