US1986391A - Vacuum heating system - Google Patents

Description

Jan. 1, 1935 0. N. CROSTHWAIT: J,R 1,986,391,

I VACUUM HEATING SYSTEM Filed May 5; 1929 N hi N Patented Jan. 1, 1935 UNITED STATES 1,986,391 VACUUM IIEATING SYSTEM David N. Crosthwait, Jr., Marshalltown, Iowa,

assignor to C. A. Dunham Company, Marshalltown, Iowa,,a corporation of Iowa Application May 3, 1929, Serial No. 360,212

16 Claims.

This system relates to an improved vacuum steam heating system, and more particularly to a system adapted to operate with steam at controlled sub-atmospheric pressures, as disclosed 5 in the patent to Dunham 1,644,114 granted tober 4, 1927.

In a system of this type, steam is supplied under a vacuum, or at a sub-atmospheric pressure, to an evacuated condensing space or radiator. If there 0 are a plurality of such radiators, theproportionate volumes of steam delivered to the radiators are controlled in accordance with the radiating capacity of each radiator and the distance of these radiators from the source of supply. A reducing valve, thermostatically operated valve, pr generator-control mechanism is provided for regulating the sub-atmospheric pressure of the steam in the radiator or radiators.

consequently the amount of heat given out by the radiator. A return main for withdrawing air and condensate from the radiator leads through a thermostatically controlled steam trap which prevents the escape of steam from the radiator. An exhausting mechanism operates on the return main to withdraw condensate and maintain the vacuum in. the system. A difierential pressure controller connected between the supply and return sides of the system governs the operation of the exhausting means so as to maintain a substantially constantand predetermined difference in pressure between the supply and exhaust sides of the radiator, no matter what the absolute pressure of the steam in the radiator may be.

In heating buildings in many sections of the country, provision must be made to care for sudden and severe wind conditions. For example, in certain localities there are times when high winds accompanied by falling temperatures come from the north. In such instances, the north side of a building is hard to heat, whereas the other sides may be heated with.relative ease. In order to combat this condition, it has been proposed to have separate and distinct heating systems for the difierent portions of a building so that steam at a higher pressure and temperature can be supplied to the heating system in that portion of a buildingsubjected to the more severe weather, conditions, while lower pressure steam can be. supplied to the system or systems in those portions of the building Where less heat is required. However, in many instances the cost resulting from the duplication or multiplication of parts makes this method of procedure prohibitive.

The general object of this invention is to provide an. improved vacuum heating system of this type involving two or more separate and distinct radiating or condensing systems for diiierent The pressure of the steam determines its temperature, and

parts of the building, all of the systems being supplied from, the same source of steam, and a single exhausting mechanism being utilized to maintain the requisite subatmospheric pressures throughout the various parts of the heating system. The present invention relatesto certain improvements in the system disclosed and claimed broadly in applicants copending application Serial No. 285,885, .filed June 16, 1928.

A particular object of the present invention is to provide means whereby the condensate withdrawn from the radiating system operating at the higher pressure is revaporized, and the resultant steam utilized for heating purposes in the system operatingat the lower pressure.

Another object is to provide means whereby the steam or other gases withdrawn from the higher pressure system. may be discharged either into the supply or return mains of the system operating at the lower pressure.

' Another object is to greatly simplify the piping connections by the use of electric control circuits. Another object is to provide an apparatus of this sort, in which either of the constituent radiating systems can be operated at the higher or the lower pressure, as desired, or both systems can be operated at the same sub-atmospheric pressure as a single unit.

Numerous other objects and advantages of this system will be apparent from the following detailed description of one approved form of apparatus suitable for carrying out the principles of this invention. 7

In the accompanying drawing:

Fig. 1 is a diagrammatic elevation showing the principal features of the entire heating apparatus.

Fig. 2 is a detail elevation, partially in vertical section, of one of the radiator inlet valves and inlet orifices.

