US2210325A - Refrigeration control system - Google Patents

Description

Aug. 6, 1940. A, B NEWTON 2,210,325

REFRIGERATION CONTROL SYSTEM Filed Feb. 20, 1939 3 Sheets-Sheet l (Iiiorneg Angra, 1940. A, B, NEWTON 2.210,325

REFRIGERATION CONTROL SYSTEM Filed Feb. 20, 1939 3 Sheets-Sheet 2 nvenfor aNeMwa /yw ra/w mlgag gg Aug. 6, 1940. n A B. NEWTON 2,210,325

REFRIGERATION CONTROL SYSTEM so oo mo wo mo ao HEAD Pnsssum:

fnnentor Alwin IaNwhmn MMM Patented Aug. 6, 1940 UNITED STATES PATENT OFFICE BEFRJGERATTON comm. SYSTEM Ware Application February 20, 1939, Serial No. 257,407

side of the refrigerating apparatus decreases to a` desired low value whereby needless operation of the evaporative condenser is prevented and circu# lation of refrigerant through the refrigerating apparatus is assured.

Another object of this invention is to control the operation of the evaporative condenser in accordance with the pressure on the high pressure side of the refrigerating apparatus to maintain the pressure on the high pressure side of the refrigerating apparatus within a desired range, and also to control the evaporative condenserin accordance with the temperature of theair entering the evaporative condenser to allow the desired range of pressure on the high pressure side of the refrigerating apparatus to rise as the temperature of the air increases. This maintains the total power consumption by the fan means of the evaporative condenser and the compressor at a minimum at all times.

Still another object of this invention is to additionally control the evaporative condenser in accordance with pressure on the low pressure side of the refrigerating apparatus to cause the pressure on the high pressure side of the refrigerating apparatus to decrease within the desired range as the pressure on the low pressure side of the rerigerating apparatus increases where fairly wide fluctuations in suction pressure are encountered. This also maintains vthe total power consumption by the fan means and the compressor at a minimum.

Other objects of this invention reside in the- 40 combination of elements for obtaining the desired sequence of operation as is more fully set forth in the specification, claims, and drawings, in which Figure 1 is a diagrammatic illustration of form of this invention, and

Figure 2 is a diagrammatic illustration of another form of this invention.

Figure 3 is a graph plotting horsepower per ton of refrigeration against head pressure of the refrigerating apparatus of Figure 2.

Referring now to Figure 1 a medium to be cooled is enclosed in an enclosure I0. For purposes of illustration the medium is assumed to be air within a walk-in box I for commercial refrigeration work but also may be air within a spacefor air one 4r' conditioning work. The medium is cooled by means of a cooling coil taking the form of an.

evaporator Il. Refrigerant is supplied to and withdrawn from the evaporator II by means of arefrigerating apparatus generally designated at I2 which may comprise a compressor I3 operated by an electric motor I4. Compressed refrigerant passes from the compressor I3 through a high pressure line I5 to a coil I 6 of an evaporative condenser generally designated at II. Condensed r'efrigerant is collected from the coil I6 in a receiver I8 and the liquid refrigerant flows from the receiver I8 through a liquid line I9 to the evaporator II. Evaporated refrigerant is Withdrawn from the evaporator II through a suction or low pressure line 20 by the compressor I3. The supply of refrigerant to the'evaporator II may be regulated by a thermostatic expansion valve 2| having a thermostatic bulb connected to the outlet of the evaporator II. Since such a construction is conventional in the art a further description thereof is not considered necessary it being suicient to state that when the compressor I3 is operating the evaporator Il performs a cooling function.

The evaporative condenser I1 may comprise a casing 25 enclosing the condenser coil I6. The casing 25 is provided with air inlets 26 and air is drawn through the inlets 26 and over the condenser coil I6 by means of a fan 2I operated by an electric motor 28. Air is discharged from the fan 2'I through a discharge duct 28. A spray 30 sprays Water in contact with the air circulating in the casing 25 and in contact with the condenser coil I6, the water being collected in a sump 3I. The Water is withdrawn from the sump 3| through a pipe 32 by an electrically operated circulating pump 33 and delivered through a pipe 34 to the spray 30. The water contacting the air provides evaporative cooling for the condenser coil I6. Suitable means (not shown) for supplying water to the sump 3| to make up water lost during the evaporation process may be provided.

The operation of the compressor I3 and hence the refrigerating apparatus as a whole is contrplled by a temperature responsive controller generally designated at 36 responsive to the temperature of the medium within the enclosure I8 and a unitary control arrangement generally designated at 3l. The unitary control arrangement 31 comprises a control device 38 responsive to variations in pressure on the low pressure side of the refrigerating apparatus, a pressure responsive device 39 responsive to the pressure on the high pressure side of the refrigerating apparatus and a ycall for cooling by the temperature responsive controller 36 the refrigerating apparatus cannot be placed in operation until the pressure on the high pressure side of the refrigerating apparatus decreases to a predetermined low value and .the pressure on the low pressure side of the refrigerating apparatus increases to a predetermined high value, which for example may be a defrosting value.'y The compressor is then maintained in operation until either the demand for cooling is satisiied, or the pressure on the high pressure side of the refrigerating apparatus increases to a predetermined'high value, or the pressure on the low pressure side of the refrigerating apparatus decreases to a predetermined low value.

