Technical Resources
Wire Ampacity Chart: NEC Table 310.16 Copper and Aluminum at 60, 75 and 90 C, Termination Rules, Temperature Correction and Bundling Derating
NEC Table 310.16 ampacities for THHN, THWN, XHHW and USE from 14 AWG to 1000 kcmil in copper and aluminum, why the 75 C column is the one that usually governs, the small-conductor cap in 240.4(D), the ambient correction and conductor-count adjustment factors, and how the lug's temperature rating ties the whole thing together.
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RV 12 V Electrical Panel Wiring: Fuse and Wire Size by Circuit, Battery Disconnects, Busbars, ANL and Class T Fuses, and the ABYC E-11 Rules That Apply on the Road
How to wire a 12 V DC system in an RV, van or boat that passes an RVIA or ABYC inspection: main fuse type by battery chemistry, wire gauge by amps and length at 3 percent drop, branch fuse sizes for the common loads, busbar and disconnect placement, and the 7 in rule.
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PoE Power Budget and Cable Length: 802.3af, at, bt Power per Port, Voltage Drop on Cat5e, Cat6 and Cat6A, and Why CCA Fails on PoE
How much power reaches the device at the end of a PoE run: the four PoE classes and their watts at the switch and at the load, the pairs and current involved, the 100 m limit and what happens past it, the derating for bundles under NEC 725.144, and the resistance numbers that make copper-clad aluminum cable a PoE failure.
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DIN Rail Terminal Blocks vs Power Distribution Blocks vs Busbar: Which One Belongs in a Control Panel, With UL 1059, UL 1953 and UL 508A Spacing Rules
For UL 508A panel builders and anyone wiring a control enclosure: the three ways to split power and land field wiring, what each is listed to, the current and wire-size ranges, the spacing and bonding rules, and a selection table by function.
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EMT Bending Guide: Take-Up and Gain for 1/2, 3/4 and 1 in Benders, 90s, Offsets, Saddles, Kicks, Multiplier Table and the NEC 358.26 Bend Limit
The numbers a hand bender needs: take-up and gain by bender size, the offset multiplier and shrink table, three- and four-point saddle math, back-to-back and kick bends, the 360 degree rule between pull points, and the mistakes that put a bend in the wrong place.
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HDMI Cable Length Limits: How Far 4K 60 Hz, 4K 120 Hz and 8K Signals Run on Copper, Active, Fiber AOC and Extenders, HDMI 2.0 vs 2.1, and In-Wall Ratings
The real distance limits for HDMI at each resolution and refresh rate, why the numbers fall as bandwidth rises, when to move from passive copper to active copper, fiber active optical cable or an HDBaseT extender, what the certification labels mean, and the CL2 and CL3 rules for cable inside walls.
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Extension Cord Gauge Chart: Amperage and Wattage by Wire Gauge and Length, Voltage Drop, SJTW vs SJEOW vs STW, and OSHA Rules for Job Sites
Which gauge extension cord carries a given load over a given distance without overheating or starving the tool, with the amp and watt ratings by gauge, voltage drop at 25 to 200 ft, the jacket letters decoded, and the OSHA 1926.405 and NFPA 70E rules for cords on construction sites.
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PV String Sizing at Record Low Temperature: Voc Correction, Maximum Modules per String for 600 V, 1000 V and 1500 V, and NEC 690.7
How to calculate the maximum number of modules in a PV string so cold-morning open-circuit voltage never exceeds the inverter, connector and conductor rating: the temperature coefficient method, the NEC Table 690.7(A) method, worked examples at 600, 1000 and 1500 V, and where to find record low temperature.
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How Many Ground Rods Do You Need? NEC 250.53 Two-Rod Rule, the 25 Ohm Test, Soil Resistivity and Rod Spacing, Length and Diameter
When one rod is enough, when the NEC requires two, why almost every inspector now requires two without a test, how soil resistivity sets electrode resistance, and how rod length, diameter and spacing change the result, with the formula and a table.
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NEMA Enclosure Ratings Explained: 1, 3R, 3, 3X, 4, 4X, 6, 12 and 13, IP Equivalents, and Which Rating Each Location Needs
What each NEMA 250 enclosure type protects against, the nearest IP equivalent, why IP and NEMA do not convert exactly, and a location table for disconnects, junction boxes, combiners and controls indoors, outdoors, in washdown and in corrosive sites.
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Cable Jacket Ratings Explained: CMP, CMR, CMG, CM, CMX, LSZH and Direct Burial, Where Each Is Allowed by NEC 800.113 and Article 725
What each communications and low-voltage cable jacket rating means, the flame test behind it, the substitution hierarchy that lets a higher rating replace a lower one, and a room-by-room table of which rating the NEC requires for Cat6, coax, thermostat and speaker cable.
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Neutral Bar and Ground Bar Sizing: Positions, Wire Range and Bonding by Service Size, for Panelboards, Subpanels and Transfer Switches
How to pick an add-on neutral or ground bar: count the terminations, match the wire range to the largest conductor, choose the main lug size from the service, and know when the bar must be bonded to the enclosure and when it must be isolated.
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