642 Modern Refrigeration and Air Conditioning Copyright Goodheart-Willcox Co., Inc. 25.1.2 Checking Electrical Supply The electrical outlet for a refrigerator-freezer must provide the correct electrical supply. Be sure to read the electrical ratings on the appliance. Check these against the electrical supply provided at the wall out- let. Modern household refrigerators and freezers may need more current than older, simpler refrigerators and freezers. There should be a separate circuit from the ser- vice panel to the refrigerator-freezer outlet. Plug in a lightbulb or other small electrical load and turn off the circuit breaker to determine which breaker con- trols that circuit. Check the ampere rating of the circuit breaker and compare this to the ampere rating of the refrigerator-freezer to ensure they are compatible. Avoid using an extension cord between the refrig- erator power cord and the wall outlet. If an extension cord is too long, it could cause a voltage drop. The resulting voltage at the refrigerator-freezer may be too low. Voltage at the refrigerator outlet can be easily checked with a voltmeter or multimeter, Figure 25-3. The circuit capacity (wire size, etc.) is checked in the following way. If, at the instant of starting, the volt- age at the refrigerator outlet drops more than 10 V, the wiring in the circuit is not heavy enough. A flicker in the lights at the instant the refrigerator starts is a sure sign of a poor electrical supply. It is very important to ground the refrigerator. All removable electrical parts, like fans, thermostats, and timers, are already safety grounded. If the wall outlet has a three-prong socket and the unit has a matching power cord plug, there is grounding. Otherwise, a wire must be attached between a metal part of the refrigerator-freezer cabinet and a good ground, such as a water pipe. The type of plug used on the appli- ance’s power cord indicates the voltage and grounding. Most plugs will be three-prong with a ground. Refer to Chapter 13, Electrical Power, for more information about electrical power, circuit design, grounding, and plug and receptacle configurations. Safety Note Check for Ground Always check for proper grounding in the outlet box that supplies current to the refrigerator-freezer. A com--mco mon method is to take a voltmeter reading from the “live” wall receptacle connection to the receptacle ground connection. A full voltage reading indicates that the out--t let is properly grounded, as shown in Figure 25-3.3 25.1.3 Checking for Proper Ventilation Since domestic refrigerators are air-cooled, proper ventilation is very important. Yet, many kitchens are designed without adequate space for air movement around the appliance. In these rooms, only refrigerator- freezers with forced-draft condensers should be used. The fans draw cool air in at the floor level and circulate it over the condenser. The warm air is then exhausted back into the kitchen at, or near, floor level. Nothing should be placed in front of such openings to block airflow. Many domestic refrigerators have a natural- convection condenser that is mounted on the back. Some are protected by a shroud. The shroud helps pro- mote a chimney effect, increasing the rate of natural airflow over the condenser. With this type of condenser, air spaces must be provided at the bottom, back, and top of the unit to ensure good air circulation. Having shelves or cabinets over a refrigerator-freezer with a natural-convection condenser is not recommended. Many freezers and some refrigerators have hot- wall condensers. For these units, at least 2″ (51 mm) of space must be allowed between the refrigerator or freezer cabinet and surrounding surfaces. Some room for air circulation is necessary to allow heat transferred to the cabinet to dissipate. 25.1.4 Starting a Refrigerator After testing the wall outlet with a voltmeter to be certain the correct electrical power is being supplied, put the temperature control in the off position. Connect the electrical cord to a wall outlet. Then, adjust the tem- perature control to the middle of its range and make Check for Ground Always check for proper grounding in the outlet box that supplies current to the refrigerator-freezer. A mon method is to take a voltmeter reading from the “live” wa ll receptac le connection to t h e receptac le groun d connection. A f ull voltage reading indicates that the ou l et i s proper ly grounded, as shown i n Figure 25- . HZ Off A COM Fused 10 A 600 V HOLD MIN MAX RANGE HZ Ω v V Ω V A HZ HZ V HZ A Neutral Ground Hot Goodheart-Willcox Publisher Figure 25-3. When checking a wall receptacle ground terminal, the multimeter measures ac voltage between the hot (live) wire and ground.