Central heating always on but no hot water

[Pistol]

I've a fully pumped system with 2 Honeywell motorised zone valves (V4043H) fitted. I removed the covers from each of these and found that the manual lever for the heating one moves really easily and clearly does not move the valve and must be detached from it. It's stuck open in the flow position. The hot water one has considerable resistance and the pipe really heats up fast when this is locked on the hook - this is the only way I can get hot water. I will go ahead and replace the heating valve, from the symptoms I've described do you think this will fix the problem?
Happy Xmas.

 

[ArtfulBodger]

I think if you replace both valves it will solve your problem(s)

 

[Agile]

Dont rush into anything !!!

The heating valve may be in perfect working order!

It could just as easily be a control fault. You need to measure the voltage on the motor contacts to see if its being powered. If you feel the top of the motor and its warm then its probably is being powered.

Finding an electrical fault is easy for some people and difficult for others.

Tony

 

[Pistol]

Thanks for the tips. The motor is permanently humming on the heating valve. When the valve is fully open should the microswitch contacts be open or closed? If I remove power from the valve am I right in assuming that it should return to the closed position by virtue of the spring?

 

[Agile]

Most modern valves are powered to open then and the motor stalls and remains powered as long as the valve needs to be open.

When power is removed the valve closes under spring power.

There are some older models which are powered open and powered closed with associated fiddly wiring.

Others particularly for wood and solid fossil fuel are powered closed and spring opened if power is removed.

Tony

 

[Paul Barker]

You must trace your live signals these are 230v.

Programmer sends two seperate 230v signals out one to heating one to hot water depending whether programmed to come on at the time. Modern programs use 3 for water on and 4 for heating on. The off signal is not used on S plan wiring which you have.

This is sent one to the roomstat other to the cyl stat. If the stat is not satisfied it sends the 230v on to the particluar zone valve, this moves into place micro switch operates and sends the live to the boiler and pump.

Check both pathways with a 230v test screwdriver or better a meter to see if everything is OK to the point of the zone valves. Then see if zone valve moves accordingly and if it passes the 230v on to boiler/pump (pump may be controlled seperately by boiler because of a pump overrun requirement)

If zone valve doesnt move a new synchronous motor may fix it, if it moves but doesn't pass on power a new microswitch or just change the head.

A new Honeywell 2 port valve is £36 plus vat. To change the head is very easy. Try it first, so you don't have to drain down. If it doesn't work drain down undo the two nuts and reuse them on the new valve.

 

[Pistol]

Thanks Tony. I've removed one of the motor wires (the blue one) but the spring hasn't pulled the valve closed. This means the valve is stuck open. This is turn means the microswitch is always closed which will always fire up the boiler and pump independent of whether or not the timer is active. So I need to change the valve. Sorry to ask such silly questions but I'm a novice trying to get my heating working again. Last question...does the whole thing have to be changed meaning draining the system? I know that the motorhead is interchangeable without draining but I would think the vlave itself (the bit in the water) is the bit that's seized?