US2249706A - Heating system - Google Patents

Description

July 15, 1941. w. T. FERGUSON HEATING SYSTEM Filed Aug. 2, 1938 H g a a m E a R T m z mw m 5 M W f m Patented July 15, 1941 UNITED STATES PATENT or FlCE HEATING SYSTEM Warren T. Ferguson. Waban, Mesa. assignor to Anderson Products, Inc., Cambridge, Mass. a corporation oi Massachusetts Application August 2, 1938, Serial No. 222,604

18 Claims.

vents may permit the air to escape too rapidly or too slowly, with the result that certain radiators receive steam sooner or later than others. When conditions of this type are present, a building will be heated unequally; that is to say, some of the rooms will be too warm, other rooms too cold.-

In the ordinary situation where the system isautomatic, heat being supplied in successive cycles, a thermostat is provided in one room, and the rise and fall of temperature in that one room controls the operation oi the source of steam.

It is obvious, thereiore, that unless the system is careiully balanced so that on each heating cycle the proper amount of steam will be supplied to the various radiators to produce proper temperatures in all the-rooms, the. heating of the building in general will be unsatisfactory.

In the heating system of which a typical form.

is disclosed in the accompanying drawing, I show aso-called one-pipe system in which a single pipe is used to convey steam to the radiators and condensate from the radiators back to the boiler. My invention, however, could be used with a so-called two-pipe system in which'an' additional pipe is provided at the other end of the radiators for the return oi condensate.

In the system disclosed I contemplate using air vents on the radiators or the so-called vacuum type; that is to say, the valves are oi the type which permit the escape of air, but close when heated by steam and which stay closed under the influence of a negative pressure in the 'system.

In the ordinary vacuum system of this type, if the piping and other fittings are tight, a" substantial negative pressure will develop between heating cycles due to condensing oi the steam, and unless this negative pressure is dissipated before the start of the next heating cycle, the air valves on'the radiators will not function to vent air on the subsequent heating cycle, so that such steam as may be generated will float through the system more or less aimlessly, with a corresponding uncertain supply oi heat to the radiators. 1

If, on the other hand, at the start of each cycle, the system is recharged with air at atmospheric pressure, this air mustbe driven from the system and the radiators before the steam can reach the latter. Because of this fact. through the use 01 valves on the radiators, which may be adjusted to vary the venting rate, the

steam distribution on any given heating cycle may be accurately controlled, and in this way, uniform heating through a building may be obtained.

'A further object of my invention, therefore, is to provide means whereby the system may be recharged with air at atmospheric pressure prior to the start of the next heating cycle. One'means for accomplishing this result is disclosed in the I patent to Ferguson et al.. No; 2,062,565, issued Dec. 1, 1936, in which an'electrically operated valve is provided to break the vacuum at the start of each heating cycle. In Ferguson et al. the system is opened to the atmosphere regardless oi the temperature or pressure that may prevail at the commencement of the cycle.

' This invention constitutes an improvement thereover in that means is provided for opening the system to the atmosphere whenever the general temperature of the system falls to a predetermined point; and it is contemplated that by suitable adjustment of there n leans provided, the system will be opened prior? to the. commence ment of the next cycle'which,'oi course, is under the control of a room thermostat.

When reference is made to reopening of the system prior to the start of the next heating of the system takes place exactly at the time that the heat source is placed in operation. The start 01 the cycle is reached when steam is liberated in such quantities that distribution thereof to the radiators commences.

Anotherjobject of my invention is to provide a valve so constructed that when it opens to admit air to the. system at a selected predetermined iallingtemperature, the valve will be opened to full capacity quickly so that the pressure in the system may be rapidly brought back to atmospheric.

Another objectof my invention is to provide automatic means whereby the temperature at temperature is low and the rate of radiation is high, my valve will open at. a higher temperature to admit air to the system than that at which it will open when the outside tempera-ture is lower.

A further object. of my invention is to provide a suitable valve which may be adjustable so that the opening and closing temperatures may be accurately controlled.

