The ideal pressure is around 1-1.5 bar, and is often indicated by a green section on the dial. Low pressure can reduce efficiency or even a breakdown, so it’s good to get familiar with the pressure gauge.
Although it is best to check the water pressure or refill the system when the system is cold, the pressure gauge can help you determine the issue if your heating system suddenly stops working in winter. If the pressure is low, refill the system in accordance with your boiler’s instruction manual. You can also ask your friendly heating specialist when they’re there to service your boiler, they’ll be happy to show you how this is done.