Vaillant e-bus controls for system boiler simple system

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I am renewing my CH and DHW entirely with (amongst other bits):
Vaillant Ecofit-pure 630, system boiler
Vaillant Sensocomfort 720F wireless controller/room thermostat
Vented, indirect HW cylinder

There is currently only 1 CH zone, being the whole house (although each rad will then have a smart TRV, but that's not relevant to my questions).

The cylinder will need a temperature sensor to feed back to the 720F receiver, allowing it to work out when to fire the boiler to satisfy the set temperature of the DHW.

Will a wired VR10 temperature sensor be ok, attached on the cylinder to provide temperature data to the 720F's receiver / wiring centre?

If I'm just using DHW and/or CH with no zones, is a wiring centre VR66(2) also needed?

Vaillant tech wouldn't speak to me as I'm not an "installer" and my actual installer (whilst brilliant) is a bit unsure as their preferred electrician normally deals with anything like that and they're away at the moment, and I want to nail down the required parts list ASAP.

Thanks in advance.
 
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Vaillant tech wouldn't speak to me as I'm not an "installer" and my actual installer (whilst brilliant) is a bit unsure as their preferred electrician normally deals with anything like that and they're away at the moment, and I want to nail down the required parts list ASAP.

That's odd, they speak to me on the phone and respond to emails (usually), although I am not an installer. Trouble is, they are not very technically knowledgeable. Tech email is - RochesterTechnical <technical@vaillant.co.uk>
 
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To answer my own questions to aid future readers:

A VR10 NTC temperature probe is correct and connects to the VR66/2 to measure tank temp. If the cylinder doesn’t have a preformed temp sensor pocket, cut a patch of insulation, stick the sensor to the tank with thermal paste, stick the insulation back over the sensor and affix with some tape. The wiring box does have the (less efficient) ability to use an on/off tank thermostat but that defeats the point of the precise control that can be achieved with the 720F and eBUS.

The 720F receiver supposedly integrates into the boiler underneath and connects directly to the boiler by eBUS. There is no dedicated power + eBUS connection port, or hangers, on an Ecofit pure 630 so I mounted the receiver externally, gave it 240V, then daisy chained the eBUS to the vr66/2 then on to the boiler.

If you have a system boiler, with just 1 flow and 1 return, a VR 66/2 is correct and is needed to operate the 2 2 zone valves (S plan) or 1 3 position valve (Y plan). The Vaillant supply chain has both VR66 and VR66/2 in it, both have the same Vaillant part number, but I was told only the /2 works with 720(F) controls. I had to purchase several “VR66s” until I finally got a /2 as no retailer, that I could find, specified /2 or not and they’re all the same Vaillant part number.

There is an error in the wiring diagrams supplied with the 720 (and others) for a system boiler, 1 heat zone and 1 cylinder. The wiring diagram says use basic system code 2 - that’s not correct - with a vr66/2 you need to use system code 1 on the 720 and position 1 on the vR66/2’s rotary selector switch.

It’s hot water priority, which I did know, but then confused myself when the 720 called for heat on the radiators and nothing happened with the heating valve. The cylinder had cooled a bit when the power was off for wiring, so was warming but in priority to the heating, so of course the heating valve wouldn’t be energised. After working that out, all is well.
 
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It’s hot water priority, which I did know, but then confused myself when the 720 called for heat on the radiators and nothing happened with the heating valve. The cylinder had cooled a bit when the power was off for wiring, so was warming but in priority to the heating, so of course the heating valve wouldn’t be energised. After working that out, all is well.

That is correct and the reason you cannot supply both CH & HW is that the boiler itself now knows which demand it is servicing and now you can set separate flow temperatures for each mode. I have mine set to max temperature for HW flow, 60 cylinder and I think 60 for CH, but the system actually optimises that latter, for best condensing efficiency. On standard controls, you only see one flow temperature setting. HW flow temperature, has to be set higher than the cylinder temperature, otherwise the boiler would never be able to satisfy the demand.

I set my CH to come on first, then an hour later it does the HW, that way the house is remains warm, whilst it spends the 20 minutes so so heating the water back up - we don't even miss it for those minutes.
 
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