Moving Heat From Room To Room
Written by Elizabeth Wood
Editor In Chief, United Home Improvement

Heating systems are tricky business. It is important to know and understand the characteristics of your heating system and the different functions it serves. Venting, distribution of heat, flue gas condensation, and air quality are all areas that need to be carefully evaluated. Not to mention the individual parts that makes up your heating system. Parts include boilers, pumps, burners (furnace), pipes, fans, zones, circulators, and thermostats. It is essential that you know how all of these parts work together in order to gain full control over how heat moves from room to room.

Creating Heat

In most cases, a furnace or burner is the main source of heat within the house. They operate by drawing in the air from rooms through ductwork or surrounding space. The furnace then filters and heats the air. This heated air is circulated back into the rooms, rising to higher levels and producing warmth. A furnace can either be sealed combustion or non-sealed combustion. Sealed combustion draws air from a duct that goes from the furnace to the outside. Non-sealed combustion draws air from the surrounding space, the house itself.

Moving Heat

Forced hot-air heating works by drawing air inside a heat exchanger, where it is warmed with a flame of natural gas, propane or fuel oil, or with heated electric coils. A fan or blower then sends the warmed air through the house ductwork. The fan is timed to cycle off shortly after the burner shuts off. The timing of the fan is crucial for keeping cold air from being pushed through the system and for keeping the hot air from backing up.

The fan pushes the air so that it circulates and enters individual rooms through a vent or register in the floor or wall. Keep in mind, indoor air moves continuously through the system, so a furnace filter is used to contain dust other airborne particles.

Certain homes operate on a heating system that uses water to move heat, measured in Btu's (British Thermal Units) from a heat source (boiler) to the heated space. This is typically referred to as a hydronic system. Two common systems include "hot water base board heat" and a system that uses cast iron radiators or tubing in the floors, ceilings or walls to circulate heated water. With hydronic heat, a boiler works by heating water and moving it through pipes or tubing to radiators, where it warms the surrounding air. The boiler fires and heats the water to an average temperature of 80°F to 85°F for radiant floors and 180°F to 200°F for baseboard heat.

Controlling Heat

A thermostat, circulators and zone valves are used to control hydronic heating systems. They are installed on the supply pipe to push or prevent hot water from entering a given loop. Older hydronic systems generally have a slow speed circulator that is mounted on the side of the boiler. This device is used to pump water from the heating units toward the boiler. More modern systems use small individual circulators, one for each heating zone. These circulators are used to pump water away from the connection to the compression tank or expansion tank. A thermostat is used to turn on the circulators or zone valves in each heating zone.

Forced air heating systems are controlled by fans and dampers. Fans circulate the hot air through ductwork that travels into individual rooms. Dampers are used to prevent hot air from entering certain zones.

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