How Does the Aquastat on a Boiler Work? The aquastat monitors the water temperature in the boiler through the use of a copper bulb that stays in contact with the water inside the boiler and that shuts down the boiler automatically if the low- or high-temperature set point is exceeded.Click to see full answer. In this way, what does a boiler Aquastat do?An aquastat is a device used in hydronic heating systems for controlling water temperature. To prevent the boiler from firing too often, aquastats have a high limit temperature and a low limit. The boiler will re-fire if the boiler water temperature drops below a range around the high limit.Similarly, where is the Aquastat located? Most aquastats have a sensor that is inserted in an immersion well. The immersion well is located inside the boiler where the water circulates. The sensor senses the temperature. Consequently, how do you test an Aquastat on a boiler? How to Conduct Basic Boiler Aquastat Controller Tests: Turn thermostat down – Turn the wall thermostat all the way down so it is not calling for heat. Check incoming voltage – Check the low voltage transformer output: Check thermostat switch terminals: Check burner power terminals: Check circulator terminals: What temperature should a boiler be set to? Your boiler controls explained To maximise efficiency, we recommend setting your radiator dial to 75 degrees and your hot water to 60 degrees. Once you’ve got your boiler running at the optimal temperature, you’ll want to set the timer for when you need heating the most. With a combi boiler, hot water is on demand.