 E4 Electrical Installation #2 Wire Sizing and Materials

 © 2005 Refrigeration Training Services - E4#2 Wire Sizing and Materials v1.2 2 AMPACITY Ampacity is: The AMPerage handling capACITY of wire, fuse, or CB It is the amperage draw PLUS a 25% safety factor Or, the amperage load x 1.25 = Ampacity Example: Name plate amperage is 12 amps 12 amps load x 1.25 = 15 amps ampacity Ampacity is the value used to determine the correct size of wires, fuses, and circuit breakers for inductive (motor) loads ACITY AMP

 © 2005 Refrigeration Training Services - E4#2 Wire Sizing and Materials v1.2 3 Wire Insulation The insulation on a wire is a factor in its rated ampacity Examples of wire insulation descriptions: TW –Thermoplastic, Wet (and dry) locations THHN –Thermoplastic, High-Heat resistant, Nylon

 © 2005 Refrigeration Training Services - E4#2 Wire Sizing and Materials v1.2 4 Wire sizing Wire is rated in AWG (American Wire Gauge) The lower the number, the thicker the wire The lower the number, the higher the amperage capacity

 © 2005 Refrigeration Training Services - E4#2 Wire Sizing and Materials v1.2 5 Ampacity and Wire Insulation 30*30# 10 20*25# 12 15* 20 # 14 Maximum Amp Ratings* Ampacity for Type TW & UF Wire size AWG * According to the electrical code, the overcurrent protection shall not exceed 15A for #14, 20A for #12, or 30A for #10 Ampacity for Type THHN (However, insulation is a factor in locations above 86  F) *

 © 2005 Refrigeration Training Services - E4#2 Wire Sizing and Materials v1.2 6 Wire Marking Marking on the cable usually indicates wire type, insulation, conductor size, and application. Following are some examples: –NM: Non Metallic casing enclosing the wire –MC: Metal Clad casing enclosing the wire –UF: Underground Feeder –SEC: Service Entrance Cable –#12 AWG: Size 12 American Wire Gauge

 © 2005 Refrigeration Training Services - E4#2 Wire Sizing and Materials v1.2 7 Some Examples of Common Indoor Wiring Materials Non Metallic cable (NM, Romex®) Armored cable (AC, MC, BX) Rigid Metallic Conduit (EMT, “Thinwall”)

 © 2005 Refrigeration Training Services - E4#2 Wire Sizing and Materials v1.2 8 “Romex”  Two #12 wires with a bare ground wire Type TW insulation Non-metallic cable

 © 2005 Refrigeration Training Services - E4#2 Wire Sizing and Materials v1.2 9 MC (Metal Clad) or Armored Cable (AC) Insulating Bushing

 © 2005 Refrigeration Training Services - E4#2 Wire Sizing and Materials v Electric Metallic Tubing (EMT) Connector Coupling

 © 2005 Refrigeration Training Services - E4#2 Wire Sizing and Materials v Outdoor Wiring For outdoor condensing units, the wiring materials must be flexible, liquid tight, and damage resistant Following is one example of the wiring used

 © 2005 Refrigeration Training Services - E4#2 Wire Sizing and Materials v Flexible Liquid Tight Conduit 90 ° Connector Coiled metal for flexible strength Plastic sheathing to make it “liquid tight”

 © 2005 Refrigeration Training Services - E4#2 Wire Sizing and Materials v Unit Ratings The unit data plate contains important electrical information Based on the information on the following slide, wire and circuit breaker sizes can be determined

 © 2005 Refrigeration Training Services - E4#2 Wire Sizing and Materials v Sample A/C Electrical Data What is the wire size and circuit size for the above unit? Unit RatingVoltage Compressor RLA 208/ Compressor LRA 7 ½ Tons OFM FLA MCAMOCP Note: The overcurrent protection device must be a fuse or HACR breaker. * The circuit may be fused at a maximum of 35 amps (MOCP) A unit with 25.6 ampacity (MCA) requires: a minimum 30 amp circuit # 10 wire Note: For ampacity calculations of a multi-motor assembly, 25% is added only to the largest motor. Example: 19.0 x 1.25 = for OFM = 25.6 MCA LEGEND RLA – Rated Load AmpsFLA – Full Load Amps LRA – Lock Rotor Amps MCA – Minimum Circuit Amps OFM – Outside Fan Motor MOCP – Max.*Overcurrent Protection

 © 2005 Refrigeration Training Services - E4#2 Wire Sizing and Materials v Common HVACR Ratings The following table is a useful guideline for determining the wire and circuit breaker sizes for the most common motor amperages

 © 2005 Refrigeration Training Services - E4#2 Wire Sizing and Materials v Wire and Circuit Breaker Sizing for Motor Loads 0 – 1215# – 1620# – 2430# # # 6 Total Unit AmpsCircuit Breaker Amps Wire Size

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