Vaillant ecoTec plus 428 open vent - control system wiring

31 Oct 2007
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United Kingdom

Existing central heating/DHW system is an vented S-plan supplied by a clapped out gas boiler which is to be replaced. I am considering having it replaced with a Vaillant ecoTec plus 428 open vent boiler.

I would like the existing programmer and S-plan wiring to be reused for the controls. However I am told that I need to buy the Vaillant controls (V65 and VRT 360) to provide time and temperature control over the system. A brief review of the manuals seems to confirm this.

Is it possible to wire this boiler using a non Vaillant CH/DHW programmer or are the Vaillant components a requirement ?

thanks and regards,

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They are not a requirement, conventional controls can be used with the 4 series like any other Vaillant boiler. I say 'Vaillant' but the 4 series is a sort of hybrid Vaillant/Saunier Duval/Glowworm made in the UK for the UK market.

Your installer may have run out of wires for the necessary pump overrun thus wishes to circumvent this by doing as you describe with the VR65.
Thanks Simon,

I'd appreciate it if someone could elaborate on your 'pump overrun' comment, as I think I'll need to understand it a bit more before I have this conversation with my installer.


For the 400 series you will need permanent live, switched live, neutral, earth and a pump live, so 5 core heat resitant flex will be needed.

The pump live is supplied from the boiler/pcb and this controls when and how long the pump runs for after the boiler switches off (pump over run)

A Simon says there is no need for the VR65 on this system, but could be used so that the ch flow temp could be set to 60C or below, then when the hw is needed to be heated the VR65 would tell the boiler to heat the flow to a higher level to heat the dhw cylinder quicker and to your required set temperature.
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