Scalding HW/delayed CH (Vaillant ecoTEC 637/VR65/VRT360)

28 Mar 2015
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United Kingdom
Hi I'm having issues with my hot water valve which remains on all day until the vrt360 goes on standby at night.

Quick breakdown of my setup as follows:

Vaillant ecoTEC 637 system boiler w/eBUS
VR65 Control Center via eBUS
VRT360 Controller via eBUS
2-port valve for HW wired to VR65 using E/N/L wires only on the Purple DHW terminal
2-port valve for CH wired to VR65 usinng E/N/L wires to the CH terminal
1 extra pump wired to the CH terminal on the VR65 (due to large extended house with lots of radiators)
Cylinder with analogue thermostat w/manual temp dial wired to CYL on the VR65

I have checked all electronic wiring which appears to be correct.

I have tried changing the d.70 diverter valve position setting on the boiler between 0 and 1 to see if it makes any difference to the HW valve behaviour, but no luck.

When set to 0, if a CH request is received, the VR65 turns off the HW valve and turns on the CH valve. But when the CH goes off, the HW turns back on.

When set to 1, if a CH request is received then CH and HW both stay on, or the HW stays on all the time.

Due to the HW valve always being on, this causes issues with the Central Heating either not coming on, or taking longer than usual to warm the radiators

I have set the boiler to factory settings.

If I turn down the CYL thermostat (and hear the click of the thermostat going off), the HW valve doesn't go off. Multimeter shows 230v voltage is still being fed on the HW terminal.

The CH seems fine as if I turn up the thermostat on the VRT360, the valve turns on, and if I turn it down the valve responds correctly and turns off.

Could this indicate the VR65 is faulty? Am I better off replacing it with the newer VR66 and VRT350 combo?
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