US2140701A - Control mechanism for steam heating systems - Google Patents

Description

Dec. 20, 1938. c. JENNINGS 2,140,701

' CONTROL MECHANISM FOR STEAM HEATING SYSTEMS- I Filed March 7, 1935 4 4 Sheets-Sheet 1 2 hv en for ji-k/nq C Jen/11. 1%

or ey-s Dec. 20, 19,38. c. JENNINGS 7 2,140,701

CONTROL MECHANISM FOR STEAM HEATING SYSTEM$ Filed March 7, 1935 4' Sheets-Sheet 2 y By w 4 Sheets-Shae:

I. C. JENNINGS Filed March 7,

Dec. 20, 1938. n. c. JENNINGS CONTROL MECHANISM FOR STEAM HEATING SYSTEMS Filed March '7, 1955 4 Sheets-Sheei: 4

Ftwr zeyis [LIIYLAM Patented Dec. 20, 1938 PATENT OFFICE CONTROL MECHANISM FOR STEAM HEAT- ING SYSTEMS Irving 0. Jennings, South Norwalk, Conn.

Application March 7, 1935, Serial No. 9,894

Claims.

The object of this invention is to provide a new and improved control mechanism for a vacuum steam heating system.

A vacuum steam heating system comprises a 5 boiler, or source of steam supply, radiators to which the steam is conducted, returns from the radiators leading to a receiving tank, and a vacuum pump connected to the tank or returns for removing the air or gas from the system and cre- 1e ating a vacuum in the returns.

A water pump is also usually provided to return the water of condensation to the boiler.

It is desirable to provide control mechanism so that the supply of steam will be automatically adjusted to different temperature conditions.

My improved control mechanism consists of means attached to the returns or to the receiving tank, and connected mechanism arranged so that the degree of vacuum will be automatically varied or adjusted in the return side of the system. This adjustment is preferably made by thermostatically operating mechanism.

The device is preferably connected and operated so that it works with a constant steam pressure on the supply side of the system.

The invention is illustrated in the accompanying sheets of drawings, in which:

Fig. l is an elevation partly in section of my invention applied to a vacuum heating system in which the pumping mechanism is driven by a steam turbine and additionally by an electric motor in case there is not a suificient steam differential to operate the turbine.

Fig. 2 is an elevation partly in section of the pumping mechanism and control mechanism illustrated in Fig. 1.

Fig. 3 is a sectional elevation on a still larger scale of one of the relief valves and electrically operated shut off valve, as hereinafter described.

Fig. 4 is an elevation showing how my invention can be applied to a heating system in which the pumping mechanism is only electrically driven, i. e., no steam turbine is utilized.

Fig. 5 is a sectional elevation of the pumping mechanism used in this modification, and

Fig. 6 is a sectional elevation on an enlarged scale of one of the vacuum cut-outs.

Fig. 7 is an elevation showing how my inven- 50 tion can be applied to a heating system using a thermostat controlled in accordance with the outside temperature.

Fig. 8 is an enlarged sectional View of a portion of the thermostatic mechanism Y in Fig. '7 taken 55 on the line h-h.

Fig. 9 shows the thermostat connected to the outside operating means W.

Referring first to the mechanism illustrated in the first two sheets of the drawings, and in detail, A designates a steam boiler, from which steam is lead by a supply pipe B. An ordinary adjustable pressure regulator C is interposed in this pipe so that steam will be supplied at a constant pressure.

A pressure control or differential valve D is arranged in the steam line B beyond the pressure regulator C, and pipes E and F lead from the sides of this pressure regulator D to the casing of a low pressure steam turbine G, which is connected to drive the pumping mechanism substantially as shown in reissue Letters Patent No. 18,275, granted to me December 8, 1931, the pressure regulator D acting to maintain a substantial constant steam difierential for operating the turbine.

The supply pipe B then connects to the radiators H and the radiators connect by a suitable return pipe I to the receiving tank J of a socalled Wet vacuum pumping system. The turbine G drives the pumping mechanism, which consists of a Nash pump K connected to remove the air or gas from the return side of the system, and a centrifugal pump L, shown in Figs. 1 and 2, the impeller of which is connected to remove the water of condensation from the tank J, and preferably to return the same to the boiler A.

An additional pumping mechanism consisting of a Nash pump K and impeller L is connected to the other side of the tank J relatively to the pumping mechanism previously described and this second or additional pumping mechanism is driven by an electric motor M.

A switch S operated by a float in the tank J is connected to throw the motor M into operation, when the water rises to a high level in the tank J so that the water of condensation always will be removed.

The supply pipes to the radiators are preferably provided with orifices N, suitably proportioned to assist in maintenance of proper flow of steam into the radiators under control and influence of the vacuum.

The foregoing constitutes an approved form of a vacuum steam heating system.

