Gas Heat


The use of Gas furnaces today utilize two types of mediums.  Natural gas or liquefied petroleum also known as in the HVAC community as LP Gas for which provides the GAS Heat.  When using a conversion on average one cubic foot of natural gas is 1050 BTU’s of heat energy per. The different types of LP gas can be butane, propane or a mixture combination of both.  Propane is the most common gas for heating use within our homes and businesses. The use of Propane, unlike natural gas, produces an average of 2200 BTU’s of energy per cubic foot.  Almost all appliances today can be converted to operate on either medium with minimal changeover or original OEM parts.  The heat can be used to either produce hot water in a water type heating container or to condition air via a conduction type heat exchanger.

There are different types of forced air heating unit exchangers that use gas. These types are: Vertical Flow (up or down), horizontal flow or crawlspace low flow.  

Vertical Flow units take the cool air from the space to be conditioned using the rear of the unit and then sends it across the exchanger out of the top.

Vertical flow units also remove the cold byt taking air from the top of the unit and discharges it from the very bottom.

Crawlspace flow units stand about are used in a basement type setting or with deep crawl spaces under a home.  These applications sometimes need to take into account heat loss because of the ductwork for which they use.  

Finally there is the Horizontal furnace which are positioned horizontally crawl spaces or floor joists and have their intakes and discharges parallel to each other some distance away.

HVAC Gas HeatGas furnace components are very much basically the same.  The differences however can be found in different type of ignitions, safetys, placement of such and finally efficiency.  Basic gas furnaces have components that are as follows:

-Heat Exchanger

-Fuel Controls

-Fuel Ignition Systems

-Combustion Monitoring

-Ventilation for the Furnace

-Fan motor and blower

-Limit switches

-Safety Controls

Terms that are used often when referring to gas heat or furnaces are pilot light, pilot valve, thermo-couple, fan motor, fan blower and heat exchanger. Gas heat is quick and can be very economical. Lets look at a basic gas heat unit. Think of it this way, there are two chambers, one is the combustion gas chamber and the other is the fresh air chamber (the chamber that will provide the heat straight out of your vent).

The fan motor is what draws suction from your return vent, across the heat exchanger and discharges to your supply vents. The blower motor is what blows the combustion gases away from your unit. Each area has a safety for which is not satisfied will cause a shut down. For the more technical at heart the explanation is as follows; fuel combustion takes place inside of the furnace heat exchanger, with the byproducts or heated gases, being passed through the exchanger venting to the atmosphere via the blower motor. The now heated area of the exchanger is in turn used to transfer heat to the conditioned space air as it passes over the exchanger.

Fuel is delivered via a gas valve in gas heat applications. There are many different types of gas valves in use today so be sure to get all the correct documentation and name plate data if you plan to change yours out.