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1950-51 Theatre Catalog, 9th Edition, Page 378 (356)

1950-51 Theatre Catalog, 9th Edition
1950-51 Theatre Catalog
1950-51 Theatre Catalog, 9th Edition, Page 378
Page 378

1950-51 Theatre Catalog, 9th Edition, Page 378


Air filters are a necessary component of the air cycle. There are two types of filters-the throw-away type, which is discarded after usage, and the permanent, all-metal type. The latter, although it costs threaand-a-half times as much as the throw-away, is the best buy. It will prove to be the most economical throughout its five-to-ten year lifetime.

And remember, it costs money to tear down a system. This is necessitated most frequently by dirt in the filters. Properly cleaned, and they can be cleaned, using the right tools and the right technique, the permanent type will justify its original cost.

Some Theory

The refrigeration cycle revolves about the compressor, condenser, liquid receiver and cooling coils, plus the various conducting gas and liquid pipe lines. The compressor, the heart of the refrigeration cycle, pumps the hot gas or refrigerant at high pressure through the discharge line to the condenser.

The outside of the condenser tube wall is cooled by water, which condenses the hot gas in the tube to a liquid, at high pressure. This liquid flows to the receiver and thence through liquid lines to expansion valves, which, essentially, are needle


CASE HISTORY: During a hot spell, the air-conditioning system of a 1000-seat house was short-cycling badly, The main trouble was the water supply. The kids were everywhere under the fire hydrants, and there just wasnit enough. water to go around.

The water pressure, abnormally low, was unable to force water up to the evaporative condenser, set up 54 feet above the street. Further, there was no iimake-up water,, to feed into the lievapf, This meant dragging buckets of water up four flights of stairs. What to do? The solutioneand the only one: Put in a small pump in the water line feeding the condenser. Thatis what the theatre maintenance engineer did. The pump. actuated by the pressurestat, went to work whenever the water pressure fell too low to push itself upstairs.


valves. The valves allow only a small

discharge of the refrigerant to now

through the cooling coils or evaporator. Here pressure is reduced. The liquid expands, becomes gas, and the temperature drops.

As the refrigerant comes through the cooling coil, it is vaporized by the heat of the coil. (The heat is from the air of

HUGE QUANTITIES OF WATER are required to dissipate the heat of the compressor action in any large central plant system, with proportionately smaller quantities in smaller systems. Cooling towers such as below are capable of spray cooling 900 gallons per minute, and while relatively trouble tree in operation they also require periodic cleaning, painting and maintenance care.

the theatre, the air that will be redistributed.) This gas flows back to the compressor through the suction line, and the cycle is repeated.

The Compressor

The compressor is the most vital part of the entire cooling system. It requires experienced, intelligent handling. The crankcase of most compressors is fitted with an oil-level gauge or bullseye. The crankcase must hold just the right amount of oil. Too little oil will cause the bearings and other moving parts to bind. This condition, of course, will occasion excessive wear and overload on the motor.

On the other hand, over-filling of the crankcase will cause slugs of oil to be tossed abouteand pounding. A noisy condition will result too, from broken compressor valves. These can be detected by testing for temperature differences in the cylinder heads.

The Condenser

Heat removal is the condenserls job. The heat must be taken away from the refrigerant in order that it can be converted from a gas to a liquid. There are three types of condensers: air, water, and evaporative. In theatres, the evaporative type is used most commonly.

Since it combines the functions of the air and water types, the evaporative condenser is similar in its maintenance needs; and tips for its care will apply to all three types. The evaporative condenser takes away large quantities of heat by using very little mechanically circulated water and air. As a result, less power is required to run the system.

To get the utmost out of this most efficient piece of apparatus, it is good practice to treat the water with a softening solution. This will help to keep the solid matter from forming scales on the coils. A shortage of water over the coils will cause high head pressure and short cycling.

Short cycling can be due to dirt in spray heads, to a stoppage of the circulating pump on the condenser, or fans, strainers, and coils. It is difficult to overemphasize the importance of keeping the cooling coils, over which the air is passed, free from dust and dirt. Dirt acts as an insulation. A heavy crust of it can be removed properly only by using a high-pressure spray treated with a cleansing agent.

Care, too, should be exercised in seeing to it that the condensation pan drains are open. Stagnant pans will give off unpleasant odors. And an overflow would be damaging to the building.


These selected tips on maintenance, aided and abetted by true case histories, make it Very plain that: there are a vast number of ttbugs" that can foul up complex air conditioning equipment; prevene tive maintenance is the most economical way of taking care of the air conditioning plant; and when something does go wrong, the quickest way to get the machinery fixed and the surest way to avoid high blood pressure is to reach for the telephone and call up the nearest theatre maintenance engineer.

1950-51 Theatre Catalog, 9th Edition, Page 378