Annex b is information and not part of the required code. I will be using software etap for underground duct ampacity calculations. With this mobile application you can easily anywhere will be able to determine the area of air ducts and various shaped pieces, which is especially important in terms of construction. Mar 01, 2008 electrical conductor heating calculations can be complicated, but there are software programs for determining the potential derating of feeder conductors in large electrical duct banks. Duct calculator is a powerful tool that provides access to duct calculation and sizing capabilities either. Although local authorities may require these calculations. Understanding the nehermcgrath calculation and the ampacity. Underground duct bank ampacity calculation electric power. Heating calculations for electrical duct bank consulting. For a similar duct bank at 19 ft deep, the ampcalc result was 225 a, a 24% reduction of current carrying capacity from the nec value based solely on burial depth. Cfm and sizing calculations design master software. In a duct bank, data and electrical cables are laid out within pvc conduits that are bundled together. Conduit duct bank calculations construction monkey. Find out how to determine the optimal cable sizes, physical attributes, and maximum derated ampacity using nehermcgrath method and iec 287 standard.
The module presents a unique solution combining standard and nonstandard calculation methods. Aug 11, 2010 learn about cable ampacity features in etap 7. Raceways can be created using the underground duct bank raceway wizard in addition to the standard graphical drag and drop method. A rackmounted load bank is a specific type of temporary portable load bank that is occasionally employed during data center commissioning to more accurately simulate the electrical and heat load of the critical computer systems prior to the computers actually being installed. Voltage drop or rise is compared against voltage drop and rise limits which are set by the user in the program options form. Also an in depth discussion about the advantages of duct banks, what affects cable rating in duct banks and underground amperage. Calculate thermal r, dielectric losses, yc, ys, etc.
The cymcap software is dedicated to the calculation of ampacity and temperature rise calculations for power cable installations. Modeling one heat source or heat sink in the installation. Duct banks are groups of conduits designed to protect and consolidate cabling to and from buildings. The application allows you to save the results of calculations csv format and send them by. Cable thermal analysis software cable thermal capacity. Impedance and voltage drop calculations once needed parameters are specified, cable impedance and voltage drop calculations are performed and continuously updated as data is changed. Basic steps that cable ampacity software tools use are discussed below. Construction monkey calculator that provides duct bank details including spoils, concrete, excavation amount.
Practical power cable ampacity analysis ced engineering. Duct bank ampacity calculation lets talk about the 18 duct system. Dec 06, 20 for example, for a 500 mcm 5 kv cable, nec table 310. Building load calculations are done using the ashrae cltd method and compare favorable with other loads programs such as elite chvac, carrier hap, trane trace, and carmel loadsoft. Powerful tool for thermal system as air conditioning system, refrigerating cooling system design. When it comes to sizing ductwork, you probably rely on a ductulator or its digital equivalent to. Simply stated, the purpose of ceps is to calculate all relevant cable electrical.
Nehermcgrath institute professional engineers certify. The cymcap software is dedicated to the calculation of ampacity and temperature. We provide sustainable solutions that help our customers effectively manage electrical, hydraulic and mechanical power more safely, more efficiently and more reliably. The calculation methods used to design the duct bank were a mixture of traditional cable rating calculations, analytical calculations for floor surface temperatures and magnetic field levels and finite element methods to determine shielding requirements. Circuit requirements the duct block was designed to carry the following xlpe. Cable sizing and its effect on thermal and ampacity values in. As with voltage drop, underground duct bank calculations are not a code requirement. It applies to low voltage wiring up to 2000 volts and is not used for mv ductbanks. Pressure drop in the duct system can also be calculated. If exhaust duct exits through motorized louvers, the design must be interlocked to assure full open prior to operation. In the nm calculation there are many variables in the 30 to 40 equations used to account for the number of conductors, number and size of adjacent conduits, number and size of adjacent duct banks, coefficient of surface emissivity, number of cables, axial spacing. Electrical conductor heating calculations can be complicated, but there are software programs for determining the potential derating of feeder conductors in large electrical duct banks. Described methodological procedure needs to be followed in order to obtain good and accurate results.
Duct bank heating calculations are essential for critical environments data centers electrical heating calculations may need to be performed when large amounts electrical duct banks with significant amounts of conduits and conductors are routed below grade in the earth. The program includes 2 procedures placed on customized command bar use to know the value of the coefficient k. Turn to design master hvac for your complete hvac design and drafting solution. Normally, a good compromise between the best use of duct space and greatest ampacity is achieved by installing each threephase circuit in a separate duct. A underground duct bank cable ampacity and thermal calculation study will determine. However, singleconductor cables without shield may have greater current. This online ductulator calculates the dimensions for both round and rectangular duct options one dimension should be entered by the user for rectangular duct. Ductsize lets you create a complete duct system from start to finish, and gives you control over every aspect of the design. There are three main options for using the wizard to create new raceways with associated conduits. In electrical engineering, nehermcgrath is a method of estimating the steadystate temperature of electrical power cables for some commonly encountered configurations. Any conceivable underground duct bank configuration can be input into the software. Voltage drop or rise is compared against voltage drop and rise limits which.
