Help, my boiler is being lazy!

[StephenStephen]

Hi there, I just wanted to check it's not something I can check before I get an engineer out...
Basically the system boiler isn't heating the water for the hot water tank as hot as it used to.
Details: Worcester Bosch Greenstar 35 CDi Classic, about 4 years old, serviced annually by the local company that installed it, always worked well.
I noticed today that it just isn't heating the water going to the tank as hot as it used to. Thermostat on tank is up and clicked on, tap water power on boiler is set higher, not sure what else to look at,
Thanks for your thoughts, let me know if you want different info or pics.

pictures below:

 

[dilalio]

Are any of your rads getting hot?
Check for crossover at any mixer valves (showers etc). Cold could be crossing over to hot.

 

[Lower]

when the boiler is firing to heat the hot water only, what number do you get on the digital display?

 

[Johnmdc]

On this system boiler when you have external motorised valves only the thermostat with the picture of the radiator is used.
The one with the picture of the tap doesn't do anything unless it has an integral motorised valve. (Which you don't)
So basically you need to turn up the thermostat with the picture of a radiator on it.

 

[StephenStephen]

when the boiler is firing to heat the hot water only, what number do you get on the digital display?

It goes up to about 50, then drops back to about 42

 

[StephenStephen]

On this system boiler when you have external motorised valves only the thermostat with the picture of the radiator is used.
The one with the picture of the tap doesn't do anything unless it has an integral motorised valve. (Which you don't)
So basically you need to turn up the thermostat with the picture of a radiator on it.

Thank you - I'll try that in the morning

 

[StephenStephen]

Are any of your rads getting hot?
Check for crossover at any mixer valves (showers etc). Cold could be crossing over to hot.

I've not noticed any hot radiators - I'll check in the morning
Is this something that could change by itself?
Could this effect the temperature of the pipes coming out of the boiler?
It's been working fine until very recently and no recent changes in the plumbing.

 

[dilalio]

I've not noticed any hot radiators - I'll check in the morning
Is this something that could change by itself?
Could this effect the temperature of the pipes coming out of the boiler?
It's been working fine until very recently and no recent changes in the plumbing.

OK. No.
If there's a noticeable difference (to you) in the flow from boiler then boiler is the place to start.
Put your heating on and see how the boiler performs.
When on DHW, can you feel heat going into the cylinder coil?
Check motorised valves are opening and closing according to demand.

First things first, turn boiler stat up as mentioned above.

 

[StephenStephen]

Thanks all, yes that worked - turning up the central heating temperature control increased the temperature going to the cylinder coil.
The feeds to all the CH loops remained cool beyond their motorised valves.
I assume the hot water motorised valve is working correctly - it's making a noise on being turned on and turned off, and the hot water is moving through it.
Much appreciated and relieved

 

[CBW]

Check for crossover at any mixer valves (showers etc). Cold could be crossing over to hot.

Would that still happen on an unvented cylinder?

 

[dilalio]

Would that still happen on an unvented cylinder?

Yes. It could. Depends if supplies are balanced!