If you use a hydronic system like a coal boiler for home heating, you have likely seen or at least heard of the aquastat. However, you may not know much about its role in coal boilers until it malfunctions. Since it is a critical component of your coal-fired boiler system, understanding how it works can help you take better care of it, use it to save on costs, and know what to do if it breaks down. Here is an overview of what it is and how it works to get you on the right track.

Introduction to Aquastats

The aquastat is an essential component of your boiler that lets you enjoy the benefits of your home heating system without having to worry about it constantly. It automatically controls the temperature of water in the boiler. To help you better understand its role, think about what a thermostat does for the air conditioner or a heat pump. In the same way that the thermostat controls the temperature for heat pumps and air conditioners, an aquastat is the boiler’s heating control center.

How It Works

In order to carry out its crucial role, the aquastat features a copper bulb sensor that stays in constant contact with water in the boiler. Whenever the water reaches a pre-specified temperature, it will either shut down or turn on the boiler automatically. Using these basic actions, it ensures that the water constantly remains within the desired temperature range.

It is noteworthy that despite its misleading name, the boiler is not designed to boil water. If the water in it were to reach boiling point, the resulting steam would create a buildup of pressure in the system resulting in catastrophic effects. Therefore, the aquastat keeps water hot but below boiling point.

A high-limit aquastat will shut the boiler down when the water temperature reaches the set value. The high-limit aquastat, on most coal boilers, will turn the unit back on. A high-limit aquastat has a built-in differential of roughly 10F. Once the water temp drops 10F below the set value, the aquastat will turn the boiler back on. Our coal boilers have two high-limit aquastats, one is used primarily, and the other is set 20F above the other for safety in case of failure.

The aquastats maintain close control over the system’s water temperature, preventing potential overheating and meeting the household’s heating needs.

You can also find aquastats that will operate circulators only when the water is warm. You can also turn the boiler off if the water temperature cools due to the fire going out. There are endless possibilities you could use aquastats on your boiler.

How to Use It to Save on Fuel Costs

Making a simple adjustment, turning down the water temperature of the aquastat during the warm season, can result in worthwhile fuel savings. Failure to make this adjustment will keep the boiler’s heating capacity at the maximum level required during winter. Experiment with a lower setting of around 140-160 degrees Fahrenheit or lower to find the optimum level for your household’s hot water and heating needs.

Getting a Replacement

When your aquastat fails, getting the right replacement can be a challenge. The trick is to identify the part number on the faulty one and look for an exact match. In the event that part numbers are not an exact match, ensure that the operating range, bulb type, and capillary length are exact equivalents. Additionally, the two should have similar switching and reset actions, applications, and differentials. Give us a call we can help get you the correct aquastat.

When to Call the Experts

Though the aquastat is a small component of your boiler, it is the heart of the system. Suppose its settings are wrong, or you get an incorrect replacement. In that case, your system may not work or result in higher energy costs, overheating, or the unit may not work at all. Consider seeking expert assistance if you suspect an aquastat-related problem.