Intermittent Hot Water Problem

[Newb1e]

I have an Ideal Icos HE12 boiler with a Danfoss dual channel 7-day timer control. I replaced the PCB in the boiler about 6 months ago because the old one went kaputt! It has been fine since but just recently we have found that the hot water is running out even when the timer control for hot water is on. I have found that resetting the timer control (i.e turning it to manual off and then back to auto on) results in a call for heat and the boiler fires up as it should.

This leads me to believe the issue is with the timer control and I should replace it, but I wanted to check this with someone who knows these systems much better then me. Don't want to replace the timer control if it could be, for example, a thermostat in the hot water tank (although it does not make sense to me that it would be). Could it even be the PCB that I installed as it was a refurb?

Please give me some expert advice

Thanks

Mark

 

[kbdiy]

Sounds to me like the thermostat on the cylinder is the likely suspect, cutting out too early and therefore not allowing a full tank of water to be heated.

Have you tried just turning it up to max and see if the boiler fires up again?