The fan 28 and the water circulating pump 33 of the evaporative condenser I1 are controlled by a relay generally designated at 4|, the relay 4|. in turn being controlled by the unitary control arrangement 31; The arrangementl is such that the fan 28 and water circulating pump 33 are stopped and hence the evaporative condenser is rendered inoperative when the pressure on the high pressure side of the refrigerating apparatus decreases to a predetermined low value which for example may be the value which permits starting of the compressor.

The temperature responsive controller 36 may comprise a bellows 43 charged with a volatile fluid for operating a lever 44 against the action of an adjustable tension spring 45 for in turn operating a mercury switch 46. For purposes of illustration it is assumed that the parts are so arranged that when the temperature of the medium within the enclosure I0 rises to 42 the mercury switch 46 is tilted to a `closed position and when the temperature within the enclosure decreases to 40 the mercury switch 46 is tilted to the open position.

The pressure responsive device ,38 of the unitary control arrangement 31 may comprise a bellows 48 connected by a pipe 49 to the low pressure or suction line 20. The-bellows 48 operates a lever 50 pivoted at 5| against the action of an adjustable tension spring 52. One end of the spring. 52 is ,connected to the lever 50 and the other end is connected to a nut 58 A screw threadedly mounted on a screw 54. By rotating the screw 54 the tension in the springv52 may be varied to adjust the pressure setting of the pressure responsive device 38, The lever 50 carries in an insulated manner a bridge member 55 provided with contacts 56 and 51. The contact 56 engages a` contact member 58 mounted on a terminal post 59 and the contact 51 engages a contact member 60 mounted on a. terminal post 6|. `Concentrically located cams 62 and 63 are utilized for independently positioning the contact members 58 and 60. For purposes of illustration it is assumed that upon an increase in pressure on the low pressure side of the refrigerating apparatus the contact 56 iirst engages the contact member 58 at 10 lbs. and theny the contact 51 engages the contact member 60 at 35 lbs. Upon a decrease in suction pressure the contact 51 first disengages the contact mem- -ber 60 at 35 lbs. and the contact 56 disengages `vided with abutments 13 and 11.

The bellows 65 operates a lever 61 pivoted at 68 against the action of an adjustable tension spring 69. One end of the spring 69 is connected to the lever S1 and the other end is connected to a nut 10 screw threadedly mounted on a screw 1|. By rotating the screw 1| the tension in the spring 69 is varied to adjust the pressure setting of the pressure responsive device 39. The lever 61 carries an abutment member 12 preferably made of insulating material and pro- The abutment 13 is adapted to engage a contact Vmember 14 carried by a terminal post 15 to separate the contact member 14 from a contact 16. The abutment 11 is adapted to engage a contact member 18 carried by thel terminal post 6| to cause the contact member 18 to disengage a contact 19. For purposes of illustration it is assumed that upon an increase in pressure on the high pressure side of the refrigerating apparatus contact member 18 first disengages contact 19 at 140 lbs. and the contact member 14 disengages contact 16 at 200 lbs. Upon a decrease in pressure on the high pressure side of the refrigerating apparatus contact member v14 rst engages contact 16 at 200 lbs. and the contact member 18 engages contact 19 at 140 lbs.

The relay or starter 40 may comprise an operating coil 8| for operating a bridge member 82 with respect to contacts 83 and 84 and a bridge member 85 with respect to contacts 86 and 81. When the operating coil 8| is energized the bridge member 82 engages the contacts 83 and 84 and th bridge member 65 engages contacts 86 and 81 and when the operating coil 8| is deenergized the bridge members.82 and 85 disengage their respective contacts by means of springs gravity or'other means (not shown).

If desired the unitary control arrangement 31 may be provided with an overload cut-out generally designated at 89. This overload cutout may comprise a heater element 9| connected between a terminal and the contalct 86. The heater element affects a thermostatic latch mechanism forvseparating contacts 92 and 93 when the current ow through the heater element 9| becomes excessive. The latch -mechanism may be manually reset to reclose the control contacts 92 and 93 following separation of these contacts upon an overload condition. Power is supplied to the compressor motor I4 and to the unitary control arrangement 31 by means of line wires 91 and 98 leading from some source of power (notshown), the line wire 91 being connected to the contact 16 and the line Wire 98 being connected to a terminal 99.

For a more detailed description of the construction of the unitary control arrangement 31 reference is made to application Serial No. 196,447 led March 17, 1938 by Albert L. Judson and Carl G. Kronmiller.

Assume now that the temperature within the enclosure |0 increases to 42 to close the mercury switch 46, that the pressure on the high pressure side of the refrigerating apparatus decreases to lbs. to cause contact member 14 to engage contact 16 and contact member 18 to engage,kv

contact 19 and that the pressure on the low pressure side of the refrigerating apparatus increases to 35 lbs. to cause contact 56 to engage contact member 58 and contact 51 to engage contact member 60.v A circuit is thereupon com' pleted from the line wire 91 through contact 16,

contact member 14, terminal post 15, wire |00,

mercury switch 46, wire |0|, terminal post 59,

contact member 58, contact 56, bridge member 55, contact 51, contact member 60, contact membei` 18, contact 19, wire |02, contact 84, wire |03, contacts 92 and 93, wire |04, operating coil 8|, wire I 05, and terminal 99 back to the other line wire 98. Completion of this circuit energizes the operating coil 8| to move the bridge member 82 into engagement with contacts 83 and 84 and to move the bridge member 85 into engagement With contacts 86 and 81.

