Sorry – this is a long post.
I replaced a very old and failing Sunvic timer (I think an MP2) a few months ago using a Drayton LP722 Programmer.
At the same time I replaced the capacitors in the share valve in the system – a Sunvic Unishare 3-Port MoMo motorised valve, as in this webpage : http://www.seered.co.uk/sunvic.htm (which is “Seered” from this forum’s page)
The system worked fine for a few months, but one morning there was no hot water or central heating.
No matter what the boiler won’t come on. The pilot light is there, and you can hear the switching happening, the pump runs, the boiler power light comes on, but no actual firing up of the boiler.
I’ve gone through the tests in step 17 of this post (The FAQ post stickied to the top of this forum):
http://www.diynot.com/forums/plumbing/boiler-central-heating-faqs.175736/page-2
but have a couple of weird results. Before I give up and call someone in, can I just run through the results and double check in case anyone has any ideas / spots any stupid errors of mine?
The Drayton LP722 is wired as per Drayton’s instructions, for a Mid-Position Valve System, with the programmer set to “P”. This is the same as the wiring shown in this post ( http://www.diynot.com/network/D_Hailsham/albums/16/31288 ) – with the sole exception of terminals 7 & 8 in the wiring centre being swapped (so logically it’s the same).
The Sunvic 1901 valve is supposed to be “industry standard wiring” so apart from the valve not returning by spring as per the tests, it should produce the same results(?)
I did some initial tests and suspected the cylinder stat – a very old Sunvic type that I cannot find anymore, so I replaced with a Drayton HTS3 – but I get the same results - and voltages.
Here are my results (in red) interleaved with the relevant tests from the FAQ (Sorry reproduced so much here, but I couldn't see how to shorten with out removing the context):
Mechanical: valve sticking or valve passing.
The valve is not sticking, it rotates fully as called for by the programmer.
CH Only Test (Port A open)
Turn Power OFF at main connection for the system (turning CH and HW OFF at programmer is not sufficient) This resets the valve to rest position
Disconnect white valve wire from terminal T5 and grey wire from terminal T7.
Connect white and grey wires to permanent Live (T1)
Turn Power ON
Valve should move over so port A is open and boiler light (check by feeling that only the pipe from port A gets hot)
If the valve does not move, Switch S1 is not moving over.
If the valve moves but the boiler does not light, switch S2 is not moving over. (check 240V on orange)
The valve moves, the pump runs, the boiler power light comes on
Checking the orange share wire I get 240V…
HW Only Test (Port B open)
Power OFF (valve returns to rest position)
Turn HW stat to lowest
Disconnect grey and white from permanent Live (T1) and temporarily make safe (e.g connect to spare terminals in the wiring centre)
Disconnect cylinder stat Common from T6 and connect to permanent live (T1)
Power ON
Turn cylinder stat to max.
Boiler should light. (check by feeling that only the pipe from port B gets hot)
If it does not light, the cylinder thermostat is suspect (check for 240V at Common and Call terminals of cylinder stat and at terminal 8 ).
The pump runs, the boiler power light comes on.
I get 240V at Common and Call and the terminal. BUT I also get 190V from the HW-OFF at the cylinder stat – that seems odd to me. This is why I replaced the Stat but I get the same from the new one.
CH and HW Test (Ports A and B open)
Power OFF
Turn cylinder stat to lowest
Disconnect cylinder stat wire from permanent live (T1) and reconnect to original terminal (T6)
Disconnect white wire from temporary location and connect to permanent Live (T1)
Power ON
Valve should move to mid position
Turn Cylinder stat to max
Boiler should light (check that pipes from ports A and B both get hot).
If boiler does not light cylinder stat is faulty
Pump runs, the boiler power light comes on, boiler doesn’t light. I have changed cylinder stat – but it still doesn’t work
Power OFF
Reconnect white and grey to original terminals (T5 and T7)
Turn HW OFF and CH ON
Set CH stat high
Turn Power ON
Valve should move to Port A open, boiler light and Port A get hot.
Pump runs, the boiler power light comes on, boiler doesn’t light.
Turn CH OFF, so boiler goes out.
