The Exhibitor (1960)

Importance of Hot-Water Temperature Control How Temperature Control Can Affect Effective Operation of Equipment ■ One of the “headaches” that afflict owners and managers of buildings in cities where the water is corrosive, is replacing pipes because of damage done by action of the water. This damage espyecially affects the hot-water dis¬ tribution systems, if the water is overheated. The more corrosive waters are usually the soft waters (those with a low content of min¬ eral salts), such as the supplies of New York and the majority of cities along the Atlantic seaboard. However, certain hard waters may also be corrosive if the mineral salts are large¬ ly calcium and magnesium sulphates. The Schuylkill River water in Philadelphia offers an example. Heating the hot-water supply above 140 Fahrenheit is imnecessary and is destructive to the pipes. It speeds up the clogging process that renders iron pipe useless and it speeds up the dezincification process that weakens the structure of yellow-brass pipe. Since a temperature of about 120 Fahrenheit is as high as the human hand can endure, a temperature of 140 Fahrenheit should suffice for most pur¬ poses. Overheating Effects Although suitable anticorrosion treatment applied to water will minimize corrosion of the piping under normal conditions, its effec¬ tiveness will be diminished if the water is greatly overheated. To obtain a general picture of the hotwater situation in New York, temperature¬ recording devices were recently installed in a group of typical buildings. Two of the tem¬ perature-record charts are shown (Figures 1 and 2). The record is made as follows: The circular chart is set on a machine that has a revolving disk mechanism — like a phonograph turntable — which causes the chart to revolve very slow¬ ly, making a complete revolution in one week. The days and hours are shown on the rim of the chart. During the week, a pen, controlled by a thermometer device on the hotwater supply main, traces a line that con¬ tinually registers the temperature of the water. The temperatures are indicated on the lines that radiate from the center of the chart. The record obtained in a building where there is good temperature control is shown ftgU't I By W. J. Ryan Technical Manager Water Service Laboratories^ Inc, (Figure 1). Examination of the chart will show that, except for occasional dips, the tem¬ perature of the water supplied to the tenants remained near 140 Fahrenheit practically the entire time. Even during the dips, the tem¬ perature did not go below 120 Fahrenheit. This building is assured of a supply of hot water at the right temperature at all times. Hit WaferSuppfy Th*fmotiatie Sham Aayulator ‘ ‘ r Sfaam m. ( //of Wator Tah/i L ' ' Condanood i^Stoam Co/d Wa/trFotd BoHar Figure 3 Temperature Variance Observe what was going on in the building represented by the other chart (Figure 2). The temperature varied continually over a wide range, from 150 Fahrenheit to over 200 Fahrenheit. In fact, at many times the tem¬ perature was in excess of 200 Fahrenheit — the highest reading the chart will show. At a temperature above 212 Fahrenheit some of the water will instantaneously flash into steam when a hot-water faucet is opened. The person who turned on the water could easily be sccdded. In addition to increasing the corrosiveness of the water, overheating and wide fluctuations of temperature cause ex¬ cessive expansion and contraction strains that help initiate leaks at screwed joints. If the building has iron pipe or iron hotwater tanks, corrosion may give the water a rusty color. The users will then waste large volumes of water hoping for clean water to appear. This wastes heated water and overloads the hotwater generator — aggravating an already bad state of affairs. Conditions such as those shown (Figure 2) were found to exist in many buildings and are doing enormous damage to the piping — damage which the owner may be unaware of imtil he is faced with an extensive and ex¬ pensive repiping job. Controlling the hot-water temperature is not difficult and usually requires very little, if any, expense for equipment. The first re Figure 4 quirement is to see that a thermometer is in¬ stalled on the hot -water supply main at some convenient point where the engineer or su¬ perintendent can read it. If the temperature is too high at any time, the operation of the con¬ trols should be investigated. Thermostatic Regulators If hot water is supplied from tanks heated by steam coils, it is the usual practice to in¬ stall thermostatic regulators on the lines that admit steam to the coils. Essentially, this reg¬ ulator consists of some type of diaphragm valve controlled by an expansion element im¬ mersed in the tank water. It is well to have a thermometer on each tank (Figure 3). If the water is heated by an instantaneous heater, a thermostatic mixing valve should be installed on the hot-water supply line from the heater and care should be taken to keep the valve adjusted to control the temperature (Figure 4). Incidentally, the hotwater supply piping between the boiler and the mixing valve should be red brass, regardless of what kind of pipe is used in the remainder of the system. Red-brass pipe is required because the water in that particular part of the system is at a very high temperature. Irrespective of what means are used to heat water, it is not difficult to keep the temperatxire under con¬ trol, if the importance of doing so is under¬ stood. Some people have the misconception that the hot-water supply should purposely be overheated in order to provide hot enough water at distant outlets. This should not be done. The proper way to secure hot water throughout the building is to see that circu¬ lation is maintciined by means of a thermo¬ statically controlled circulation pump on the main return. Such a pump should be installed wherever the circulation is sluggish because of pipes being partly clogged with rust or because of long horizontal lines of pipiag. Whenever occasion affords, it would be well for architects and engineers to emphasize the need for hot-water temperature control, not only to protect their clients’ investments in buildings but also to protect themselves agciinst possible vmjust criticism ai-ising from too rapid failure of the pipes in the buildings they design. fieure 2 80 MOTION PICTURE EXHIBITOR-1960 THEATRE CATALOG Edition April 6, 1960