US2261593A

US2261593A - Quick freeze control

Info

Publication number: US2261593A
Application number: US235325A
Authority: US
Inventors: Charles B Spangenberg
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1938-10-17
Filing date: 1938-10-17
Publication date: 1941-11-04
Anticipated expiration: 1958-11-04

Description

c; B. sPANGENBl-:RG '2,261,593

QUAICK FREEZE CONTROL Nov.l 4, 1941.

Filed Oct. 17, 1938 Patented Nov. 4, 1941 QUICK FREEZE CONTROL Charles B. Spangenberg, Minneapolis, Minn., as"- signor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application October 17, 1938, Serial No. 235,325

12 Claims.

This invention relates to a control system for a refrigerating apparatus having evaporator means for cooling a'space and for freezing a substance.

'I'he prime object of this invention is to provide a control system for such a refrigerating apparatus wherein the refrigerating apparatus is normally controlled by a thermostat to maintain desired temperature conditions within the space and wherein the refrigerating apparatus may be operated independently of the thermostat until the suction pressure decreases to a predetermined low value indicating that the evaporator means has frozen the substance. When this occurs the refrigerating apparatus is then returned'to the normal c ontrol by the thermostat.

Another object of this invention is to provide in combination with the above arrangement means for stopping operation of the'reirigerating apparatus when the head pressure becomes excessive.

Still another object of this invention is to provide in combination with the above arrangement means for preventing starting of the refrigerating apparatus by the thermostat until the head pressure decreases to a predetermined low value and the suction pressure increases to a predetermined high value whereby the starting load on the compressor is decreased to aminimum and compressor I1.

a liquid line 22'into the evaporator I3 under the control of an expansion valve (not shown).

Evaporated refrigerant is withdrawn from the evaporator I3 through asuction line 23 by the A fan 24 operated by a motor 25 may be utilized for cooling the condenser 20. Since the arrangement thus far described is conventional in the art a further descriptionv thereof is not considered necessary, it being suilicient to state that when the compressor I1 is operating a cooling action is performed by the evaporator I3.

The operation of thepcompreyssor I1 and the condenser fan 24 is controlled. by a relay or starter generally designatedl at 21. 4The relay or starter 21 is in turn controlledby a temperature responsive controller 28 responsive to 4the temperature within the fixture I0, a suction pressure responsive controller 29 responsive to the pressure o'n the low pressure side of the refrigerating apparatus and a head pressure responsive controller 30 responsive to the pressure on the high pressure side of the refrigerating apparatus. The

controllers

28, 29, and 30 acting in conjunction with the relay or starter 21 operate to start the compressor I1 and the fan 24 only when the temperature within the xture I0 increases to a predetermined high value, the pressure on the low whereby automatic defrosting of the evaporator l novel manner in which the above sequences of operation are obtained.

For a more thorough understanding of this invention reference is made to the accompanying drawing in which is diagrammatically disclosed the preferred form of this invention.

A iixture to be cooled may take the form of a cabinet or box designated at I0 having a storage compartment II and a cooling compartment I2. Located within the cooling compartment I2 is an evaporator I3 provided with a plurality of trays I4 in which a substance such as water or a confection may be placed to be frozen. A drip pan I5 collects condensate from. the evaporator I3 during the Adefrosting cycle.

Refrigerant is supplied to and withdrawn from the evaporator I3 by means of a refrigerating apparatus generally vdesignated at I6 which may comprise a compressor I1 operatedby an electric motor I8. Compressed refrigerant flows from the compressor I1 through a high pressure line I9 into a condenser 20 andthe condensed refrigerant is 'collected in a receiver 2I. Liquid reirigerant'iiows from the receiver 2| through pressure side of the refrigerating apparatus increases to a predetermined high value and the pressure on the high pressure side of the refrigerating apparatus decreases to a predetermined low valueand also operate to maintain the compressor I1 and the fan 24 in operation until either the temperature in the fixture I0 decreases to a predetermined low value, or the pressure on the low pressure side of the refrigerating apparatus decreases to a predetermined low value or the pressure on the high pressure side of theI refrigerating apparatus increases to a predetermined high value. AA manually operated controller generally designated at 3| is utilized for starting the compressor I1 and the fan 24 independently of the temperature responsive controller 28 to maintain the compressor I1 and `fan 24 in operation until the pressure on the lowipressure side of the refrigerating apparatus decreases to the predetermined low value or the pressure on the high pressure side of theV refrigerating apparatus increases to the predetermined high value for the purpose of quickly freezing the substance in the trays I4.

