Safety thermostats

Reset a tripped thermostat

Each boiler has a safety thermostat rated at 165° with a reset button: two are drawn on the steam boiler and one on the coffee boiler. There is no one-shot fuse in the parts list. This is a retailer's published method.

1. Unplug, let it go cold and take the top panel off.
2. Press the centre button of each thermostat fully. A click means it had tripped.
3. No click and still no heat: test across its two spade terminals with a meter. No continuity with the button pressed means the thermostat needs replacing.

They trip when a boiler overheats: a scaled steam temperature sensor that reads low, or overshoot at a high steam setting.

The same retailer says a failing relay shows as wild temperature swings or never reaching the set point. The two relays are on the left side panel behind the reservoir tray: the top one, with 4 wires, is the coffee boiler.

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