Movement of the bridge member 85 into engagement with the contacts 86 and 81 completes a load circuit for the compressor motor I4 which may be traced from the line wire 91 through contact 16, wire |06, terminal 90, heater element 9|, contact 86, bridge member 85, contact 81, Wire |01, compressor motor I4, wire |08 and terminal 99 back to the other line wire 98. Completion of this circuit causes operation of the compressorA motor I4. y

Movement of the bridge member 82 into cngagement with thecontacts 83 and 84 completes a maintaining circuit for the operating coil 8| which is independent of contact 51, contact members 60 and 18, and contact 19. This maintaining circuit may be traced from the line wire 91 through contact 16, contact member 14, terminal vpost 15, wire I 00, mercury switch 46, wire IOI, terminal post 59, contact member 58, contact 56, bridge member 55, wire |09, Contact 83, bridge member 82, contact 84, wire |03, contacts 92 and 93, wire |04, operating coil 8|, wire |05, and terminal 99 back to the other line wire 98. Completion of this circuit maintains the operating coil 8| energized and hence the refrigerating apparatus in operation until either the temperature within the enclosure I0 decreases to 40 to open themercury switch 46 or the pressure on the high pressure side of the reirigerating apparatus increases to 200 lbs. to separate contact member 14 and contact 16 or until the pressure on the low pressure side of the refrigerating apparatus decreases to 10 lbs. to separate the contact mcmber 58 and contact 56.

The relay 4I for controlling the operation of the fan 28 and the water circulating pump 33 may comprise relay coils ||2 and I I3 for operate ing an armature I I 4 which in turn operates switch arms V| I5 and ||6 with respect to contacts |I1 and 8. When either of the relay coils I I2 or ||3 are energized the switch arms ||5 and IIG are moved out of engagement with their respective contacts I I1 and I I8 and when the relay coils I|2 and |I3 are deenergized or both coils I I2 and I I3 are simultaneously energized the switch arms I|5 and I|6 are moved into engagement with their respective contacts II 1 and I I8 by means of springs gravity or other means (not shown). Power is supplied to the fan 28 and the water circulating pump 33 by means of line wires |20 and |2| leading from some source of power (not shown). tact I|8 a circuit is completed from the line wire |20 through wire |22, contact IIB, switch arm |16. wire |23, fan motor 28and wire |24 back to the other line wire |2I to cause operation of the fan 21. engagement with contact II1 completes a circuit from the line wire |20 through Wire |25, contact II1, switch arm II5, wire |26, pump 31, and wire |21 back to the other line wire |2I.

The relay coil ||3 is connected by wire |29 to the contact 16 and by Wire |30 to the terminal post 6|. Relay coil I|2 is connected by wire |30 and wire |32 to the terminal post 6| and by wire When the switch arm ||6 engages con- Movement of the switch arm I I5 intol |33 to the terminal 99. By reason of these wiring connections it is seen that the relay coil ||3 is connected in parallel with contact 16 and contact member 14, mercury switch 46, contact 56 and contact member'58, and contact 51 and contact member 60 and that relay coil I|2 is connected in parallel with contact 19 and contact member 18, and operating coil 8|. It is also seen that the relay coils I|2 and ||3 are connected in series at all times across the line wires 91 and 98. The polarity or impedance values of the relay coils I|2 and ||3 are such that when they are connected in series across the line wires 91 and 98 neither relay coil |I2 nor II3 will be energized suiiiciently to move the armature I4 towards the right so that under these conditions the relay 4| will remain dropped out.

vAssume now that the operating coil 8| is deenergized by reason of the fact that one ofthe switches controlling the same is open, for example, the mercury switch 46 of the temperature controller 36, and accordingly the compressor I3 is stopped. If now the pressure on the high pressure side of the refrigerating apparatus decreases to 140 lbs. to move contact member 18 into engagement with contact 19, a circuit is completed from line wire 91 through contact 16, wire |29, relay coil II3, wire |30, terminal post 6|, contact member 18, contact 19, wires |02 and I 03, contacts 92 and 93, wire |04, operating coil 8|, wire |05 and terminal 99 back to the line wire 98. Completion of this circuit energizes the relay coil |I3 sufciently to pull in the relay 4| to'stop operation of the fan 21 and the water circulating pump 33. The impedance value of the relay coil |I3 is such that the operating coil 8| is not energized suil'iciently by this circuit to pull in its relay or Starter. The relay coil ||2 is substantially shorted out by this circuit so that the relay coil |I3 can pull in the relay 4I. Accordingly, when the compressor I3 is not operating and the pressure on the high pressure side of the refrigerating apparatus decreases to a predetermined low value, illustratively 140 lbs., the fan 21 and the pump 33 of the evaporative ccndenser I1 are stopped. When the various contacts and switches are closed to energize the operating coil 8|, the relay coil I|3 is substan- .tially short-circuited so that it no longer influences the armature I I4.

Assume now that the various Acontacts and switches close to energize the operating coil 8| to start the compressor I3 in the manner outlined above. Almost immediately following starting of the compressor I3 the suction pressure decreases sufficiently to move the contact 51 out of engage-V ment with the contact member 60 but the compressor is maintained in operation by the above outlined maintaining circuit. As long as the pressure on the'high pressure side of the refrigerating apparatus remains below 140 lbs. during operation of the compressor, a circuit is completed from the line wire 91 through contact 16, contact member 14, terminal post 15, wire |00, mercury switch 46, wire IOI, terminal post 59, contact member 58, contact 56, bridge member 55, wire |09, contact 83, bridge member 82, contact 84, wire |02, contact 19, contact member 18, terminal post 6|, wires |30 and |32, relay coil I I2, wire |33, and terminal 99 back to the line wire 98.