A further objectof my invention is to provide a valve which, having automatically opened to permit recharging the system with air, will automatically close upon the generation of steam and remain closed until the temperature again falls to a predetermined point, at which point it will open, provided the negative pressure with-' in the system is not greater than a predetermined amount, determinable by the valve construction. If the negative pressure is excessive at the time the temperature has fallen to the aforesaid predetermined point, then the valve will not open until the negative pressure has been dissipated to a suflicient degree.

These and other objects of my invention will appear as the description progresses with the aid of the accompanying drawing in which Fig. 1 is a diagrammatic showing of a heating system including my invention.

Fig. 2 is a vertical section of my automatic valve.

Fig. 3 is a vertical section of my automatic valve combined with an automatic adjustment operable in accordance with outside temperature conditions.

Referring now to Fig. 1, 2 is a source of steam which may be supplied with heat through any suitable means, as, for example, an oil burner 4. The oil burner 4 is caused to operate automatically and periodically by use of a thermostat 8 positioned in one of the rooms to be heated.

When the thermostat 6 closes, it operates a relay 8 which, in turn, closes the circuit Hi to the oil burner, causing the latter to supply heat to the boiler 2 to generate steam.

A steam main I2 extends from the boiler, connecting with risers l4 and IE. to which are atdiators is immaterial.

On each radiator is provided an air vent 22 of the so-called vacuum type.

able in the open market. It is merely necessary that these valves vent air until heated by steam,;

struction is shown in Fig. 2, in which there isa vertical nipple 26 adapted to be threaded into a connection on the main [2. The nipple 26 extends to a base 28 on which is mounted a shell 30 secured to the base by a lock nut 82 which engages a flanged lower edge 34 of the shell 30, to form a fluid tight connection. In the center of the top of the shell is a vent 36 forming at 38 a valve seat.

In the center of the base is mounted a supporting stem 40 which is adjustable vertically a limited amount. The particular construction dis- It is believed unnecessary to show in detail the construction of such vents, as they are well known and procurtached radiators i8 and 20. The number of rainwardly extending flange 46 is a split washer 48 which straddles stem 48 at the reduced portion 58.

It will be observed that the reduced portion is of a length somewhat greater than the thickness oi washer 48, so that the stem 40 may be I screwed up and down within sleeve 42 an amount equal in distance to the difference between the length 01' the reduced portion 50 and the thickness of washer 48. The purpose of this construction will presently become apparent.

- In order to seal the construction just described against leakage, a gasket 52 and lock nut 54 are provided within the lower end of sleeve 42.

Carried on the upper end of stem 48 is a sealed bellows 58 which is maintained at a minimum predetermined length by a tubular stop member 88. This stop may be of any suitable construction, it merely being intended to hold the bellows against collapse below a predetermined point. The bellows that I use must be of construction sufllciently strong to withstand large differences in pressures, as I contemplate that my bellows shall normally carry a very substantial negative pressure; that is to say, before the bellows is sealed, it shall be evacuated suillciently so that the vacuum will begreaterthan 20" of mercury. A small amount of water or other volatile liquid is in the bellows, from which steam will be generated when heat is supplied.

On the upper end of bellows 56 is a suitable seat 88 on which rests a valve pin 62 which terminates in a conical form, as at 64, for suitable engagement with valve seat 38. Valve pin 62 carries an inverted open bottom diving bell type float 66 which extends downwardly about bellows 56. v

By having a high vacuum in bellows 56, I have found that it is possible to control within a few degrees the temperature at which bellows 56 will begin to expand or contract regardless of the surrounding pressure, provided, of course, it

degree, I have found that they may be made in a quantity so that all will commence expanding at substantially the same predetermined temperature within manufacturing tolerances. That is to say, when a high vacuum is present in thebellows, the effect of surrounding negative pressures is substantially eliminated, and the temperature is the dominating influence; In bellows not using a high vacuum, elongation and contraction is affected not only by temperature but also by the surrounding pressure of the system. This I consider an outstanding feature of my invention, as it permits accurate control.

