Worcester Heatslave 20/25

[schoie936]

Boiler burner has started firing when hot water tap is turned on and the separate heating/water controller in the kitchen is set to off. Is this a fault with the flow switch or motherboard?

 

[muggles]

Neither, it's supposed to do that

 

[schoie936]

Thanks for your reply muggles

Taken from the manual

"Flow Switch The domestic mains water inlet is connected to a flow switch which detects when a domestic hot water tap has been opened. This activates the burner and pump when the Domestic Hot Water mode or the Central Heating and Domestic Hot Water mode is selected. If the Facia mounted operating switch or programmer (if fitted) is set to OFF or set to Heating On only, then only the pump will be activated."

programmer is set to OFF so shouldn't it just activate the pump?

 

[schoie936]

Off mode The central heating system will remain off unless there is a demand via the frost thermostat (when fitted), whereby the frost thermostat will activate the pump and burner until the demand is satisfied. The burner will remain inoperative in all other circumstances. If a demand for domestic hot water is made at a tap or shower, primary water will be pumped from the Heatslave tank through the domestic hot water heat exchanger. This will provide a limited output of domestic hot water depending on the amount of heat stored in the Heatslave tank.

 

[oilhead]

Has this only just started happening?
How long have you had this boiler, are you new to the property?
If you are a long term resident, has anything else been changed recently?

 

[schoie936]

Had the boiler from new its 15 years old now (like triggers brush many new parts). Only just noticed that the burner has started ffiring when programmer is set to off & there is a demand for hot water. I certainly cant recall that it did this before and it seems to be against what’s quoted from the manual above. Any help will be very much appreciated.

 

[oilhead]

Do you have the integral timeswitch or a remote one? If there is a feed to the DHW terminal on the pcb, then the boiler will fire on demand. Your slave tank will also be kept up to temperature. You need to get busy with a multimeter to work out what is happening.