The Recommended Test Range for Boiler Water

Hydronic Heating

• With hydronic heating, a boiler heats water that flows through pipes to baseboard convectors to warm the house. The water for such boilers needs to be set between 160 and 200 degrees Fahrenheit, according to "Principles of Home Inspection: Systems & Standards" by Carson Dunlop. The maximum temperature that will cause the boiler to shut off is 210 Fust below a boil. This boiling threshold will be lower for homes with boilers at higher altitudes, where water boils below 212 degrees F. Pressurized boilers compensate for this and allow water to boil at 212 F even at high altitudes.

Steam Heating

• Steam heating uses a boiler to turn water into steam by heating it to 212 F. The steam rises through copper pipes to radiators in the house. The steam gives off its heat and turns back into water to return to the boiler. Pressurized systems can be used if you home is at high altitude and water boils at a temperature lower than 212 F.

Temperature Range

• During operation, the boiler maintains a temperature range for the water based on the differential setting. A range of 10 degrees Fahrenheit is recommended for a boiler. This means that the boiler maintains a temperature within 10 degrees of the set temperature. For instance, if the boiler is set to 150 F, when the water cools to 140 F, the boiler fires to bring the water back up to the set temperature.

Aquastat

• Control of the temperature of the water inside the boiler is done with an aquastat and a thermostat. These combine to keep the boiler working at the set temperature and within the differential range. The thermostat monitors the room temperature to decide whether the boiler even needs to heat the water. In the summer, this will prevent the boiler from needlessly heating water, saving fuel costs.