Central heating comes on when hot water only selected!

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I have a gas boiler, Suprima 70, which has had a new control panel fitted by qualified engineer. This cured the lock out situation. I have recently noticed that although hot water only is selected, and heating is switched off, the rads all come on twice a day with the hot water. The thermostat is turned way down to 5C. Is this a wiring problem or something else?
Thanks
 
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3 port zone valve or heating 2 port zone valve needs replacing. It is stuck in either mid position for the 3 port, or stuck open if a 2 port.
 
Thanks guys.
It is a 2 port valve, Honeywell V4043H. I will turn off the power when house empty and see if the valve is stuck and if power reaches motor. I can get the Synchron motor as a spare part on the web.
Any hints I need to follow when doing this? Should I try to turn the valve with pliers to free it if necessary, or will that cause more probs?
 
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if you are wanting the htg to be off then you dont want an electrical feed to the actuator ;)
remove the powerhead from the valve and check to see if the spindle on the valve body is freely operating and also check the actuator head to see if the lever on the side of the valve has any resistance on it
 
also check that the valve has not been left in the manual postion. even if the spindle is free , it does not mean that the ball inside tha valve has not swollen, which will cause let by.

check the valve is in auto, let the system cool right down , then turn on your hotwater and feel the flow pipe into the heating about 12 inches after the valve... if it gets hot its the more than likeley the ball.

you may get away with replacing the ball and plate which will cost about a tenner, sometimes its also just the motor on the valve, also about a tenner.

best of luck.
 
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.
 
Didn't read whole post. Port A should go to rads, and B to HW cylinder. If you have zero experience then I would suggest calling someone in.
 

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