It is normal for people to have problems with Vaillant thermostat from time to time. We have here some solutions that might work for you
Vaillant Wireless Thermostat Not Working
I would check the batteries in the remote thermostat and make sure they are not low. Next, check that the end receiver and thermostat are communicating. If not, simply clear and rebind the units.
Most unlikely to be interference from your WiFi transmitter – the frequencies are very widely spaced apart ( WiFi 2.5GHz or 5GHz against your thermostat communicating (RF) at 0.85GHz). The interference from another wireless thermostat with a separation frequency of less than 0.025GHz or electrical interference from an adjacent power supply (within 0.6m) or shielding from a large metallic object are more likely source (s) of interference.
So, confirm that the batteries in the remote thermostat are recharged and not low. Then double check to confirm that the thermostat and receiver are in synch. If not, clear and rebind the units.
If the receiver is set up properly, if it fails to communicate with the remote thermostat so that it calls for heat unless overridden by the frost protection settings.
If the solutions above fails then you might probably require the services of a ‘Registered Professional Gas Engineer’ engineer to access the receiver – unless it has been retrofitted, it will be within the room sealed part of the boiler housing.
Once you have triggered that option, fix the problem once and for all by:
Using my preferred (cheaper) solution to replace the Valiant wireless control with an externally (external to the boiler) Honeywell (or Drayton, Hive, Nest el al) system. Full replacement of the Valiant controller with a like for like original (OEM) is an expensive option.
Hard wiring is also an option, but again (for a Valiant) you will need a ‘Registered Professional Gas Engineer’ to access the interface point.
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Vaillant Boiler Not Responding to Thermostat
You should turn heating on from the stat, and then turn it off whilst observing the radiator symbol on the boiler. That should reveal to you whether demand has successfully been stopped. The symbol should either disappear or flashing.
It could be either
- A faulty receiver or thermostat, OR
- A badly wired boiler (these are 2 options to wire these, low voltage or 240v).