Greenstar Heatslave 1 18/25 hot water issue

[AndyH562]

Hi,
CH fine, the HW works only when I set the temperature high but once it reaches temperature and the boiler stops firing the water turns cold
It has a new diverter valve and a new Honeywell controller.
So when the hot water tap is opened and the hot water is up to temperature the water runs cold quicky and the boiler does not fire.
Any ideas would be very much appreciated!

Thanks,
Andy

 

[Exedon]

If you have a multimeter and are competent to work with mains voltage first thing to check is that the flow switch is operating correctly.

 

[AndyH562]

I do have a multimeter but not the knowledge to check the flow switch is working correctly.
Appreciate the advice.

 

[oilhead]

Identify the terminals from the flow switch and test each one to a neutral before switching on a tap. The one that is live is the feed to the switch. When you have identified that one, switch on the water and test the other terminal to neutral. If it doesn't show a feed, then the switch is faulty. For further test, isolate the power and bridge the two terminals. Turn off the CH demand, turn the DHW thermostat down and switch the boiler back on. If the burner fires, you have proved a faulty switch.

 

[AndyH562]

Perfect
Thank you very much for the detailed response.
You're time is very much appreciated!
Andy