Replacement Thermostat

[picasso]

Worcester bosch ri boilers suffer from this problem (heating staying on ) when a Honeywell 3 port valve is used, the back voltage (usually about 100v) is enough to keep boiler on, there is a capacitor suppliec by wb to stop this.

 

[ianmcd]

@picasso is correct the Ri has a problem with three port valves I had fotgotten about that, it is an easy fix though

 

[fixitflav]

Worcester bosch ri boilers suffer from this problem (heating staying on ) when a Honeywell 3 port valve is used, the back voltage (usually about 100v) is enough to keep boiler on, there is a capacitor suppliec by wb to stop this.

Interesting, I hadn't heard of that. But any idea why the problem has just arisen, when it's been OK for years?

 

[RP66]

Don't know if this helps but been playing around with different settings of timer and thermostat.
Timer calls for heat and hot water plus thermostat on - result radiators and water warm up.
Thermostat reaches desired temperature and clicks off but the radiators get hotter.
Switch heating off from timer radiators continue to get hotter.
Switch hot water off from timer, radiators cooldown.
Therefore tried switching the hot water off completly from timer then radiator system works fine switching on and off via the thermostat.

 

[Echo the husky]

Interesting, I hadn't heard of that. But any idea why the problem has just arisen, when it's been OK for years?

The capacitor can age with use, where its capacitance value drops. A very common problem in all sorts of things that use film capacitors in mains positions.

 

[fixitflav]

Don't know if this helps but been playing around with different settings of timer and thermostat.
Timer calls for heat and hot water plus thermostat on - result radiators and water warm up.
Thermostat reaches desired temperature and clicks off but the radiators get hotter.
Switch heating off from timer radiators continue to get hotter.
Switch hot water off from timer, radiators cool down.
Therefore tried switching the hot water off completely from timer then radiator system works fine switching on and off via the thermostat.

Read my #15. And posts on UK Plumbers' Forum.

 

[RP66]

Thanks for your help looks like I need a plumber

 

[picasso]

Bit more about the problem

https://diy.stackexchange.com/quest...nge-wire-boiler-stays-on-in-heating-only-mode