1. Formulas Review forNABCEP PVI Exam Part2Sarah RaymerDirector of Education and Training ServicesSolPowerPeople, Inc.

2. Notice to viewers:Photovoltaic (PV) Installer Resource Guide(Revised August 2012, version 5.3) Please click hereto download a copy.The PV Resource Guide is an excellent resource forthose planning to take the NABCEP Solar PV InstallerCertification Exam.While it remains a useful study resource it, as always,is NOT the definitive guide to the exam. Also, wewould like to remind readers that unlike the examquestions in the NABCEP Certified PV InstallerExam, sample questions in this guide were notwritten under the supervision of a professionalpsychometrician. 3. Notice to viewers:The newly revised NABCEP Installer ResourceGuide Version 5.3 includes the Solar Installer JobTask Analysis WITH links and suggestedreadings on where to locate information to helpyou learn and understand those concepts!Verify System Design, ConfirmString Sizing Calculations [Sect. 5] 4. http://www.solarpaneltalk.com/showthread.php?727-Any-NABCEP-certified-members-aroundPost:I wonder if this certification is as tough toacquire as some folks gossip it to be...Comment:Why, yes, yes it is.I have been in the industry for a few years as afull time professional & also teach the NABCEPCert of Knowledge and PV Advanced courses ata local community college & I had troublepassing it. 5. Some Need-to-KnowFormulas http://www.sengpielaudio.com/calculator-ohm.htmBasic ElectricalFormulasVoltage DropCalculationsMaximum CircuitCurrentCalculationsConductor andOCPD Sizing Its actually neither 6. BasicsThe Formula Wheel 7. The Power EquationThe Magic TriangleThe Electric Power Law 8. Ohms Law Ohms Magic Triangle Note: V is often an Ein equations. They are interchangeable. 9. Its neither! 10. Voltage Drop 11. Voltage DropNEC 2011 Code references - additional notes:210.19[A][1] 12. Voltage DropNEC 2011 Code references - additional notes:215.2[A][4] 13. Voltage DropCh , Table 8 2011 NEC Codebook 14. Voltage DropThe formula: CM = [25 x I x L] VdropCM Circular millsI single phase current [amps]L one-way lengthVdrop % voltage drop 15. Voltage Drop CM = [25 x I x L] VdropCM is the circular mills diameter of the conductor [seeNEC Chapter 9, Table 8]I is the Imp/amps [Are you looking at 1 string, 2strings, max power conditions or STC?]Length is ONE-WAY distanceVdrop is the % of the Voltage of the system that islost, so: If 240V, < 1%: 240V x .01 = < 2.4V If 48, < 2%: 48V x .02 = < .96V 16. Voltage DropFormula approach:What do we know?What do we need to know?CM = [25 x I x L] Vdrop Look at the problem What is given What is asked ClarifyRefer to diagrams and codebook 17. Voltage Drop Example 1- # 47 of the NABCEP 2009 Study Guide: D = 60 Feet System is a 24 V system Vdrop = < 2% [2% of 24V = 24V x .02 = .48] I =7A Imp one string when Im is flowing What wire size [CM] could we use to stay under 2%? 18. 24 volt system, 2 strings of 2 modules inseries 19. Voltage Drop WHAT DO WE KNOW? D = 60 Feet System is a 24 V system Vdrop = < 2% [2% of 24V = 24V x .02 = .48] A = Question involves junction box to combiner box circuit: 2modules in series, 7 amps each, when Im is flowing We are looking at one string! SVA, PAA- series volts add, parallel amps addCM = [25 x I x L] VdropWHAT DO WE NEED TO KNOW? What wire size [CM] could we use to stay under 2% [