Testing a 2 port zone valve?

[Dushami]

I’ve a problem with my mains pressure hot water tank not heating. I’m suspecting it’s the 2 port zone valve actuator (Siemens CZV222). Can anybody help me test this theory?
The system boiler works fine & any call for central heating fires it up.
The Water tank works when I switch on the aux heating element, it’s just that the boiler doesn’t fire up when I switch the water on at the controller. Normally we leave the water switched on all the time since the heat loss in the pressurised tank is so small.
If I switch on the water at the HW/CH controlle & slide the lever on the valve actuator from auto to manual, the boiler briefly fires up, but almost immediately goes off again. I’m assuming that there is some gubbins in the zone valve actuator that tells the HW/CH controller that it’s opened OK & maybe this is knackered? It’s either than or my controller is buggered. Any suggestions?

 

[stem]

With the hot water set to be 'on' if the valve has opened, when you slide the manual lever from auto to manual it should be loose and floppy. If there is some resistance the valve hasn't opened. This could be because the valve is faulty, or the controls haven't switched it on. If you have a multimeter and can test for 230V between the motorised valve's brown and blue wires, and find 230V present you will know the controls are telling it to open and the valve is faulty.

There is a microswitch inside the motorised valve that when the valve is fully opened by its motor, it operates the microswitch and starts the boiler. The manual lever is there for opening the valve when the system is being filled or drained, so the manual lever doesn't generally need to go far enough to operate the microswitch, (some do and some don't) it sounds like yours might just be operating it temporarily.

 

[ianmcd]

If I switch on the water at the HW/CH controlle & slide the lever on the valve actuator from auto to manual, the boiler briefly fires up, but almost immediately goes off again. I’m assuming that there is some gubbins in the zone valve actuator that tells the HW/CH controller that it’s opened OK & maybe this is knackered? It’s either than or my controller is buggered. Any suggestions?

That is exactly how it works, the lever is a manual valve used for filling the system, it will not fire the boiler, have you checked the over heat thermostat on your HW cylinder ? if you are not sure where it is post a pic of it and someone will tell you how to test it, really simple 5 second job, if that hasnt tripped most likely the synchron motor inside the HW motorised valve unlesss you have been fitting new controls or something

 

[Dushami]

It’s a tempest stainless from Telford Copper Cylinders.
Nothing new has been fitted.
It’s the motorised valve head that I think is gubbed. Here is a picture with the HW motorised valve head removed

 

[Dushami]

With the hot water set to be 'on' if the valve has opened, when you slide the manual lever from auto to manual it should be loose and floppy. If there is some resistance the valve hasn't opened. This could be because the valve is faulty, or the controls haven't switched it on. If you have a multimeter and can test for 230V between the motorised valve's brown and blue wires, and find 230V present you will know the controls are telling it to open and the valve is faulty.

There is a microswitch inside the motorised valve that when the valve is fully opened by its motor, it operates the microswitch and starts the boiler. The manual lever is there for opening the valve when the system is being filled or drained, so the manual lever doesn't generally need to go far enough to operate the microswitch, (some do and some don't) it sounds like yours might just be operating it temporarily.

I’ll get my multimeter. I can turn the valve easily when I’ve removed the MV.

 

[Dushami]

And… the bit that sticks into the valve, that turns easily, only moves about 20 degrees, is that normal?

 

[oldbuffer]

1.. That motorised zone valve is a key element in the safety system for an unvented cylinder. It should NOT be left in the open position.
2. Those cylinders should only be worked on by someone with a current "G3" accreditation.
3. If the valve turns easily with the head (actuator) removed, I'd suggest replacing the actuator. Like for like, same make and model.
4. The new actuator will need to be wired into the wiring centre exactly as the old one:
4.1 Electric power off to all parts of the system. Best turned off at the main switch on the consumer unit.
4.2 Open the wiring centre and identify the leads from the old actuator. Likely to be brown, blue, green/yellow, grey and orange wires. May also be an additional white.
4.3 Cut each wire an inch or so from the its terminal.
4.4 One by one remove each stub from its terminal and replace with the same coloured wire from the new actuator.
4.5 If the old and new actuators have a white wire, attach to terminal in the same way, or, if not used, seal the end with insulating tape.
5. You might be able to get away with changing just the motor, but its more fiddly and you have to join the wires within the valve.
6. 20 degrees is about right for a Honeywell valve, and some others.

