They are also referred to as control knobs and temperature knobs, they control either the temperature or are used to switch the Chaffoteaux boiler on or off and can be found on the front of the boiler. They normally have a shaft that protrudes from the knob directly through the front of the boiler onto the printed circuit board. The shaft when turned, turns a potentiometer that's located on the printed circuit board and if the knob is turned too hard the shaft is designed to break hence protecting the Chaffoteaux printed circuit board from damage and an expensive repairs.
Chaffoteaux 65100690 Knob

Part: 65100690

Price: £4.35
Chaffoteaux 61001495 Knob

Part: 61001495

Price: £4.35
Chaffoteaux 992027 Knob

Part: 992027

Price: £4.35
Chaffoteaux 65100687 Knob

Part: 65100687

Price: £4.35
Chaffoteaux Temperature Selector 60040802

Part: 60040802

Price: £23.74
Chaffoteaux 61312930 Minima Control Knob

Part: 61312930

Price: £5.80
Chaffoteaux 997250 On-Off Push Button Kit

Part: 997250

Price: £10.77
Chaffoteaux 60081979 Knob

Part: 60081979

Price: £7.67
Chaffoteaux 61010740 Calydra Knob

Part: 61010740

Price: £4.35
Chaffoteaux 998603 Knob

Part: 998603

Price: £7.23
Chaffoteaux - Hot Water Knob - 61001498

Part: 61001498

Price: £3.96
Chaffoteaux 61016290 Knob

Part: 61016290

Price: £5.91