' Completion of this circuit energizes the relay coil |I2 sufficiently to attract the armature. II4 to stop operation of the fan 21 and the pump 33. As soon as the pressure increases above 140 lbs. to move contact member 18 out of engagement 1 40'lbs., regardless of whether the compressor 3 l|1 are, stopped when Lthe pressure on the high' pressure' side of the refrigerating apparatus. decreases t'oa predetermined low value. illustratively is operating or not.l insures that the condenser will not be undercooled'when the-temperature ofthe' air entering the evaporative condenser becomes'z low to insurethat there'will always be suiiicient head pressure in' the refrigerating system ,to .circulationof refrigerant therethrough. A In addition to this beneiicial feature needless operation of the evaporative condenser isl prevented resulting in quite 'a saving from the standpoint of operating cost. The relay4| may be vofthe heat operated type or equipped with a damping device. such a's a dash-pot.' for vretarding the frequency oi" operation' thereof. I

Referring now to Figure 2 thek saine enclosure I0, refrige'ratingy apparatus` I2, and evaporative condenser '|11 are utilized as are utilized in Figure land accordingly like reference characters for like parts have been set forth. The refrigerating apparatus I2 may be controlled in any suitable manner as farfas this modification is concerned butfor purposes of illustration it is shown to be controlled in the same manner as the refrigerating `apparatus of Fignre 1 is controlled by means .of the temperature responsive controller 36 and the unitary control arrangement 31 to maintain conditions within the envof illustration in this application the motor |45 is shown to comprise rotors |41 and |48 operated by eld windings |49 and |50. The motor rotors |41 and |48 rotate the shaft |44 in opposite directions through a reduction gear train the arrangement being such that when `the eld winding |49 isenergized the dampers |40 are moved towards a closed position and when the iield winding |50 is -energized the dampers |90- are moved towards an open position. The energizations of the eld windings |49 and |50 are controlled by a relay generally designated at |53 which may comprise series connected relay coils |54 and |55 for operating an armature |56 which in turn operates a switch arm |51 with respect to contacts |58 and |59. Power is supplied to the vmotor |45 end to the relay |53 by means of line wires |8| and |62 leading from some source of power (not shown). A step-down transformer |63 has a primary |64 connected across line wires |6| and |62 and a secondary |65 connected by wires |66 and |61 to the ends of the series connected relay coils' |54 and |55 for reducing the voltage of the relay control circuit. Accordingly it is seen that the relay coils |54 and |55 are connected in series across the source of power. When the relaycoil |54 is more highly energized than the 'relay coil |55 the switch arm' |51 is moved into engagement with the contact |58 to complete a circuit from the line wire |6| through Wire'.|69,.switch arm |51, contact |58, wire |69,

line wire |62 to energize the iield winding |50 to move the dampers |40 towards an open position.

-When the relay coil |55 is more highly energized than Ithe relay coil |54l the switch arm |51 is moved into engagement with the contact |59 to complete a circuitfrom the line wire |6| through wire |68, switch arm |51, contact |59, wire |1|,

eld winding |49, and lwire back to the other line wirel |82 to energize the iield winding |49 to move the dampers |40 towards a closed position. When the relay coils |54 and |55 are equally energized the switch arm |51 is maintained spaced midway between the contacts |58 and |59 pressure side of the refrigerating apparatus which may comprise a bellows |16 connected by a pipe |11 tothe high pressure line |5v for operating a lever |18 against the action of an adjustable tension spring |19. The-lever |18 `operates a slider |80 with respect to arresistance element |8| and a slider |82 with respect to a center tapped resistance element |83. The slider |80 and the resistance element |8| form a control potentiometer for the. series connected relay coils |54 and |55 of the relay |53. For purposes of illustration it is assumed that the slider |80' assumes an extreme left hand position when the pressure on the high pressure side of the refrigerating apparatus decreases to 85 lbs.`and assumes an extreme right hand position lwhen the pressure on the high pressure side of the refrigerating apparatus assumes a value of l5 0'lbs. For intermediate pressure values the slider |80 assumes corresponding positions between the limits dened.

The relay |53 is also controlled by a temperature responsive controller generally designated at |85. This temperature responsive controller may comprise a bellows |86 connected by a capillary tube |81 to a bulb |88, the bulb |88 containing a volatile uid so that the bellows |86 is operated in accordance Awith temperature changes. The bulb |88 is located in the path of the air entering the evaporative condenser I1 and usually this air is outside air. |89 against the action of a tension spring |90, the lever |89 in turn operating a slider |9| with respect to a resistance element |92. The slider |9| and resistance element |92 form a compensating potentiometer for shifting the control range of the pressure responsive controller |15. For

kpurposes of illustration it is assumed that when the temperature of the air entering the evaporative condenser is at 70 the slider |9| assumes an extreme right hand position and as the air temperature increases from '10 the slider |9| is moved progressively towards the left until the temperature reaches 100 at which time the slider |9| assumes an extreme left hand position.