 

[ianmcd]

It’s a tempest stainless from Telford Copper Cylinders.
Nothing new has been fitted.
It’s the motorised valve head that I think is gubbed. Here is a picture with the HW motorised valve head removed View attachment 294469

on the large white thermostat box there is a small black plastic cap, remove that its only finger tight, under there you will see a tiny pop up button press that and if it clicks then that has it been reset and that was the fault, if it doesnt then the motorised valve motor is the fault

PS you can not leave that set up running with the actuator removed like that

 

[Dushami]

I’m off to get a replacement. There is 233V across those motorised wires when the HW is switched on. Seems like the motor is gubbed. When I slide the auto / man lever right over, that’s when the boiler kicks in. It stops if I let it come back a few mm into the locked position. I’m assuming that’s the micro switch you’re talking about. I see I can buy a replacement motor, but it seems a bit risky. I might buy one and fit it to this MV head & keep as a spare…I’ll post back if this all works. Thanks

 

[Dushami]

on the large white thermostat box there is a small black plastic cap, remove that its only finger tight, under there you will see a tiny pop up button press that and if it clicks then that has it been reset and that was the fault, if it doesnt then the motorised valve motor is the fault

PS you can not leave that set up running with the actuator removed like that

That wasn’t the fault, but at least that’s checked. Mains is off to all this, I’m not leaving it like this for any length of time.

 

[Dushami]

1.. That motorised zone valve is a key element in the safety system for an unvented cylinder. It should NOT be left in the open position.
2. Those cylinders should only be worked on by someone with a current "G3" accreditation.
3. If the valve turns easily with the head (actuator) removed, I'd suggest replacing the actuator. Like for like, same make and model.
4. The new actuator will need to be wired into the wiring centre exactly as the old one:
4.1 Electric power off to all parts of the system. Best turned off at the main switch on the consumer unit.
4.2 Open the wiring centre and identify the leads from the old actuator. Likely to be brown, blue, green/yellow, grey and orange wires. May also be an additional white.
4.3 Cut each wire an inch or so from the its terminal.
4.4 One by one remove each stub from its terminal and replace with the same coloured wire from the new actuator.
4.5 If the old and new actuators have a white wire, attach to terminal in the same way, or, if not used, seal the end with insulating tape.
5. You might be able to get away with changing just the motor, but its more fiddly and you have to join the wires within the valve.
6. 20 degrees is about right for a Honeywell valve, and some others.

I’m happy to change the actuator & wire it in. Anything else will need an expert. It seems straightforward to wire in.

 

[ianmcd]

I’m happy to change the actuator & wire it in. Anything else will need an expert. It seems straightforward to wire in.

Technically just by removing the actuator head you have contravened regulations as you are noy G3 qualified so should not be touching it as it doubles as a safety device.
But if you are determined to change it buy one of these and simply cut the existing cable, and join the new actuator to the other end, and plug them together, that way you are not opening the wiring centre where if you get it wrong could be dangerous.

REGE105 REGIN 5 WAY PLUG / SOCKET WITH STRAIN RELIEF 5060026573891 | eBay

With strain relief. Complete with locking latch for added security.

www.ebay.co.uk

 

[stem]

1.. That motorised zone valve is a key element in the safety system for an unvented cylinder. It should NOT be left in the open position.

I've seen a few that have been manually latched open where the motor has failed and the occupier has left them manually open to get hot water. One claimed it had been like that since they had moved in 8 years earlier. As it's a safety device it's always surprised me that the cylinders don't come with a special valve without the manual lever and one that a standard powerhead wouldn't fit.

 

[Dushami]

All fixed. Thanks for all the input.

 

[ianmcd]

I've seen a few that have been manually latched open where the motor has failed and the occupier has left them manually open to get hot water. One claimed it had been like that since they had moved in 8 years earlier. As it's a safety device it's always surprised me that the cylinders don't come with a special valve without the manual lever and one that a standard powerhead wouldn't fit.

couldnt agree more @stem , also how many times have we seen a synchron motor seized in the made position? definately not fit for purpose