No hot water

[WeeStu]

Hi I am having problems with a glowworm compact100e. DHW is only working when heating is on.When a call for dhw is made, the boiler fires as normal with no hot water at the tap. If the heating is on for 15 mins or so, and a hot tap is opened the hot water is ok.
I have changed the dhw diaphragm at the flow switch, and have found no improvement. Would the next step be to refurb/replace the diverter valve or should I be looking at a different solution.
thanks in advance

 

[mountainman]

Have you checked that the flow switch is making?
Also check the wiring harness.

 

[WeeStu]

Thanks Mountainman, I thought that as the boiler was firing up ok in dhw mode that the flow switch was fine, which was making me think that the diverter was where the problem is.

 

[mountainman]

Could be worth checking the plate heat exchanger too. I've had a few scaled recently.
As a generalisation I find that if the diverter is faulty then you get hot water going down the heating flow when only hot water is selected and a hot tap turned on.

 

[WeeStu]

Need to wait on pipes cooling down to try and see if the hot water is going down the heating flow.
I noticed a small build up of scale on the brasswork when I changed the diaphragm earlier, hope thats not pointing to a replacement plate heat exchanger.

 

[WeeStu]

Ive reduced hot water flow to 4 litres/minute and lo and behold water is piping hot. There is no temp rise in ch flow pipe which rules out diverter.
Would best guess be blocked plate heat exchanger now?
Dont think I'll get away with telling the missus that she cant get more than 4 litres/minute hot water