[D8831ACP], Letter from William Dennis Marks to Edward Hibberd Johnson, 1888



"Your attention is respectfully invited to the following features of construction now being incorporated in the station and system of the Edison Electric Illuminating Company of Philadelphia, Penna. ### In this Report no effort is made to elaborate on details but simply to bring out clearly the most radical features of departure from our best and most reliable central station practice. ### I. Dynamos. ### The Constructors of this station have undertaken the application of a new type of dynamo of double the capacity of the largest dynamo the Parent Company have approved, and which it has taken this Company years to approach. This new type of dynamo is to be completed within the limited time allowed for the construction of the Philadelphia station. ### You will readily recall to mind the numerous meetings held previous to the commencement of construction on the New York stations, and that for some three years the question as to size of dynamos was very carefully considered at these meetings. The dynamo known as type "32" having a maximum capacity of 140 volts and 575 amperes was finally decided upon as being a long step in avance of al previous practice, and as being a safe and conservative size of dynamo to apply in stations of the proposed capacity of the New York stations. This size was also decided upon for use in the stations of the Philadelphia Company and of the Chicago Company. The questions of relative proportion between station capacity and requisite output in a district were very carefully considered, the result of all conferences being that it was deemed unwise to make the station units larger than two hundred horse power each. ### In accordance with this decision the original plans of the Philadelphia station incorportated the use of the No. 32 dynamos. These plans have been entirely changed, and the Philadelphia Company have requested the Machine Works to build a dynamo to be known as type No. 56, whose maximum capacity shall be 140 volts and 1,000 amperes; two of these dynamos to be driven by one engine will require at least 440 horse power, to operate them to their full rated capacity. III. The Philadelphia Company have received the following letter from Mr. Edison: Orange, N.J. May 12th 1888 ### I have your letter of the 10th instant. I believe Babcock Boilers and 160 pounds pressure, high speed engines and good engineers with good pay, 1,000 ampere machines with a margin in them for three hours of 1200 amperes and an extra 30 volts that is 140 volts to take care of the future improvements in high resistance lamps." Yours very truly, Thos. A. Edison [Marginalia: "As marks got more lights than by old plain 400 hp is good unit."] ### "It will be noted that the above letter is a cautious endorsement of the larger units, and does not guarantee anything. ### Under date October 16th, 1888, the Edison Machine Works write as follows: Schenectaday, N.Y. Oct. 16, '88 ### Edison Electric Light Co. ### We have your favor of the 15th instant, and in reply beg to say that we have not as yet made a test of the No. 56 dynamos which we are building for the Philadelphia Co." Yours truly, Sam'l Insull ### IV. "The dynamos will occupy much larger floor space than the dynamos the Light Company advised the Philadelphia Company to use. [Marginalia: "Not per light"] On account of occupying this large floor space, it is not possible to arrange the dynamos in the same positions on the floor as the original plans using No. 32 dynamos called for. See plan 'A'. ### V. The new arrangement of No. 56 dynamos is shown by the plan 'B' attached herewith. By reference to the plan orginally furnished the Philadelphia Company, it will be seen that the No. 32 dynamos were arranged in regular order, and there was given ample space around each dynamo for manipulating the brushes and taking care of the commutator and bearings while this space is considered to be ample, it has still been reduced to the minimum amount required in practice. ### Several central station managers have stated that while the space shown on our plans appears to be ample it is found in practice that the dynamos are somewhat crowded. ### VI. By further reference to original plan 'A' it will also be seen that ample room is left in the entral part of the station between the rows of dynamos for placing of the necessary electrcial apparatus, for the equipment of the station. ### VII. By reference to the floor plan 'B' showing arrangement of dynamos as now indicated by the Constructors of the Philadelphia station, it will be seen that there is no regularity in the position of the machines; also that the space around the machines is reduced to such a small amount that it is impossible for a man to pass between them. It will furthermore be noted that owing to the relative angles at which the dynamo pulleys are placed to correspond with the engine pulleys, that the belt holes are of necessity exceedingly large so as to admit the passage of the belts and that in numerous instances these large belt holes come almost directly under the commutators of adjacent dynamos, thus making it a very dangerous undertaking for an attandant to climb over the dynamos hastily. He must climb over them because there is not room for him to pass around them. ### Practical experience in attendance on central stations have proved that it is absolutely necessary in all stations to so place the dynamos and electrical apparatus as to give easy access, and make them available for prompt and quick action of employees in case of accident. ### Those of us who have had this pratical experience in operating dynamos in central stations know as a fact that very often something occurs when the promptest movements on the part of the attendant are necessary to save dynamos from damage, and we know that at such certain times it is important that the man operating the station can get around all the machines quickly, and with perfect safety. It will be impossible to do this under the proposed arrangement