Document BwN7KBNOGR72QM1LDgEd558m

American Society of Heating and Ventilating Engineers Guide, 1932 base at the bottom of an enclosed combustion chamber. The products of combustion pass up around baffles within the heating element or drum, and out the flue at the back near the top* They are well adapted not only for residence room heating but also for stores, offices, etc. Radiant heaters make admirable auxiliary heating appliances to be used during the occasional cool days at the beginning and end of the heating season when heat is desired in some particular room for an hour or two. The radiant heater gives off a considerable portion of its heat in the form of radiant energy emitted by an incandescent refractory that is heated by a Bunsen flame. They are made in numerous shapes and designs and in sizes ranging from two to fourteen or more radiants. Some have sheetiron bodies finished in enamel or brass while others have cast-iron or brass frames with heavy fire clay bodies. An atmospheric burner is supported near the center of the base, usually by set screws at each end. Others have a group of small atmospheric burners supported on a manifold attached to the base. Most radiant heaters are supported On legs and are portable; however, there are also types which are encased in a jacket which fits into the wall with a grilled front, similar to the ordinary wall register. Others are encased in frames which fit into fireplaces. Gas-fired steam and hot water radiators are popular types of room heating, appliances. They provide an economical form of heating apparatus for intermittently heated spaces such as stores, small churches and some types of offices and apartments. They are made in a larger variety of shapes and sizes and are similar in appearance to the ordinary steam or hot water radiator connected to a basement boiler. A separate com bustion chamber is provided in the base of each radiator and. is usually fitted with a one-piece burner. They may be secured in either the vented or unvented types, and with steam pressure, thermostatic or room temperature controls; Warm air radiators are similar in appearance to the steam or hot water radiators. They are usually constructed of pressed steel or sheet metal hollow sections. The hot products of combustion circulate through the sections and are discharged out a flue or into the room, depending upon whether the radiator is of the vented or unvented type. Luminous flame reflector heaters reflect the radiation from the flames themselves into the room from a polished metal surface. They usually operate with a yellow flame since all of the air for combustion is mixed with the gas as it is being burned. Probably the nearest approach to the wood fire in appearance is made by the gas log. The base and burner assembly are similar to the con struction used in radiant heaters. The logs are usually constructed of fire clay and may be secured in a variety of imitation wood designs. When in operation they closely resemble burning logs. The coal basket, which is another popular design of fire place heater, usually has a cast-iron base and frame with a burner assembly similar to the ordinary radiant heater. Fire-clay radiant elements resembling lumps of coal are placed in the frame and supported above the flames. The hot gases passing up around the elements cause them to glow, thus resembling a glowing coal fire. >' 292 Chapter 19--Gas Heating Appliances Garage Heaters Garage heaters are usually similar in construction to the cabinet circulator space heaters, except that safety screens are provided over all openings into the combustion chamber to prevent any possibility of explosion from gasoline fumes or other gases which might be ignited by an open flame. They are usually provided with automatic room tem perature controls and are well suited for heating either residence or commercial garages. CONVERSION HEATING SYSTEMS Residence heating with gas through the use of conversion burners in stalled in coal-designed boilers and furnaces represents a common type of gas-fired house heating system, especially in natural gas territories. In many conversion burners radiants or refractories are employed to convert some of the energy in the gas to radiant heat. Others are of the blast type with luminous flames, operating without refractories. In each case an attempt is made to transfer the majority of the heat from the gas to the medium to be heated within the fire pot itself because of the low heat transfer that takes place in the flue passages. Many conversion units are equipped with sheet metal secondary air ducts which are inserted through the ash pit door. The duct is equipped with automatic air controls which open when the burners are operating and close when the gas supply is turned off. This prevents a large share of the circulation of cold air through the combustion space of the ap pliance when not in operation. By means of this duct the air necessary for proper combustion is supplied directly to the burner, therefore making it possible to reduce the amount of excess air passing through the com bustion chamber. Conversion units are made in many sizes both round and rectangular to fit different types and makes of boilers and furnaces. They may be secured with manual, push button, or room temperature control. SELECTION OF GAS BOILERS While gas-burning equipment can be and usually is so installed as to be completely automatic, maintaining the temperature of rooms at a pre determined and set figure, there are in use installations which are manually controlled. Under such control the temperature variations are consider able because the human body does not react as readily to temperature changes as does a thermostat, and a. greater boiler output is required quickly to regain comfortable temperatures. Experience has shown that in order to effectively overcome the starting load and losses in piping, a manually-controlled gas boiler should have an output as much as 100 per cent greater than the equivalent standard cast-iron column radiation which it is expected to serve. Boilers under thermostatic control, however, are not subject to such' severe pick-up or starting loads. Consequently, it is possible to use much lower selection or safety factors. A gas-fired boiler under thermostatic control is so sensitive to variations in room temperatures,.pressure of 293