8 MASS. EXPERIMENT STATION BULLETIN 408 



domestic refrigerator is 40T. Opening the door once for 30 seconds caused a 

 rise in temperature of five degrees, while a six-degree rise was caused when the 

 time was doubled. When the door was opened twice within five minutes, the 

 temperature rose about eight and nine degrees when the doors were kept open 

 30 and 60 seconds, respectively. 



Six door openings occurring within five minutes of one another and lasting for 

 30 and 60 seconds caiised a rise in temperature of nine and thirteen degrees, 

 respect'vely. When six door openings were made within five minutes of one 

 another and for 30 seconds duration each, and this procedure repeated after 

 one half hour, the maximum rise in temperature was eleven degrees. This test 

 may be considered as approximating conditions in a home refrigerator during 

 a meal hour. 



The return of the refrigerators to normal temperature was quite rapid. A 

 temperature within two degrees of normal was reached in from one-half to one 

 hour after one or two door openings. 



After a series of door openings the recovery time was longer, one and one-half 

 hours being required to reach 42^F., after a series of six door openings; while 

 after 12 openings within an hour and a half, the time required was three and one- 

 half hours. When these door openings were made during the three meal hours 

 of a da}', the mean refrigerator temperature was approximately five degrees 

 higher than the theoretical setting for about 12 hours, or 50 percent of the time. 



The rise in cabinet temperature was influenced by the length of time the doors 

 were left open and also by the number of openings, the latter having the greatest 

 effect. For instance, two door openings for 30 seconds each caused a greater 

 increase in temperature than one opening for 60 seconds. 



Although the door openings did cause fluctuations in the refrigerator tempera- 

 tures, the increases in temperature did not noticeably affect the keeping quality 

 of the foods stored therein. 



Effect of Load, Door Openings, and Operating Temperatures 

 on Power Consumption 



No great difference was noted in the power consumption of the refrigerators 

 when different sized loads were present. Table 2 shows the effect of door open- 

 ings and operating temperature on power consumption. The door openings 

 caused an increase in power consumption of 9 to 11 percent. 



A decrease in the operating temperature of only six degrees, to 35^F., required 

 80 percent more energy than that required at 41°F. 



Table 2. Effect of Door Openings and Operating Temperatures on the 

 Power Consumption of Loaded Domestic Refrigerators 