In ordinary operation the highest temperature to which the bellows 56 will be subjected is about 212 F. or slightly above, so that sleeve 42 must be-adjusted with'respect to the base 28 so that when the stem 40 is screwed to its downmost position, the expansion of bellows 56 at 212 or .resultsf; j I I Let us assume that the temperature outdoors is thereabouts will be sufficient to cause the closing of valve 38.

It is believed apparent that ii the valve stem 40 is then screwed upwardly so that valve pin 62 is brought closer to valve seat 38, the valve will close or open as the case may be at a temperature below 212".

Thus, if it is desired to close or open the valve at a temperature, for example,

this vacuum packed construction. it is possible to: provide valves in quantity, all or which will A open at a-given'setting, allowing iorlmanufac turingtolerance, atfany predetermined falling temperature; a

Having described the elements of my system, I will'now setforth a typical cycle 'of'operation' andthe' methodlof adjustment tos ecure different moderately coldysay," for example, 40 The room in "whichth'e thermostat 6 is located cools} lawman-5 closes; "and summer '4 is put'in op"- e'r'atio' team is "in ue course generated in' boiler-'2 "andpasses along main l2.

Valve 2 4 being cold, is openfandthe' entire system prior tbthe generation o f'steamfis' at atmospheric pressure. f I r Steam, on reaching'" the valve 24, passes "upwardly through nipple :26 into" engagement with bellows 56, whichexpands as thetemperature rises. If it is 'desired' that valve 24' close and open at, for example, 178 'F.', the distance betweenvalve seat 3Band valve pin 62 must be'adjusted to a position such that when thebellows 56 is at"178 F., the expansion will be sufllaient to close the port. v f

Thus, shortly after the generationbf steam and before the steam has reached the radiators, valve 24 will automatically close. The steam then passes along main I2 to the risers l4 and [6, driving before itthe "air in the system, which in turn is forced through the'radiators and out into the atmosphere through vents: 22. 'While this is taking place, the system pressure will rise, ordinarily, only a few ounces, as this is suiiicient gated position Thebellows 58 is vacuum packed for the express purpose of enabling the valve to open under conditions of high negative pressure. That is to say, unless the negative pressure within the bellows, combined with the contractive force of the bellows structure when in elongated position, is greater than the elongating ,force caused by the negative pressure surrounding'the bellows, the valve will not open.

As the radiators cool and the temperature of valves 22 falls, these valves, being of the vacuum type, remain closed because of the negative pressure in the system, and air cannot re-enter the radiators through these vents. Only a small negative pressure, ordinarily not over one inch of'mercury,.is:necessary to hold this type 01' valve closed. I

As the temperature of the radiators falls, the temperature of the entire system in general falls and at valve 24 the temperature, which, at the time the oil *burner '4 ceased operation,-was---in the neighborhood of 212 R, will also commence todrop. r1 Inwthe" situation described, valve -.24 will reopen at-approximately the temperature at which'it originally' closed, namely 178v F., pros; vided at that timerthe prevailing temperature and negative pressure in the system are'less thanthat necessary-to maintain bellows -.56 in elon- If, them the temperature has dropped below 178 F., then-temperature necessaryto-maintain' the valve closed; and the negativepressu'rein the is the critical pressure at which the bellows will contract by virtue of the vacuum packing) then valve: 24 will'open'andair willpass into the system through vent-36, which will be opened quickly to full capacity asthe cool 'inrushing air passes bellows 56, dropping the temperature and to force'the steam to all 'ofthe radiators. Occawhat higher, but in any event, the pressure in the" system during the time steam is supplied is positive. I

In due courseQthe radiators will'be iilled with steam and vents 22 will close. The'jradiators will give up their'heat to the surrounding air so thatthe' room temperature will rise, with the result that in' time thermostat 6 will junction to stop the operation of oil burner 4andithe generation of steam in boiler 2. p v j I As theradiators cool, the steam in the system willcondense and'a negative pressurewill develop; The speed with which the negative pres; sure develops; is controlled by the rateof con densation and the tightness of the system. f If the system is tight, as it shouldbe, the negative pressure'will, in the ordinary case develop to at least Illinches of mercu'ry'gand generally g'oes mercury.

negative pressureand of the latter.

