Document 8R0ZOYoRopMjnn7y69dbeNQD5

American Society of Heating and Ventilating Engineers Guide, 1929 through additional thermostats placed in the room and controlling the direct radiators. There should be a vacuum system of steam circulation, and the thermostats should be of slow or intermediate acting type, operating on the supply valves to the radiators. Hot-Water Radiators . Hot-water radiators lend themselves to automatic heat control, especially where the circulation of water is of the forced type, but as the radiators heat and cool rather slowly, there will be some temperature fluctuation or range at the thermostat, especially when the radiator --Thermostat Double M/xing Dampery.^ T Moving Slowly \-s Fig. 4. Cold Air Shut-off Damper. / Operatedby Pneumatic Manual Valve Diagram of a Method of Control for a Unit Ventilator surface is excessive in amount. It is wise to use supply valves which will close tightly and to place lock-shield valves on the return ends of radiators, to facilitate repairs, and the lock-shield valves may prove invaluable in equalizing.with great nicety the circulation. In residence heating with hot water it often suffices to install a general thermostat in some representative room, which controls the draft, as with coal, or which controls the fire, as with gas or oil, but there should always be furnished in addition a thermostat in the water or circulating medium which will reinforce the general thermostat and which will prevent boiling over in case the general thermostat should be subjected to unfair exposure, such as an open window. Wartn-Air Heating Systems With warm-air heating from furnaces, with fans, as in public buildings, it is always necessary to provide a supply of tempered air for cooling after the rooms become warm. A duct thermostat and dampers easily and positively will accomplish this, either by mixing some cold air with 264 Chapter XVI--Automatic Heat Control heated air from the furnaces in an intermediate chamber, or by injecting some hot air from the furnaces into the cold air at the fan inlet, recir culating a measured and controlled part of the air around the furnaces. The room temperatures are controlled by intermediate thermostats and double mixing dampers the same as for a steam system. Warm-air heating for residences may be controlled by a general thermostat in a representative room, and again, as with hot water, an additional thermostat at the furnace in the warm-air chamber is desirable to reinforce the general thermostat. Service Hot Water It is safe to say that no service hot-water heater should ever be installed without automatic heat control. Automatic heat control for this service not only saves fuel, but also prevents scalding and damage to materials. It also brings about a great reduction in maintenance of valves, pipes, Thermostats Dud tv Room ch-- Te^eredAiP^.-V Insulated Slab /Mixing Dampersfor Tempering Mixing Dampers' Controlled by " Thermostat m Each Room i * * f\ 'Fan Fig. 5. An Arrangement for Tempered' Air with Warm Air Furnaces and fixtures. A unit type thermostat is most desirable, since it will function whether or not the general mechanical apparatus is in service, and will control steam and return valves or draft dampers, oil or gas fires, or electric heaters, In hotels, hospitals, and similar institutions, there should always be at least two independent water heaters, one having very hot water for kitchen uses, the other having wafer of medium temperature for bath and lavatory purposes, both controlled automatically; Thermostatic anti-scalding devices are available for showers and the like, but these will not prevent the great heat waste due to maintenance of scalding temperatures for bath water. No kitchen administration is-satisfied without very hot water, but this demand is intermittent and small in volume as compared with usual bath and lavatory demands, Oil Burner Control No oil burning apparatus, unless provided with automatic heat control, can compete in operating cost with coal. An approved method for residence heating with oil is to install the following combination: I;; A general thermostat in a representative room, controlling the electric supplyto the burner motor. 2. A second thermostat in the' boiler or furnace which will take control should No, 1 265