worcester greenstar 28i hot water issues

[freezy121]

Hey guys,

Having issues with a worcester 28i junior combi. Heating is fine but when the hot water is in use it stays hot for around 30 seconds to a minute than runs cold. The boiler does not lock out and the hot water does not come back on. If the taps is then closed and re opens the same process happens. Hot for a short while than cold again.

I have thought it could be down to two things either the pump or the plated heat exchanger being partially blocked.
Could anyone offer any advice as it would be greatly appreciated?

 

[chrispalmer1977]

Plate h/ex for sure!
Either have it descaled or have it replaced. Is there a scale reducer fitted to incoming cold to boiler?

 

[picasso]

Are you sure the hot water signal is being recognised by the boiler ?

 

[chrispalmer1977]

I'd say it was as it works for about 30 secs.... I went to one last week doing exactly the same thing....removed it, de-scaled it, refitted....perfect!

 

[picasso]

Could be the heat exchanger cooling down if the heating been on, would need to be in front of the boiler to be sure.