An Introduction to Basic Heating by Steam or Hot Water

Most of the steam or hot water heating systems furnish comfort to people in homes, offices, and industrial buildings. A much more specialize application of steam or hot-water heating would be called “process heating” used in industry. We will be only be concerned with the comfort application is this article.

In its most simple form these heating systems will consist of a (1) boiler, where heat is generated; (2) piping to carry the heat to the (3) transfer surfaces, where heat is given off. Other additional equipment is needed to make the system operate properly, such as safety controls to make the boiler come on when heat is needed and to shut down when it is not. There are many different types of boilers, heat transfer equipment, and piping designs.

Residential heating boilers are divided into two classifications steam and hot-water. They both can be available in cast iron or steel. The boilers can be fired by wood, coal, oil, gas, or electric. As one might expect each fuel has its own controls and accessories to make it function properly. What is the essential difference between a steam and a hot-water boiler? In a steam boiler there is a space above the water line where steam collects before entering the piping system. The hot-water boiler does not need a space at the top because water is what circulates in the system instead of steam.

Heat is generated by the burning of fuel inside the combustion chamber of the boiler. This heat is adsorbed by the water. This water then circulates through out the entire piping in a hot-water system. If it is a steam system, the water turns to steam inside the boiler and then circulates as steam through the entire piping system.

With steam or hot-water circulating through out the piping system there still needs to be way to get the heat from the piping into the space requiring heat. This is done through the used of heat transfer equipment. Heat is transferred by either radiation, convection or conduction. Heat transfer equipment uses one or more of these to put the heat from the boiler into the space needed to be heated.

Heating accessories are needed in both systems for them to work properly. Steam traps, air vents, and steam pressure controls are essential to the safety of the steam heating system, while circulating pumps, gauge glasses, check valves are needed in a hot-water system operation of the heating plant. We have covered heating in a very general manner in order to introduce the difference between a hot-water heating system and a steam heating system. As we advance in future articles we will be able to understand that progress in maintaining “comfort” comes from a thorough knowledge of the physics and chemistry of gases, liquids, and solids.