Vaillant VRC 430 weather compensator

3 Aug 2008
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United Kingdom

I am having an ecoTEC plus 831 combination boiler fitted as a replacement boiler to a central heating system that already has wireless temperature thermostats and thermostatic radiator valves in each room.

There is also a central control unit for the wireless room thermostats that connects to the current boiler on it's "room thermostat" input.

The result is that if any room thermostat is demanding heat, the appropriate TRV is opened automatically and the central control unit turns on the boiler. When no room thermostats are demanding heat, the TRVs are all closed and the central control unit turns off the boiler.

I'd like to have the VRC 430 weather compensator added to the new boiler when it is installed to take advantage of weather compensation, but I wish to retain my existing room thermostat controls.

In reading the literature for the VRC 430, it states that on the boiler "The connecting link between terminal 3 and 4 must not be removed". As I understand it from the literature for the ecoTEC plus though, the existing room thermostat needs to be connected to this input and thus the link will be removed.

I am therefore confused. Does this mean that it is not possible to utilise a VRC 430 when existing room thermostat controls need to be retained?

Thanks for your help,

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The 430 connects via the ebus connection, it can be mounted in the front of the boiler or wall mounted and used as a room stat so no other stat connection is required

How many room stats do you have?
There are 10 room stats, each one controls a TRV on the rad in the room that it is in.

Each room stat then talks wirelessly back to the main control unit, which connects to the current boiler on it's stat connection.

According to the ecoTEC install manual, the link between terminals 3 and 4 would be removed to connect to a "3rd party" stat.

But the install manual for the VRC 430 says not to remove that link.....


the link between 3 & 4 is made when your existing stats call for heat so i cant see any reason why this will not work with the 430 installed on the ebus terminals
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Ok, will give it a go....

I was worried that "The connecting link between terminal 3 and 4 must not be removed" in the VRC 430 manual meant it wouldn't work....

But maybe they meant ""The connecting link between terminal 3 and 4 must not be removed, unless you also have a separate room thermostat"....



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