'Ihe relay or starter 21 may comprise a core 33 carrying an operating coil 34 and an armature 35 pivoted by a pin 36 to the core 33. The armature 35 carries in an insulated manner a contact a1 adapted. to engagy a contact as and also carries in an insulated manner contacts 39 19v and 88 back to the other line wire 69. Comand 48 adapted to engage stationary contacts 4| and 42. Wliexrthe operating'coil 34 is energized the armature 35 is attracted to move the a circuit from the line wire 68 through wires 8| The amature 35 also carries a bracket 43 the` I purpose of which will be pointed out m'ore fully hereafter.

'I'he temperature responsive controller 28 may comprise a bellows 45 charged with a volatile fluid for operating a lever 46 against the action of an .adjustable tension spring 41 which in turn operates a mercury switch 48. For purposes of illustration it is assumed that the parts are so arranged that when the temperature within the fixture I8 increases to 42, the mercury switch 48 is tilted to a closed position, and when the temperature decreases to 40, the mercury switch 48 is 4tilted to an open position, as shown.'

The suction pressure responsive controller 29 may comprise a bellows 58 connected by a pipe 5|* to the suction pressure line 23 for operating a lever 52 against the action of an adjustable tension spring 53. 'I'he lever 52 carries irran insulated

manner contacts

54 and 55 which are adapted to engage sequentially adjustable -stationary contacts-56 and 51, respectively.r vFor purposes of illustration it is assumed that when the pressure on the low pressure side of the refrigerating apparatus increases to lbs., the contact 54 engages the contact'56 and when the pressure increases to 32 lbs. the contact 55 engages the contact 51. Upon a decrease in suction pressure the 'contact 55 first disengages the contact 51 at 32 lbs. and then the contact 54 disengages the contact 56 at 10 lbs.

The head pressure responsive controller 38 may comprise a bellows, 59 connected by a pipe 68 to the high pressure line I9 for operating a lever -6I against the action of an adjustable tension spring 62. The lever 6| carries in an insulated manner contacts 63 and` 64 which are adapted to engage sequentially adjustable

stationary contacts

65 and 66, respectively. For purposes of illustration it is assumed that as the pressure on the high pressure side of the refrigerating apparatus decreases, the contact 63 engages the contact 65 at 190 lbs. and the contact 64 engages the contact 66 at 140 lbs. Conversely, upon an increase in head pressure the contact 64 first disengages the contact 66 at 140 lbs. and then the contact 63 disengages theV contact 65 at 190 lbs.

Power is supplied to the compressor motor I8, to the fan motor 25 and to the control system by means of line wires 68 and 69 leading from some source of power (not shown).

When the temperature within the xture I8 increases to 42 to close the mercury switch 48 the pressure on the low pressure side of the refrigerating apparatus increases to 32 lbs. to close the

contacts

54, 56 and 55, 51 and the pressure 'on the high pressure sideof the refrigerating apparatus decreases to 140 lbs. to close the

contacts

63, 65 and 64, 66, a starting circuit is completed from the line wire 68 throughwire 18,

contacts

65 and 63, wire 1I, contacts'54 and 56, wires 12 and 13, mercury switch 48, wires 14 and 15,

contacts

51 and 55, wire 16,

contacts

64 and 66, wires 11 and 18, operating coil 34, and wires pressure responsive controller 38.

`pletion of this circuit energizes the operating coil 34 to pull in the relay or starter 21.

Movement of the contact 48 into engagement vwithlthe contact 42 completes a circuit from the line wire 68 through wires 8| and 82, contacts 48 and 42, wire 83, compressor motor I6, and wire 8'4- back to 'the line wire 69 to operate the compressor .1. Movement of the contact 39 into engagement with the contact 4I completes and 85, contacts 39 and 4I, wire 86, fan motor 25, and wires 81 and 88 back to the line wire 69 to operate the condenser fan 24. Accordingly when the relay or starter 21 is pulled in the compressor I1 and the `fan 24 areplaced in operation.

