How to bypass or override Vaillant Timeswitch 140

9 Dec 2020
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United Kingdom
Hi all,
Apologies if this is a dumb question but..
I am planning to replace the VRT 30 thermostat connected to my Ecotec Plus boiler with the new Nest Thermostat E.
The boiler also has a Timeswitch 140 fitted.
So, I was wondering how I can bypass or override the Timeswitch so that I can do all the timings etc from the Nest E Thermostat.
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Thanks for the help - the TimerSwitch has an always-on feature I was not aware of.

Unfortunately, once I got started, the labels on the Thermostat don't match up with the choices presented in the Nest app.

The nest app talks about Common and Normally Open.
But the VRT-30 and the Boiler thermostat connections are labelled 3,4,5

The Vaillant thermostat wires are as follows
Red goes to 3/L,
green to 4/*
Black to 5/N

Can someone help me translate from Vaillant numbers to Nest labels? Thanks

The boiler manual states the following:
VRT 30 (room thermostat) - Wall-mounted, 3-wire connection to terminals 3-4-5

Terminals 3 and 4 are linked together when the boiler is supplied.
If external controls are used, this link must be removed, and the controls connected across terminals 3 and 4.
Terminal 5 is an additional neutral connection for external neutrals such as from the anticipator of a room thermostat.

Thank you.


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3&4 to NO and COM on the nest, safely isolate the N , nest E doent use a N it uses batteries, dont touch any links at the boier, and it doesnt matter which way round you connect the wires at the nest
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Thank you, Ian - seems to be working now - much appreciated.
Local official Nest recommended installation guy who lives around the corner - wanted £80 to fit!!
Probably would have taken him 10-15mins max.

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