No Hot water with Celtic Boiler

[Giggler]

We have an old Celtic FF boiler which is no longer heating water.

The heating system is fine but when you turn the hot water tap on the boiler no longer switches on. When the heating is on and you turn on the tap the boiler turns off.

Anyone have any ideas what the problem may be and if it is repairable. We were hoping not to have to replace the boiler until we renovated the kitchen.

Also if it is repairable would it be an expensive job if getting a plumber in?

Any advice appreciated

Thanks

Moira

[Ed Sirett]

Just to make sure that I'm not barking up the wrong tree...

This is a typical budget style Combi boiler by Chaffoteaux.

If you had not said that the heating is turned off by running a tap I would have said the most likely cause is the diaphragm on the DHW side. It might still be that.

Likely

Either: the diverter valve is moving just fine and the micro-switch that tells the boiler to do HW has failed. Or: the diverter valve is not being moved quite enough to make the microswitch operate but is being moved enough that the flow to the rads is cut (which then causes the boiler to turn off due to it's internal thermostat).

The spares required for this are probably a microswitch and/or a diaphragm and some inhibitor. Less than half a day to fix if all goes well, and assuming this diagnosis is correct.

[John]

IIRC the diverter valve has a black casing containing two microswitches mounted on the end of the operated shaft. The factory fitted switches are not especially robust so I used to use a higher current rated type when renewing them. A couple of these switches will be only in the order of a fiver and its a trivial job to swap them as long as you ensure they remain in place as you refit the casing lid.