of dynamos in the Philadelphia station. ### IX. By close examination of the plans, it will be readily seen that there is no direct passage either fore and aft of the station, or from side to side, without clambering over the large machines. ### Another important point is that in time of short circuit it may happen that the station will be in absolute darkness and it is imperative that the station attendants have free passage-ways, that are well known,so as to easilty and safely find their way between machines without any risk of personal injury. ### X. According to the plans furnished by the Edison Machine Works, these dynamos will have above the floor a height of 43 inches at the commutator. You will readily see how this compares with the height of a man, and that even where the space is 18 inches wide, it is exceedingly dangerous to crowd between a rapidly moving belt and a dynamo base frame when there is an open belt hole ready for a man to fall into. Where the space is reduced to a few inches, it is only possible to do it at risk of life and limb. ### XI. A careful examination of the position of dynamos marked X, will show it to be impossible to give proper attendance to the brushes. There is no passage from one side of the commutator to the other. The height of the commutator from the floor appears not to have been considered. ### XII. In view of the foregoing general facts I now state specifically that if the above described plan of arranging dynamos is carried out in the Philadelphia station, it will be found utterly impossible to give the requisite careful and prompt attention to the adjustment of brushes, oiling of bearings, setting of rocker arms, opening and closing of dynamo switches and the various other work which is actually required to be performed to keep the station in operation. [Marginalia: "Nonsense"] ### The safety, economy and convenience of the station have been entirely sacrificied to the effort to secure within a limited floor space double the capacity of apparatus which should be placed therein. ### Under the described conditions it will be found to be absolutely impossible to operate more than 75 per cent. Of the apparatus and even this can only be done at great risk and disadvantage. ### XIII. I also believe that in order to meet the requirements of the Philadelphia Company for getting this abnormal dynamo capacity within the floor space provided, that the Edison Machine Works have been forced to devise such a type of dynamo as will not compare favorably in commercial effeciency and other features of operation with the previous types of dynamos endorsed and used by the Light Company in their central stations. ### ELECTRICAL APPARATUS ### XIV. In arranging for the placement of the electrical apparatus in a large central station, it is of vital importance that ore feature is constantly kept in view, which is, that all of the apparatus connected with the regulation of the station or the indication of pressure or quantity of current should be so placed that one man can have complete survey of the entire apparatus and govern and direct the regulation of the entire station at one time as far as possible. ### To accomplish this the various types of apparatus must be assembled together each by itself and yet each kind in such location as to give easy supervision and control over all. ### XV. In this particular the constructors of the Philadelphia station do not profit by the past practice or experience of the Light Company in the construction of central station apparatus, or in the location thereof. ### It is not proposed to apply in the Philadelphia station any type of apparatus which has been proved a standard for use in our central stations. Previous to planning and ordering the out fit of electrical apparatus no consultation was held with men who have had long practice and experience in the construction of other stations, and in the placing of electrical apparatus connected therewith. ### XIV. New types of dynamo ampere meters, feeder ampere meters, main ampere meters, neutral ampere meters, and other appliances have all been devised and ordered at a largely increased cost over standard appliances. Elaborate working drawings have been made for each one of these types of ampere meters, regardless of whether or no they will correctly indicate the quantities of current which it is desired to register. The feeder equalizers are proposed to be of an entirely different type from anything heretofore constructed. ### XVII. Many of us have followed from year to year the construction and improvement of these various appliances, and we know from actual practical experience that while electrical apparatus can be constructed according to a certain plan, the standardizing and correct indication of currents by that apparatus are quite another matter. ### XVIII. The electrical apparatus is not in any manner placed as is usual, or as has been essential in our experience for economical operation of an Edison station. In large stations of this character it is beyond question necessary that the apparatus should be so assembled together that but few station operatives will be required when the station is working at its maximum capacity, and that during the hours of minimum load, a correspondingly reduced number of operatives would only be needed to take care of the regulation and indication. ### XIX. These results cannot possibly be accomplished if the apparatus is located in the Philadelphia station as it is now proposed according to the plans. The electrical apparatus is not in any manner placed as is usual, or as has been essential in our experience for economical operation of an Edison station. In large stations of this character it is beyond question necessary that the apparatus should be so assembled together that but few station operatives will be required when the station is working at its maximum capacity, and that during the hours of minimum load, a correspondingly reduced number of operatives would only be needed to take care of the regulation and indication. ### XIX. These