Some unvented gas fireplaces: Chillbuster models.
In order to make a gas log fireplace a legally vent-free gas log fireplace there are some very specific rules to be followed. Unvented gas fireplaces have to have a maximum BTU output of 40,000 BTU. This limit will lower the amount of flames and the amount of dangerous carbon emitted into the room because of the flames. The ceramic logs stack specifically to match the flames of the burner so there is little or no contact between the fireplace flames and the logs.
Oxygen Depletion Sensors are alway installed on vent-free gas log fireplaces to ensure safe use in the home. ODS usually consists of a thermocouple and a pilot. A thermocouple is a complex, simple tool for generating energy from heat. With no moving parts it is very rare a thermocouple fails. The tip of the thermocouple has different types of metals that create a small electric charge when heat conducts and transfers across each metal. This small millivolt charge runs through a electric wire in a copper sleeve to a threaded metal bolt that becomes magnetized from the millivolt charge. The threaded bolt screws into the control valve where another magnet is mounted with the reverse magnetic pole meeting the electro-magnet on the end of the thermocouple. When the thermocouple transfers heat to create a millivolt that runs through copper to magnetize the steel the magnets push one another apart to allow gas to flow through the valve. Should the pilot flame go out the tip of the thermocouple cools and within seconds the steel bolt demagnetizes, attracts the inner magnet and snaps closed so gas cannot flow through the valve.
When there is a draft, ceiling fan or when an unvented gas fireplace is installed outdoors there can be some problems with the pilot but the role of this system is to gauge oxygen in the fireplace. Because the pilot os a single weak flame surrounded by large strong flames the pilot is not the first place or the easiest location to reach and burn oxygen. If oxygen is low the first place that will be effected is this small pilot flame. As the pilot flame reaches higher and higher seeking oxygen the flame will lift higher and higher off the tip of the thermocouple and usually the thermocouple will cool and stop all gas flow before the pilot even dies.
This is a very simple but very effective way to make the fireplace safe with no moving parts that can break down or get damaged. When a customer calls to complain about the fireplace going out the problem is usually that they have forgotten the process for lighting the pilot. Rarely we will have to clean the fireplace if it has not been maintained. The metal tube that the pilot lights from has a sensor at its base. Depending on the geographical location and depending on the installation there can be dust, dander, pet fur, or pollen build up inside this sensor. A can of air or a vacuum cleaner can usually clear the area within a few minutes.
This video should show the realistic flame patterns and the realistic logs of the chillbuster brands. These gas fireplaces are made to be safe indoors without the costly work of cutting through the roof or building a chimney.
Each of these burners has several different gas log sets that can be used on this burner. The ceramic logs on a vent-free burner are always designed specifically for that burner and unvented logs from a different set cannot be used with another unvented burner because the logs stack to avoid the flames of each burner configuration.
For more information about chillbuster gas fireplaces or any information about vented or vent free gas fireplace please contact us at Service@Grill-Repair.com and at 954.2.GRILL.2.