Faulty timeclock or mid position valve?

[guychopper]

hi there i have a problem with my heating system. The problem started with turning the ch on,I could not turn it on when the hw was on.If i turned it on the light to indicate that it was on lit up but the heating did not come on.If i turned the hw off then turned the ch on i would hear a click,light on,ch on.I could not then turn the hw on.
I reset the clock then tried again,unfortunately the ch light did not work now.The hw worked fine so i went to the local stores and purchased a replacement clock.The clock was exactly the same model so i thought that would sort the problem. Unfortunately i had the same prob!
I had my sparky friend round to have a nose over it and he done a bit of head scratching.he checked the system over and tried a few things.He removed the clock and bypassed it,valve worked ok,ch and hw.He switched the clock so hw turned the ch on,worked ok.He thinks there might be a prob with the mid positon actuator as when he tested it he was getting different voltage readings off it and this could have maybe damaged the timeclock.
can anybody shed a bit more light on the situation please? I have replaced the timeclock,but not fitted yet(old one still on)and was going to get a new mid pstn actuator to go on the existing valve.Am i barking up the wrong tree?

 

[twgas]

Has, to your knowledge, the system ever worked properly?
Is there a wire connected to HW off (this is usually No3 on the programmer)?
Do you have a meter with which to test for voltages?

 

[guychopper]

Hi there just a quick lowdown on our system.We moved in 3 years ago and had the timeclock,roomstat and cylinder stat changed.It was the old type clock so we went digital.Also we hadn't used the ch or hw so dont know if there was ever a fault before.Had a problem with the boiler which was when we had the hw on, the boiler would fire up then make a loud vibrating noise(like a bus outside your house),then cut out.To get round this we had to have the heating on also to stop this happening.We had a gas engineer sort the problem out.After that it worked fine.
Now ive just taken the clock off and had a look at the wiring behind.The four numbers are as follows 1-hw off,2-ch off,3-hw on and 4-ch on.I have wires going into 1,3 &4. Nothing going into 2.

 

[guychopper]

also my meter is on its way out but i can get hold of another one if so.

 

[twgas]

yeah, I should have said No1 NOT No3

Then you need to check voltages in wiring centre on wires from 3-port:
HW on, cyl stat up,CH off; orange - 240v, white - 0v, grey - 0v.
HW on, cyl stat down, CH off; orange - 0v, white - 0v, grey - 240v
HW off, cyl stat up or down, CH off; orange - 0v, white - 0v, grey - 240v
HW off, cyl stat up or down, CH on; orange - 240v, White - 240v, Grey - 240v.

 

[guychopper]

Hi there please accept my apologies for the late reply,i wont bore you with the story. I've done as suggested and here are my results.
1) orange 240v,white 27v,grey 0v
2) orange & white 0v,grey 240v
3)orange & white 0v,grey 240v
4)orange & white 0v,grey 240v

The 1st result gave a slightly different result than you would have expected.The last result was also different to what you expected.

As i mentioned in an earlier post the hw controls fine,the clock works as expected. The problem is the ch,the backlight of the clock lights up to say that you,ve pressed the function but nothing else. There is an led which should light up and a click (relay?) be heard. Can anything be read into the 27v recieved in the 1st result? Thanks look forward to your reply

 

[twgas]

27v on the white @ 1) is fine - a little back feed through the valve circuitry.
As you are getting no power with CH on I would be checking the roomstat for power, 240v in and out, if 0v in either prog fault or wiring/connection to r/stat, if 240 in but 0v out r/stat fault, if 240v out wiring/connection from r/stat to wiring centre (connection to white wire from valve)
hth

 

[guychopper]

Hi there i've turned the central heating on the timer but nothing happens. I've taken the front off the roomstat and checked the voltage. I have 3 wires: red which connects to no1,yellow which connects to no3 and a blue wire which is not connected(tucked away in box behind). The voltage reading i am getting off both red and yellow is 27v.
I have a brand new timeclock which i can fit but have a query with this.If i have a problem with the motorised part of the 3 port valve could that affect the new timeclock (blow it) as i have already returned. 1 Also what would be the best way to check the timeclock before fitting?
It just seems strange to me that the hw side work ok on the clock but the ch doesnt
Thanks.

 

[twgas]

turn OFF power, remove prog from backplate, link l & 4, refit prog, reinstate power. Does heating now work, with room stat up and go off with roomstat down?
if yes then you have a faulty prog, if no, do you have 240v or 27v at roomstat?

 

[guychopper]

Hi there just fitted the link and the central heating works with the roomstat. Will try fitting the new timeclock now,here goes !!

Thanks

 

[guychopper]

Just fitted new timer and still no good

As its the same timeclock the only thing i havent changed over is the backing plate. Could this have any small effect on it? Also would i be able to check this new timeclock.If it is this i must be very unlucky!

Thanks

 

[guychopper]

Hi there i've been up to allsorts today. Firstly i returned the clock to the shop and got them to check it out.They tested it by putting a bit of flex with a live and neutral to it and trying the clock,it worked fine. I returned home and tested my original clock in the same way, hw water worked fine but ch did not work at all. Returned to the shop where he tested it and confirmed that ch did not work.Got a new clock off the shelf and tested it there,worked fine.Returned home with it,fitted it,hw worked fine ch did not

I'm getting a bit confused with the strange goings on. Any more suggestions would be greatly appreciated.I will happily persevere.

Thanks

 

[twgas]

Is there a switch on the back, P-G, should be set to P(umped).
Have you tried HW and CH together?

 

[D_Hailsham]

Hi there i've turned the central heating on the timer but nothing happens. I've taken the front off the roomstat and checked the voltage. I have 3 wires: red which connects to no1,yellow which connects to no3 and a blue wire which is not connected(tucked away in box behind). The voltage reading i am getting off both red and yellow is 27v.

27v sounds like back feed.

Check room stat
Find the white and grey valve wires and disconnect them. make a note of terminal nos
Check voltage on "white wire" terminal with CH ON and room stat up, should be 240V.
Turn stat down and voltage should drop to 0v.
If you get the correct voltages with turned stat up and down then the stat is OK and so is the CH side of the timer.
Turn CH OFF
Check cylinder stat
Disconnect orange wire. Make a note of terminal no
Measure voltage on the "grey terminal" with the HW ON and HW stat high (boiler should light); should be 0V. Voltage on "orange terminal" should be 240V .
Turn HW stat down (boiler goes off); voltage should now be 240V on "grey" and 0v on "orange".
Turn HW stat up and HW OFF at timer (boiler goes of); should get same results.

Check Valve
Connect white wire to a permanent live, turn HW ON and HW stat up. Valve should go to mid-position (feel pipes) and boiler run.

Reconnect Orange wire and connect grey wire to permanent live.
Valve should go to CH only (feel pipes) and boiler light.

If the result are OK the problem is not in the valve, timer or either stat. We need to look elsewhere. Reconnect the white and grey wires to the correct terminals so the boiler works while we scratch our heads.

 

[guychopper]

Hi there just checked the back of the clock to confirm what you asked. The clock is set to pumped. Im sure that i tried turning both on as well but just to confirm i have just done it. Can't believe my eyes it just worked

I just put the timer straight on without the backup battery in or 2 jumper switches. I was going to leave the jumper switches out as they are for frost protection and a temperature control option. I will remove the timer and place the battery in the clock. Fingers crossed that it works again,i will do that now and give it a go. Thanks for all your help,here goes