The receiving tank J is provided with a relief valve 0, which is adjusted to open and admit atmospheric air into the receiving tank when the highest vacuum, which is to be maintained in the system, is reached. This vacuum for purposes of illustration may be six inches, which, with properly proportioned radiators, is ample to draw enough steam through the system to fill the radiators to heat the building under the coldest conditions.

A pipe I is connected to the top of the tank J and has two branch pipes II and I2 connected thereto, these pipes having relief valves 2 and 3 at their ends. Interposed between the respective. relief valves and the pipe H! are electrically operated shut-011" valves and 4 controlled thermostatically and preferably by a plurality of three position thermostats.

The details of the right hand relief valve 2 and shut-ofi valve 5 are shown in Fig. 3. The relief valve consists of a casing I5, screwed into the end of which, is a plug or bushing IS, the inner end of which forms a valve seat against which a valve I1 is held by a spring [8, arranged on a fluted stem [9. A check nut 2| is threaded on the bushing l6.

By this arrangement the valve I! can be adjusted to open inwardly at any desired pressure by adjusting the bushing l6 and locking the same in adjusted position by check nut 2 I.

The casing I5 is screwed into a casing 22 to which the branch pipe II is connected. This casing 22 is provided with a valve seat against which a valve 23 closes, the valve being held closed by a spring 24. The stem of the valve 23 is connected to a solenoid 25, which Works inside of-an electro-magnet 26 arranged in a casing 21 secured on top of the casing 22. Thus valve 23 is normally held to its seat but is raised therefrom by the solenoid 25, when the electromagnet 26 is energized.

The left-hand relief valve 3 is similarly constructed and communication between this relief valve and the pipe [2 is controlled by a similarly constructed solenoid operated shut-off valve 4.

A thermostatic controller consisting of one or more three-position thermostats T-T set in key positions in the building to be heated is. electrically connected to the magnets 26-26.

The operation is as follows:

The device is preferably connected and operated so that it works with a constant steam pressure on the supply side of the system.

Assuming that the heating system is to be started into operation, and that the building or area to be heated is too cool. Under this condition, the moving member of one or more of the thermostats T-T' will be at the left hand position, Fig. 1, and both valves 23 will be closed.

As the steam is turned on, the pumping mechanism will be started into operation and a vacuum will be created in the return side of the system up to six inches until the relief valve 0 opens.

The relief valve 0 is constructed the same as valve 2 or 3 and the same has a knob 20 on its end so that the vacuum can be tested by hand manipulation thereof.

The steam differential thus created between the supply and the return sides of the system will cause steam to flow into the radiators. The parts thus far described should be designed so that sufficient steam under this vacuum will flow through the orifices to completely fill the radiators H, and bring the same up to a temperature ample to heat the building under the coldest conditions.

Traps P may be supplied on the outlet pipes of the radiators, as shown. In some instances, it is proposed to omit these traps and use slightly larger radiators so that steam will not pass into the returns.

Assume that the thermostats T are set to maintain a normal temperature in the building of '71 degrees, .and to shift at 70 and 72 degrees.

When the building heats up to a point beyond 70 degrees, the thermostat arm or arms will assume a central position, solenoid control valve 23 will open, and the relief valve 2 will be connected to the tank J. This will maintain a vacuum on the return side of the system of say four inches. This will create a difierential sufficient to fill the radiators at the point at which relief valve 2 is adjusted which may be, say half full, due to the restriction of the orifices. The parts are preferably so designed that the system will work normally at this point.

If the last shifting of the thermostat arm or arms produces too much heat, a thermostat arm or arms will go over to the right hand position, cutting out relief valve 2 and connecting relief valve 3 to tank J. This valve 3 may be set to maintain say two inches of vacuum in the return side and maintain only sufficient steam difierential to fill the radiators, say one-eighth full of steam. This supplies the slight amount of steam needed for mild weather.

With the above described arrangement, and assuming that the turbine is operating, the temperature of the building or area to be heated will be accurately controlled by the thermostats, while maintaining a constant pressure on the supply and with practically no current used for the vacuum pump.

When there is not enough steam passing through the system to drive the turbine G to 0perate the pumps K and L, the motor equipment will be started by a vacuum cut-out V.

The details of this vacuum cut-out V are shown in Fig. 6. The same consists of a casing 28 to which the pipe Ill is connected by pipe 29. This casing has a diaphragm 30 and a spring 30' opposing the pull of the vacuum on the diaphragm, these parts being connected to an electric snap switch 20.

This vacuum cut-out V is preferably set to maintain a vacuum just below two inches, the setting obtained by the valve 3, as otherwise the motor driven pump would run all the time.

The float control, of course, is always operative to start the motor M of the motor driven pumps K and L if the turbine D fails to handle the condensate.