Sometimes, when the temperature has decreased to the pointat'whi'ch the bellows is actuated," for example, 178 F;,'the negative pressure at that timewillbel'ess than the critical controlling pressure for the bellows-.- This being causing rapid contraction so, it will be' seen that the temperature at the because the negativepre'ssure surrounding the bellows at that time is greater than the contractive 'force exertedby thenegative pressure within the bellows plus the contractive tendency of the bellows itself when in elongated position.

That is to say, (the negative pressure in the system may be even greater than the extent of the negative pressure within the bellows, in which case the bellows will be held in elongated position to maintain the valve closed, even though the/temperature has fallen below'the normal; opening point, In suchcases 'however,

the negative pressure in the system willbe' dissipated either'byfslow leakage" or by. thegeneration Y of vapors in the 'boiler after the application of heat thereto.i Upon the dissipation of some 01' the negative pressure in the system, a point will be reached where the negative pressure in the vacuum packed bellows will be suflicient to overcome the elongating effect of the decreasing surrounding negative pressure of thesystem, and

.the valve at thispoint will reopen.

depending on the particular system, the outdoor temperature, the time betweencycles and the radiation characteristics of the heated space, but may be considered as representative of the conditions that quite often prevail.

- At closin of valve At end of heatin At opening of valve At start of cycle cycle g 24 to atmosphere 150 F 212 F 212 F. to 216 F- 180 F. fefififefiififfi'fi 125' F 18 212 F 150 F. a Temperature oi heated space. 68 F. to 70 F 69 F- t 70 F-- ,72" F 72 F. to as F.

' Pressure within system if valve 24 Atmosphericillbs... lbs. to less than O lbs. to 1 lb Negative but less opened prior to start of burner. I 1 l I ban 1 g Vacuum condition within system Negative 18 Ha... 01 1 lb Negative 14% Hg. if burner started prior to opening 7 a of valve 24 Thus, using a valve 24 of myconstruction, the system will always be open whenever the temperature at the valve is less than the operating temperature thereof, as determined by construcby the temperature falling below the critical point,'with the negative pressure at that time also being below the critical'point; or inother cases, the decreasing negative pressure may control the reopening as it passes the-critical point,

thetemperature having previously fallen below the critical-point of, for example, 178 F.

The critical point for pressure control is determined by the characteristics of the particular heating system, and degree of vacuum packing of the bellows is adjusted to conform therewith.

The critical negative pressure should be at least inches of mercury, for when the negative pressure drops below that point, the heat transfer characteristics are such that maintenance of a vacuum is no longer justified. In a reasonably tight system in proper operating order, the negative pressure developed during the off part of each cycle should reach at least this degree of negative pressure. If the bellows is packed to operate at a critical pressure of, for example, inches of mercury, and the system with which the valve is used never reaches as high a negative pressure as that, it is obvious that the temperature at the valve will controlthe reopening. If, on the other hand, the bellows is vacuum packed to :have a critical operating temperature at 10 inches of mercury, then in the ordinary case the system pressure will control the reopening, for the temperature will have fallen below the critical temperature point before the negative pressure of the system will have fallen below the critical pressure point.

Thus, through the use of the vacuum packed bellows, the system is maintained closed as long as either the negative pressure or temperature is in excess of its respective critical point, and reopens only when both the pressure and temperature are belowthe respective critical pressure and temperature.

