What Is an AquastatAn aquastat is similar to a thermostat. It controls the temperature inside a boiler. Unlike a thermostat, however, an aquastat does not maintain a single temperature. Instead, it keeps your water within a certain range, set by the manufacturer or the homeowner. This range falls between the:

  • High Limit. The high limit setting prevents the boiler from overheating by shutting down the burners when the water gets too hot.
  • Low Limit. The low limit setting ensures the water stays at a suitable and comfortable temperature by triggering the burners whenever the boiler gets too cold.

Aquastats monitor the temperature with a probe made from sensitive material such as copper, which expands or contracts in reaction to heat. The probe extends into the boiler, allowing the aquastat to constantly track the temperature inside.

What Are the Types of Aquastats?

There are three types of aquastats: single-function, dual-function, and triple-function. Single-function aquastats have a high limit or a low limit, but not both. Dual-function aquastats have both a high and low limit. Triple-function aquastats not only have a high and low limit; they’re also connected to your home thermostat and circulator pump. 

Circulator pumps control water flow through the boiler and the radiators or hot water baseboards in your home. When your home temperature falls too low, the thermostat triggers the aquastat, which triggers the circulator, which starts the water flowing.

What is a Differential?

To prevent the circulator from jamming, homeowners need to pay attention to the differential, the difference between the high and low limit. The minimum differential is 10°F, but to prevent the circulator from locking up, experts recommend a minimum of 20°F. Most appliances require water that’s at least 120°F, making it one of the most popular low limits. Heating your boiler to 200°F can cause problems with the pressure valve, making it the most common upper limit on aquastats.

Protect Your Aquastat with Agway

Aquastats are just one of many crucial components Agway’s EnergyGuardTM program covers for our natural gas customers. EnergyGuardTM protects your essential home systems from damage caused by ordinary use. Home insurance won’t pay for this type of wear and tear, but we will.

Once your service starts with Agway, you automatically become an EnergyGuardTM member. Afterward, whenever your furnace, boiler, air conditioning, or internal wiring breaks down, you can turn to us for repairs*. We dispatch a vetted contractor to make repairs, and you never have to pay a service fee or deductible. Don’t let a breakdown wreck your wallet. Sign up today and start saving on repairs!

*Coverage depends on which commodity is purchased.