Movement of the contact 31 of the relay or starter 21 into engagement with the contact 38 completes a maintaining circuit for the operating coil 34 which is independent of the

contacts

55 and 51 of the suction pressure responsive controller 29 and

thecontacts

64 and 66 of the head 'I'his maintaining circuit may be traced from the line wire 68 through wire 18,

contacts

65 and 63, wire 1|, -

contacts

54 and 56, Wires 12 and 13, mercury switch 48,

wires

14,89, and 98,

contacts

31 and 38, wires 9| and 18, operating coil 34, and wires 19 and 88 back to the other line wire 69. Completion of this circuit maintains the operating coil 34y energized until either the temperature within the xture I8 decreases to 40 to open the pressor I1 and the fan 24 are placed in operation only when the temperature within the ilxture I8 increases to 42, the suction pressure increases to 32 lbs. and the head pressure decreases to 140 lbs. and is maintained in operation until either the temperature in the iixture I8 decreases to 40, or the suction pressure decreases to 10 lbs. or the head pressure increases to 190 lbs. Accordingly the temperature within the fixture I8 is maintained between 40 and 42. Since the compressor I1 cannot be started until the pressure on the low pressure side of the refrigerating apparatus increases to, 32 lbs. defrosting of the exterior surface of the evaporator I3 is afforded during each cycle 'of operation of the refrigerating apparatus. Since it is impossible to start the compressor I 1 until the head pressure de-` creases to lbs. the starting load on the compressor motor `|8 .is decreased to a minimum. Since the compressor I1 can be stopped when either the suction pressuredecreases to 10 lbs. or the head pressure increases to lbs. safe operation ofthe compressor is afforded.

The manuallyoperatedcontrol means 3| may comprise a rod 95 slidably mounted in a suitable support 96. A compression spring 98 located between the support 96 and a suitable operating knob 91 maintains a collar 99, mounted on the rod 95, against the support 96. In other words, the rod 95 is at all times urged to the right by the compression spring 98. The rod 95 carries a latch |88 which isadapted to engage the Vto engage a contact |04. Contacts-IM and The vcontrol o f the upon returned to the normal control circuits in |03 are so arranged that they are sequentially closed upon left hand movement of the rod 95,` the contact IOI engaging i'lrst the contact |02 and then the contact 03 engaging the contact |04. When the relay or starter 21 ls pulled in following left hand movement of the rod 95, the bracket 43 engages the latch |00 to hold the contact IOI in engagement with the contact |02 but allowing the contact |03 to separate from the contact |04. When the bracket 43 disengages the latch upon dropping out of the relay or starter, the spring 98 moves the rod 95 to the right, as shown in the drawing.

Assume now that the pressure on the high pressure side of the refrigerating apparatus is below/190 lbs. to cause the

contacts

63 and 65 to engage and that the pressure on the low pressure side of the refrigerating apparatus is above 1bs.,to cause

contacts

54 and 56 to engage. If now the operator pushes the button 91 to overcome the spring 98, the contact IOI first engages the contact |02, and when the contact I 03 engages the contact |04 a starting circuit for the operating coil 34 of the relay or starter 21 is completed, this starting circuit being traced from the line wire 68 through Wire 10,

contacts

65 and 63, wire 1I,

contacts

54 and 56, wires 12, |06, and |01, contacts |03 and |04, wires |08, 9|, and 18, operating coil 34 and wires 19 and 80 back to the line wire 69. Completion of this circuit energizes the operating 'coil 34 'to pullin the relay or starter 21 which causes the bracket 43 to latch behind the latch' |00. After relay or .starter 21 has thus been pulled in to start the compressor I1 and fan 24, theeope'rator releases the button 91 .but the latch |00 is caught by the bracket 43 to hold the contact |0I in engagement with the contact |02. A maintaining circuit is completed through the contacts IOI and |02 which may be traced from the line wire 68 through wire 10,

contacts

65 and 63, wire 1I,

contacts

54 and 56, wires 12, |06, and IIO, contacts IOI and |02, wire 90,

contacts

31 and 38, wires 9| and 18, operating coll 34 and wires 19 and 80 back tothe otherline wire 69. Completion of `this circuit maintains the operating coil 34 energized and the compressor and fan in operation until either the suction pressure decreases to 10 lbs. to separate the

contacts

54 and ,56 or the pressure on the high pressure side increases to 190 lbs. to separate the

contacts

63 and 65. When either of these contingencies occur therelay or starter 21 drops out and the bracket 43 is released from the latch |00 Whereupon the contacts IOI and |02 are separated.

