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Heating Systems Sub-Atmospheric Steam C. A. Dunham Company Administrative and General Offices 450 E. Ohio Street, Chicago, 111. Factories: Marshalltown, Iowa; Michigan City, Ind.; Toronto,.Canada; London, England C. A. Dunham Co., Ltd. 1523 Davenport Road, Toronto, Ont., Canada 17/ HEATING C. A. Dunham Co., Ltd., (Of the United Kingdom) Morden Road, London, S.W. 19 SERVICE England See "Dunham Heating Service" in local telephone directory in all principal cities. The accumulated experience of the entire Dunham Organization is put at the disposal of the Heating, Ventilating and Air Conditioning Engineer. This cooperation is available for Modernization Work and Repairs, as well as for new construction in industrial, com mercial, housing and other projects. The Dunham Differential Heating System, circulating sub-atmospheric steam, maintains desirable temperatures throughout a building by automatic control of both steam temperature and steam volume. The system is a simple two-pipe system in which all the essentials of circulation, distribution and control are co-ordinated. Control of the temperature of the steam is accomplished by controlling the pressure or vacuum of the steam in the supply piping and radiators to balance exactly the heat input with building-heat-loss. The Dunham Differential System distributes a varying supply of heat equal ly, automatically and continuously through the heated space. Desirable building tem peratures are automatically maintained under varying weather conditions. A positive continuous circulation is main tained as a fundamental function of the system. This maintains unusually con stant temperature levels throughout the building. The Control- is Fully Automatic. The RT (Resistance Thermometer) Con trol Equipment, which is an integral part of the System, is fully automatic. Begin ning with a maximum radiator heat output obtained by steam circulation at a pressure of 2 pounds and a temperature of 218 F or more as required, the output is progres sively reduced according to the demands of the weather, by a reduction in the rate of steam admission to the system, which automatically causes a reduction in steam pressure and temperature so that steam may be circulated at varying temperatures down to about 133 F. Further reduction in heat-output is obtained by partial filling of radiators with sub-atmospheric steam until the point is reached at which the need for heat ceases and the supply of steam is completely shut off. The distribution of the steam supply is automatically main tained under all variations in supply by the co-ordinated functioiHng.of the Traps, Pump, Differential Controller and Regu lating Orifices at radiator inlets. C. A. Dunham Company Healing Systems Sub-A tmospheric Steam DUNHAM UNIT HEATERS Type R Type C--A specially designed unit heater for industrial and com mercial applications. Designed for discharging large volumes of heated air downward to working levels, distributing heat evenly over large areas. 10 sizes from 136 to 2000 sq ft EDR. Four types of diffusers. Type R--Blower type unit for industrial and commercial applications. Available in 16 standard sizes, each with various combinations of Btu and cfm out put. Floor, wall and suspended types, with and without by-pass or mixing dampers. All sizes and types either direct connected or belt drive. Type V--Horizontal propeller fan type. 35 sizes. Capacities from 65 to 1200 sq ft EDR. Type D--Horizontal propeller Type D fan type. 12 sizes. Capacities from 558 to 2360 sq ft EDR. DUNHAM PUMPS Tested and Rated with A.S.H.V.E. Code and Code of Vacuum Return Line Heating Pump Manufacturers' Section of Hydraulic Institute. Vacuum Pumps Type DVD--Designed for use with Dunham . Dif ferential Heating. Capable of maintaining whole sys tems under vacuums as high as 25 in. Built in 9 sizes. Capacities 2500 to 65,000 sq ft EDR. VRD (VacReturn Line) built in same sizes. Type VR--Meets all code tests for air and simultane ous air and water handling capacities. No moving parts or close clearances in exhauster unit. Built in 11 sizes. Capacities 2500 to 150,000 sq ft EDR. DV (Dif ferential Vacuum) built in same sizes. Condensation Pumps Pump and motor assembled on rigid cast iron base. Bronze fitted centrifugal pump has non-corrosive shaft. Enclosed type Impeller. Liberal size ball bearings. Receiver tank equipped with float switch and push button starting switch with over-load protection. Type CH-Model B, Single and Duplex--66 sizes Type VR of varying capacities and discharge pressures. Capaci ties 2000 to 50,000 sq ft EDR; 60 cycle d.c. or a.c. 1750 rpm; 25 or 50 cycle a.c., 1450 rpm. Type CHH-Model B, Single and Duplex--49 sizes of varying capacities and dis charge pressures. Capacities 2000 to 50,000 sq ft EDR; 60 cycle d.c. or a.c. 3450 rpm; 25 or 50 cycle a.c., 2850 rpm. Type CV--48 sizes of varying capacities and discharge pressure. Capacities 2000 to 25,000 sq ft EDR. 1018 Single Unit Type CH--Model B CHH--Model B, same connections Duplex Unit Type CH--Model B CHH--Model B, same connections 1019 Type CV