Fitting Vaillant VR65 and VR10 to existing System

26 Jan 2006
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United Kingdom
Last year, I had an open vent Vaillant 415 Eco tech plus boiler fitted by a Corgi fitter. I had, prior to fitting, upgraded the system electrics for my old boiler, using a Horstmann 425 mechanical programmer and Drayton Digistat RF1 room thermostat. An existing pair of five wire, 2-port, zone valves were retained for CH and DHW, The mechanical cylinder stat was also retained .
Now to my questions -:
At present, water temperature is set at the cylinder thermostat and the DHW control in the boiler is superfluous. Consequently, I intend to purchase a VR65 interface, and make use of the e-bus wiring which was installed for this reason when the boiler was fitted.
May first query is with regard to the VR10 Standard sensor supplied with the VR65. The manual (accessed on line) shows the installation of a NTC or VR10 to the UniStore but gives no information on fitting the supplied VR10 to a standard HW cylinder. In addition, I am confused about the terminology: Is the standard VR10, supplied with the VR65, also known as a NTC or is this a different device?
(The VR65 has separate connections for NTC and Cylinder Thermostat.)

Secondly, I do realise that the VR65 assumes that the 2-port valve for DHW is a spring return device, but rather than replace a perfectly good valve, I would use the VR65 to operate a suitable relay, which would provide the necessary supply to shut and open the valve. Obviously, if the valve became defective at a later date, I would replace it with a spring return type and remove the relay. What is your opinion on this?

I would appreciate your comments on both my proposals, or would it be better to fit a VRT 360f with the VR65 to the e-bus and remove the present, perfectly serviceable control system? The cost of the VRT 360f is quite high and I see no real advantage in using it, apart from more varied programming, to that provided by my present system.
The VR65 alone is much cheaper and, as I understand it, would allow water temperature to be set at the boiler.
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For optimal use the VR65 should be used with a full set of Vaillant controls all connected via ebus.

The 360 will allow you to control everything from one place, ie HW and CH. The VR65 will boost the flow temp from the boiler when a call for HW re-heating is required so enabling a lower standard system temp to be set at the boiler, to keep the boiler condensing for longer.

The VR10 is supplied as a seperate entity. Whilst in theory I cannot see why it would not work fixed to the outside of the cylinder and using heat transfer paste, it is not how it was intended for use.

What 2 port valve do you have at present? MoMo? Most valves are spring return. The only connections to the valve will be the brown and blue. The microswitch is not used with the VR65.

The VR65 should also have its own fused isolater as well.
Thanks Dave for your reply. I do realise that the full Vaillant system would be slightly more efficient but, due to the cost of a VRT360F controller, it would take some considerable time to offset its cost. Hence the reason for my trying to make the best of what I have got installed.
The valves are Satchwell Mo Mo, without a spring, and this is why I proposed a relay for the HW valve to get around this problem. I realise you may think I am tight, but these valves were fitted when I moved in here, approximately 31 years ago and have performed faultlesly ever since. Hence very loath to replace them with spring return at £75 a time. The VR10 is supplied in the box with the VR65, it is just very confusing to me when they talk about a NTC and a VR10 as being separate and different items. From what I gather, the VR10 is a NTC and senses the cylinder temperature and routes this information back to the boiler via the VR65 and e-baus. Wheras the excisting cylinder thermostat would just indicate either demand/satisfied to the boiler without bringing the boiler water temperature control into use, which is what I am trying to do.
Is this assumption correct? Thanks again for the feedback.
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Things must have changed, as I have never had a VR65 supplied complete with a VR10, although I haven't fitted a VR65 for approx 9 months now.

The VR65 will work better with the ntc rather than the cyl stat. This will make for more efficient running as the boiler/VR65 will modualate better.

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