motorized valve sticking when hot

[paradigm]

A query on a gas fired CH and HW system with honeywell V4043H motorized valves. The CH works fine, so does the HW when the system is switched on from cold.
When the water warms up, the HW valve sticks in the open position. The electrics must be ok. Do I replace the whole valve?

 

[D_Hailsham]

Don't recognize that number! Is it a Smartfit system?

 

[paradigm]

The correct number of the valve is V4043H.

 

[seco services]

Thats not a smartfit code either.

 

[D_Hailsham]

The correct number of the valve is V4043H.

OK. That's a regular 2-port zone valve.

Does the cover have a little bump (about 5mm across) at one end? If so the actuator (that's the box part) is removable.

Turn the power off
Remove the end screw and lift the cover off.
You will see two screws in diagonally opposite corners
Undo them and the actuator can be removed. NO water will escape.

Now try turning the valve spindle by hand (it will turn less than a quarter turn).

If it's easy to turn, the problem is in the actuator. But if it's stiff, try lubricating the shaft with a little WD40 or silicon lubricant.

If that doesn't fix it, you can replace the seals round the spindle using Part No "272752A/U CARD". This will require draining down to below the valve.

 

[paradigm]

Thank you D_H. The valve was fitted ~38 years ago and does not have the bump. I have already stripped it down and have cleaned the cog on the servo motor and on the ratchet. I will now lubricate the spindle as you suggest and report.

 

[misterdubya]

I will now lubricate the spindle as you suggest and report.

You cannot remove the actuator.

 

[paradigm]

My previous description of symptoms was incorrect. The valve does not stick and its number is immaterial.
From cold: when power is supplied the valve opens, the extractor fan starts after ~20 seconds and the gas is ignited after ~30s. After ~ 2 minutes the gas is extinguished but the valve remains open and the circulating pump continues working.
The problem is thus electrical?

 

[seco services]

Thats not a valve issue then.

 

[D_Hailsham]

My previous description of symptoms was incorrect. The valve does not stick and its number is immaterial.

It helps to know what's really wrong!

the valve opens
fan starts after ~20 seconds
gas is ignited after ~30s
After ~ 2 minutes the gas is extinguished but the valve remains open and the circulating pump continues working.

The problem is thus electrical?

More likely to be a faulty gas valve.

You will need a Gassafe registered engineer to sort it out.

 

[gasafengineer]

the valve opens
fan starts after ~20 seconds
gas is ignited after ~30s
After ~ 2 minutes the gas is extinguished but the valve remains open and the circulating pump continues working.

More likely to be a faulty gas valve.

What leads you to believe it's a gas valve fault?

 

[D_Hailsham]

the valve opens
fan starts after ~20 seconds
gas is ignited after ~30s
After ~ 2 minutes the gas is extinguished but the valve remains open and the circulating pump continues working.

More likely to be a faulty gas valve.

What leads you to believe it's a gas valve fault?

After ~ 2 minutes the gas is extinguished but the valve remains open and the circulating pump continues working.

The valve remaining open means that the valve motor is still working.
The pump still working tells us that the microswitch in the valve is still closed.

Voltage is therefore still getting to the boiler. So something is causing the gas valve to shut off.

OK, it might not be a faulty gas valve, but it's definitely something in the boiler (we don't know which make/model the OP has), so either way the services of a GSR person will be required.

 

[gasafengineer]

Hope the OP hasn't already gone out & purchased a gas valve , prime example of being called to a breakdown & the customer standing there with a part.