The relay |53 may also be controlled by a pressure responsive controller |95 responsive to pressure on the low pressure side of the refrigerating apparatus. 'I'he pressure responsive controller |95 may comprise a bellows |96 connected by a pipe |91 to the suction line 20y for operating a lever |98 against the action of an adjustable spring |99. The lever |99 operates a slider 200 with vrespect to 'ia-resistance element 28|, the slider 200 and resistance element 20| forming a compensating potentiometer for shifting the control point of the pressure responsive controller The bellows |86 operates a lever- |15 within the desired control range. For pur- 75 poses of illustration it is assumed that when the suction pressure is 21 lbs., the slider 200 is in the extreme right hand position and when the suction pressure dcreases to 14 lbs., the slider 200 is in the extreme left hand position.

The relay |53 is also controlled by a balancing potentiometer formed by a slider 203 and a resistance element 204, the slider 203 being operatively connected to the motor shaft |44. As the motor |45 operates the dampers from a closed position to an open position, the slider 203v is moved from an extreme right position to an extreme left position.

The left end of the relay coil |54'is connected by wires 206, 201, 208, and 209 to 'the left ends of the resistance elements I8I, |92, 20|, and 204 and the right end of the relay coil |55 is connected by wires 2|0, 2| I, 2|2 and 2|3 to the right ends of the resistance elements I8I, |92, 20|, and 204. By reason of these wiring connections it is een that resistance elements |8 I, |92, 20|, and 2 04 are vconnected in parallel with the series connected coils |54 and |55. The junction of the relay coils |54 and |55 is connected by wires 2I4, 2I5, and 2|6 to the center tap of the center tapped resistance element |83, by wire 2|1, variable resistance 2|8 and wire 2|9 to the slider |9I, by wire 220, variable resistance 22| and wire 222 to the slider 200 and by wire 223, variable resistance 224 and wire 225 to the slider l203. Accordingly all of the various potentiometers are connected in parallel with respect to each other and with the series connected relay coils |54 and |55.

Omitting for the time being the controlling action of the temperature responsive controller |85 and the pressure responsive controller |95 let it be assumed that the pressure on the high pressure side of the refrigerating apparatus is 1171/2 lbs. and that the dampers 140 are in the mid-position shown in the drawings. As the pressure on the high pressure side of the refrigerating apparatus increases the slider |80 is moved, towards the right to decrease the energization of the relay coil |55 and increase the energization of relay coil |54 whereupon the switch arm |51 is moved into engagement with the contact |58 to move the dampers |40 towards an open position. Movement of the dampers |40 towards an open position causes left hand movement oi vthe slider 203 which decreases the energization of the relay coil |54 and increases the energization of the relay coil |55. When the slider 203 .has moved suciently far-to the left to rebalance the energization of the relay coils |54 and |55 the dampers I 40 are maintained in their newly adjusted position. Likewise, upon a decrease in pressure on the high pressure side of the refrigerating apparatus the slider |80 moves to the left to decrease the energization of the relay coil |54 and increase the energization of the relay coil |55 whereupon the switch arm |51 is moved into engagement with the contact |59 to move the dampers |40 towards a closed position. Movement of the dampers |40 towards a closed position causes right-hand movement of the slider 203 which decreases the energization of the relay coil |55 and increases the energization of the relay coil |54. When the slider 203 has moved suilciently towards the right to rebalance the energizations of the relay coils 54 and |55 the motor |45 is stopped to maintain the dampers |40 in their newly adjusted position. Accordingly the dampers |40 are positioned in accordance with variations in pressure on the high pressure side of the refrigerating apparatus to maintain the pressure within desired limits.

'Ihe resistance 224 associated with the slider 203 is so adjusted that complete movement of the slider 203v across its resistance element 204 is required to rebalancethe action of movement of the slider |80 throughout only a portion of the total resistance ISI, illustratively, a movement corresponding to a lb. change in head pressure. In other words, with the slider |30 in the position shown in Figure 2 the dampers |40 are in a mid position this occurring at 1171/2 lbs. pressure. As the pressure decreases to 1121/2 lbs. the dampers |40 are moved to a completely closed position and as the pressure increases to 1221/2 lbsithe dampers |40 are moved to a completely open position. Accordingly a 10 lb. change in pressure on the high pressure side of the refrigerating apparatus is all that is required to cause complete opening and closing movement of the dampers |40. Since the dampers |40 control the volume of air passing through the evaporative condenser |1,.they control the cooling effect of the evaporative condenser, and' since the cooling eiiect of the evaporative condenser determines the temperature in the condenser and hence the pressure on the high pressure side of the refrigerating apparatus, the pressure responsive controller therefore maintains the pressure on the high pressure side of ,the refrigerating apparatus within a desired range, illustratively 10 lbs.V

Assume now that the temperature of the air entering the evaporating condenser is 85, the

slider |9I is therefore in the mid position as shown. The slider 19| therefore has no effect upon the energization of the relay coils |54 and |55 and accordingly the control range of the pressure controller |15 is maintained between 1121/2 and 1221/2 lbs. The compensating potentiometer formed by the slider |9| and the resistance element I 92 acts to shift the control range of the control potentiometer of the pressure responsive controller |15. As the temperature decreases, the slider I9| moves towards the right to shift the 10 lb. control range of the control potentiometer towards the left, and as the temperature increases to move the slider I9| towards the left, the 10 lb. control range of the pressure controller |15 is shifted toward the right, this being made possible by the resistance element 2|8 which is of a relatively low resistance value. Accordingly, for variations in temperature of the air entering the evaporative condenser I1 the range of pressures on the high pressure side of the refrigerating apparatus are shifted as follows:

Temperature Pressure Pounds Summing up as the temperature of the air increases the range of pressures maintained on the high pressure side of the refrigerating apparatus is raised and as the temperature decreases the range of pressures is lowered.