An additional switch 34 may be supplied and connected independently of the vacuum regulator V so that the motor driven equipment can be run continuously if the turbine is to be stopped for repair, or otherwise.

The electric connections are indicated in the first two sheets of the drawings, the motor M, as well as the solenoids, being operated by a power circuit of say 220 volts, and the relays R and R by a lower Voltage current, which is stepped down through a transformer U, to provide low voltage current for the thermostats T and T which control these relays.

Referring now to the third sheet of drawings, it will be noted that I have shown therein how my improvement can be applied to a vacuum heating system in which the pumping mechanism is driven only through an electric motor. The parts shown in this drawing having the reference letters and numbers, previously referred to, are the same in construction as employed in the mechanism shown in sheets one and two, the principal difference being that the turbine driven pumps are omitted, and that the valve 3 is omitted. In this modification an additional vacuum 7 regulator V is employed similar in construction to vacuum regulator V, previously described, these two vacuum regulators being set to maintain vacuums of say six inches and four inches, respectively. The left hand motorized Valve 23 opens up when only a very small diiferential is required for low heat, under which condition the motor driven pumping mechanism runs on float control and acts as a condensation pump only.

The object of putting in the relief valve I3, Fig. 4, controlled by the motorized valve is so that when the system has been operating on the vacuum regulator V, at say six inches of vacuum, and it is desired to change over to the vacuum regulator V some means must be provided to lower the vacuum down near the lower setting of say four inches.

The new apparatus shown in this figure consisting of the two vacuum cut-outs V and V, the solenoid valves, the relief valve I3 and the ther mostats and electric connections can be made up for attachment to existing vacuum heating systems at small expense and can be applied thereto to regulate the operation thereof so that steam will be much more economically used than in the systems as originally installed.

The fourth sheet of drawings, Figs. 7, 8 and 9 shows a modification of the invention where a thermostat controlled by the outside temperature is employed to regulate the amount of steam supplied to the radiators in the space to be heated. The principal parts shown in this drawing have the same reference letters previously referred to, but a thermostat Y with outside mechanism W has been substituted for. the inside thermostats T and T.

The parts are the same as are shown on sheets 1, 2 and 3 except that additional relief valves and motorized valves have been added. Each of these relief valves and motorized valves is the same as shown in Fig. 3. They are indicated on Fig. 7 with small letters a, b, c, d, e, and f.

Referring to Figs. '7, 8 and 9, the outside controlled thermostat Y consists of a frame 31 on which is mounted a corrugated bellows 3|, connected to a rack 32, supported by suitable bearings in frame 37. This rack meshes with the pinion 33 attached to a shaft 36, free to turn in bearings 33 of the frame 31. The shaft 36 supports a series of Mercoid switches a, b, c, d, e and 7. These switches are spaced progressively around the shaft 36 so that when it is rotated electric circuits connected respectively to motorized valve a, b, c, d, e, and f will be closed successively.

The bellows 3| is connected by a pipe 35 to a tank W located outside of the building. The tank W, the pipe 35, and the bellows 3| are completely filled with a liquid, such as alcohol. A spring 34 keeps the bellows 3| in a contracted position. If the temperature outside rises, the liquid expands and causes the bellows 3| to lengthen in proportion to the outside temperature. The lengthening of the bellows 3| causes the rack 32 to move to the right, rotating the pinion 33, the shaft 36, and successively closing the contacts in the Mercoid switches a, b, c, d, e and 1. These in turn operate to open the motorized valves a, b, c, d, e, and f.

For any given outside temperature a motorized valve will be open, which through the adjustment of its attached vacuum relief valve will give the correct vacuum to partly fill the radiator with suficient steam to heat the building under the existing conditions. If the weather gets colder the diaphragm will contract, causing the shaft 36 to rotate in the reverse direction and open a motorized valve which is connected to a vacuum relief valve set for a higher vacuum. This will cause a greater portion of each radiator to fill with steam, the same as previously described where inside thermostats T and T were used.

Referring particularly now to Figs. 1 and 2, there is illustrated a system, not zone-d but with two thermostatic stations, represented by inside thermostats T and T, these being in a seriesparallel relationship so that either T or T may call for heat irrespective of what the other one is calling for, but both T and T must agree it is too hot before the relay-operated solenoids are actuated to give minimum heat supply.

In the position shown, namely, the desired and normal condition of say 71 F., the blade 54 of thermostat T, which is not of the detent type, is in the midor uncontacted position. Blades 59 and 51 of detent type thermostat T are snapped over onto the 71" contact, not shown as they are not connected and are merely used as mechanical stops. Consequently, neither relay R, which operates to reduce the heat, or relay R, which operates to increase the heat, are energized.

