Boiler Aquastat - How to set it

It is the coldest day of the year and your boiler is chugging along. However you notice that your house is slowly cooling off even though the boiler is running. Then you notice that the boiler is shutting down even though your house is not up to the thermostat temperature setting.

You look into the situation farther and notice that you boiler temperature is below say 180F. What is shutting the boiler off? The device that controls the temperature of your boiler is called an aquastat. This device senses the temperature of the water in your boiler, and then fires the burners to keep the water at the temperature call for by the aquastat.



The other role that this device may play is to keep the boiler from getting too hot and making steam. However for this time we will concentrate on the lower side and the heat of the water. If you have a house that has barely enough baseboard or radiators for that really cold day then you need your water to be very hot or around 200F. This will give the water enough BTU's to carry around the piping to give off to keep your house warm. The downside is that it also makes your boiler less efficient when it needs to heat the water this hot.

So, now you know that if you need more heat you can turn the aquastat up higher to get more heat and turn it lower on the milder days to save energy. Another way to do this is to buy and install a smart control that will do that automatically for you. These are called an outdoor reset control and will vary your boiler temperature according to the outdoor temperature, saving you money and keeping you warm all at the same time.

Now, the one thing you need to know yet. The aquastat is usually a gray box with a screw driver slot in a little wheel that has numbers on it. It is often hidden pretty well and may take some looking to find it. Some of the newer boilers may have a digital one that is in a bigger gray box. Read the instructions to learn to change the temperatures.

Setting your aquastat correctly can save a lot of money and it can be the difference between keeping you warm or not.