results cannot possibly be accomplished if the apparatus is located in the Philadelphia station as it is now proposed according to the plans. The electrical apparatus is practically divided into four sections--each isolated from the other and without communicating passages. ### By inspection of the plans, it will be seen that the main 'bus rods are to be mounted the entire length of the station on each side and that the dynamo ampere meters, the main ampere meters and feeder ampere meters are not assembled at any special point, but are distributed along the walls of the station covering fully 160 feet of wall in length and over 7 feet in height. ### Above these must be placed the dynamo regulators and the potential indicators; nearly one-third of all conductors, aggregating six sets of heavy copper 'bus rods, are incorported to indicate the current on twenty-four main and neutral ampere meters. A large number of ampere meters and safety catches are placed close down to the floor. ### Assuming that this arrangement of apparatus was placed on a wall space with ample passage ways for the operatives, it would even then be an impracticable and exceedingly inconvenient method of arrangement, but the fact must be considered that the wall space is limited to scarecely two ft. between the dynamo base frames and the walls and that into this limited space must be set up and mounted against the wall all of the feeder connections, feeder safety catches, ampere meters, cables, 'bus bars, switches, dynamo ampere meters and various other devices occupying a projection from the wall which would be in many places less than 14 inches. ### XXI. It now becomes manifest that the proposed plan is utterly impracticable and cannot possibly be worked even if it is set up. ### XXII. No man however small can crowd with safety between the operating dynamos and uninsulated electrical apparatus carrying heavy currents at moderately high potential, even at times when the station is operating under normal and perfect conditions, but when crosses or grounds occur on the outside system or when dynamos are accidentally operated improperly, or when an armature burns out, or when any one of the numerous accidents happens which at some time do occur in a central station it must be evident that it will become impossible for a man to reach with the necessary alacrity the point of accident and control the station in time to save the apparatus from serious damage if not entire demolition. ### XXIII. It is proposed to place the dynamo regulators something more than 7 feet above the floor and to control them by cords and levers. This arrangement is impracticable. In addition thereto it is not intended to place the dynamo regulators collectively at one point. ### XXIV. Those of us who understand the practical manipulation of a station and the CLOSE ATTENTION AND QUICK MOVEMENTS REQUIRED AT such times as dynamos are changed over, will seriously ask the question how it is going to be possible to give the close and accurate attention absolutely essential during this performance, which often takes place many times during twenty-four hours. ### XXV. The steam pipes leading from the boilers down to the engines and passing through the space between the dynamos and the walls on each side of the station actually block up the passage and practically divide the electrical apparatus into four sections. ### This makes it necessary even at times of minimum load to employ on this floor four sets of men to operate and control the station. It requires quite close attention to keep a number of dynamos at such constant potential as are required with one standard set of 'bus bars, but when it becomes necessary to maintain the regulation of three or four standards we must reckon it is quite outside of the range of ordinary possibilities. ### XXVI. They dynamos are so large that it is impossible for the operatives in one section of the room to see what is going on in another section, neither is there any point where the Superintendent of the room can have complete supervision of operations. Each dynamo will require three cables of a capacity of 1,500,000 circular mils per
cable, for making connections between the dynamos and the 'bus rods on the walls; the forty dynamos will require 120 of these cables. The plans do not show any practicable and safe method for placing these cables under the floor, as will become necessary. ### XXVII. In view of the many disadvantages thus made manifest concerning the dynamos and the arrangement of electrical apparatus I feel that we cannot too strongly condemn the proposed arrangement. It cannot fail to be impracticable, inconvenient and very expensive in many ways. ### XXVIII. The plans submitted of this station indicating the future arrangement shows that it is intended to incorporate entirely too much apparatus of abnormal capacity the majority of which is placed very badly. The capacity and output of the station have been greatly over-rated. All of these features cannot fail to result in an exceedingly expensive station to operate, very high cost of repairs and danger to employees and correspondingly diminished net profits to the Company. ### XXIX. In addition to the electrical features of this station which have been above noted, there are many features in the steam plant that may be considered as departing from what is generally accepted as the best steam practices in the United States, some of which may be briefly noted as follows: ### XXX. STEAM PRESSURE: ### I am informed that it is intended to carry a working pressure of 150 pounds per square inch, which is from 40 to 50 pounds more pressure than is carried in any of the Edison central stations. The Pearl Street Station is operating with the highest steam pressure which averages 100 pounds per square inch. Under this high steam pressure extraordinary difficulties are encountered in keeping joints, packing, valves valves and other places steam tight, in sound condition and free from leaks and blow-outs. [Marginalia: "Not so" E] While it is admitted