Document Y9pbzRaVGVOw4oVDYRg3Q3dBO

910 CHAPTER 39 zone. In Figs. 3 and 4 the heating equipment controls and safety devices, which are always essential, are not shown. These devices are described in the previous section Residential Control Systems. Important con siderations in panel heating controls are means of preventing the intro duction of excessively hot water in the event of control failure, which might damage the panels, and a manual boiler by-pass or other means of reducing the water temperature to prevent too rapid drying out of new panels. (See Chapter 24, Panel Heating.) The control arrangement for electronic systems are similar to Fig. 4 but all controls act on the electronic relay which coordinates the signals from the room thermostat, the outdoor element, and the return water control bulb to vary the flow of water in proportion to heating demand. INDIVIDUAL ROOM CONTROL The ideal temperature regulating system for any building is one that promotes maintenance of a desired temperature in every room at any time, regardless of location and occupancy. Individual room temperature control is recognized as the answer to proper thermal environment in schools, hospitals and offices. Demand for it is increasing, to meet individual requirements in apartment homes, hotels and separate residences. Control of the temperature in each room or possibly of adjacent rooms having the same orientation (as in an apartment home) overcomes many of the problems encountered when attempting to regulate the temperature of a building as a whole, or of large areas or zones. Each individual ther mostat regulates the heat input for its particular space regardless of expo sure to sun and wind and occupancy. The end result of individual room control is fuel economy and comfort of the occupants. Each room shorn have a thermostat that controls valves or dampers on all the controUabe sources of heat or cooling effect. One uncontrolled source of heat in 8 room in which a thermostat controls other sources of heat, or cooling; will lead to eventual unpopularity of the thermostat or control system- ZONE CONTROL Zone control for any heating, ventilating, or air conditioning system employed where it is desired to control the heating or cooling effect m number of rooms or areas, which have similar orientation and occupaWy> through one set of controls. Under certain conditions, particularly Automatic Control 911 buildings of limited size, it is possible to consider the entire building as a single zone. In such cases, as in small residences, a single thermostat is used to control directly the automatic firing equipment, main heating valve, or the cooling equipment. In large buildings the demand for satis factory temperature control makes it necessary to sub-divide the building into suitable zones separately controlled. There are a number of factors to be considered in zoning, in order that heating requirements in a single zone will be approximately consistent throughout its extent. 1. Exposure may be a factor to be considered, with particular reference to pre vailing winds, sun effect, and the shelter afforded by surrounding structures and topographical features. 2. Occupancy may be a determining factor, in that the indoor temperature re quirements for the activities carried on in various portions of the building may vary, and the hours of occupancy likewise may differ. 3. The physical characteristics of the building will enter into the subdividing of the heating system into zones by reason of the fact that satisfactory temperature conditions throughout a single zone of given extent may not be enjoyed equally in buildings of dissimilar types of construction. Also, the height of the building and its horizontal extent and form are considerations which must be borne in mind. 4. The cost of the zone control equipment for such additional zones as might seem otherwise desirable, often will influence the decision as to.the final number of zones to be employed. In buildings of considerable size, accepted practice dictates that there shall be at least one zone for each exposure, although each exposure very pos sibly should be sub-divided vertically into two or more zones, for the higher struc tures. Also, the presence of two or more wings, having the same general exposure, may suggest the desirability of more restrictive zoning. When the street floor, or any other portion of the building is used for public occupancy or activities which differ from those carried on in the remainder of the building, it is desirable to provide separate thermostats and controls for each individual area. For zones which have outside exposures, the control for the zone must, in some manner, respond to the effect of the outdoor temperature, the sun exposure, and the variations of the wind as they effect the temperature and conditions in the zone. Additional Features Provisions may also be made to maintain a predetermined low economy temperature in each zone during periods of non-occupancy; to facilitate quick warming-up following such periods; and to follow those portions of periodCyC'e contrl with normal heating effect during the occupancy A control panel, at a central location, may be arranged so that manualfeet switches for each zone may raise or lower the operating temperature. Ime. switches, if desired, may be provided for obtaining, automatically, ;^ay-night or other predetermined control program which the operators be building may desire. The characteristics of the regulators which are Jierated by the zone controllers depend upon which of the basic systems th ^ con*'rl ^ employed in a given installation. Shut-off, mixing or 0f 0 j mS valves, and various forms of devices to reset or pilot the action i educing valves and to control firing means, are some of the more comund re^a*'ors which are used to control the flow of steam or hot water, feinTf 6 command f zone controllers. The characteristics of these trriii1 a ,s Usuaily are determined by the manufacturer of the type of contro er which is selected. DESIGN COORDINATION out rheatjTg or col'n8 plant designed to meet maximum conditions with- egard to controllability, may be unduly costly to operate and difficult