The pressure value of the suction pressure is an indication of the load on the compressor resulting from changes in the cooling load. An increase in suction pressure indicates an increase in cooling load on the compressor and a decrease in suction pressure indicates a decrease in cooling load on the compressor. A change in suction pressure also has a marked effect on the operation of an evaporative condenser., In a refrigeratingapparatus 'where the suction pres-1 sure varies widely, it is advisable to utilize the pressure controller |95 responding to changes in suction pressure for adjusting the control point of the head pressure responsive controller |15. The value of the resistance 22| located in series with the slider 200 or the suction pressure controller |95 is made relatively high so that the suction pressure controller |95 operates toshift the control point of the head pressure responsive controller |15 within thel0 lb. control range. Assume that the suction pressure is substantially 1'71/2 lbs. and the outside temperaturel is substantially then the control point of the head pressure controller |15 is substantially 1171/2 lbs. If now the suction pressure increases to 21 lbs., the control point is lowered to substantially 1121/2 lbs. and when the suction pressure decreases to 14 lbs. the control point is raised to substantially 1221/2 lbs. This raising and lowering of the control point of the head pressure controller |15 within the control range is accomplished by vthe suction pressure controller regardless of the position of the control range as determined by the outside temperature controller |85.

Figure 3 is a graph plotting horse power per ton 0f refrigeration against head pressure of the refrigerating apparatus of Figure 2 to illustrate how the control arrangement of Figure 2 at all times maintains the total horse power per ton of refrigeration at a minimum regardless of changes in outside temperature and changes in suction pressure. Curve A illustrates the horse power per ton of refrigeration required to operate the compressor against varying head pressuresV with a suction pressure of substantially 14 lbs. Curve B indicates the horse power per ton of refrigerationrequired to operate the compressor against varying head pressures with a suction pressure of substantially 21 lbs. cates the horse power per ton of refrigeration required to drive the fan of the evaporative condenser to maintain various head pressures in the l `ture of the outdoor air is 85 and the suction pressure is substantially 2l lbs.` By adding the curves A and C, the total horse power per `ton of refrigeraion required to operate the compressor and the-fan of the evaporative condenser when the outdoor temperature is 85 and the suction pressure is 14 lbs. is indicated at curve E. If under these conditions the head pressure A of the refrigerating apparatus is maintained at substantially 1221/2 lbs. as indicated by the low point G on the curve E, the least amount of horse p ower per ton of refrigeration is required to operate the compressor and the fan and therefore the system will be operated most efliciently at this value of head pressure. 'I'his is exactly what is accomplished by the above outlined control system.

By adding the curves B and D, the total horse power per ton of refrigeration required to operate the compressor and the fan of I.the evaporative condenser is indicated by the curve F when the outdoor temperature is 85 and the suction pressure is 21 lbs. It is here noted that the low point H of the curve F occurs at a head pressure of substantially 1121/2 lbs. and there- Curve C indifore it is most economical to control the evaporative condenser to maintain a head pressure V ture is substantially '10 and thek suction" presv sure is 14'-lbs., andcurve J illustrates'the horse power per ton of refrigeration required vto operate the' fan when the outdoor temperature is 70 andthe suction pressure is 21 lbs. l By adding curve I and curve A, the total; horse power per ton of refrigeration required to operate the compressor and the fan when the outdoor temperaturel is '70 and the suction'pressure. is 14 lbs. is indicated by the curve K. The curve `L Y indicates the total horse power per ton oi refrigeration required to operate the vcompressor and the fan when the outside temperature is 70 and the suction pressure is 2l lbs. The low point M on the curve K occurs at substantially 95 lbs.

' and therefore it ismost economical to operate the evaporative condenser to maintain a head pressure of 95 lbs.-when the outside temperature is 70 and the suction pressure is 14 lbs. Likewise, the low point N on the curveL indicates that it is most economical to operate the evaporative condenser in a manner to maintain a 1.

head pressure of substantially v85 lbs. when the outside temperature is 70 and the suction pressure is 21 lbs. Accordingly, when the outside temperature is 70, the head pressure is 'caused to be varied by the above outlined control: system from 85 lbs. to 95 lbs. as the suction pressure decreases from 21 lbs. to 14 lbs. to give the most efficient operation.

Curve 0 illustrates the horse power per ton ci' refrigeration required to operate the fan of the ton of refrigeration required to operatetheyfan when the outside temperature is and the suction pressure is 21 lbs. By adding curves O and A, curve Q is obtained which indicates the total horse power per ton of refrigeration required to operate the compressor and the fan of the evaporative condenser against varying head pressures when the outside temperature is 100 and the suction pressure is 14 lbs. By adding curves P and B, curve R is obtained which represents the total horse power per lton of refrigeration required to operate the compressor and the fan against 5,

varying head pressures when the outside temperaturel is 100 and the suction pressure is 21 lbs. Low point S on the curve Q indicates that it is most economical to operate the evaporative condenser to maintain a head pressure of substantially 150 lbs. when the outside temperature is 100 and the suction pressure is 14 lbs., and the low point T of curve R indicates that it is most economical to operate the evaporative condenser to maintain a head pres-sure of substantially lbs. when the outside temperature is 100 and the suction pressure is 21 lbs.