It will be seen that under this condition electric current flows from input line 66 to contact 61 of relay R, through contact 68, along line 69, through contacts 10 and II and along line 12 to operating coil of solenoid valve 5; out of coil through line 13 to power line lead 16. The solenoid valve is thus opened and so allows relief valve 2 toleak enough air into tank J to a maintained value of say 4" vacuum, approximately enough to half fill the radiators. Ordinarily the turbine driven pump L runs to create vacuum and pump back returns to the boiler; however, the motor driven pump may have to operate, then the vacuum regulator V, being adjusted to maintain approximately 6" vacuum in the system, keeps electrical switch in the closed position, and so, by means of lines 1! and 18 also 81 and 88, the pull-in coil 89 of motor starter S is kept energized, which in turn closes main magnetic switch of starter S so that current flows to pump motor M from supply lines 84, 85, 86 through lines 8|, 82 and 83.

The thermostatically operated relays and associated controls operate irrespective of whether the turbine driven pump or the motor driven pump, or both, are operating, and the manner of operation is not affected thereby.

Having described the position of controls and path of current for the normal or satisfied condition, it will now be shown what happens if outside conditions change to cause say thermostat T to call for more heat by blade 54 moving over into contact with the 70 terminal contact. Low voltage current from step-down transformer U now flows along lines 5253, blade 54, lines and 6|, to coil of relay R, and along lines 64 and 65 back to transformer secondary. The relay armature is pulled over to core, thus separating contacts 10 and II, which interrupts the circuit of operating coil of solenoid 5, which causes the valve portion of the solenoid to close, thus disconnecting relief valve 2 from tank J.

If the heating pump is being operated by the normally continuously running turbine driven pump, the vacuum in tank J is thereby kept up to say the 6 vacuum required to completely fill the radiators. 6" vacuum, will open slightly to maintain this vacuum, whereas if, due to turbine side being Tank relief valve 0, being set at.

unavailable due to inspection, overhaul, etc., the motor side is operating the heating pump, the vacuum will be built up until vacuum regulator V operates to open switch 7, which in turn breaks the circuit of pull-in coil 89 of starter S, which causes main magnetic switch to open and cut oil power to pump motor M.

It is clear that if level of condensate in tank J is such as to close float switch S that the motor M will operate to return the condensate to boiler A until low level setting is reached, when the switch S will open, thus causing starter S to open and so stop motor M. It will be further seen that hand switch 34 of starter S may be used to place coil 89 in shunt across input wires 85 and 86, thus giving continuous operation.

Upon the temporary condition of underheating being overcome by the extra heat supplied due to said complete filling of the radiators, the blade 54 of thermostat T moves away from the 70 F. contact and by de-energizing of relay R, restores power circuit to solenoid and system reverts to the satisfied or normal condition previously outlined.

We will now assume that the outside conditions change so that the half-filled radiators, secured with 4 vacuum in tank J, causes overheating at thermostat T so that blade 54 positions on the 72 F. contact. We then have a closed low voltage circuit from secondary of transformer U, along lines 52, 53, blade 54, line 56, blade 5'! and, as stated before, if space or room in which T is placed is also too warm, blade 5'5 will be positioned on 72 contact and current will flow along line 62 to coil of relay R, through coil and along lines 63 and 65, back to secondary. Energization of relay R causes contact 5? to position on contact 69, thus giving a power circuit from input line 66, through contacts 67 and 69, along line 5 1 to operating coil of solenoid valve 4, through coil and along line 75 to input line "it. The valve portion of solenoid 3 is now open, placing relief valve 3 in connection with tank J.

This relief valve is set to maintain 2 vacuum in tank J, which will correspond say to a oneeighth filling of the radiators, which, while the normal condition for mild weather, would correct the temporary over-heat condition, and thermostat blades 54 and/or 51 would move back to the 71 F. position, thus de-energizing relay R, which de-energizes solenoid 4 and energizes solenoid 5, thus re-establishing the normal or satisfied condition.

Had blade 57 of thermostat T not been on 72 F. position, the entire radiation system will be maintained at l vacuum on return line, which will cause space containing thermostat T to overheat more or less shortly after space containing thermostat T has overheated. This will cause blade 5'! to position on the 72 F. contact and give control circuit previously outlined.

In the extremely improbable case that space containing T did not come up to 72 F., then the normal amount of heat, i.- e., radiators half filled, would be supplied to entire system so that one part of the building would be at 71 F. and

' the other part would be slightly overheated.

