Gas valve unit with bypass flow

A valve unit for adjusting gas flow to a combustion apparatus, the valve unit comprising:

• a valve member that moves relative to a valve seat in response to a signal input to a coil, for varying a high-capacity gas flow rate through the valve unit,
• a first opening port;
• a second opening port that is smaller than the first opening port, the first and second opening ports being disposed downstream of the valve seat;
• a closure member that is movable between an open position, in which said high-capacity gas flow rate is communicated via the first and second opening ports to an outlet, and a closed position against the first opening port, in which a low-capacity gas flow rate is communicated via only the second opening port to the outlet,
• a closure solenoid for selectively moving the closure member between the open position and closed position to selectively establish a high-capacity gas flow rate or low capacity gas flow rate, respectively, to the outlet;
• and
• an adjustable member that is adjustable for varying the opening area of the second opening port, to enable adjustment of the low-capacity gas flow to the outlet of the valve unit.