HELP!! Hot water runs for only 40 seconds before going cold

[KirstyV]

Hi,

I have a worcester bosch boiler, only 1 year old. The central heating is working fine, but after running the hot water for about 40 seconds it goes cold again.

It goes cold because the pressure within the boiler (not water pressure) drops dramatically and the boiler goes into shut down.
I've tried running the central heating at full pelt over night to increase presure, but the same thing still happens.

Any ideas pretty please??

 

[doitall]

I like your logic KirstyV

What model WB is it.

Are you saying when you open the tap the boiler pressure drops.

 

[KirstyV]

It's a Greenstar 37CDi.

After speaking with a plumber the electronic numbers on the front relate to temperature not pressure. Dropping from 70+ (I was running central heating on full) to sub 20.

Pressure gauge drops slightly, but not significantly