The valve 24 is adjusted so that regardless of whether the falling temperature or decreasing negative pressure controls the reopening, the

negative pressure at the time of reopening will be not less than about 10 inches of mercury. The following figures are illustrative of a typical cycle of operation of a heating system in 24 is 178 F. andthe critical negative operating pressure of the vacuum packed bellows is 15 inches of mercury. The figures given will vary,

may be developed 'in the system, and the reopenv which the critical operating temperature of valve ment of the next heating cycle which launder the control of thermostat 6. Obviously, on a cold day the next cycle will be inaugurated by' thermostat 8 sooner than on a warm day; and therefore in cold weathervalve 24 will be adjusted to close and open at' a higher temperature than on a warm day. Thus, if the temperature outside should new fall to zero. it is contemplated that the'stem 40 would be screwed downwardly to move valve pin 62 and valve seat 28 farther apart so that the temperature at the valve will have to rise to a higherpoint before the valve will close, and conversely the temperature will have to fall only a few degrees before the valve will open.

Thus, regardless of the outside temperature, valve 24, if properly adjusted, will always open to bring the pressure in the system back to zero before the start of the next heating cycle. It has been foundthat through the ordinary range of temperatures, a single setting of valve 24 will suflice; that is to say, the temperature at valve continuously.

. Thus, by my invention I have provided a simple, economical and accurately operating valve whereby the system is automatically recharged with air before the commencement of each cycle.

1 This is, as previously pointed out, essential where the distribution ofsteam through the radiators is controlled by the rate of venting of air through the adjustable vents 22. Furthermore, by the use of my valve no limit is placed on the vacuum that ing is controlled principally'by the falling temperature. As previously set forth,- however, where the system is exceptionally tight, it is possible that the vacuum created in the system may exceed the vacuum of the bellows, so that the falling temperature in such cases is not the sole control. These circumstances, however, prevail only in special'instances.

A modified form of my valve 24 is shown in Fig.

3. With respect to opening to rec arge the sys-' tem with air prior to the start of each cycle and closing after the generation of steam, the operation of the form shown in Fig. 3 is identical with that shown in Fig. 2.

The principal difference resides in the provision of automatic means for adjusting the position of the thermostatic bellows i8 vertically as the outdoor temperature fluctuates. As previously pointed out, it is desirable on cold days that the valve close and open at a high temperature and on warmer days at a lower temperature. This condition is automatically provided for in the construction I have devised.

- In Fig. 3 it will be observed that the thermostatic bellows 56 instead of being mounted on adjustably threaded engagement withbase I 12.

Extending downwardly through sleeve is'a hollow tube I4 whichis inv connection with the interior of bellows B8. The tube 14 is carried in any convenient mannerto the wall 76 of the building and extends therethrough to terminate in the elongated bulb 18;. .'I'he,,-bellows 68,

tube 14, andbulb-TIB form ajsealed unitand are completely filled with any suitable liquid. Alco-- .hOLiOr example, wouldbe'satisfactory, as it will 1 not freeze under suchconditions aswould be nor- 1 .mally encountered.. e 1

It. is. apparentthat as the temperature drops, heliquid inbulb '18 will contract, thereby drawng liquid from the-bellows 68 ,through tube l4.

;,;This',necessarily causes contraction of bellows 68 and lowers the .position of valvepin 62 with respect to valve seat 38, making it necessary for the 'thermostatic ,bellows-flit? to expand a greater amount beforethe. valve will close., This means the lower the outside temperature, the higher the temperature at which the valve .will open and close.

Conversely, as the temperature outside rises, the liquid in bulb 18 will expand, forcing part of the liquid through tube N, into bellows68 which will thereupon be elongated to move thermostatic bellows 56 and valve pin, 62 upwardly, reducing the amount of movement required to close the valve. Thus, at higher outdoor temperatures the valve will open and close at lower temperatures than would be the case when the outdoor temperatures were low.

It. is believed from the foregoing explanation that the operation of this automatic control is apparent. On cold days the heating cycles, due

to more rapid heat radiation, will be more frequent than on warm days; that is, thetime interval between the cessation of operation of burner I and the commencement of operation on the next cycle'will be less than when the temperature outdoors is higher. Therefore, it is essential that valve 24 operate toopen the system to the atmosphere, sooner on cold days than on warm days.

to a predetermined point'in relation to the outside temperature.

