Wire Sizing Worksheet

Transcription

1 Description: In this worksheet you are going to determine: wire sizing, over current sizing, and disconnect sizing for multiple questions on the sample data below. Additionally, you will be using actual manufacturer specs to size all of the above LEGEND RLA Rated Load Amps FLA Full Load Amps LRA Lock Rotor Amps MCA Minimum Circuit Amps OFM Outside Fan Motor MOCP Max.*Overcurrent IDF - Indoor Fan Motor COMP - Compressor Note: For ampacity calculations of a multi-motor assembly, 25% is added only to the largest motor. So if the compressor has a RLA of 10 (almost always the largest load is the compressor) then you multiply the RLA by 1.25 to get the total amperage for the compressor. You then add that number to the remaining loads to determine the total amp rating of the unit. Sample Electrical Data: Finding total amperage: Comp Amps: 10(RLA) IDF Amps: 2.0 (FLA) ODF Amps 1.5 (FLA) Compressor is the largest load so: 10 amps X 1.25 = 12.5 amps then you just add that to all the remaining loads: 12.5 amps (compressor) amps (IDF) amps (ODF) = 16 amps total Finding Conductor Size: From your wire size chart, you round up to the amperage shown in chart. Look for the corresponding wire size.through using this chart you will soon memorize the most common sizes

2 Wire Amps Size / / /0 225 Using the wire sizing chart: 1. With the given amps you round up to get the correct wire size. As an example, if you have a load that requires 17 amps, you would install #12 wire, because #14 wire only goes to 15 amps, 2 amps shy of the required. 2. If you know the wire size you have, then you are able to determine maximum allowable amperage Things to keep in mind: 1. This is the amp ratings for THHN / THWN insulated wire. If the ambient temperature goes up, the allowable amp rating goes down. Almost all of the wire that we use is the dual rated THHN / THWN. 2. Another consideration is how many wires you are installing into one piece of conduit, known as the conduit fill. By code you can only install a fixed number of wires into a conduit.

3 1. Sample Electrical Data: Comp Amps: 11.2 (RLA) IDF Amps: 2.4 (FLA) ODF Amps 1.8 (FLA) 2. Sample Electrical Data: Comp Amps: 21 (RLA) IDF Amps: 3.4 (FLA) ODF Amps 2.8 (FLA) 3. Sample Electrical Data: Comp Amps: 35 (RLA) IDF Amps: 8 (FLA) ODF Amps 3.5 (FLA) 4. Sample Electrical Data: Comp Amps: 4.5 (RLA) IDF Amps: 1.1(FLA) ODF Amps 0.8 (FLA)

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5 A. Model 38GK... 5 TON C. Model 50YX... 2 TON B. Model 38TDB... 4 TON D. Model 38CE...