The drawing illustrates an example of an apparatus including two separate radiating systems adapted to operate simultaneously at difierent sub-atmospheric pressures, although it will be apparent as the description progresses that more than two such systems could be operated in the same manner. Several portions of the apparatus are common to the two heating systems, principal among which are the generator A, the exhausting mechanism indicated generally at B, the flash tank C, the accumulator tank D, the driving motor E for the exhausting mechanism, the electrically operated cut-off valve F controlling the exhaust outlet from the flash tank C, and the switch mechanism G for reversing the electrical control circuits. There are also numerous auxiliary connections between these several parts, as hereinafter described.

The generator or boiler A which may be of any approved form, furnishes steam to header 1,

from which a drip pipe 2 leads back to the lower portion of the boiler at 3. A normally closed drain connection for the system is indicated at 4.

The exhausting mechanism B is substantially the same as that disclosed in the Dunham patent, hereinabove referred to. A centrifugal pump 5 directly coupled with and driven by the motor E withdraws water through pipe 6 from the lower portion of tank 7 and projects this water upwardly through the ejector 8, discharge manifold 9 and pipe 10 back into the upper portion of the tank 7. A partial vacuum is created by the liquid stream within the ejector casing, and the air and condensate withdrawn from the radiating systems through pipe 11 and one-way check valve 12 are entrained within the liquid stream and delivered into tank '7. The air escapes through pipe. 13 and outwardly opening check valv'e**14. Since condensate is continually delivered to tank 7, the water level within this tank will gradually rise and when a certain level is reached the float 15, through lever and link connections 16; will open the valve 17, whereupon the pump 5 will force'water from the tank 7 through pipe 18, cheok'valve 19 and normally open cut-oh valve 20, into drip pipe 2 and thence back into the generator A. When the water level within tank 7 has been suiilciently lowered the valve 1'7 will be closed by the downward movement of float 15.

*' The condensate and gases withdrawn from the two radiating systems pass from the return mains of these systems (hereinafter described)- tank D when the systems are operating at or above atmospheric pressure. Normally, however, the air vent 24 will be closed since a partial vacuum will exist in the accumulator tank D and pipe 23. r A' branch pipe 23 leads to a pressure gauge which may be located in a convenient position on the tank 7.

The motor Eis controlled from starter 25, connected through leads 26 and 26' with the motor. The power lines running to starter 25 are indicated at 27 and 28. The wires 29 and 30 of a control circuit 'lead from starter 25 to the various control switches hereinafter described. A normally closed switch 31 may be connected in circuit with one of the wires 29 or 30, this switch being opened by a pressure operated controller 32 connected by pipe 33 with the exhaust pipe 11 when a'certain desired maximum vacuum has been attained in the main exhaust pipe 11.

A normally open switch 34 connected by leads '35 and 36 with the starter 25 is adapted to'be closed by a float mechanism 37 positioned in accumulator tank D in case the liquid in said tank rises above a predetermined maximum level. As a result the pumping. mechanism. will be started to withdraw this condensate from tank D, regardless of the pressure conditions existing in other portions of the system.

Steam is delivered from the header 1 through the separate supply mains H and H to the two radiating systems. The principal elements of each of these systems are substantially identical and comprise a main cut-oil valve J, a reducing valve K, a plurality'of radiating units L, a return main M, a differential pressure controller N, and

other auxiliary elements and connections, as hereinafter described. The elementsof the radiating system at the right hand side of Fig. 1 are indicated by unprimed reference characters, whereas the similar elements of the radiating system at theleft of Fig. 1 are indicated by similar primed reference characters. As here shown, the right hand system comprises two radiators "L, whereas the left hand system has only a single radiator L, but it is to be understood that the number of radiators in each system could be increased as found necessary or desirable.