Since my valve operates to open when the temperature has fallen to a predetermined point, regardless of the negative pressure in the system, provided, of course, that the negative pressure is not so. great. that it' is enabled to overcome the contractive effect of the vacuum-packed bellows, and since. the temperature atwhich it opens is varied in relation to the outside temperature either through the manual adjustment of Fig. 2 or the automatic adjustmentof Fig, 3, I am enabled .to insure, by proper initial adjustment, opening of the system toward the end ofthe ofi portion of the cycle. Thus, the system;,is;recharged at a'suitable time so that the adjusted vents 22 may come into play to give the proper distribution of steam on each cycle. H1

1 While I have shown apreferred for-m ofnmy systems and valves which are used to carry out the methodof heating described, I wish it to be distinctly-understood that I do not intend to be limited thereby but onlyby the appended claims.

I claim 1. A method of heating by steam" in whicheach cycle comprises the followinglsteps, setting a -sourceof steam in operation at a predetermined falling enclosed spacev temperature, supplying radiators with, steam, sealing the system, discontinuing the supply of steam, then allowing the steam to condense to create-a substantial negative pressure, thereafter opening said system'to-the atmosphere at a point remote from said radiators to recharge the system with air, saidv opening taking place only when thetemperature atsaid stantially negative, but is less negative than a predetermined negative amount, and thereafter setting said-steam, source in operation tocommence a second cycle as the temperature, in said enclosed space falls again to said predetermined 2. A-" meth od, of heating temperature. l

enclosed. spaces by steam; utilizing a system which normallyvents air from the radiatorsduring each heating cycle,

' comprising. the-steps of setting a source of steam in operation, conveying the steam to the radi ators, sealing thesystem, discontinuing the supply of steam, then allowing. the steam in said system tocondense to createa substantial negative pressure, reopening said system to' theatmosphere, while said negative pressure'stillexists, said reopening taking place at a point remote from said=radiators and occurring when the temperature thereat has fallen below a substantially predetermined degree and the negative pressure in said system is-considerably less than atmosafter the cessation of .the previous cycle, but an adequate time before the start of the next cycle.

In this wayI am enabled to maintain a negative pressure in the system through that portion of the oficycle, which is most important. By that I mean that toward the. end of the cycle, even though there may be a large negative pressure in the system, the heat transference is quite limited, and asa practicalmatter it makes but little difof the subsequent cycle or some time before. It

, appears that the most'desirable time to break the vacuum is when the temperature has fallen ference whether the vacuum is broken at the start pheric' and-becoming more negative, but is-less negative than a predeterminednega-tive amount,

and thereafter iesetting said steam source in operation at a predetermined falling enclosed space pressure, reopening said system to the atmosphere at a point remote from said radiators while said negative pressure still exists, and whenithe temperature thereat has fallen below a substani tially predetermined degree and the negative pressure in said system is considerably less than atmospheric and becomingless negative, and is less negative than a predetermined negative amount, and thereafter resetting said steam source in operation at a predetermined falling enclosed spacetemperature. e

4.1A method. of heating enclosed spaces by steam, utilizing a steam boiler, a source of heat, a plurality of radiators positioned in said enclosed spaces, and pipes for conducting steam from said boiler to said radiators, in which each cycle comprises the following steps, setting said source of heat in operation at a predetermined fallingenclosed space temperature, supplying said radiators with steam, venting air from said radiators through air vents thereon, sealing the system,-

from said radiators to recharge the system with.

air, said opening arranged to take place after the negative pressure has receded to a degree slightly less negative than said predetermined negative mosphere,' thermostatic and pressure operated means for maintaining said valve closed after the termination of the heating portion of each cycle,

'7. A steam heating system comprising a steam boiler and heating means and radiators to which steam is supplied intermittently by connecting pipes, a vacuum relief valve positioned on said pipes and connecting said system with the at-- said thermostatic and pressure operated means including an expansible, hollow, sealed unit operable .both by temperature and pressure cooperatdegree, and thereafter closing said system at said remote point at a predetermined rising temperature less than the temperature of the water in said boiler at that time, whereby each heating cycle will comprise the provision of a positive pressure in the system while steam is being supplied, a negative pressure in the system after the supply of steam is discontinued until the system is opened for recharging, and a return to atmospheric pressure prior to delivery of steam to said radiators during the next heating cycle.