Boiler should go out but valve stay in CH only position
If boiler does not go out, check voltage on orange wire.
If orange has 240v, the actuator is faulty
If orange has 50-150v, there is a problem with the boiler
0V on Orange wire
If these tests are passed, the problem is elsewhere.
Testing other components
Cylinder thermostat: disconnect wires from CALL (1) and SAT (2) terminals when checking, this prevents false readings due to back feed.
There should be 240V on Call (1) when stat is turned up and 240v on Sat (2) when stat is turned down
Stat up – call 150V, satisfied 70V
Stat down – call 50V, satisfied 160V
Room thermostat: disconnect wire from Switched Live when checking to prevent false readings due to back feed.
There should be 240v on Sw L (3) when stat is turned up and 0V when it is turned down.
240V turned up
24V (24, not 240) turned down…
Note: you may find that terminals 1 (live) and 3 (Sw Live) of the thermostat have been swapped over. This is not too important for modern digital thermostats but should be corrected if you have the older mechanical thermostat.
Given the voltages this appears to be wired correctly.
Programmer: Check voltages at CH ON, HW ON and HW OFF terminals when programmer set to appropriate positions. Also check the voltages when the timer is used to switch on/off.
Checking directly at the programmer terminals, and at the various settings (CH+HW off, CH only, HW only, CH+HW On), I get:
With cylinder thermostat up:
Terminal: CH+HW Off / CH-On / HW-On / CH+HW On
CH-ON: 0V / 240V / 0V / 240V
HW-ON: 0V / 240V / 240V / 240V
HW-OFF: 240V / 240V / 0V / 0V
With cylinder thermostat down:
Terminal: CH+HW Off / CH-On / HW-On / CH+HW On
CH-ON: 0V / 240V / 0V / 240V
HW-ON: 240V / 240V / 240V / 240V
HW-OFF: 240V / 240V / 240V / 240V
This does not look right to me – the HW-OFF appears to be giving 240V in situations when it should not be, and calls for CH or HW?
End of tests
So, given that it worked ok for 3 months, the tests give results that to me are odd, any ideas welcome!
I replaced a very old and failing Sunvic timer (I think an MP2) a few months ago using a Drayton LP722 Programmer.
At the same time I replaced the capacitors in the share valve in the system – a Sunvic Unishare 3-Port MoMo motorised valve, as in this webpage : http://www.seered.co.uk/sunvic.htm (which is “Seered” from this forum’s page)
The system worked fine for a few months, but one morning there was no hot water or central heating.
No matter what the boiler won’t come on. The pilot light is there, and you can hear the switching happening, the pump runs, the boiler power light comes on, but no actual firing up of the boiler.
I’ve gone through the tests in step 17 of this post (The FAQ post stickied to the top of this forum):
http://www.diynot.com/forums/plumbing/boiler-central-heating-faqs.175736/page-2
but have a couple of weird results. Before I give up and call someone in, can I just run through the results and double check in case anyone has any ideas / spots any stupid errors of mine?
The Drayton LP722 is wired as per Drayton’s instructions, for a Mid-Position Valve System, with the programmer set to “P”. This is the same as the wiring shown in this post ( http://www.diynot.com/network/D_Hailsham/albums/16/31288 ) – with the sole exception of terminals 7 & 8 in the wiring centre being swapped (so logically it’s the same).
The Sunvic 1901 valve is supposed to be “industry standard wiring” so apart from the valve not returning by spring as per the tests, it should produce the same results(?)
I did some initial tests and suspected the cylinder stat – a very old Sunvic type that I cannot find anymore, so I replaced with a Drayton HTS3 – but I get the same results - and voltages.
Here are my results (in red) interleaved with the relevant tests from the FAQ (Sorry reproduced so much here, but I couldn't see how to shorten with out removing the context):
Mechanical: valve sticking or valve passing.
The valve is not sticking, it rotates fully as called for by the programmer.
CH Only Test (Port A open)
Turn Power OFF at main connection for the system (turning CH and HW OFF at programmer is not sufficient) This resets the valve to rest position
Disconnect white valve wire from terminal T5 and grey wire from terminal T7.