By reason of the above outlined control system of Figure 2 and by reason of the graphic showing of Figure 3, it is seen that the control system of Figure 2 operates to control the operation of-the evaporative condenser to maintain the total horse power per ton of refrigeration at aminimum at all times regardless of changes f 0 evaporative condenser when the outdoor tem-. perature is 100 and the suction pressure is 141 lbs., and curve P illustrates the horse power *per*V in outside temperature and changes in suction 75 power against head pressure in a manner similar to that of Figure 3` and change the limits of the control system of Figure 2in accordance with the data obtained from such curves. In other words, by changing the limits of the various controllers of Figure 2, it ispossible to alter the systemof Figure 2 to maintain the total horse power at a minimum at all times. This wouldbe particularly applicable where the cost of electrical power is charged on a demand basis.

The proportioning motor |45 which controls the operation of the dampers |40 may also be utilized for shutting off the fan 21 and the circulating pump 23 when the dampers |40 are moved substantially `to a closed position since at this time the circulation of air and water is not needed. In order to carry this out the shaft |44 of the motor |45 is provided with a cam 230 for operating a cam follower23| which in turn operates a.v

mercury switch 232 and is also provided with a cam 233 for operating a cam follower 234 for in turn operating a mercury switch 235.

A circuit for the circulating pump 33 is completed from the ,line wire |6| through wire 231, mercury switch 232, wire 238, circulating pump 233 and wire 239 back to the other line wire |62. Accordingly, when the mercury switch 232 is closed the water circulating pump 233 is in operation. The cam 230 is so arranged that when the dampers are moved to almost a closed position the'switch 232 is opened' to stop operation of the circulating pump 33.

The fan motor 28 is controlled by a circuit leading from the line wire IBI through wire 240, mercury switch 235, wire 24|, fan motor 28, and

wire 242 back to the other line wire |82. Ac-

. cordingly, when the switch 235 is closed the fan y extreme iclosed position. This results in a further saving inasmuch as it is not necessary to have the circulating pump 33 and the fan 21 op- `erating when the dampers |40 are in a closed position. From the above it is seen that I have provided ,a control system for an evaporative 'condenser of a refrigerating apparatus wherein the total horse` power or the total horsepower per ton of refrigeration required to operate the compressor of the refrigerating apparatus and the fan of the evaporative condenser is maintained at a minimum at all times regardless of changes in outside temperature and changes in suction pressure, wherein suflicientlyhigh head pressures are maintained to insure circulation ofrefrigerant through the refrigerating apparatus and wherein needless operation ofy the evaporative condenser is prevented. l

While in Figure 2 damper means |40 are shown for purposes of illustration for controlling the rate of air iiow through the evaporative condenser 1, this may be equally as we'll accomplished by changing the speed of the fan 21 and such is within the contemplation of this invention. It is to be understood that the various pressure and temperature values utilized in setting forth this invention are utilized for purposes of illustration only and that they may be varied to suit operating conditions of various installations.

Although for purposes of illustration two modications of this invention have been disclosed,

other forms thereof may become apparent to those skilled in the art upon reference to this dis-closure and therefore this invention is to be limited only by the scope of the appended claims and prior art.

I claim as my invention:

1. In a refrigerating apparatus having evaporator means for cooling a medium, means for circulating refrigerant through the evaporator vmeans and a condenser for condensing the refrigerant, the combination of, cooling means including water circulating means, air circulating means and means for contacting the air and I Water to provide evaporative cooling of the conratus and means controlled by the conjoint action of all of the control means for controlling the cooling effect of the cooling means.

2. In a refrigerating apparatus having evaporator means for cooling a medium, means for circulating refrigerant through the evaporator means and a condenser for condensing the refrigerant, the combination of, cooling. means including water circulating means, air circulating means and means for contacting the air and water to provide evaporative cooling of the condenser, control means responsive to the pressure on the high pressurelside of the refrigerating apparatus, control means responsive to the condition of the air before it contacts the water, control means responsive to the pressure on the low pressure side of the refrigerating apparatus and means controlled by the conjoint action of all* ofthe control means for controlling the -circulation of the air and hence the cooling effect of the cooling means.

3. In a refrigerating apparatus having evaporator means for cooling a medium, means for circulating refrigerant through the evaporator means and a condenser for condensing the refrigerant, the combination of, cooling means including water circulating means, power driven air circulating means and means for contacting the air and water to provide evaporative cooling of the condenser, means responsive to pressure on the high pressure side of the refrigerating apparatus for controlling the circulation of air to maintain the pressure on the high pressure side of the refrigerating apparatus within a desired range, and means responsive to the temperature of the air and cooperating with said pressure responsive means for also controlling the circulation of air to raise the range of pressures maintained on the high pressure side of the refrigerating apparatus as the temperature of the air increases.

4. In a refrigerating apparatus having evaporator means /for cooling a medium, means for circulating refrigerant through the evaporator means and a condenser for condensing the refrigerant, the combination of, cooling means including Water circulating means, power driven air circulating means and means for contacting yel() the air and water to provide evaporative cooling of the condenser, means responsive to pressure on the high pressure side of the refrigerating apparatus for graduatingly regulating the circulation of air to maintain the pressure on the high pressure side of the refrigerating apparatus within a desired range, and means for stopping circulation ofthe water when the pressure on the high pressure side of the refrigerating apparatus decreases to substantially the lower limit of the desired range.