Taking the case where space surrounding thermostat T was at 71, blade 55 in mid-position,v

but space around T was 70, consequently blade 50 would position on 70 contact, thus establishing the low voltage circuit from secondary of transformer U along lines 52 and 58, blade 59, through 70 contact, along line 6|, through coil of relay R along lines 64 and 65 back to transformer Secondary. This energization of R sepa rates contacts 70 and H, thus precluding current flow to solenoid 5, which consequently stays closed. Also, as contacts 5'! and 59 are open, solenoid valve 4 is .de-energized and so stays closed. Seeing that relief valves 2 and 3 are inoperative, the maximum vacuum of say 6" is maintained in receiver J and return line I, with resultant complete filling of the radiators, which would quickly correct the condition of underheating of space surrounding T, and so blade 50 would leave contact 70 and return the system to the previously described satisfied condition.

Conversely, if space surrounding T became overheated, blade 57 would position on the 72 contact, but circuit through low voltage thermostat-relay combination would not be complete unless and until blade 55 of thermostat T closed on the 72 contact of T due to its space being overheated. When this occurred the operation would be as previously described as overheating of space around thermostat T.

An alternate system is shown in Fig. 4, this arrangement providing for full vacuum, say 6, in tank J and return line I when space to be heated falls to say 70 F., a vacuum of 4 when space is at the .desired 71 F. and a means of relieving the tank to atmospheric pressure when space is overheated, say 72 F. The operation of the motor driven air and water pump is as previously described, namely, that it is brought'into action by closing of water level float switch S or vacuum regulators V and V, either individually or in combination.

Taking the condition shown, 1. e., the normal or satisfied condition of say 71 F. in spaces surrounding T and T, there is no closed circuit through the thermostats and relay coils and so the relays are de-energized in the position shown.

The current flow in the power circuit is from input line 55 along line 68, through contacts 69 and '10, along line 7 I through contacts 72 and 73, along line 74, through coil of solenoid 23, along lines 85 and 91 to input line 99. The consequent opening of solenoid valve 23 allows relief valve I 3 to leak down the vacuum in tank J and return line I to say 4 vacuum, corresponding to say one-half filling of the radiators, which will give the desired 71 F. in spaces to be heated. The power also flows in circuits to and through vacuum regulator V and float switch S as follows: from input line 99 along lines 97, 96 and 79, through contacts 80 and 84, along line 15, through switch of vacuum regulator V, which is set to maintain l vacuum in tank J, along lines 92 and 90, through pull-in coil 89 of magnetic starter S, along lines 88 and 87 back to input line 65. Under these conditions the vacuum regulator V will cut motor driven pump in at say 3 /2" vacuum and cut it out at say 4 vacuum, thus maintaining an average value of l vacuum.

The water level float switch circuit is constant for all operating conditions, being from input line 09, along lines 91, 96 and 94, through switch 8 along lines 93 and 90, through coil 89, along lines 88 and 87, back to input line 66, so that the switch S will be closed when the high water level is reached in tank J and will cause pump to operate to bring water level down to the low level when switch S will open and stop motor M of pump. As this operation is common to all conditions of operating, it will not be repeated in subsequent descriptions.

Now assume that space around one of thermostats (take T), drops down to 70 F., then blade 54 will position on 70 contact and establish the following circuit: from secondary of low voltage transformer U, along line 52, blade 54, through 70 contact, along lines 55 and 6|, through coil of relay R, along lines 63 and 65 back to transformer secondary.

The energization of R opens contacts 69 and 70, thus de-energizing solenoid 23, which then closes, rendering relief valve l3 inoperative; also, contacts I6 and 61 are now closed, which cuts into operation vacuum regulator V, set for say 6" vacuum, due to following circuit: input line 99, along line 18, through switch of V, along line 11, through contacts 16 and 61, along lines I06 and 90, through coil 89, along lines 88 and 81 to input line 66.

Vacuum regulator V will close its own switch portion at say vacuum and so actuate starter S to operate pump to bring up the vacuum in tank J and return line I to say 6 when vacuum regulator switch will open and cause motor to stop, thus giving an average vacuum of 6". The fact that vacuum regulator V is still in the circuit is of no consequence, as it is of a lower setting and so would have its own switch in the open position during the time that V is in operation.

This 6" vacuum in the return line will cause complete filling of the radiators and will quickly correct the underheated condition, and blade 54 will resume the midor disconnected position and system will revert to the normal or satisfied condition of 71 previously described.

It will be clear that exactly the same operation would have occurred if we had used thermostat T as the one calling for more heat, with the non-essential exception that the low voltage circuit would have been from secondary of transformer, along lines 52 and 58, blade 59, through 70 contact, along lines 60 and 6| to the coil of relay R and along lines 63 and 65 back to transformer secondary. The operation of all the associated equipment would be exactly as described for T calling for more heat.

It will be also seen that, under the condition of T calling for more heat, T cannot obtain operation of relay R to cut down the heat, as blade 51 of T gets its feed from the 72 contact of thermostat T, whereas blade 54 of T is on the 70 contact. Conversely, T could not obtain control of relay R to cut down the heat if T is calling for more heat or is satisfied, as the blade 5! of T would not be on the 72 contact as would be necessary to complete the feed line to relay R. Also, if either thermostat calls for more heat when the other thermostat is already doing so, it merely duplicates an existing circuit and does not alter or upset the operation.