relay or starter 21 is therecluding the temperature responsive controller 28. It is here noted that the auxiliary circuit including the contactsf,|03 land |04 is in parallel i with the mercury switch 48 of the` temperature responsive controller, the

contacts

64 and 66 of lthe head pressure responsive controller 30 and the

contacts

55 and 51 of the suction pressure responsive Vcontroller y29 so that the relay or starter 21 and hence the compressor I1 may be 'placed in operation independently of the temperature of the fixture I0 and the cut-in pres- ,sures on the highV pressure side and the low pressure side of the4v refrigerating apparatus. In

other words, by manual manipulation of the controller 3I'the compressor I1`may be started regardless of the temperature within the enclosure I0 providing the suction pressure is not exces- .sively low and the head pressure is not excessively high. It is also here noted that the auxiliary maintaining circuit including the contacts IOI and I 02 is in parallel with the mercury switch 48 of the temperatureS responsive controller 28 so that the compressor I1 may be maintained in operation regardless of the temperature within the fixture I0 until such time as the suction pressure decreases to 10 lbs. or the head pressure increases to lbs. By reason of the auxiliarystarting and maintaining circuits the compressor I1 may be maintained in continuous operation until the suction pressure decreases to the cut-out value of v1I) lbs. at which time freezing ofthe substance in the trays I4 is assured thereby giving a very rapid freezing action. After the compressor has been stopped by the suction pressure controller 29, the manualcontroller 3| is rendered inoperative so that the compressor I1 is subsequently placed under the normal control including the temperature responsive controller 28.

From the above it is seen that I have provided a control arrangement for a refrigerating apparatus having evaporator means for cooling a space and for freezing a substance wherein the compressor is operated under normal control to maintain desired temperature conditions within a space and still provide intermittent defrosting of the evaporator means, wherein the compressor may be operated independently of the temperature responsive controller until the suction-pressure decreases to a predetermined .low value for quickly freezing the substance and wherein the compressor is returned to the normal control by the temperature` responsive controller after the substance has been frozen.

Although for purposes of illustration one form of this inventionhas been disclosed other forms thereof may become apparent to those skilled in the art upon reference to this disclosure and therefore this invention is to be limited only by the scope of the appended claims and the prior art.

I claim as my invention:

1. In a refrigeration system including a refrigerating apparatus having a compressor and evaporator means-for cooling a space and for the control yof the compressor to the temperature responsive control means.

2. In a refrigeration system including a re-` frigerating apparatus having a compressor and evaporator means for vcooling a space and for freezing a substance, the combination with saidapparatus of, controlmeans responsive to the temperature of the space for normally controlling the compressor to maintain the space temperature Within desired limits, control means responsive to the pressure on the low pressure side of the refrigerating apparatus for always stopping operation of the compressor when the l' pressuredecreases ltofa. predetermined low value, control meansresponsive to the pressure on the high pressure side of theyrefri'gerating apparatus for alwaysstopping operationof thecompressor when the pressure increases to a predetermined .high value, and means for operating the com- -pressor independently of the temperature responsive control means .until the compressor is r frigerating apparatus having a compressor and evaporator means for cooling a space and for freezing a substance, the combination with saidapparatus of, control means responsive to the temperature of the space, control means respons'ive to the pressure on the low pressure side of the refrigerating apparatus, mechanism controlled by both control means to start the compressor when the space temperature increases to ananas determined high value and the pressure on the high pressure side decreases to a predetermined low value and to stop the compressor when either a predetermined .high value and the pressure on the low pressure side increases to a predetermined high value and to stopgthe compressor when either the space temperature decreases to a predetermined low value or the pressure on the low pressure side decreases to a predetermined low value, and means operatively associated with -said pressure responsive control means for also controlling said mechanism to operate the compressor independently of the temperature responsive control means until the pressure responsive control means stops the compressor for quickly freezing the substance.

4. In a refrigeration system including a refrigerating apparatus having a compressor and evaporator means for cooling a space and for freezing a substance, the combination with said apparatus of, control means responsive .to the temperature of the space, control means responsive to the pressure on the low pressure side of the` refrigerating apparatus, mechanism controlled by both control means .to start the compressor when the space temperature increases to a predetermined high value and the pressure on the low pressure side increases to a predetermined high value and to stop the Acompressor when either the space temperature decreases to a predetermined low value or the pressure on `the low pressure side decreases to a predetermined low value, and means operatively associated with said pressure responsive control means for also controlling said mechanism to start the compressorl even though the lpressure and temperature have not increased to the starting values and for continuing the compressor in operation until the pressure decreases to the stopping value for quicklyfi'eezing ,the sub` stance. I

