C.W. Cummings offers the latest innovations in hydronic heating systems.
How does a hydronic system work?
How it works and why it works so well are closely tied together.
Let’s start with why you need a heating system. Well, you need a heating system so that you can be comfortable in your home even in the coldest winter weather, but also in the milder Spring and Fall heating seasons.
What makes you uncomfortable?
Being in a room that’s not warm enough?
Having cold feet?
Being in a drafty room?
All of these can make you feel uncomfortable.
When it’s cold outside, the house loses heat to the outside via conduction, convection, and radiation. How fast it loses heat to the outside depends on several factors such as how much insulation is in the walls and ceiling , how cold it is outside as compared to inside, and how hard the wind is blowing.
Conduction is the transmission of heat through a medium without perceptible motion of the medium itself. Put your hand on the hood of your car after the car has been out in the sun for a while. Your hand gets hot from direct contact with the hot metal. Convection is heat transfer in a gas or liquid by the circulation of currents from one region to another. The wind is the best example of this… warm spring breeze… cold winter wind. Radiation is the emission or propagation of energy in the form of rays, waves or particles. On a clear day in mid-winter, step out from the shadow of a building into the bright sunlight. Feels good, doesn’t it? You are being warmed by solar radiation.
Another thing to think about is that heat always moves from a warmer object to a colder one. As the house loses heat to the cold winter air, you lose heat to the house and the colder objects in it such as walls, windows, etc. To be comfortable, your heating system needs to replace the cold being lost to the outdoors. At the same time, the heat should not be drafty or create hot and cold spots in the house.
This is why a hydronic system works so well to make you comfortable. It takes the heat from the boiler or other heat source and moves it quietly and efficiently to radiators, baseboards or radiant floors, ceilings or walls. By creating these warm surfaces in each room, there is a warm object to send heat to you and the cold walls or windows. The best heating system should keep you comfortable without you even noticing it’s doing it. That’s what a good hydronic system can do for you.
What type of equipment does a hydronic system require?
First, the system requires a heat source and, as mentioned previously, this is usually a boiler in the basement or equipment room. Why is it called a “boiler” when it only heats the water and doesn’t boil it? No one knows, but a boiler is a pressure vessel with it’s own safety controls that limit the maximum pressure in the boiler, the maximum temperature and, in many areas, a low-water cut off that shuts off the fire to the boiler if it ever loses water due to a leak in the system.
At the other end of the system will be the heating units such as copper fin tube baseboard, cast iron baseboard, cast iron radiators (usually only found in older houses) or tubing imbedded in the floors, ceiling or walls (called RFH, or Radiant Floor Heating).
In between the boiler and the heating units are the piping and a few small but essential pieces of mechanical equipment that help make the system function quietly and efficiently. A typical system includes:
A pressure reducing valve that reduces the city water pressure to the lower pressure needed for the heating system.
An air separator takes the air contained in fresh water and removes it from circulation. Water needs to be “airless” to assure a truly quiet and efficient system.
Depending on whether your system uses air control or air removal, the air separator sends the air to either a steel compression tank through an air control fitting, or through an air vent that takes the air out of the system. Either type of system works well and each has its advantages and disadvantages.
Air removal systems also require a diaphragm expansion tank to accommodate the change in water volume in the system as the water heats up and cools down.
The hot water is moved through the system from boiler to heating units – and back – by small centrifugal pumps commonly called circulators. Older hydronic systems will usually have a slow speed circulator mounted on the side of the boiler pumping from the heating units toward the boiler.
If an older heating system had more than one zone, such systems usually relied on zone valves to divide the hot water flow to each zone that required heat.
More modern systems use small individual circulators, one for each heating zone, pumping away from the connection to the compression tank or expansion tank. Circulators or zone valves are usually turned on by the thermostat in each heating zone.
Depending on the piping design, each zone may also require one or two flow control valves in the piping. Contrary to its name, the flow control valve doesn’t control flow; instead, it prevents unwanted flow from occurring in an “off” zone when another zone is calling for heat. Many systems today tie the thermostats into a zone control relay box which simplifies the wiring of the thermostats to the boiler and zone valves or circulators.
For more information on hydronic components, or if you have a question about hydronic heating, contac