I just had a look and there aren't any knobs underneath the boiler
but there are a couple of 'honeywell' small metal boxes that are fixed into the pipes, they have like a metal switch sticking out each of them, could they be the equivalent of the knobs you're referring to?
but there are a couple of 'honeywell' small metal boxes that are fixed into the pipes, they have like a metal switch sticking out each of them, could they be the equivalent of the knobs you're referring to?