5. In a refrigeration system` including a refrigerating apparatus having a compressor andI evaporator means for cooling a space and for- `freezingr a substance, the combination with .said

apparatus f, control means responsive to the temperature of the space, control means responsive to the'pressure on the low pressure side of. the refrigerating apparatus, control means responsive to the pressure on the high pressure side ci the reir'igerating apparatus, mechanism the space temperature decreases to a predetermined low value or the pressure on the low pressure side decreases toa predetermined low'value or the pressure on the highV pressure side increases to a predetermined high value, and means operatively associated with said pressure responsive control means for also controlling said mechanism to operate the compressor independently of the temperature responsive control means until either the pressure on the low pressure sidedecreases to the predetermined .low value for quickly freezing the substance or until the pressure on the high pressure side increases to the predetermined high value.

, 6. In a refrigeration system including a re-V frigerating apparatus having an electrically operated compressor and evaporator means for cooling a space and for freezing a substance, the combination with said apparatus of, a relay for operating the compressor when energized, first switch means, means responsive to the temperature of the space for operating the first switch means, means for completing a circuit through the first switch means and the relay for operating the compressor to maintain desired temperatures within the space, second switch means, means responsive to the pressure on the low pressure side of the refrigerating apparatus for opening the second switch means when the pressure decreases to a predetermined low value, normally open switch means, means for closing the normally open switch means and for holding the normally open switch means closed as long as the relay is energized, and means for completing a circuit through the second switch means, the normally open switch means and the relay for operating the compressor independently of the rst switch means until the pressure on the low pres-l sure -side decreases to the predetermined low value to freeze quickly thesubstance.

7. In a refrigeration system including a refrigerating apparatus having an electrically operated compressor and evaporator means for cooling a space and for. freezing a substance, the combination with said apparatus of, a relay for operating the compressor when energized, first switch means, means responsive .to the temperature of the space for operating the first switch means. second switch means, means responsive to the v pressure on the low pressure side of' the refrigcontro' ledby all of said'control means to start the' compressorwhen the space temperature increases to a predetermined high value, the pres- 'sure on the low pressure side increases to apre- -erating apparatus for opening the second switch means when the pressure decreases to a predetermined low value, normally open switch means, means for closing the normally open switch means and for holding the normally open switch means closed as long as the relay is energized, means `for completing a circuit through the first and second switch means and the relay for operating .the compressor to maintain desired temperatures within the space and to stop the compressor when the pressure on the low pressure side decreases vto the predetermined low value, and`means for completing a circuit through the second switch means,'the normally open switch means and the relay for operating the compressor independently of the first switch means until the pressure on the low pressure, side decreases to the predetermined low value to freeze quickly the substance. 8. In a refrigeration system includingr a refrigerating apparatus having an electrically operated compressor and evaporator means for cooling a space and for freezing a substance, the combination with said apparatus of, a relay for operating the compressor when energized, rst switch means, means responsive to the temperature of th,- space for operating the first switch means, second switch means, me'ans responsive to the pressure on the low pressure side of the refrigerating apparatus for opening the second switch means when the pressure decreases to a predetermined low value, third switch means, means responsive to the pressure on the high pressure side of the refrigerating apparatus for opening the third switch means when the pressure increases to a predetermined high value, normally open switch means, means for closing the normally open switch means and for holding the normally open switch means closed as long as the relay is energized, means for completing a circuit through the rst, second and `third switch means and the relay for operating the compressor to maintain desired temperatures within the space and to stop the compressor when either the pressure on the low pressure side decreases to the predetermined low value or the pressure on the high pressure side increases to the predetermined high value, and means for completing a circuit through the second and third switch means, the normally open switch means and the relay for operating the compressor independently of the rst switch means until either the pressure on the low pressure side decreases to the predetermined low value or the pressure on the high pressure side increases to the predetermined high value to freeze quickly the substance;

9. In a refrigeration system including a refrigerating apparatus having an electrically operated compressor and evaporator means for cooling a space and for freezing a substance, the combination with said apparatus of, a relay including an operating coil and a load switch and maintaining switch which are closed upon energization of the operating coil, means for completing a circuit through the load switch and the electrically operated compressor for operating the compressor when the operating coil is energized, first switch means, means responsive to the temperature of the space for closing and opening the first switch means as the space temperature increases above or decreases to respectively a desired value, second and third switch means, means responsive to the pressure on the low pressure side of the refrigerating apparatus for closing the second mally open switch means, the third switch means and the operating coil to maintain the compressor in operation until the pressure on the l'ow pressure side decreases to the predetermined low value to freeze quickly the substance.

