Quote:
Originally Posted by COLVERT
Harry. That passing of the boiler heat to the CH circuit sounds like it might be the temperature sensor. The sensor could be sending an OVERHEAT signal to the circuit board. As a safety feature the board would open the diverter valve to get rid of what it thinks is excessive heat in the boiler.
It's not demand opening the valve, but maybe just a faulty sensor signal.
Could be why the temperature to kill the bacteria will never be achieved.
Colvert.
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Yesterday evening I got the bright idea to reset the boiler to factory defaults, followed by setting the system to call for HW. For the very first time it did what it had been asked to do. Just the once so far, I will try it again as more water is used, before calling it a fix and boxing it all up.
I have never touched the boiler settings, apart from tweaking the user setting for maximum output temperature, to get hotter water in the cylinder.
It has led me a merry dance, trying lots of ideas as to why it wouldn't heat the water on demand. I have tried three different valve actuators following suggestions that it might be the actuator which was faulty, or not compatible. I nearly ordered a complete new valve and actuator to fit, which was known to be compatible. I even emailed Vaillant several times to ask if there was any incompatibility issues with the bits I was fitting and the boiler, they responded with no sensible answers, just offers to send an engineer out or buy a set of their very latest control modules.
Yesterday morning I ran several tests to heat HW, it responded each time by moving the 3-port to HW, flashing the call for HW on the boilers display, running a purge on the boiler (as it does before firing), then going into anti-cycling mode, before repeating - never firing to produce any HW.
The VR65 has connections for either a NTC (thermistor) cylinder or a normal bi-metal stat.. The instructions suggest the NTC sensor can only be used on a Vaillant supplied cylinder, which seemed wrong. It will actually work with any type of cylinder and gives better and more intelligent control of the boiler output for HW.