The several elements of one of the radiating systemswill nowbe described. The cut-oil valve J is normally open when the system is in operation. The reducing valve K may be of a well known form, such as disclosed in the Dunham patent hereinabove referred to.

the flow of steam at boiler pressure in the high pressure portion 39 of supply main H into the low pressure portion 40 of this supplymain. The valves in casing 38 are controlled through stem 41 from a diaphragm located in casing 42, this diaphragm being subject on one side to atmospheric pressure, and on the other side to the sub-atmospheric pressure existing in the portion 40 of the supply main H, this pressure being delivered through conduit 43 which connects with supply main H at some little distance from the valves so as not to beinfluenced by the fluctuations in pressure within the .valve chamber. A lever 44 fulcrumed at 45 and pivoted at 46 to operating stem 41, supports from its ends the adjustable weights 4'7 and 48. By properly ad justing these weights, a force is exerted through lever 44 on stem 41, which either assists or opposes the pressure differential exerted on the diaphragm in casing 42. The resultant force applied to stem 41 either opens or closes the valves. The weights 4'7 and 48 are so adjusted that when the admission of steam has built up the pressure to the desired vacuum or sub-atmospheric pressure in the portion 40 of supply main H, the-diaphragm in casing 42 will be moved to close the valves and shut off the flow of further steam into the supply main from header 1. As the steam in supply main H is condensed or otherwise dissipated, the pressure in the supply main will be lowered, so that a higher degree of vacuum than is desired will be attained, whereupon the diaphragm will be actuated in the opposite direction to open the valves in casing 38 and admit more steam to the supply main H. This action will be substantially continuous so that the steam in portion 40 of supply main H (and consequently in radiators L, as will be hereinafter ap- It comprises a pair of balanced valves in the casing 38 for controlling parent) can be maintained substantially constant at any sub-atmospheric pressure, regardless of the pressure of the steam supplied from generator A through header 1.

This steam at'sub-atmospheric pressure is'delivered from supply main H through a steam riser '49 and a normally open inlet valve 50 to each radiator L. As indicated in Fig. 2, an orifice .plate 51' is interposed in the conduit connection assess:

dividual radiator and the position of this radiator in the heating system.

A steam trap 53 is interposed between the lower portion of each radiator L and a pipe 54 leading to the return main M. When steam from the radiator enters the steam trap 53 it will expand the operating means within this trap and close the valve to prevent the escape of steam into the return main. When suiiicient condensate or air has accumulated, the valve operating means will be cooled and will contract to open the valve and permit the escape of the condensate and air through pipe 54 into the return main M and thence into the exhausting mechanism. The condensate which accumulates in supply main H is delivered through pipe connection 55, float and thermostatic trap 56 and outlet 'pipe 57 into the return main M. Return main M leads down through a cut-off valve 58 into pipe 59 and thence through valve 21 and suction strainer 22 into accumulator tank D, as already described. A drain connection 60 provided with valve 61 leads downwardly from pipe 59 to permit both of the return mains to be drained if found to be desirable. Valve 61 is normally closed.

Alternative pipe connections 62 and 63 lead through cut-off valve 64 into pipe 65 and thence into the flash tank C. It will be apparent that when valve 64 is closed and valve 58 opened, the

contents of return main M will be drawn directly into the accumulator tank D. On the other hand, when valve 58 is closed and valve 64 is opened, the condensate and air in return main M will be delivered through the alternative pipe connections 62. 63 and 65 into the flash tank C.

The flash tank C is provided for the purpose of permitting the condensate returning from the radiating system that is operating at the higher pressure to revaporize as a result of expanding to the pressure existing in the exhausting apparatus, or in the radiating system-operating at the higher vacuum or lower pressure. Such condensate as does not vaporize and accumulates in flash tank C drains through pipe 66, float trap 67 and outlet pipe 68 into the exhaust pipe 11 and is thence drawn into the exhausting mechanism B. The float trap 67 prevents any steam from being withdrawn from flash tank C through the outlet pipe 66. An equalizing pipe 69 extending from the upper portion of tank C to the float trap 67 permits the ready entrance of condensate intothe trap 67.

