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[johnscales]

Breifly.
Gravity fed system (older/simpler with tap stat on cylinder) Hot water only, or water +C/H (No C/H only option.
2 way mechanical port packed in.
Can be operated manually by the switch so valve is definitelly ok.
Changed Syncron. No Joy.
Changed head. Still no joy.
Looking for the next step.

Currently thinking to try tests using a multimeter to see whether it could be electrical. Anyone have any full, clear and concise testing tips?

 

[stem]

Your system sounds a bit of a hybrid. Systems that don't have a 'CH only' option don't generally have motorised valve(s). Usually, the hot water part controls the boiler and the heating part the pump. So what is the motorised valve you refer to controlling?

 

[ServiceNumpty]

Are you asking why your central heating isn't working?
Programmer?
Roomstat?

 

[jeff the gasman]

Just check you’re getting 230v across brown and blue. If you aren’t it’s clock or stat.
Assuming spring return valve.

 

[johnscales]

Thanks for the replies fellas. Thought my brief description was sufficient but realise I didn't state what was affected.
@stem - "So what is the motorised valve you refer to controlling?" - Hot water to rads.
@MikeCip - Are you asking why your central heating isn't working? - No. It isn't working I see that I was not clear now. The C/H stopped working and the 2 way port controlling the flow of hot water to the radiators stopped and manually needs the leaver to be moved to the open position so I assumed it was the 2-way port at fault (It is/was very old mind). However, after making the changes I detailed above even the new one is still not actuating (Hope that ties up the issue at hand).
@jeff the gasman. This is what I wanted to know how to test. Thanks. Followed by what to look at next so thanks again.
Yes indeed, it is a spring return valve. Honeywell v4044 off the top of my head I think. Can you (or anyone for that matter) confirm that if the tap stat is gone then that could would the motor working as I think that's what you had implied?
Will check the 2 port valve is receiving power with the multimeter first in any case.
Ta

 

[jeff the gasman]

Tapstat is purely hydraulic mate. Nothing to do with electrics.
Brown and blue opens the valve.
Do yo have a cylinder thermostat? It is possible to wire your system with one but not with full control.

 

[johnscales]

Tap stat Not sure if it's the same thing but it's the one with the TRV(drayton 4) looking head with a spindly wire going to a thermometer attached a third of the way up the hot water cylinder.
So that means it can't be that right? which leaves the clock/programmer if I see 230v across brown and blue.
Last one so that i'm sure, should that 230v only show when the call for c/h is made?
Thanks again.

 

[johnscales]

Ignore the question at the end of that last post. I just re read what you wrote.

 

[stem]

Currently thinking to try tests using a multimeter to see whether it could be electrical. Anyone have any full, clear and concise testing tips?

As the motorised valve you refer to is controlling the central heating, it will get its power via the room thermostat and programmer (assuming you have both) so it will be a matter of tracing the wiring back to find the point where the power is lost. If you are competent to use a multimeter safely, this is the order that I would check. First set the programmer to be 'on' and turn up the room thermostat so that it is calling for heat.

Once a problem with the neutral has been ruled out, there should be 230V on all of the L terminals mentioned below. Working backwards, the point immediately before the L finally appears will be the source of the problem.

1) Check for 230V across the motorised valve N and a known working L (eg an adjacent socket) If the Neutral is faulty, check the neutral connections of the motorised valve back to source

2) If the neutral is OK, check for 230V across the motorised valve L and N

3) Next, check the room thermostat*. Is there a Live on the 'Switched Live' output (sometimes marked N/O) that goes to the motorised valve?

4) Is there a Live supply coming in to the thermostat?

5) At the programmer / timeswitch*, is there a Live present at the 'heating on' terminal of the programmer?

6) Is there a Live present on the L supply terminal at the programmer / timeswitch?

*To test the connections at the room thermostat and programmer, sometimes the device has to be removed to access them. This can be tricky as they will need to remain 'in circuit' for the tests to be carried out.

Depending on the model of room thermostat, there may not be a Neutral connection present to connect the multimeter to. If not, an adjacent N will need to be used.

 

[johnscales]

Thanks Stem. Very useful additional steps. My task will be simplified by way of the fact that there is no room thermostat to test. Feeling positive about the task in hand now. Have performed a number of changes to the system myself in the past. Replaced the timer/programer, swapped out the pump flushed the system and balanced the radiators all thanks to help from the site but nothing electrical to date so will be a new string to the bow so to speak. I'm used to using a multimeter knowledge of which has been a godsend over the years.
I will be testing the system later and post my update.

 

[johnscales]

Update.
So far so good in terms of the fault diagnosis. No power being seen at the electrical box for the 2port valve. Compared this with the boiler and the pump as both also have electrical boxes. They showed 230/240 when hot water was being being called for. My assumption therefore is that the programmer isn’t sending power to the 2 port motor.
Was a bit hot in there to swap out the programmer (Drayton lp722) so will inspect and replace on another date. Have been reading a few threads regarding people having the same symptoms as me with this programmer often resulting with a replacement.
Also read somewhere that the issue can also be to do with the plate that the programmer is mounted on. Any tips on what to check regarding that? I was able to wiggle the programmer around a small amount. It didn’t help or hinder any though.

 

[oldbutnotdead]

If you're handy with a soldering iron as well as with a multimeter it may be worth opening the programmer up and having a look at the circuit board- I had a similar issue years ago (S-plan system with 2 heating zones and 1 hot water zone), one of the tracks on the PCB had proved to be not up to the job of carrying enough current to open a motorised valve.

 

[stem]

There's quite an easy check for the LP722 programmer. The terminals for it are as below:

If you turn the power off, remove the programmer from the backplate, add a wire link between terminals (L) and (4) 'CH ON' replace the programmer, and turn the power on. That simulates the programmer setting the heating to be 'on'. If the motorised valve opens now, the programmer or its backplate is faulty.

It's difficult to check the connections between the backplate and the programmer because you can't access them when the programmer is connected. Usually , if I suspect the backplate then I will remove it and rewire the connections via screw terminals to replicate the internal connections of the programmer, but you need to fully understand how it works to do this. It's unusual for the backplates to fail though, unless they have been damaged; usually it's a matter of the programmer not being securely fixed onto it.

 

[johnscales]

Ahh makes sense seeing the diagram. That will complete the diagnostics for the electrics stem. I bought a replacement programmer yesterday so may just change it out anyway. If it fails intermittently thereafter I can (probably) safely assume the issue to be with the backplate.
Thanks again.

 

[johnscales]

In case it helps anyone in future, just wanted to confirm that after following all the tests advised above the fault lay with the programmer. Old one out, new one in then I saw 230V at the 2way valve port electrical box.
Set programmer C/H to on and (surprisingly) didn't hear it spool up. However, confirmed it was operational by manually attempting to move the spring. There was no friction. To confirm it I switched the power off, manually tried the lever. Friction. Turned system back on called for C/H again, manually tried the lever again. No friction. Rads became hot.
Success.

Thanks again all for your help.