Hydronics is a fancy word with a simple meaning. Basically, it refers to the use of water to transfer heat. Water is one of the most efficient materials to transfer heat.
The purpose of an hvac system is to move (transfer) heat from one place to another. Therefore, the use of hydronics is a logical solution to today's energy situation. Heating systems for homes have used water for many years. The oldest systems used a boiler to produce steam. This steam traveled through a pipe to cast iron radiators. As the steam gave off its heat, it would turn back to water which is called condensate. Then it ran back down the pipe and was returned to the unit. These systems were referred to as single pipe systems.
They are no longer installed because of their low heat capacity. Also it was hard to control the temperature of individual rooms.
The next generation of steam systems used a separate pipe to return the condensate to the boiler. These systems incorporated a pump to return the water to the boiler. They are referred to as two pipe systems.
To overcome the problem of overheating individual rooms, thermostatic radiator valves were developed. These valves are installed on the individual radiators and have adjustable temperature settings. These valves open and close based on the room temperature and either allow or prevent the steam flow.
The next generation of hydronics used a lower temperature boiler. These units produced hot water and not steam. They were safer and easier to control.
The heat from the boiler was transferred to water and the water was pumped to radiators. These radiators were smaller and made of finned copper tubing instead of cast iron. As the air around them was heated, it would rise and pull cooler air into the radiator where it was heated. After the water had given up some of its' heat, it was pumped back to the boiler to begin the process again.
Some other components are added to the basic system. When water is heated, it expands. Therefore, an expansion tank is added to allow for this and still maintain proper system pressure.
Another device called a temperature/pressure (T/P) relief valve is added. If a malfunction occurs and the expansion tank cannot keep the pressure low enough, this control automatically opens. This allows water to leave the system and causes the pressure to go down.
Normally, there is a certain amount of air in any water. When this water is heated, the air breaks free of the water molecules. This air collects in the highest points of the system and can produce what is referred to as an air lock. This will stop the water flow and therefore not allow the system to work. Devices, called air vents, are installed at the high points of the system to get this trapped air out of the system. Older systems use manual air vents and periodically someone had to go around and release the air. Modern air vents use a float switch and do this automatically.
There has to be a way to put water into hydronic systems. This is usually accomplished with an autofeed valve. This valve is connected to the homes' cold water supply line. It reduces the pressure of the water, eliminates air and automatically maintains the proper amount of water in the system.
The latest innovation in hydronics is referred to as a radiant floor heating system.
There are advantages to hydronic systems. For instance, they provide quiet and gentle heating. Also, this heated water can be put to other uses such as:
1. Providing hot potable water.
2. This water can be sent to heat a swimming pool or spa.
3. In some areas, hydronics can be used to melt ice and snow from sidewalks and driveways.
These traditional systems had one major disadvantage. That is, if you wanted air conditioning in the home, you had to have a separate system. This did not make much economic sense.
Also, during the heating system, there was not an easy way to control indoor air quality. Without a duct system for heating, there was no way to clean the air or add moisture. Also, there was not a convenient way to introduce fresh air from outside.
Today, many hvac equipment manufacturers produce hydronic air handlers which combine a water coil with a blower and/or evaporator coil. You can check out our ratings page for more specific information about the units.
The latest innovation is combining hydronics with geothermal technology. This is a way of having the inherent advantages of each system without the drawbacks. Geothermal systems are among the most energy efficient hvac systems available. These systems heat the water with heat from the ground. The heat is transferred to another water system and is pumped to a coil. This coil is much the same as the radiator on a car. The water is inside this coil and a fan blows air over the coil. The air picks up heat from the water and is supplied to the home through a duct system.
To cool the home, the process is simply reversed and the heat is transferred to the ground outside the home.
The main disadvantage is that they are also the most expensive systems on the market.