An exhaust pipe 70 leads from the upper portion of flash tank C, and in this pipe are positioned the outwardly opening check valve 71, and

the electrically operated cut-01f valve F. This valve F may be of any suitable type, but is preferably a solenoid operated valve that is normally closed but which is opened when the solenoid is energized. Branch pipes 72 and 72' provided with cut-off valves 73 and 73' lead from pipe 70 to the respective supply mains H and H. Alternative branch pipe connections 74 and 74 lead through cut off valves 75, 75' and steam traps 76, 76' into the pipes 62,62 and thence into the respective return mains M and M. Normally both cut-oil? valves 75 and 75' will be closed, and one of the cut-off valves 73 or 73 will be closed, so that only one of the branch pipes 72 or 72', the one leading to the radiating system operating at the lower sub-atmospheric pressure, will remain open. If the difference in pressure existing between the two radiating systems is insuflicient to vaporize a material quantity of the condensate delivered into flash tank C, it may be found desirable to close both cut-on valves 73, 73' and open one of the cut-oil? valves 75, 75 so that the exhaust connection from flash tank C will lead into the return main of the radiating system operating at the lower pressure. When connected in this manner, the steam trap 76 or 76' will prevent any steam that may be formed in flash tank C from flowing out into the return main M, or M, as the case may be. Pipe 100 leading from exhaust pipe 70 to float trap 101, and drain pipe 102 leading from this trap to tank C, serve to return condensate accumulating in the exhaust pipe connections last described back into flash tank C.

An equalizing connection comprising the pipes 77, 78 and 79 extends from return main M to supply main H in each of the two radiating systems. In the horizontal pipe 78 are positioned a pair of surge chambers 80 and 81, a normally open cut-oil valve 82, and a one-way check valve 83 opening toward the supply side of the system. Under normal conditions the equalizing connection will be closed by check valve 83, but if for any reason the pressure in the supply side of the system should fall below that in the return side, this check valve 83 will open so as to permit an equalization of the pressures. This will prevent air or condensate from being held in the radiators or drawn back into the supply side of the system. Control pipes 84 and 85 connect the respective chambers 80 and 81 with the two sides of the differential-pressure controller N. This controller .may be the same as that disclosed in the Dunham patent above referred to, or in the copending application of McMurrin, Serial No. 174,994, filed March 12, 1927. In general, this controller comprises a casing divided into two chambers by a flexible diaphragm. The two chambers are connected respectively with the supply and return sides of one of the heating systems by the pipe connections 85 and 84, hereinabove referred to. A spring tends to urge the diaphragm in one direction, the action of the spring being balanced by the desired pressure differential between the supply and return sides of the system. When the pressure differential falls below the desired minimum, the spring will actuate the diaphragm and a stem projecting therefrom in one direction, thereby closing a normally open switch, indicated diagrammatically at 86. This switch will, through circuits hereinafter described, affect the energizetion of either the motor E or the solenoid valve F. When the desired pressure differential has again been attained, the diaphragm will overcome the spring and open the switch 86, whereupon motor E is temporarily stopped, or valve F temporariiy closed.

a The control switch mechanism G consists of a plurality of double-throw switches, one for-each branch or zone of the heating system. In the present example, there are a pair of similar double throw switches 87 and 87'. The switch 86 of differential controller N is connected by leads 88 and 89 with the central pair of contacts of switch 87. In an exactly similar manner, the switch 86 of the other differential controller N is connected by leads 88' and 89 with the central contacts of switch 87'. The control wires 29 and 30 extending from motor starter 25 lead to one pair of end contacts of switch 87, and a pair of similar branch wires 90 and 91 extend from wires 29 and 30 to the end contacts of switch 87'. The circuit consisting of wires 92, 93 and 94 connects the solenoid valve F and the other-pair of end contacts of switch 87 in series with a source of ferred to.

power, and branch wires 95 and 96 extending in parallel from wires 93 and 94 similarly connect the other pair of end contacts of switch 8'7 in this circuit. It will now be apparent that when double throw switch 87 is closed in one direction, the switch 86 of difierential controller N will be placed in control of the motor E of the exhausting mechanism through starter 25, and. when switch 8'7 is closed in the other direction, this differential controlled switch will be placed in control of the solenoid valve F. In an exactly similar manner by closing the other switch 87' in one direction or the other, the differentially controlled switch 86 of the other radiating system may be alternatively placed in control of either the motor E or the solenoid valve F. In normal operation, one of the switches 87, 8'7 will be closed in one direction, and the other switch in the other direction, according to which of the two radiating systems is operating at the lower pressure or higher vacuum.

