Snow Patrol - Set the Fire to the Third Bar Lyrics Meaning

The third bar is a reference to working class Britain and Ireland who had a single source of heating in the home which was a cheap gas fire that could be set at three levels, or bars. Setting the fire to the third bar was something you only did when family came over and you needed to heat the home properly. It's a reference to blue collar life and a point of luxury that could not be afforded every day, i.e. being together again was a special moment. Anyone who didn't grow up in UK & Ireland in the 60s, 70s, or 80s would likely be unfamiliar with this as it was a cultural thing unique to low cost housing.