Potterton suprema boiler heating not working but water is ok..

[MANDATE]

Have looked at your problem. To me it would appear there is nothing wrong with programmer or the room stat.
The problem is the 3port mid position valve.
It could just be stiff and too much resistance for the motor to drive the valve over the second half.
Test by removing the head from the spindle and try turning spindle with fingers.
If the valve spindle is free. The fault relates to the actuator head.
It could be a wiring problem or if it has worked OK, it's most likely a microswitch problem..
There are two microswitchs, each with two pairs of contacts cover four functions.
The functions include
Supply power to drive motor over first half of range
Supply power to drive motor over second half of range
Supply power out from valve to boiler/pump.
It could be the valve moves to the CH position, 2nd microswitch at fault would stop boiler from operating.
It could the valve will not go beyond mid position. This being due t 1sr microswitch problem..
So first check valve for stiffness, Then verify wiring is in order and finally replace the actuator head.
Note 5 wires
White room stat to valve
Grey. HW off to valve
Orange. Valve to boiler/pump
Blue Valve to Neutral
Green/yellow. Valve to earth

 

[gaz1234]

I agree looks like the actuator is at fault. I'll irder a new one and replace.

I think there is a problem with the programmer though as I said boiler only comes on when water control comes on which then causes the heating to work. Heating won't come in by itself without water on..

Assume a tado starter kit and extender will work and rand the heating and water controls to be left in 'on' portion?

 

[Scarum]

Just change the actuator. As Mandate has advised above if the valve spindle is stiff you should consider replacing that in the long-term as the replacement actuator may burn-out in time.

 

[gaz1234]

Just change the actuator. As Mandate has advised above if the valve spindle is stiff you should consider replacing that in the long-term as the replacement actuator may burn-out in time.

Ah so the valve spindle is inside the pipe unit and isn't part of the actuator?
Do I need to turn the water and boiler off to replace actuator?

 

[gaz1234]

Surely if the valves at fault then as you say the new one might break //www.diynot.com/diy/threads/potterton-motorised-valve.4923/ in which case would it not be worth replacing the whole unit for the Honeywell one?

 

[gaz1234]

Right so after having it in the manual position for a few days there is now no resistance on the lever when taking off manual

 

[MANDATE]

You're not supposed to use the lever while boiler is in operation. The lever is used during refilling of the system it holds the valve in mid position so water can get to both sides and prevent air locks.
When you select HW and CH, from cold the valve goes to the mid position. But this is not a permanent position.
It lasts only till one side gets satisfied and then opens up the non satisfied fully.
You need to understand the boiler gets it's power from the cylinder stat for HW and HW/CH, but not for CH only.
The power comes from the orange wire of the valve and if it does not, then actuator is faulty or not wired correctly

 

[gaz1234]

Thanks for all your help. Actuator replaced and all seems ok now. Still think there is an issue with the programmer. Probably needs a clean as switches are sticky...
The CH and HW lights are on the actuator and the switch is loose when moving from auto to manual. Assume this is correct as valve open passing water?