Another equalizing connection consisting of the pipe 97 with the one-way check valve 98 opening toward the generator, and also provided with the normally open stop valve 99, may be positioned between the discharge pipe 59 at the lower ends of return mains M and M and the pipe 18 leading back to the generator. This equalizing connection functions the same as the equalizing connections previously described in the individual radiating systems.

I will first assume that one of the radiating systerms (in the example here shown, the one at the right hand side of Fig. 1) is to be operated at a much lower temperature than the other radiating system, and consequently the lower pressure (or higher vacuum) is to be maintained in this system. In this event, the switch 87 is closed to the right to place differential controller N in control of the motor E, and switch 8'7 is closed to the left to place differential controller N of the left hand system in control of the solenoid valve F. Cut-off valve 58 is open and cut-01f valve 64 closed so that return main M will discharge into accumulator tank D and thence into the exhausting mechanism B. Cut-off valve 58 is closed and cut-off valve64 opened so that return main M will discharge into the flash tank C. Valves '73, '75 and '75 are closed and valve 73 is opened so that the exhaust pipe connection '70 leading from flash tank C will be placed in communication with the supply main H of the lower pressure system whenever the solenoid valve F is opened. The reducing valves K and K must be respectively adjusted so as to supply steam at the desired 10w sub-atmospheric pressure to the right hand system and at a somewhat higher sub-atmospheric pressure to the left hand system.

The lower pressure or higher vacuum system at the right will now operate exactly the same as the usual differential pressure vacuum system as disclosed in the Dunham patent hereinabove re- The proper sub-atmospheric pressure of the steam in the radiators L is determined by the adjustment of the reducing valve K, and the I exhausting mechanism B will operate intermittently to maintain the desired vacuum in the system and also to maintain the necessary pressure differential between the supply and return sides of the system. The air and condensate are drawn directly through return main M into the accumulator tank D and thence into the exhausting mechanism B, the air being discharged through vent pipe 13 and the condensate returned at inter-Jails to the boiler A through pipe 18.

In the other system (designated by the primed reference characters) less vacuum is required, since this system is to be operated with steam at a higher pressure, since more heat is to be radiated. Accordingly, the reducing valve K is so adjusted that supply main H will furnish steam to the radiators L at a higher sub-atmospheric pressure. The condensate and air from this system are discharged from return main M, through pipe connections 62, 63, and 65 into the flash tank C. The pressure in the flash tank C determines the pressure in the return side of this latter radiating system. Whenever the pressure differential in this left-hand system falls below the desired minimum, differential controller N will close switch 86, and through the circuits already described, the solenoid valve F will be opened so as to temporarily place flash tank C in communication with the supply main H, wherein a considerably lower pressure exists. The lowering of the pressure in flash tank C will cause the condensate therein (or a portion thereof) to be re-vaporized and the resultant steam will be drawn out through pipes '70 and '72 into the supply main H of the lower pressure system, wherein the steam is utilized for heating purposes. The lowering of the pressure in flash tank C will, through return main M, again establish the necessary pressure differential in the left hand radiating system, whereupon switch 86 will be opened and the solenoid valve F will close, so as to cut off the exhausting connections to flash tank C. Any excess condensate in flash tank will drain out through float trap 6'7 and be delivered into the exhaust pipe 11 and thence into the exhausting mechanism B, from which it is returned to the generator A in the usual manner.

We now believe it will be quite apparent that -by suitably reversing the positions and adjustments of the several valves and switches hereinabove referred to, the left hand radiating system can be operated at the lower pressure and the right hand system at the higher pressure in a manner exactly similar to that already described.

In some instances it may not be desirable to exhaust the flash tank C into the supply side of the lower pressure system, for example, where the difference in operating pressures between the two systems is not sufficient to re-vaporize a material quantityof the condensate in tank C. In such event, both cut-off valves '73 and 73' are closed, and the valve '75 or '75 leading to the return main of the system operating at the lower pressure is opened. The exhaust connection through pipe '70 from flash tank C now leads directly to the return main of the lower pressure system. The steam trap '76 or '76 will prevent the escape of steam from flash tank C and all of the condensate from this tank will be drained out through float trap 67. Otherwise the operation is the same as already described.

