Hi all,

I've recently had a new Vaillant Ecotec 424 installed - this is a vented system with DHW cylinder (single heating zone, radiators only). This replaced an ancient system which was woefully too small for the house (15kW).

I (naively) opted to carry over my Hive controller - and starting to see the downfalls now. The biggest one is that the boiler only ever sees a "demand" - it can't differentiate between DHW heating and radiator heating, so I can only set one temperature to heat to.
This is causing the DHW heating to constantly go into anti-cycle, which also stops the pump after so long. Once the temp has dropped low enough everything comes back to life. It just takes a long time to heat the cylinder like this, unless I raise the temps (not an issue in summer as CH not used).
The original installer has kindly offered to drop off a VR66 wiring box and a basic Vaillant programmer from his stock. It's my understanding the VR66 allows the separate control of the DHW and CH systems so will be a permanent fixture. Does anyone know otherwise?

I do like the look of the Evohome, but I'm struggling to see how I could get it to work with the VR66? I know I can get the VR33 Opentherm module (warranty issues aside) - but will that conflict with the VR66 and can the boiler use eBus for that and OT for Evohome?
If I need to remove the VR66, does the traditional y-plan wiring get used (which then puts a single "demand" on the boiler)?
If there is a single demand, is the Evohome is able to tell the boiler what temp to use (so higher for DHW, and lower the CH?)

Sorry for the huge list of questions, but I want to be sure I can get everything working properly before committing. I do like the look of Evohome, and the starter packs seem pretty cheap recently - but it might be wasted money and I'll have to stick with the Vaillant programmer.