Connect white and grey wires to permanent Live (T1)
Turn Power ON
Valve should move over so port A is open and boiler light (check by feeling that only the pipe from port A gets hot)
If the valve does not move, Switch S1 is not moving over.
If the valve moves but the boiler does not light, switch S2 is not moving over. (check 240V on orange)
The valve moves, the pump runs, the boiler power light comes on
Checking the orange share wire I get 240V…
HW Only Test (Port B open)
Power OFF (valve returns to rest position)
Turn HW stat to lowest
Disconnect grey and white from permanent Live (T1) and temporarily make safe (e.g connect to spare terminals in the wiring centre)
Disconnect cylinder stat Common from T6 and connect to permanent live (T1)
Power ON
Turn cylinder stat to max.
Boiler should light. (check by feeling that only the pipe from port B gets hot)
If it does not light, the cylinder thermostat is suspect (check for 240V at Common and Call terminals of cylinder stat and at terminal 8 ).
The pump runs, the boiler power light comes on.
I get 240V at Common and Call and the terminal. BUT I also get 190V from the HW-OFF at the cylinder stat – that seems odd to me. This is why I replaced the Stat but I get the same from the new one.
CH and HW Test (Ports A and B open)
Power OFF
Turn cylinder stat to lowest
Disconnect cylinder stat wire from permanent live (T1) and reconnect to original terminal (T6)
Disconnect white wire from temporary location and connect to permanent Live (T1)
Power ON
Valve should move to mid position
Turn Cylinder stat to max
Boiler should light (check that pipes from ports A and B both get hot).
If boiler does not light cylinder stat is faulty
Pump runs, the boiler power light comes on, boiler doesn’t light. I have changed cylinder stat – but it still doesn’t work
Power OFF
Reconnect white and grey to original terminals (T5 and T7)
Turn HW OFF and CH ON
Set CH stat high
Turn Power ON
Valve should move to Port A open, boiler light and Port A get hot.
Pump runs, the boiler power light comes on, boiler doesn’t light.
Turn CH OFF, so boiler goes out.
Boiler should go out but valve stay in CH only position
If boiler does not go out, check voltage on orange wire.
If orange has 240v, the actuator is faulty
If orange has 50-150v, there is a problem with the boiler
0V on Orange wire
If these tests are passed, the problem is elsewhere.
Testing other components
Cylinder thermostat: disconnect wires from CALL (1) and SAT (2) terminals when checking, this prevents false readings due to back feed.
There should be 240V on Call (1) when stat is turned up and 240v on Sat (2) when stat is turned down
Stat up – call 150V, satisfied 70V
Stat down – call 50V, satisfied 160V
Room thermostat: disconnect wire from Switched Live when checking to prevent false readings due to back feed.
There should be 240v on Sw L (3) when stat is turned up and 0V when it is turned down.
240V turned up
24V (24, not 240) turned down…
Note: you may find that terminals 1 (live) and 3 (Sw Live) of the thermostat have been swapped over. This is not too important for modern digital thermostats but should be corrected if you have the older mechanical thermostat.
Given the voltages this appears to be wired correctly.
Programmer: Check voltages at CH ON, HW ON and HW OFF terminals when programmer set to appropriate positions. Also check the voltages when the timer is used to switch on/off.
Checking directly at the programmer terminals, and at the various settings (CH+HW off, CH only, HW only, CH+HW On), I get:
With cylinder thermostat up:
Terminal: CH+HW Off / CH-On / HW-On / CH+HW On
CH-ON: 0V / 240V / 0V / 240V
HW-ON: 0V / 240V / 240V / 240V
HW-OFF: 240V / 240V / 0V / 0V
With cylinder thermostat down:
Terminal: CH+HW Off / CH-On / HW-On / CH+HW On
CH-ON: 0V / 240V / 0V / 240V
HW-ON: 240V / 240V / 240V / 240V
HW-OFF: 240V / 240V / 240V / 240V
This does not look right to me – the HW-OFF appears to be giving 240V in situations when it should not be, and calls for CH or HW?
End of tests
So, given that it worked ok for 3 months, the tests give results that to me are odd, any ideas welcome!