In case it is desired to operate both radiating systems at the same pressure, or the same degree of vacuum, both cut-off valves 58 and 58 are opened and both valves 64 and 64 closed, so that both return mains M and M drain directly into the exhausting mechanism. Either or both of the switches 87, 8'7 are closed to the right so that either or both of the differential controllers N and N are placed in control of the motor E of the exhausting mechanism. The entire heating system now operates the same as a single system, although it consists of two parallel simultaneously operating branches. It may often be found desirable to operate the system in the manner last described until most oi. the air has been withdrawn from both branches of the system, and then establish the desired difference in pressures between the two radiating systems by proper manipulation of the several valves and switches, as already described.

It might be noted that in order to facilitate the disclosure in the diagrammatic views and show all of the piping system, many of the pipes are shown at different elevations from those actually occupied. In actual installations, a great many of these pipes are grouped at practically the same level and would appear one behind the other if so illustrated.

I claim:

1. In steam heating apparatus, a source of steam, two separate radiating systems, one operating at a lower pressure than the other, an exhausting mechanism for maintaining a sub-atmospheric pressure in both systems, the exhausting mechanism being in direct communication with the system operating at the lower pressure, an exhaust connection between the outlet side of the higher pressure system and the inlet side of the lower pressure system, a cutoff valve in this connection, and means actuated by pressure variations in the higher pressure system for operating the valve.

2. In steam heating apparatus, a source of steam, two separate radiating systems, one operating at a lower pressure than the other, an exhausting mechanism for maintaining a sub-atmospheric pressure in both systems, the exhausting mechanism being in direct communication with the system operating at the lower pressure, an exhaust connection between the outlet side of the higher pressure systemand the inlet side of the lower pressure system, a cutoff valve in this connection, means actuated by pressure variations in the higher pressure system for operating the valve, and means actuated by pressure variations in the lower pressure system for controlling the exhausting means. I

3. In steam heating apparatus, a source of steam, a heating system comprising a supply main leading from the source, a reducing valve for controlling the pressure in the supply main, a return main, a radiator in communication with the supply main, connections including a thermostatic trap between the radiator and the return main, and a flash tank into which the return main discharges condensate, a second heating system, an exhausting mechanism for lowering the pressure in the second heating system, and means automatically responsive to pressure variations in the first heating system for intermittently placing an upper portion of the flash tank in communication with the supply side of the second heating system.

4. In steam heating apparatus, a source of steam, a heating system comprising a supply main leading from the source, a reducing valve for controlling the pressure in the supply main, 8. return main, a radiator in communication with the supply main, connections including a thermostatic trap between the radiator and the return main, and a flash tank into which the return main discharges condensate, a second heating system, an exhausting mechanism, means controlling the exhausting mechanism whereby it maintains a lower pressure in the second heatpipe, and a differential pressure controller connected with the supply and return mains of the first system and operating the valve.

5. In steam heating apparatus, a source of steam, a heating system comprising a radiator, a supply main, a return main, and a flash tank into which the return main discharges condensate, an exhausting mechanism, a second heating system, means controlling the exhausting mechanism whereby it maintains a lower pressure in the second heating system than the pressure in the return main of the first system and in the flash tank, a pipe connection between the flash tank and the supply side of the second heating system, a valve in this pipe, a diflerential pressure controller for operating this valve, and control pipe connections from the controller to the supply and return sides of the radiator.

6. In steam heating apparatus, a source of steam, a heating system comprising a radiator, a supply main, a return main, and a flash tank into which the return main discharges condensate, a second heating system, means for lowering the pressure in the second heating system, and means automatically responsive to pressure variations in the first heating system for intermittently placing an upper portion of the flash tank in communication with the supply side of the second heating system.

7. In steam heating apparatus, a source of steam, two separate radiating systems, means including supply and return mains for maintaining steam from the source in each of these systems, a' reducing valve in each supply main whereby the steam is simultaneously maintained at a difierent sub-atmospheric pressure in each system, an exhausting mechanism, a motor for operating the exhausting mechanism, a differential pressure contrdller for the motor connected between the supply and return sides of the system operating at the lower pressure, a flash tank, the return main of the lower pressure system leading to the exhausting mechanism and the return main of the higher pressure system leading to the flash tank, a conduit connecting the flash tank with the supply main of the lower pressure system, a valve in this conduit and a difierential pressure controller for this valve connected between the supply and return sides 01' the higher pressure system.

