URGENT Heatslave 12/14 No Hot Water (for a week now). :-(

[Mark from Wales]

Hi all.

I have a 20 year old Worcester Bosch Heatslave 12/14 Oil-fired
I'm getting about 20 seconds of hot water, then the boiler won't fire.
I can crank the HW dial right up and it'll fire and give me another 20 secs of hot water.
It won't fire again with demand from the tap.

It was losing pressure last week, plumber has changed the braided hose to the expansion vessel and the pressure relief valve. Made no difference to the hot water supply.

So, it can fire, but it seems it doesn't know when the tap is running to keep the burner going?

 

[ChrisB1982]

If it’s not registering a tap demand, that could be the sensor?

 

[exedon2]

You really need a experienced oil service engineer.
First thing I would be checking would be flow switch.

 

[ShaunCorbs]

Could be something simple as the pump or valve

 

[king of pipes]

Does the heating work ok ??

 

[SimonG]

Sika flow switch, first port of call.

You need somebody who knows how these work.