Now assume that either T or T positions on 72 F. contact, as previously described both must be on too hot, i. e. 72, before heat can be reduced and so the first one to go on too hot will overheat slightly until the other also goes on too hot, when the following circuit will be set up: from secondary of transformer along line 52, blade 54, 72 contact, line 56, blade 51, 72 contact, line 62, through coil of R, along lines 64 and 65 back to transformer secondary. The energization of relay R has the following effects: the separation of contacts 12 and 13 deenergizes solenoid 23, which closes and so disconnects relief valve |3 from tank J. Contact 80 leaves contact 84, which cuts vacuum regulator V out of power circuit, and positions on contact 8|, which energizes solenoid 23 due to following circuit: from power input 99, along lines 91, 96 and 19, through contacts 80 and 8|, along line 82, through coil of solenoid 23, along line 83 back to input 66; The valve portion of 23 is now open, thus placing tank J and return line I in direct connection with the atmosphere, which kills the system and no circulation takes place, which quickly corrects the condition of overheating.

It will be seen that vacuum regulator V is also inoperative, as contacts 16 and 6'! are separated when relay R is not energized, which is the case in this condition, so the fioat switch S is the only control that can now start the motor driven pump, which would only happen under this condition if the tank were practically full just before system went onto too hot, as with no steam circulating and condensing, the tank would not fill up.

As the condition of overheating has been corrected, the thermostat blades resume the midor disconnected position and the system returns to the normal or satisfied condition first described.

Figures 7, 8 and 9 show a means of heat control in accordance with the outside temperature, the changes in outside temperature causing corresponding changes in length of bellows 3|, position of rack 32, pinion 33, shaft 36, and mercury type electric switches a, b, c, d, e and f. The positioning of these electric switches determines which of the solenoid valves a, b, c, d, e and f are energized, and so allowing their associated relief valves to assume the open position which allows said relief valves to leak sufficient air into vacuum tank J to adjust the vacuum therein to a value sufiicient to give a predetermined and adjustable fractional filling of the radiators to satisfy the heat requirements of the building under existing conditions of outside temperature.

To describe in detail the electrical circuits and operation, take four representative conditions as follows:

Condition 1.-Figures 7, 8, 9, take the outside temperature as being 0 F., under which condition the liquid filling bulb W, pipe 35 and bellows 3|, will be at minimum volume, and compression spring 34 will have aided spring action of bellows 3| in positioning rack 32 in the farthest left position, and the attendant movement of pinion 33 and shaft 36 will move mercury electric switches correspondingly so that the contact ends of same will be in the highest position. Consequently, none of the contacts, except for a, are submerged and so all current paths through switches a, b, c, d, e and j are open.

This means that all of the solenoid valves are de-energized and in the closed position, thus rendering inoperative the associated relief valves. Under usual conditions the turbine driven pump GL will operate to maintain say 6" vacuum in tank J, also will return condensate from tank to boiler A. However, motor driven pump M may be operated as described for Figs. 1 and 2, also Figs. 4 and 6, the motor M being started and stopped by the magnetic starter S under control of water level float switch S and/or vacuum regulator V through mercury switch a as described in detail under Condition 4..

On turbine operation the vacuum in tank J is held at say 6" by action of tank relief valve 0, which leaks air into tank to prevent vacuum going beyond the desired value.

Condition 2.In this we assume the outside temperature to have raised. from 0 F., of Condition 1, to say 10 F., requiring an adjustment of inside heat supply to avoid overheating. As the outside temperature rises, the liquid in bulb W of Fig. 9 expands, the increased volume flowing through pipe 35 to bellows 3!, expanding same, thus compressing spring 34 and moving the rack 32 to the right, causing the pinion 33 to rotate to the left. The shaft 35 of Y, Fig. 7, and shown in Fig. 8, rotates with pinion 33, moving the mercury switch group, thus causing the mercury in switch 1 to close across the contact prongs. An electric circuit is now established from one line terminal in motor starting switch S along lines 48 and 64 through the mercury closed contacts of switch 7, along line 52 to solenoid valve f, along lines 59 and 49 to other side of one phase of power supply in starting switch S, thus energizing solenoid valve 1, causing it to open and connect its associated relief valve to tank J, admitting sufficient air to the tank to reduce the vacuum to say and steam volume in radiators to about of full. The turbine and motor pumping equipment operates as previously described to maintain vacuum and condensate conditions.

