Greenstar heatslave 25/32 DHW losing temp

[Keith Webster]

Hi I have a Greenstar heatslave 25/32 external boiler. For quite a while now the hot water has been losing temp after less than 5 minutes. The water drops right down to not even lukewarm. However if the heating is on, the water temp is better but still not as hot as it used to be. The CH works fine, I have had the sae firm that service the unit out to look at it but they have so far replaced the PCB and the DHW stat and neither have Mae a difference.
Wondered if there is a problem with the secondary heat exchanger? I also wondered about the diverter valve but I thought that would stop us even getting as much hot water as we get.

We had a leak on the main water line going to the boiler underground requiring putting in a new pipe to the boiler, could this have caused an issue with debris having got into the system.

Any help much appreciated.

 

[FarleyDarlo]

Fascinated to see what people post back on this, my problem is almost identical! New to oil fired boilers so thought this might be a peculiarity of the little header tank. We have a green star heatslave too had it serviced etc but hasn’t improved.

Although a 2min shower is doing my bit for water conservation I would prefer the choice of a proper hot shower

 

[snb]

There are a few points that need to be checked.
What is the hot water flow rate?
What output has the burner been set at? ( nozzle size)
Do you have thermostatic mixer showers fitted.
Does the problem happen at all tap outlets or only some?

 

[oilhead]

Classic flow switch symptoms, especially if the cold water supply is 'iffy'. The fault finding flow chart follows logical steps, but many service techies are too thick or too cocky to follow them.

 

[oilboffin]

Yup that's the one.Bob