Vaillant Boiler Pressure

Its normal

Cold pressure should be around 1.5 bar. As the boiler heats up, the pressure will rise slightly — that’s normal. 2.7 bar is high, and the pressure relief valve opens at 3.0 bar, which can cause water discharge. Best to have an engineer service the boiler and check the expansion vessel.

Hi ideally your boiler should be sitting at around 1.1 bar on a cold heating system, when the heating is on the pressure will rise due to expansion from the water circulating around the radiators getting hotter, this will then decrease as the heating system cools back down, so in answer to your question this is perfectly normal operation for the boiler.

Normal - however, you really don't want the pressure much above 1bar when cold. You're running the risk of setting off the pressure relief valve in the boiler which will drop the pressure down suddenly, but you're also putting more strain on your fittings increasing possibilities of leaks.

Vaillant usually recommends to keep it between 1.1 - 1.5 bar when the system is cold. Over pressure might break some parts in your boiler such as expansion vessel. Under pressure might cause your boiler stop working.