Hi All
This was a really helpful thread for me. I have zero experience with plumbing and electrics but I found some other great stuff on other parts of the internet.
Just today i noticed my radiators come on even when i've set central heating control unit to hot water only.
In the airing cupboard i have a Honeywell V4073A1039 3 Port Y Plan Motorised Valve.
Here's what i think i've learned from the internet so far, if anybody could correct me where i'm wrong it would be appreciated.
The Valve is made up of two parts, the silver box (actuator) which contains a motor and the bronze pipe part (ball and plate) which consists of 3 Ports. Hot water enters from the vertical port and the actuator sends it to the horizontal ports (named A and B) as required. Port A goes to the hot water tank, port B goes to the radiators.
My valve is letting hot water into the pipe which goes to the radiators even when i've set the control unit to hot water only.
I think it is the control unit which sends hot water to the vertical port in the valve + electrical current A if i want hot water only, electrical current B if i want heating only (both if I want both.) The valve interprets the electrical current as an instruction to operate the motor in the head unit to open the valve in the bronze pipe bit. I think this valve is a ball valve. For example, there should be a ball in port B blocking water going to the pipe which goes to my radiators unless i say to the control unit 'i want heating' in which it sends an electrical current down a wire to the actuator, the motor in the actuator moves the ball valve and water flows to the radiators.
I can tell that the thermostat is OK because it audibly clicks when i move it past the current room temperature.
I also (think I) learned that if i don't get central heating then it could be the ball valve is stuck or the motor is broken. to test that, disconnect the power and slowly push the small lever on the side from auto to manual, it should offer some resistance and slowly move back to auto position. If it's floppy when all power is off the problem is the motor. (it should be floppy when power is on.)
The problem might fix itself in a few days because apparently this particular valve is built to rotate the ball valve occasionally. If it doesn't i think i have to replace the whole thing (actuator and ball and plate, costs around £80) which i think involves turning off all power in the house, turning off water and most importantly seeing if i have the correct spanners to unfasten the unit!
Or i could call a plumber? If i am correct on what i've learned i'd like to give it a go myself but am nervous because i have zero experience in plubming or electric stuff.