Document b50vndJZNLaaN76EymLZOyQYk

HEATINC VENTILATING AIR CONDITIONING GUIDE 1942 load a starting resistor NEMA classification No. 15 may be used. For speed regulation resistor, classification No. 93 should be selected. On a compressor drive using an unloader, a constant torque resistor classi fication No. 15 should be used. If the compressor is started under load, NEMA classification No. 56 or 76 is used. For constant torque speed regulation, resistor No. 95 is used. SINGLE PHASE MOTOR CONTROL Where three phase current is not available or where single phase opera tion is preferred, then single phase repulsion induction, capacitor type or multispeed single phase motors may be used. Since the starting currents of all single phase motors are required to be within the starting-current limits established by the local power supply company, a suitable type of starter may be chosen from the following selection: 1. Enclosed two pole manually operated motor starters with thermal overload protection. 2. Enclosed two pole automatic motor starter operated by a push button, thermostat or.similar device, with thermal overload relay and low voltage protection. . 3. A manual or magnetic resistance type starter with,low voltage protection. 4. A manual or magnetic control for pole changing motors and for adjustable varying speed motors using an auto-transformer or resistance in the primary circuit to obtain line (or terminal) voltage drop. In selecting across-the-line control for single phase capacitor type motors it is usually very desirable to use three pole across-the-line starters. Control for multispeed, single phase capacitor motors may be selected from tables on-three phase rating when consideration is given to the increased, current and the necessary switching of connections. 696 Chapter 37 AIR CONDITIONING IN THE TREATMENT OF DISEASE Operating Rooms, Reducing Explosion Hazards, Nurseries for Premature Infants, Fever Therapy, Cold Therapy, High ' Temperature Hazards, Control of Allergic Disorders, Oxygen Therapy, General Hospital Air Conditioning IN the past few years air conditioning has made considerable progress as an adjunct in the treatment of various diseases. Among the important applications are those in operating rooms, nurseries for premature infants, maternity and delivery rooms, children's wards, clinics for arthritic patients, heat therapy, cold therapy, oxygen therapy. X-ray rooms, the control of allergic disorders, and for the physiological effects in industry. OPERATING ROOMS The widest application of air conditioning in hospitals is in operating rooms. Complete air conditioning of operating wards is important because winter humidification helps reduce the danger of anesthetic gases; summer cooling with some dehumidification is needed to eliminate excessive fatigue and to protect the patient and operating personnel; and finally, filtering for the removal of allergens from the operating room air. Reducing Explosion Hazard Explosion hazards in operating rooms began with the introduction of modern anesthetic gases and apparatus. Ether administered by the1 old drop method is still regarded as comparatively safe; but when mixed with pure oxygen or with nitrous oxide in certain concentrations the' explosion hazard may be as great as with ethylene-oxygen, or cyclopro pane-oxygen mixtures1. (See Table 1.) During the course of ethylene anesthesia, the mixture, usually 80' per cent ethylene and 20 per cent oxygen, is so rich that the danger of explosion is slight in the immediate vicinity of the face mask, but leakage of ethylene into the air may accumulate to any lower concentration, and thus introduce a serious hazard. The most dangerous period, is at the end of the operation when the patient's lungs and the anesthesia apparatus are customarily washM. out with oxygen with or without the addition of 1 Safeguarding the Operating Room Against Explosions, by Victor B. Phillips {.Modern Hospital, 46. April and May, 1936). 697