Document LpB38QbrkpQN4kYKvd8po6v4b

HEATINC VENTILATING AIR CONDITIONING GUIDE 1943 under load, NEMA classification No. 56 or 76 is used. For constant torque speed regulation, resistor No. 95 is used. Liquid rheostats for secondary control, suitable for starting and speed variation are available where an infinite member of speeds are required. The cost of the liquid rheostat are comparable to the conventional cast grid and cam switch construction in the larger sizes but more expensive in the smaller. The liquid rheostats are suitable for either constant or variable torque drives but are hot satisfactory for cold ambient con ditions, where the electrolyte could freeze during periods of non-operation. The amount of resistance in the circuit can be manually or automatically controlled. 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 coritrol 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. 698 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. ' .y 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 fn operating rooms began with the introduction, of modern anesthetic gases and apparatus. Ether administered by the' bid 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 cyclopropane-oxygen mixtures1. (See!Table 1.) During; the. course of ethylene anesthesia, the mixture, usually SO per cent'ethylene and 20 per cent oxygen,1.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 washed outwith oxygen with or without the addition of 1Safeguaniing the Operating Room Against Explosions, by Victor B. Phillips (Modem Hospital, 46, April and May, 1936); 699