Condition 3.In this, we assume the outside temperature to have raised from F., of Condition 2, to say 50 F., thus requiring further adjustment of inside heat supply to avoid overheating. As described in detail under Condition 2, the liquid in bulb W expands, actuating the bellows 3| and associated mechanism, rotating the mercury switch group, thus progressively closing mercury switches e, d and c, and establishing the following additional electric circuits: from one line terminal in motor starter S along lines 48 and 55 through mercury switch e, along line 63 to solenoid valve e, along lines 56, 5B and 49, completing one circuit; again from motor starter S along lines 48 and 66 through mercury switch (1, along line 54 to solenoid valve d, along lines 52, 5|, 5!! and 49, completing a second circuit; and again from motor starter S along lines 43 and 61 through mercury switch 0, along line 61 to solenoid valve 0, along lines 60, 59 and 49, completing a third circuit, and thus energizing solenoid valves 6', d and c, causing them to open and connect their associated relief valves to the tank J, reducing the vacuum level in like sequence to say 4", 3" and 2", and consequently reducing the volume of steam in the radiators to approximately and A; full. Again the turbine or motor driven pumping equipment maintains vacuum and condensate conditions as previously described.

Condition 4.In this we assume the outside temperature to have raised to 70 F. from 50 F. as in Condition 3. Again, as described in detail under Condition 2 and outlined for Condition 3, the liquid in bulb W expands further and through its associated parts repositions the mercury switch group, closing mercury switches b and a and again establishing the following additional electric circuits: from motor starter S" along lines 48 and 68 to mercury switch b, along line 58 to solenoid valve 1), along lines 51, 56, 50 and 49, completing one circuit, and again from motor starter S along lines 48 and 69 to mercury switch a, along line 55 through solenoid valve a, along lines 53, 52, 51, 50 and 49, completing the second circuit and thus energizing solenoid valves 1) and a and connecting their associated relief valves to tank J, consequently reducing the vacuum to approximately 1" and then to 0" or atmosphere and the steam volume in radiators to approximately V6 full and finally empty- In this, Condition 4, mercury switch a, which differs from other switches in the group, inasmuch as it is single pole, double throw, each end constituting a separate single pole switch, functions as follows: As the mercury switch group rotates, bringing mercury switch a into closed circuit position, the a contacts open, interrupting the vacuum control circuit of the motor driven pump through lines 10 and H to the vacuum regulator V, thus preventing further operation of the pump for vacuum service until the outside temperature again drops below 70.

It will be noted that in all the modifications shown, the atmospheric air admitted into the tank will be drawn out of the tank without passing through the system and that this air will relieve the air pump so that less power is required when the apparatus is operating to produce the lower degrees of vacuum as compared with the high degree of vacuum generated when all the relief valves are closed.

The details and arrangements herein shown and described may be greatly varied by a skilled mechanic without departing from the scope of my invention as expressed in the claims.

Having thus fully described my invention, what I claim and desire to secure by Letters Patent 1. Control mechanism for a vacuum steam heating system, having a pumping mechanism for removing the air or gas from the system and creating a vacuum in the return side thereof, comprising a variable vacuum relief means for maintaining the vacuum in the system at different degrees, including a plurality of differently set relief valves, and thermostatically controlled means operable by temperature variation for controlling'said valves so that different degrees of vacuum may be created in the return side of the system.

2. In a vacuum steam heating system, having a pumping mechanism for removing the air or gas from the system and creating a vacuum in the return side thereof, and having means to maintain a normal predetermined vacuum in the returns thereof, the combination with control mechanism for said system comprising a variable vacuum relief mechanism effective to maintain the vacuum in the system at different degrees, said mechanism including a relief valve, and thermostatically controlled means operable by temperature variation for throwing said valve into and out of operative connection with the return side of the system.

3. A vacuum steam heating system having a constant steam pressure on the supply side of the system, pumping mechanism for removing air or gas 'from' the system and creating a vacuum in the return side of the system, and having means to maintain a normal predetermined vacuum in the returns thereof, the combination with control mechanism for said system including a variable vacuum relief mechanism effective to maintain the vacuum in the system at different degrees, said mechanism including a relief valve and thermostatically controlled means operable by temperature variation for controlling said mechanism and valve so that different degrees of vacuum may be created in the return side of the system.

4. A vacuum steam heating system having a constant steam pressure on the supply side of the system, pumping mechanism for removing the air or gas from the system and creating a vacuum in the return side thereof, including means to maintain a normal predetermined vacuum in the return side, and variable vacuum relief mechanism effective to maintain the vacuum in the system at different degrees, including a relief valve, and thermostatically controlled means operable by temperature variation for throwing said valve into and out of operative connection with the return side of the system.

5. Control mechanism for a vacuum steam heating system having a pumping mechanism for removing the air or gas from the system and creating a vacuum in the return side of the system, comprising a plurality of progressively set vacuum relief mechanisms, and thermostatically controlled means for controlling said mechanisms progressively so that different degrees of vacuum may be created in the return side of the system.