8. In steam heating apparatus, a source of steam, two separate radiating systems, means including supply and return mains for maintaining steam from the source in each of these systems, a reducing valve in each supply main whereby the steam is simultaneously maintained at a different sub-atmospheric pressure in each system, an exhausting mechanism, a motor for operating the exhausting mechanism, a differential pressure controller for the motor connected between the supply and return sides of the system operating at the lower pressure, a flash tank, the return main of the lower pressure system leading to the exhausting mechanism and the return mainof the higher pressure system' leading to the flash tank, a conduit leading from the flash tank and having branches connecting respectively with the supply and return mains of the lower pressure system, cutofi valves in these branches, a control valve in the conduit, and a differential pressure controller for this latter control valve connected between the supply and return sides of the higher pressure system.

9. In a steam system, a generator, a header leading therefrom, two separate radiating systems each system including a supply main leading from the header, a reducing valve in the supply main, a radiator communicating with the supply 7 main, a return main, discharge connections ineluding a thermostatic trap between the radiator and the return main, a differential pressure con troller, pressure control pipes connecting the controller with the supply and return sides of the system respectively, and a switch operated by the controller in response to variations in the pressure differential between the supply and return sides of the system; a flash tank, an exhausting mechanism, valved pipe connections for alternatively connecting each return main to discharge into either the flash tank or the exhausting mechanism, an exhaust pipe leading from the flash tank and having valved branches for alternatively placing the tank in communication with a portion of either radiating system, an electrically operated cutoii valve in the exhaust pipe, and electric circuits adapted to alternatively place each of the differential pressure controlled switches in control of, either the electrically operated cutofi valve or the exhausting mechanism.

10. In a steam heating system, a generator, a header leading therefrom, two separate radiating systems each system including a supply main leading from the header, a reducing valve in 'the supply main, a radiator communicating with the the controller with the supply and return sides 35' of the system respectively, and a switch operated supply main, a return main,.discharge connections including a thermostatic trap between the by the controller in response to variations in the pressure differential between the supply and return sides of the system; a flashtank, an exhausting mechanism, valved pipe connections for alternatively connecting each return main to discharge into either the flash tank or th'eexhausting mechanism, an exhaust .pipe leading,

from the flash tankand having valved for alternatively placing the tank in um; cation with a portion of either radiating system,

switch of the system operated at the lower 'lpressure'in control of the exhausting mechanismand,

the other switchin control of the electrically operated cut-ofi valve.

11. In a steam heating system, a generator, a header leading therefrom, two separate radiating systems each system including a supply-m leading from the header, a reducing valve he 7 supply main, a radiator'communicating with the supply main, a return main, discharge connec tions including a thermostatic trap between the sure controller, pressure control pipes connect ing the controller with the supply and return sides of the system respectively, and a switch operated by the controller in response to variations in the pressure differential between the supply and return sides of the system: a flash tank, an exhausting mechanism, valved pipe connections for alternatively connecting'each return main to discharge into either the flash tank or the exhausting mechanism, an exhaust .pipe leading. from the flash tank and having valved branches for alternatively placing the tank in communication with the supply main of either radiating system, an electrically operated cut,- off valve in the exhaust pipe, and electric circuits adapted to alternatively place each of the differ ential-pressure controlled switches in control of either the electrically operated cut-oif valve or the exhausting mechanism.

12. In a steam heating system, a generator, a header leading therefrom, two separate radiating systems each system including a supply main leading from the header, a reducing valve in the supply main, a radiator communicating with the supply main, a return main, discharge connections including a thermostatic trap between the radiator and the return main, a differential pressure controller, pressure control pipes connecting thecontroller with the supply and return sides of the'system respectively, and a switch operated by the controller in response to variations in the pressure differential between the supply and return sides of the system; a flash tank, an exhausting mechanism, valved pipe connections for alternatively connecting each re-: turn main to discharge into either the flash tank or the exhausting mechanism, an exhaust pipe leading from the flash tank and having valved branches for alternatively placing the tank in communication with either the supply or return main of either radiating system, an electrically operated cut-off valve in the exhaust pipe, and electric circuits adapted to alternatively place each of the differential-pressure controlled switches in control of either the electrically operated cut-01f valve or the exhausting mechanism.