10. In a refrigeration system including a refrigerating apparatus having an electrically operated compressor and evaporator means for gization of the operating coil, means for completing a circuit through the load switch and the electrically operated compressor for operating the compressor when the operating coil is energized, first switch means, means responsive to the temperature of the spacevfor closing and opening the rst switch means as the space temperature increases above or decreases to respectively a desired value, second and third switch means, means responsive to the pressure on the low pressure side of the refrigeratingapparatus for closing the second switch means when the pressure increases to a predetermined high value and for opening the third switch means when the pressure decreases to a predetermined low value, fourth and fth switch means, means for biasing the fourth and fifth switch means toward an open position, means forovercoming the biasing means to close the fourth and fifth switch means, means operated by said operating coil to hold the fifth switch means closed against the action of the basing means as long as the operating coil is energized, means for completing a starting circuit through the first and second switch means and the operating coil to start the compressor when the space temperature increases above the desired value and the pressure on the low pressure side increases to the prede- Y termined high value, means for completing a maintaining circuit through the firstl and third switch means, the maintaining switch and the operating coil to maintain the compressor in operation until the space temperature decreases to the desired value or the pressure on the low pressure side decreases to the predetermined low value, means for completing an auxiliary starting circuit through the fourthswitch means and the operating coil to start the compressor independently of the rst switch means, and means switch means when the pressure increases to a I predetermined high value and for opening the third switch-means when the pressure decreases to a predetermined low value, normally open switch means, means for closing the normally open switch means and for holding the normally open switch means closed as long as the operating coil is energized, means for completing a starting circuit through the rst and second switch means and the operating coil to start the compressor,

when the space temperature increases above the desired value and the pressure on the low pres` sure side increases to the predetermined high value, means for completing a maintaining circuit through the iirst and third switch means, the maintaining switch and the operating coil to maintain the compressor in operation until the space temperature decreases to the desired value or the pressure on the low pressure side decreases to 'the predetermined low value, and means for completing an auxiliary circuit through the norfor completing an auxiliary maintaining circuit through the third and fth switch means, the maintainnig switch and the operating coilto maintain the compressor in operation independently of the rst switch means until the pressure on the low pressureV side decreases to the predetermined low value to freeze quickly the substance.

11. In @refrigeration system including a refrigerating apparatus having an electrically operated compressor and evaporator means for cooling a space and for freezing a substance, the combination with said apparatus of, a relay including an operating coil and aload switch and maintaining switch which are closed upon energization of the operating coil, means for completing a circuit through the load switch and the i means, means responsive to the pressurefon the low pressure side of the .refrigerating apparatusfor closing the second switch meanswhen the pressure increases yto a predetermined Vhigh value and for opening the third switch means when the pressure decreases, to a predetermined low value, fourth' and fifth switch means, means for biasing the fourth and fifth switch means toward an open position, means for overcoming the biasing means to close the fourth and fifth switch means, means operated by said operating coil to hold the fifth switch means closed against the action of the biasing means as long as the operating coil is energized, means for completing a starting` circuit through the ilrst and second compressor when the space temperature .increases above the desired value and the pressure on the low pressure side increases to the prede. termined high value, means for completing a maintaining circuit through the first and third switch means, theY maintaining switch and the operating coil to maintain the compressor in op- .eration until the space temperature decreases to the desired value or the pressure on the low pressure side decreases to the predetermined low value, means for completing an auxiliary starting circuit through the third and fourth switch means and the operating coil to start the com` pressor independently of the first switch means,

-dependently' ofthe first switch means until the switch means and the operating coil to start the pressureon the low pressure side decreases to the predetermined -low value to freeze quickly the substance.

12. In a refrigeration system including a refrigerating apparatus having anelectricallyL 01,11-,

erated compressor and evaporator means for cooling a space and for freezing a substance, the

ycombination with said apparatus of, a r'elay causing closure of said relay operated switch upon operation ofthe manual operator, a manual switch moved to closed position by said manual operator when so operated, mechanical connections controlled by said relay mechanism for holding said manual switch closed after release of said manual operator so long as the relay operated switch is in closed position, a'circuit for Y the operating means of said relay controlled by` and m'eans for completing an auxiliary main-jf coil to maintain the compressor in operatioxrinvnamed circuit.

said manually operated switch, and means responsive to a condition indicating that the substance has been frozen for interrupting said last CHaRLEs B. SPANGENBERQ.