Present value (PV) is the current value of a future sum of money or stream of cash flows given a specified rate of return. Future cash flows are discounted at the discount rate, and the higher the discount rate, the lower the present value of the future cash flows. The 225-ampere panelboard is protected by a 200-ampere main circuit breaker. Using the 120% rule, 270 amperes from all sources is permitted. In this example, the two inverter outputs are combined in a panelboard.
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How Do You Calculate Present Value?
Can a 100-ampere panelboard bus be protected by a 200-ampere main breaker circuit breaker? The answer is no; you must protect all conductors, including the bus, at rated ampacity. NEC 705.12(B)(2)(3)(b) states that the sum of the main circuit breaker rating (or the feeder breaker) and 125% of the inverter output are not to exceed 120% of the panelboard bus rating.
- Therefore, the capacity of a PV system is rated either in MWDC via the aggregation of all modules’ rated capacities or in MWAC via the aggregation of all inverters’ rated capacities.
- The utility and PV system overcurrent devices provide the necessary limitation.
- If the system is not interconnected with a utility or other primary source, then the requirements of NEC Chapters 1-4 and Article 690 are applicable.
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- It may seem redundant, but the process for determining conductor ampacity begins the same way as for minimum overcurrent protection.
Photo 2 is a picture of an array I took during an inspection at an apartment complex. An off-grid system that is not interconnected with any other primary sources of electricity would only be subject to NEC Chapters 1-4 and Article 690. Some requirements are duplicated in NEC Articles 690 and 705 because application is dependent https://www.bookstime.com/ upon the interconnection. To learn more about or do calculations on future value instead, feel free to pop on over to our Future Value Calculator. For a brief, educational introduction to finance and the time value of money, please visit our Finance Calculator. A company is evaluating a business deal to sell a given asset.
PV System Contribution
Connecting a utility-interactive PV power system can be accomplished on either the supply side or the load side of the facility’s main service disconnect. Where a panelboard is present value of annuity table supplied by a utility or other primary source, the PV system will be an additional source of electricity. The conductor and OCPD must have an ampacity of at least 18 amperes.
PV tables are used to provide a solution for the part of the present value formula shown in red, this is sometimes referred to as the present value factor. The purpose of the present value tables is to make it possible to carry out present value calculations without the use of a financial calculator. Because the sun generally will be shining for more than three hours a day. If it didn’t, you probably wouldn’t be installing a PV system! Anytime maximum current is expected to continue for three hours or more, it’s a continuous current, and there are requirements that must be considered.
Formula for PV in Excel
If the inverter were tested with larger overcurrent protective device rating during the certification process, then a larger OCPD may be allowed. In that case, the installation instructions should provide the information. I recommend that plan reviewers or inspectors consider the minimum required OCPD rating as the maximum unless someone can show you differently. If the designer can provide documentation that a larger ODPD rating is permitted by the manufacturer in accordance with the listing, then approval is possible. A new panelboard with a larger bus rating or a smaller main breaker rating (if load permits) could be installed.
- Periods can be presented in weeks, months or years and discount rates normally go from 0 to 20% with intervals of 0.25% or 0.50% between them.
- The actual minimum required rating is 50 amperes in this example.
- Photo 2 is a picture of an array I took during an inspection at an apartment complex.
- Where CFAC is the capacity factor calculated using an AC-rated capacity and ILR is the inverter loading ratio.
- This present value calculator can be used to calculate the present value of a certain amount of money in the future or periodical annuity payments.
- Stocks are also often priced based on the present value of their future profits or dividend streams using discounted cash flow (DCF) analysis.
- After almost a decade of experience in public accounting, he created MyAccountingCourse.com to help people learn accounting & finance, pass the CPA exam, and start their career.
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