The software is suitable for use with windows 7, 8. The exhaust must be screened to keep debris from entering unit. Online ductulator duct size calculator ductcalc online duct. The output also includes air velocity when air static loss is an input friction method or it includes. It calculates the right airflow volumes and duct sizes for your system. Consideration must also be given for louver design and actuator. Cable pulling calculations generator capabilitymotor starting. Ampcalc is suitable for cable installations utilized in industrial, commercial and utility electrical power distribution systems. Usamp prime software models all types of underground power cables pipetype, extruded, and solid paper. If you can design the ductbank system so that you have three sets of 6 conduits, with each set of 6 conduits in its own concrete, and the three concrete banks separated from each other by, let us say, 5 feet edgetoedge the 5 feet is a guess, not a code requirement, then you can use the tables that apply to the voltage. Electrical engineers designing electrical duct banks must understand the soils thermal properties and the effects it will have on the overall installation. Read round duct diameter inches and friction loss per 100 of duct inches of water.
A prime example would be a data center application. The screen must be a minimum 75% open area andor exceed load bank duct area by a minimum of 50%. When you dont have the software and want to do quick calculations on simple ductbanks, annex b is a good tool. The calculation determines the proper cable sizes to carry specified loads in designing new systems and upgrading power cable.
Excel, calculation, sizing, duct, pressure, loss, drop, local. Nehermcgrath calculations are important, especially if the design sizing will ever be fully loaded. Models duct banks, pipe cables, extruded cables, directly buried cables, casings, or mixtures thereof. Computes steadystate and transient ampacities and temperatures for multiple cables with equal or unequal loading. In this example, i use a 4,000amp duct bank with a design load of 3,000 amps and increase the load factor to approximately 85%. Duct bank calculator construction monkey calculator that provides duct bank details including spoils, concrete, excavation amount. I will be requesting information for cables from the cable manufacture, want to make sure i request the correct items. Cable sizing and its effect on thermal and ampacity values in underground power distribution over the past decade, underground power distribution has become increasingly popular due to its reliability, safety, aesthetic characteristics, as well as the ever increasing focus on the environmental impacts of the various stages of.
I was wondering what all information for cable is required to use nehermcgrath equation. Learn how to save design time using the raceway rulebook to autolayout cables within duct banks. Modeling up to three duct banks in a single installation. The electrical design engineer must use only spuapproved electrical analysis software. We use etaps stateoftheart cable thermal software module and. Calculations are in accordance with the industry accepted nehermcgrath calculation procedures. This example illustrates that most electrical duct bank installations will typically not require any derating based on the heating calculations. Duct designer streamlines duct design and improves calculation precision, letting you optimize your designs. The accuracy of the software provides increased confidence when upgrading power cable installations and designing new ones. The very first step that needs to be taken when designing an underground cable system is to define which circuits needs to be routed through the duct bank.
Cable in duct bank derating mikibg electrical 27 dec 12 07. Uniform underground raceway all conduits are same size and spaced equally. Duct sizing calculations include constant pressure drop, constant velocity, and static regain. Load bank sizing calculations part five electrical knowhow. By estimating the temperature of the cables, the safe longterm currentcarrying capacity of the cables can be calculated. Enter duct airflow cfm, duct velocity fpm, duct length and the number of bends. Load bank sizing calculations part three electrical knowhow. The results should be validated with a hand calculation or order of magnitude estimate. Miscellaneous calculations project projection construction monkey calculator that determines the revenue, cost, and manpower for a project over a period of time. Improper heating calculations can lead to an undersized duct bank, which can be a costly mistake to fix if its even possible.
Oct 05, 2018 learn how to do your own duct bank calculation. The earth and dirt rho are again set at the standard 90. The multiple duct banks module mdb is the extension to cymcap designed to determine the steady state ampacity of cables installed in several neighboring duct banks andor backfills with different thermal resistivity. This program is especially beneficial for our clients who are designing duct banks that deviate from the nec duct bank tables. In the bank robber you play as a criminal having recently being released or recently put back in convict who, as the title suggests is looking to rob a bank. Electrical engineers use powertools to perform harmonic analysis, transient stability analysis, short circuit analysis, and to determine demand load, voltage drop, arcflash hazard analysis and protective device coordination. We use etaps stateoftheart cable thermal software module and accurately determine the ampacity and thermal limitations of different underground raceways and duct banks. Timecurrent coordination for all new overcurrent protective devices and existing devices. Include many heat exchanger models for detailed structure design or sizing calculation, such as coils and. The application is designed for engineers hvac working in the field of design and installation of ventilation systems. Verify all calculations with a professional engineer. When it comes to sizing ductwork, you probably rely on a ductulator or its digital equivalent to determine the dimensions for your ducts. Additionally, various wire sizes can be used within the duct bank configurations. For example, for a 500 mcm 5 kv cable, nec table 310.