5. In a refrigerating apparatus having evaporator means forcooling a medium, means for circulating refrigerant through the evaporator means and a condenser for condensing the refrigerant, the combination of, cooling means including water circulating means, power driven air circulating means and means for contacting the air and water to provide evaporative cooling of the condenser, means responsive to pressure on the high pressure side of the refrigerating apparatus for controlling the circulation of air to maintain the pressure on the high pressure side of the refrigerating apparatus within a desired range, means responsive to .the temperature of the air for also controlling the circulation of air to raise the range of pressures maintained on the high pressure side of therefrigerating apparatus as the temperature of the air increases, and means for stopping circulation of the water when the pressure on the high pressure side of the refrigerating apparatus decreases to substantially the lower limit of the desired range.

6. In a refrigerating apparatus having evaporator means for cooling a medium, means for circulating refrigerant throiigh the evaporator means and a condenser for condensing the refrigerant, the combination of, cooling means including water circulating means, power driven air circulating means and means for contacting the air and water to provide evaporative cooling of the condenser, means responsive to pressure on the high pressure side of the refrigerat- 'ing apparatus for controlling the circulation of air to maintain the pressure on the high pressure side of the refrigerating apparatus within a desired range, and means responsive to thepressure on the low pressure side. of the refrigerating apparatus for additionally controlling the circulation of air to cause the pressure on the high pressure side of the refrigerating apparatus to approach the lower limit of the desired range as the pressure on the low pressure side of the refrigerating apparatus increases.

7. In a refrigerating apparatus having evaporator means for cooling a medium, means for circulating refrigerant through the evaporator means and a condenser for condensing the refrigerant, the combination of, cooling means including water circulating means, power driven air circulating means Vand means for contacting the air and water to provide evaporative cooling of the condenser, means responsive to pressure on the high pressure side of the refrigerating apparatus for controlling'the circulation of air to maintain the pressure on the high pressure side of the refrigerating apparatus within a desired range, means responsive to thetemperature of the air for also controlling the circulation of air to raise the range of pressures maintained on the high pressure side of the refrigerating apparatus as the temperature of the air increases, and means responsive to the pressure on the low pressure side of the refrigerating apparatus for additionally controlling the circulation of air to cause the pressure on the high pressure side of the refrigerating apparatus to approach the lower limit of the desired range as the pressure on the low pressure side of the refrigerating apparatus increases.

8, In a refrigerating apparatus having evaporator means for cooling a medium, means for circulating refrigerant through the evaporator means and a condenser for condensing the refrigerant, the combination of, cooling means including water circulating means, air circulating means and means for contacting the air and water to provide evaporative cooling o'f the condenser, means for controlling the operation of the refrigerant circulating means including means responsive to the pressure on the high l circulating refrigerant through the evaporator means and a condenser for condensing the refrigerant, the combination of, cooling means including water circulating means, air circulating means and means for contacting the air and water to provide evaporative cooling of the condenser, means for controlling the operation of the refrigerant circulating means including means responsive to the-pressure on the high pressure side of the refrigerating apparatus for preventing starting of the refrigerant circulating means until the pressure on the high pressure side of the refrigerating apparatus decreases to a predetermined value, and means responsive to the pressure on the high pressure side of the refrigerating apparatus for interrupting circulation ofair when the pressure on the high pressure side of the refrigerating apparatus decreases to said predetermined value.

10. In a refrigerating apparatus having evaporator means for cooling a medium, means for circulating refrigerant through the evaporator means and a condenser for condensing the refrigerant, the combination of, cooling means including water circulating means, air circulating means and means for contacting the air and water to provide evaporative cooling of the condenser, means for controlling the operation of the refrigerant circulating means including means responsive to the pressure on the high pressure side of the refrigerating apparatus for preventing starting of the refrigerant circulating means until the pressure on the high pressure side of the refrigerating apparatus decreases to a predetermined value, and means vresponsive -to the pressure on the high pressure side of the amnesia water to provide evaporative cooling of the con= denser, means for controlling the operation of the refrigerant circulating means including means responsive to the pressure on the high pressure side of the refrigerating apparatus for preventing starting of the refrigerant circulating means until the pressure on the high pressure side of the refrigerating apparatus decreases to 'a predetermined value, and means responsive to the pressure on the high pressure side of the refrigerating apparatus for interrupting circulation of air and water when the pressure on the high pressure side of the refrigerating apparatus decreases to said predetermined Value.

12. In a, refrigerating apparatus having evaporator means for cooling a medium, means for circulating refrigerant throughv the evaporator means and a water cooled condenser for condens ing the refrigerant, the combination of, means for controlling the operation of the refrigerant circulating means including means responsive to the pressure on the high pressure side of the refrigerating apparatus for preventing starting of the re frigerant circulating means until the pressure on the high pressure side of the refrigerating apparatus decreases to a predetermined value, and means responsive t0 the pressure onV the high pressure side of the refrigerating apparatus for decreasing the supply of Water to the Water cooled condenser when the pressure on the high pressure side of the refrigerating apparatus decreases to said predetermined value.

ALWm B. NEWTON.

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