Zone valve fault ?

[gregoski]

Hi all, I'm new to this forum and I think it is absolutely fantastic, I've found so many answers here as I am proud diy'er, anyway I suspect zone valve on my HW is permanently open, basically when HW is off and CH set to on at the control panel I get very hot water coming from taps all the time.
The slider is in auto mode and when I put my hand on the pipe connected to valve's outlet it is very hot.
My question is how to test zone valve, it is common honeywell 2 port valve.

Thanks

 

[footprints]

When the power is off does moving the lever to "man" give any resistance and do you get a whirring sound when you release it back?
If not chances are yes it is stuck in the open position.

 

[stem]

The water at the taps may still be hot when the valve is closed, because you have 200 litres or so of it stored in an insulated cylinder.

A basic test of the valve can be made by switching off the heating and hot water, and allowing the pipes to cool completely. Then, with the hot water selected to 'off' start up the central heating. Does the pipe going to the Hot Water motorised valve heat up as rapidly as the one going to the central heating? If it does then it is not closing properly and water is glowing through it. It would be normal for it to get warm due to conduction of the pipes, but it shouldn't be hot.

It is rather unusual for a valve to stick open, because they are pulled closed by a spring. They normally fail in the closed position.

 

[gregoski]

Thanks footprints, Yes when the power is off it gives resistance on lever when moving to man/open and it is whirring when released on way back to original position.
At the moment I've turned all off to cool down and will check pipes temperatures as suggested by stem

 

[gregoski]

Took zone valve off to confirm and found blockage see images

 

[footprints]

Check the point at which the cold feed from the loft joins the system, chances are it will be even worse there. I would clean as much crug out of the pipework while you have it drained and fit a new valve you will never get the inside really clean on the old one.

 

[gregoski]

I have installed new honeywell zone valve and yes I had to remove the whole pipe assembly to clean it, yes it was really clogged up.
It is now working as it should, I'm now quite worried about the rest if the ststem including the boiler.

 

[footprints]

Most of the solid stuff will be around the area you found it, near the cold feed entry. The black sludge (which is a form of rust) tends to solidify where cold water enters the hot system, don't ask me why, I'm a pipe strangler not a scientist . Your system has a fault that is causing sludge to form, usually due to air entering the system either from a pipework fault, or leakage leading to constant fresh water entering.

A couple of fairly simple things you can check.
Tie up the ball valve in the header tank note the level of the water when cold and check daily for a week or so to see if the level drops, if it does you have a leak that needs fixing.

Get someone to help and get them to switch the system on and off hot water heating separately and together all the combinations, while you watch the tank. if water pours from the open vent into the tank it is pumping over.

Then take a bottle or jug (the old style milk bottles were ideal) fill it about three quarters full from the tank then push it up over the vent pipe that discharges over the tank so the open end is at the bottom of the container then as your assistant goes through the on/off operations again, watch it and see if the water is sucked up the open vent if so it is sucking in air.
Both result in air entering the system.

 

[gregoski]

Thanks footptints, I will do that, this sytstem is very old and probably never looked after properly, I have already done a lot of cleaning work including 5 radiators were removed for flushing, we only live there since May and obviously when cold days came and CH was in use all the faults started.

 

[gregoski]

I have 2 tanks in the loft,

Then take a bottle or jug (the old style milk bottles were ideal) fill it about three quarters full from the tank then push it up over the vent pipe that discharges over the tank so the open end is at the bottom of the container then as your assistant goes through the on/off operations again, watch it and see if the water is sucked up the open vent if so it is sucking in air.
Both result in air entering the system.

The open vent pipe on top of central heating tank is actually submerged in tank's water ( by about 5-10 mm) is this ok?
Obviously the bottle test can't be done at this point. I will have to lower the level of water in the tank

 

[footprints]

No the pipe should terminate above the water level generally speaking the water level will be about half way up the tank and the pipe will just pass through the lid by an inch or two.

 

[gregoski]

Thanks for all your advice, Happy Christmas

 

[gregoski]

Looks like this is not the end of problems with my zone valves, I've turned off CH earlier on this evening and noticed that all radiators stay hot.

Using the same method as before I've checked zone valve for CH and it shows the same symptoms also the lever has very little resistant movement when powered off.

Well another busy evening for me, I wonder if it is caused by the same rusty sludge.

 

[footprints]

Never rains but it pours!
You could try a sludge remover like
http://www.screwfix.com/p/fernox-f3-central-heating-cleaner-500ml/51463
Then flush repeatedly before adding an inhibitor.
Lots out there but I would stick with Fernox or Sentinel brands myself, they are not a magic cure but worth a try.
I tend to think Power flushing is often an expensive add-on con but might be worth considering as a last resort.

 

[gregoski]

Thanks mate, I had Sentinel X800 added to the system 2 weeks before first valve fault than I have put X100 inhibitor, I'm worried that these products dislodge large chunks of rusty sludge.
Than it travels in the system to cause trouble, anyway nothing more I can do at the moment, I will probably replace second valve, do another flush and see what will happen.
Cheers