6. Control mechanism for a vacuum steam heating system having a pumping mechanism for removing the air or gas from the system and creating a vacuum in the return side thereof, comprising a plurality of progressively set, vacuum control valves and thermostatically controlled means for throwing said valves progressively, into and out of operative connection with the return side of the system.

'7. In a vacuum steam heating system having pumping mechanism for removing the air or gas from the system and creating a vacuum in the return side thereof, and having means to maintain a normal predetermined vacuum in the returns thereof, the combination with control mechanism for said system comprising a variable vacuum relief mechanism effective to maintain the vacuum in the system at different degrees, said mechanism including a relief valve, a solenoid operated valve for throwing said relief valve into and out of operative connection with the return side of the system, and thermostatically controlled means operable by temperature variation, having operative electric connections to said solenoid, whereby different degrees of vacuum may be created in the return side of the system.

8. Control mechanism for a vacuum steam heating system having pumping mechanism for moving the air or gas from the system and creating a vacuum in the return side thereof, comprising a plurality of progressively set, vacuum relief valves, and means comprising thermostatically controlled solenoids and cut-out valves for throwing said relief valves progressively, into and out of operating connection with the return side of the system.

9. Control mechanism for a vacuum steam heating system, having a pumping mechanism for removing the air or gas from the system and creating a vacuum in the return side thereof, comprising a variable, vacuum relief mechanism including a plurality of relief valves respectively set to open under different pressure conditions in the system, whereby to maintain the vacuum in the system at different determined degrees, and thermostatically controlled means for controlling said mechanism, so that different degrees of vacuum may be created in the return side of the system.

10. Control mechanism for a vacuum steam heating system having a pumping mechanism for removing the air or gas from the system and creating a vacuum in the return side thereof, comprising a variable vacuum relief mechanism including a plurality of relief valves connected to said pumping mechanism and respectively set to open under different pressure conditions in the system, whereby to maintain the vacuum in the system at different determined degrees, and thermostatically controlled means connected to throw said valves respectively into and out of operative connection with the return side of the system, in accordance with variations in temperature.

11. Control mechanism for a vacuum steam heating system having a pumping mechanism, for removing the air or gas from the system and creating a vacuum in the return side of the system, comprising a plurality of vacuum control valves of relatively different pressure setting, and thermostatically controlled means for controlling said mechanisms so that different degrees of vacuum may be created in the return side of the system.

12. In a vacuum steam heating system, having an inlet side, a radiator, a return side, and pumping mechanism for removing air or gas from the system and creating a vacuum. in the return side thereof, the combination with restriction means in the inlet side to the radiator effective to produce a fractional filling of the radiator under the influence of variations in the vacuum, and control mechanism for said system comprising a variable vacuum relief mechanism effective to maintain the vacuum in the system at different degrees, said mechanism including a relief valve, and thermostatically controlled means operable by temperature variations for throwing said valve into and out of operative connection with the return side of the system.

13. In a vacuum steam heating system comprising an inlet side having a constant steam pressure therein, a radiator, a return side, and pumping mechanism for removing air or gas from the system and creating a vacuum in the return side thereof, the combination with restriction means in the inlet side to the radiator effective to produce a fractional filling of the radiator under the influence of variations in the vacuum, with control mechanism for said system including a variable vacuum relief mechanism. effective to maintain the vacuum in the system at different degrees, said mechanism. including a relief valve and thermostatically controlled means operable by temperature variation for controlling said mechanism and valve so that different degrees of vacuum may be created in the return side of the system.

14. In a vacuum steam. heating system comprising an inlet side having a constant steam pressure therein, a radiator, a return side, and pumping mechanism for removing air or gas from the system and ceating a vacuum in the return side thereof, the combination with restriction means in the inlet side to the radiator effective to produce a fractional filling of the radiator under the influence of variations in the vacuum,

and variable vacuum relief mechanism effectivev to maintain the vacuum in the system at difierent degrees, including a relief valve, and thermostatically controlled means operable by temperature variation for throwing said valve into and out of operative connection with the return side of the system.

15. In a vacuum steam heating system, having an inlet side, a radiator, a return side, and pumping mechanism for removing air or gas from the system and creating a vacuum in the return side thereof, the combination with restriction means in the inlet side to the radiator effective to produce a fractional filling of the radiator under the influence of variations in the vacuum, and control mechanism for said system comprising a variable vacuum relief mechanism effective to maintain the vacuum in the system at different degrees, said mechanism including a relief valve, a solenoid operated valve for throwing said relief valve into and out of operative connection with the return side of the system, and thermostatically controlled means operable by temperature variation, having operative electric connections to said solenoid, whereby difierent degrees of vacuum may be created in the return side of the system.

IRVING C. JENNINGS.

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