that on locomotives and steam ships high pressures are used careful investigation proves that there is not at the present date any important stationary steam plant in use in the United States that is successfully operating at a pressure approaching 150 pounds per square inch. ### XXXI. STEAM PIPING ### It is proposed to make the main vertical steam pipe of considerably less than half the area shown by the original plans furnished from the Light Company. The builders of the leading high speed engines have been particular in impressing on us the importance of ample carrying capacity in the steam pipes, and actual experience has proven that we cannot depend upon calculations concerning friction, travel of steam, condensation, etc., but we have been compelled to provide piping ample in size to take care of emergencies which always arise in operating a stationand at times when we least expect these emergencies and are least prepared to take care of them. ### XXXII. It is proposed to put together the live steam system by screwing the pipes into malleable iron fittings with an occasional flange joint. This is not in accordance with the best steam practice. All leading engineering firms prefer to put such systems together with flange joints throughout. ### XXXIII. Engines. ### The engine are the same in cylinder dimensions as used in the New York and Chicago stations. It is intended to strengthen the shaft, cross head, piston rod and connecting ron and other necessary working parts to operate the engines at a speed of 230 revolutions per minute. With the increased speed and presure it is expected to force the engine to develop from 400 to 450 H.P. You will recollect our previous experiences in early central station work and the results; excessive depreciation and heavy repairs, many of which the Light Company were obliged to pay. The number of engines proposed for the station has been increased from 18 to 20. ### XXXIV. Water Separator. ### The water separator designed for this plant is not in our opinion constructed upon good mechanical principles to accomplish the results which are necessary. ### XXXV. Feed Water Heater. ### The feed water heater is not to be constructed according as the best steam practice has proven to be necessary Specific instances can be given where expensive repairs and changes have been made necessary by using heaters of a character similar to the one proposed for the Philadelphia station. ### XXXVI. Smoke Stack and Blowers. ### I have been given to understand that it is only intended to carry the smoke stack a nominal height of 25 feet, more or less, above the roof of the building, the idea being to rely upon pressure blowers giving a forced draught to the furnaces. Blowers have been placed in our central stations for use in emergencies only and not for constant service because it is considered that a forced draught is not economical, is injurious to the boilers and also that blowers are as unreliable as other machinery in constant use. Where a station depends for its actual and efficient operation upon a pressure blower it will readily be sen that if a breakdown in this department occurs at a time of heavy load the station must of necessity fail to perform its duty, on account of not having a smoke stack giving good natural draught. The short smoke stack and blowers are also considered to be objectionable because of the smoke and fine ashes which must of necessity settle in the neighborhood adjacent to the station and thereby become a nuisance. ### XXXVII. Rated Capacity of Station. ### You will readily recall to mind that at the numerous meetings held previous to the commencement of construction on the New York central stations, the maximum capacity of a large central station was very carefully considered. In connection with this was discussed the size of the central station units and the total output of the station; also the size of conductors and the number of feeders leading from the station to various points in the district; also the quantity of coal required per 24 hours for the operation of stations of certain sizes, the expediency of storing the large amounts of coal and carrying away the large amounts of ashes necessary to stations of large output. ### XXXVIII. Assuming that a minimum of but 125 loads of coeal per day are required, this will mean one load of coal to be delivered at least every 12 minutes in the 24 hours; not counting the carting away of ashes. ### All of the coal for this station must be delivered, and all fo the ashes carted away through a blind alley which is 12 feet wide. You can readily conceive that it is possible for a time to arrive wherein the size of a station and its output will require a constant procession of coal carts and ask carts, and that the work connected with such a constant delivery of coal and ashes will become a great nuisance to the community. ### XXXIX. The conclusions arrived at from the consideration of all these questions concerning large stations determined us upon the size of the New York stations; also the Chicago and Philadelphia stations. The results of our conferences have all been discounted by the Philadelphia Company who propose to make their nominal station capacity 100,000 lights, and to embrace a district reaching from the Delaware to the Schuylkill Rivers, and between Callowhill and South Streets. ### XL. There is a possibility that the first four enginees and eight dynamos to be installed in the station can be started and operated, without any bad results and apparent success will seem to be derived from the apparatus employed, under the minimum load usually demanded of a new Edison station, but as the scope and output of the station becomes enlarged from year to year, the difficulties will be incrased and the inconveniences will correspondingly be made manifest." Yours very respectfully, [unsigned] Gen'l. Supt.








Folder Set



[D8831ACP], Letter from William Dennis Marks to Edward Hibberd Johnson, 1888

Microfilm ID



Thomas A. Edison Papers, School of Arts and Sciences, Rutgers University