Heating only works when hot water is enabled - WTF?

[axelbrant]

Hi all,

Context:
- Worcester Bosch Greenstar 30CDi Classic System
- Hive Receiver and Thermostat

This started only recently:
- Switching heating on the thermostat in its own does not ignite boiler and provide heating
- When switching on Heating is followed by switching on Hot Water, then we have heating working
- Even if leaving BOTH Heating and Hot water ON together, after around 15 minutes heating stops anyway

Some observations:
- I have replaced Hive Receiver front plate, so I'm confident that signals are transmitted to boiler correctly
- Boiler shows no errors
- Heating system pressure is fine
- If heating at least sometimes works, then this is not with pumps or anything?

I can't figure out what is happening - please please can anyone help with any advice?

 

[gas112]

faulty central heating motorised valve its opening but not making the microswitch to bring boiler on ,

 

[axelbrant]

faulty central heating motorised valve its opening but not making the microswitch to bring boiler on ,

Can you suggest from the below list, which part should be replaced?

Worcester Bosch Diverter Valves (uk-plumbing.com)

 

[gas112]

put a pic up of your airing cupboard where the valves are

 

[axelbrant]

faulty central heating motorised valve its opening but not making the microswitch to bring boiler on ,

Can you suggest which part exactly should be replaced:
- Diverter Valve (body, actuator, motor)
- Hydraulic Valve

 

[axelbrant]

Pictures. Sorry for the mess.

 

[muggles]

Well, you've managed to miss it in all your photos, but you're looking for the other one of these...

 

[gas112]

pic 3 with pump and the valve with silver head on it , its the one to heating that is faulty you can just change the head on it no need to change entire valve

 

[axelbrant]

Yes found the other one, is this it?

 

[gas112]

yes honeywell powerhead
https://www.screwfix.com/p/honeywel...-replacement-powerhead-22mm-compression/326fv

 

[axelbrant]

Thanks a lot, you guys are amazing!

 

[muggles]

I think Gas112 called it correctly though and it's actually the one I drew an arrow to, rather than the other one

 

[Elkato531]

Might be a good idea to get that megaflo serviced as well. Looks like its been discharging through the tundish for a while.

 

[axelbrant]

UPDATE: I have changed the powerhead the same day on Friday, and it all worked like a charm!!!

But - midday today I'm afraid this is all over again - no reaction to thermostat signals. the new powerhead is somewhat warm, even if the underlying pipes are cold.

Please guys, any further advice on this?

Maybe that's something with wiring and I should rewire the whole box below? It really has 4-5 wires coming into the same slot at times..
How would I test the powerhead is operational?

 

[axelbrant]

Looks like the hot water valve was closed despite the fact it was switched on. So replacing the other one as well. Will replace just a motor (£15 instead of £50 for the whole powerhead).