-1 3. In 'a steam heating system, a generator, 2. header'leading therefrom, two separate radiating systems each system including a supply main leading from the header, a reducing valve in the supply main, a return main, discharge connections including a thermostatic trap between ,the radiator and the return main, a differential pressure controller, pressure control pipes connecting the controller with the supply'a'nd return -"'ides of the system respectively, and a switch oprated, by, the controller in response to variations .m' the pressure differential between the supply and-return sides of the system; a flash tank, an exhausting mechanism adapted to withdraw gases and condensate from the system and return condensate to the generator, a motor for drivingthe exhausting mechanism, valved pipe connections for alternatively connecting each return main-to discharge either into the flash tank or the exhausting mechanism, an exhaust pipe leadvinglfl from-the flash tank and having valved iivranchesfor alternatively placing the tank in communication-with a portion of either radiat- 3i? electrically operated cut-oif valve ust pipe, electric circuits connecting supply main, a radiator, an' open pipe connection including a restricted inlet orifice between the supply main and the radiator, a return main,

discharge connections including; a thermostatic trap between the radiator and the return main,

a differential pressure controller, pressure control pipes connecting the controller with the supply and return sides of the system respectively,

, theswitches, the cut-off valve and the motor, and radiator and the return main, a differential pres-v 1 and a switch operated by the controller in re-. sponse tovariations inthe pressure difierential betweenvthe sup ly and 'retum sides oi. the system, a flashtank, an' exhausting. mechanism adapted to withdraw gases and condensate from the systems andreturn'condensate tothe generator, a motor for driving theexhausting mech- I 'anism, valved pipe connectionsv for alternatively connecting each return main to discharge either into the flash tank or the exhausting mechanism, anexhaust pipe leading-from the flash tank and having valved branches tor alternatively placing the tank in communicationwith a portion of either radiating. system, an electrically operated cut-0E valve in the exhaust pipe, electric circuits supply main, a radiator communicating with the supply main, a return main, discharge connections including a thermostatic trap between; the

radiator and'the return main, a difierential pressure controller, pressure control pipesfconnecting the controller with the-supply and return sides of the system respectively, and a switch j operated by the controller in response to variations in the pressure differential between: the supply and return sides of the system; a flash tank, an exhausting mechanism adapted to withdraw gases and condensate from the systems 7 and return condensate to the generator, a motor for driving the exhausting mechanism, valved pipe connections for alternatively connecting each return main to discharge either into the flash tank or the exhausting mechanism, an ex-' haust pipe leading from the flash tank and having valved branches for alternatively'placing the tank in communication with the supply main of either v radiating system, an electrically operated cut-off valve in the exhaust pipe, electric circuits connecting the switches, the cut-off valve and the motor, a maximum pressure regulator con- 'nected with the exhausting mechanism including a switch positioned in the motor-control circuit, and double-throw switches in said circuits where- ;byeach differentially controlledswitch may be tern'atively placed in control of either the elec-. l't'rically'operated cut-ofl.v valve 'or' the motor.

,16. Iii a steam heating: system, Ta, source of steam, a heating system comprising'ia radiator,

asupply' main, a; return main and ;.,a' ;flash tank nto. which the return-{main discharges condensate,- and means for maintaining a sub-.at-

mospheric pressure in the ma tank, revaporizing the condensate" therein; withdrawing the re sultant steam'and'iutilizing this-steam'tor heat-. ing purposes, said means comprising arrexhaust ingapparatus, ,a conduit, connection including a secondheating system between the flash-tank and exhausing apparatus, a valve in this connection at the outlet of the flash-tank, and means automatically responsive to pressure variations in the first heating system for opening and clos ing the valve.

DAVID N. CROSTHWAI'I, JR.

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