Non Vented
Many smaller heaters and fireplaces are available as non-vented appliances. All the combustion products are released into the room air. Many of these units have special processes that help clean up the exhausted products and also incorporate safety features that shut the heater off if too little oxygen is present.
Many areas of the country do not allow unvented heaters in residential locations. Juneau is one city that outlaws them. Arrowhead LP Gas does not recommend the use of non-vented heaters in any residential areas. They produce odors because they burn the dust and other air contaminants present in the room. They also generate lots and lots of moisture.
Two locations that are suitable for non-vented heaters are greenhouses, where plants love the moist exhaust, and outdoor patios.
Vented
Vented appliances send the products of combustion (moisture, CO2 and other byproducts) out a chimney/vent pipe. There are three types of venting currently in use.
Conventional flue (BVent) systems use oxygen from the room where the heater is located to feed the fire.These types of appliances are not to be installed in bathrooms or bedrooms or other small areas where a person may linger with the door closed, because of the possibility of running out of oxygen. They must be installed according to manufacturers specifications to ensure they have an adequate air supply. Venting is typically purchased separate from the appliance.
Direct vent (sealed combustion) systems utilize two pipes - one grabs air from outside for feeding the fire in the appliance, the other transports the exhaust back outside. Because direct vent heaters are not removing already-warmed air from inside and then sending it out as exhaust, they are typically more efficient. They also are usable in bedrooms and bathrooms, because the inside air is not affected by the appliance - the air system is sealed. Most direct vent heaters and waterheaters come with specific vent pipe, which cannot be altered. Most need to be located on an outside wall. Direct vent gas fireplaces are more flexible in their venting - allowing horizontal or vertical vent configurations. Vent pipe for fireplaces is usually sold separate from the appliance.
Power vented systems require an electric blower to force the exhaust air from the appliance to the outside. Power vented appliances allow venting to run great horizontal distances and even in a downward direction if necessary. They are often a more expensive option, but allow greater flexibility in locating an appliance in the middle of a room. Some power vent systems are conventional flue, while others are direct vent. Quite a few options exist for vent material for these types of sytems. See the appliance manufacturer's specification for the individual appliance.
In all vented appliances, the manufacturer's venting specifications must be followed for safety and best performance of the appliance. There are specifications for how high the conventional flue vent top should be above the roof line. (Duravent specifications.) There are also specifications on where the termination cap of a direct vent appliance can be located - with relation to other exhausts, windows, entry ways, etc. (NFPA54 table.)
If you have a question about the proper venting of your appliance, or in choosing the proper type of appliance for your situation, please give us a call at Arrowhead LP Gas.