5. A method of heating enclosed spaces by steam, utilizing a steam boiler, a source of heat, I

a plurality of radiators positioned in said enclosed spaces, and pipes for conducting steam from said boiler to said radiators, and a negative pressure breaking valve remote from said radiators, in which each cycle comprises the following steps, setting'said source of heat in operation at a predetermined falling enclosed space temperature, supplying said radiators with steam, venting air from saidv radiators through air vents thereon,

ing to open said valve when the temperature at said valve has dropped to a predetermined degree and the pressure in said system is substantially negative but less negative than a predetermined negative amount, said thermostatic means operable to close'said valve when the temperature thereat has risen to approximately said predetermined degree. V

8; A heating system; for heating enclosed spaces, comprising a steam boiler, a source of heat, radiators connected by piping to said water boiler, vents on said radiators, means for closing said vents when the pressure within said radiators is less than atmospheric, and a valve including an expansible, hollow, sealed unit aflectcd by both temperature and pressur remote from said radiators and attached to said piping and operable to open said system to the atmosphere when the temperature at said valve is very much greater than the temperature in said enclosed spaces but less than a predetermined temperature, which latter temperature is less than the temperature of the water in said steam boiler at the time of reopening of said valve and the pressure within said valve is negative a substantial amount but less negative-than a predetersealing the system, discontinuing the supply of steam, then allowing the steam to condense to create'a negative pressure in said system, maintaining the system sealed thereafter until the temperature and pressure at said negative pressure breaking valve conform to the following requirements, that the temperature is less than a to atmospheric.

6, A method of heating by steam, utilizing the so-called vacuum type system which includes a steam boiler, comprising the step of reopening the system to the atmosphere during each neating cycle when the pressure in the system is nega-' tive a substantial but definitely limited degree and the temperature in the system is much higher than the spaces to be heated but substantially 'lower than the temperature of the water in said steam boiler, Y

mined negative degree.

9. In a steam heating closed spaces, in combination, a steam boiler and a source of heat, a plurality of radiators, pipes for. conducting the steam to said radiators, air

erated, expansible, sealed unit operatively related" to said valve, said valve opened by the actuation of said unit under the influence or the falling temperature of the system, said falling temperature at the time of opening of said valve being substantially greater than the temperature of said enclosed spacesv but less than the temperature of the water in said steam boiler, said valve closed-by the actuation of the same unit under the influence of steam generated after said valve is opened, the temperature at which said valve is closed always being less than the temperature of the water in said water boiler at the time of closing, said unit also actuated by the system pressure to prevent opening .of said valve whenever the system pressure is more negative than a predetermined substantial negative amount.

10. In a steam heating system for heating enclosed spaces, in combination, a steam-boiler and a source of heat, a plurality of radiators positioned in said enclosed spaces, pipes for conducting steam created in said boiler to said radiators, air vents on said radiators, means controlled by the temperature of one of said enclosed spaces for starting and stopping the said source of heat, means for insuring atmospheric pressure within said system prior to the distribution or steam on system for heating eneach heating cycle, said means comprising a combined temperature'and pressure controlled valve positioned on said system remote trom the said enclosed spaces and adapted to open said system to the atmosphere at a predetermined high falling system temperature considerably above that or said enclosed spaces lithe pressureat said valve is less than a predetermined negative degree, the temperature at which said valve opens always being less than the temperature of the water in-said boiler, the pressure control or said valve providing means for preventing the opening of said valve whenever the negative pressure saidvalve opens or closes-always being less than the boiler water temperature but substantially greater than'the temperature of said enclosed '14. A heating system for heating enclosed spaces. including a steam boiler and a source of heat, comprising radiators with vents thereon, pipes connecting said boiler to said radiators:

means for closing said vents when the pressure in said system is in excess of said predetermined negative degree, said temperature control arranged to close said valve at a temperature-alwithin said radiators is less than atmospheric, and a valve remote from said radiators and connected to one of said pipes to open and close said system to the atmosphere, said valve comprising a vacuum-packed bellows arranged to expand at a predetermined valve temperature substantially in excess of the temperature of said enclosed spaces, but less than the boiler water temperature, to close said valve, and arranged to contract at substantially said predetermined valve temperature substantially in excess of the temperature of said enclosed spaces but less than 1 the boiler water temperature, at which falling means including said air vents for sealing the system after steam has been generated, and means for reopening the system to the atmosphere after the supply of steam has been discontinued, said system opening and sealing means comprising avalve having a combined thermo-:

static and pressure operated element the thermo static phase of said element adapted to close said valve upon the application or heat above a substantially predetermined degree and adapted to open saidvalve when the temperature thereat has fallen below said substantially predetermined degree, the pressure phase oi said element adapted to prevent said thermostatic phase from opening said valve when the pressure in said system is more negative than a predetermined substantlal negative amount.

12. In a steam heating system for heating enclosed spaces, means for opening and closing said system to the atmosphere under certain conditions, said means comprising a valve connected to said system, thermostatic and prwsure diiIerentisl operated means'related to said valve, said pipes for conducting the steam to said radiators,

air vents on the radiators permitting the steam to reach said radiators at predetermined times,

and means for opening'and' closing said system to the atmosphere, said means comprising a valve remote from said radiators and connected to one of said pipes, having a vacuum-packed bellows therein operable to open under the influence of a falling system temperature provided the negative system pressure does not exceed a predetermined negative degree and operable to close under the influence of steam generated after said valve is opened, the temperature at which temperature the resultant eiIect of the pressure within and without the bellows is insuflicient to hold the bellows elongated, said bellows also arranged to contract at a substantial determinable negative system pressure when the system pressure is decreasing, at which pressure the resultant effect of the pressure within the bellows as determined by the bellows temperature at the time and the said negative system pressure is insuflicient to hold said bellows elongated, thereby to open said system to the atmosphere.

15. A method oi maintaining a substantially uniform temperature in an enclosed space by steam, comprising the steps oi'setting a source of steam in operation at a predetermined falling space temperature, transmitting said steam to a radiatorto raise said space temperature, sealing said system, discontinuing the supply of steam at a predetermined rising space temperature, allow- I ing the steam in said system to condense to create radiator when the temperature at said remote point is less than a predetermined temperature but in excess of said space temperature and while a substantial negative pressure less than a predetermined greater negative pressure prevails in saidsystem, and thereafter resetting said steam source in operation at the initial predetermined falling space temperature.

16. In a steam heating system for heating enclosed spaces, in combination, asteam boiler and a source of heat, a plurality of radiators, pipes for conducting the steam to said radiators, air vents on the radiators permitting the steam to reach said radiators at predetermined times, and means for opening and closing said system to the atmosph'ere, said means comprising a valve remoteirom said radiators and connected to one of said pipes having a vacuum packed bellows therein operable to open under the influence of a decreasing negative system pressure when the pressure has decreased to a point less than a substantial predetermined negative pressure, provided the temper'ature at said valve does not exceed a .predetermined degree, said predetermined deafter the space temperature has fallen to a predetermined point, transmitting said steam to a radiator to raise said space temperature, sealing said system, discontinuing the supply 01 steam after the space temperature has risen to a predetermined point, allowing the steam in said system to condense to create a substantial negative presuniform temperature in an enclosed space by steam, comprising the steps of supplying steam after the space temperature has fallen to a predetermined point, transmitting said steam to a radiator to raise said space temperaturasealing said system, discontinuing the supply of steam after the space temperature has risen to a predetermined point, allowing the steam in said system to condense to create a substantial negative pressure in the system, and thereafter reopening said system to permit entrance of air therein at a point remote from said radiator when the temperature at said remote point is less than a predetermined temperature but in excess of said space temperature and while a substantial negative pressure less than a predetermined greater negative pressure prevails in said system.

WARREN T. FERGUSON.

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