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Lighting and Electrical

Lighting and Circuit Sizing

Two building-electrical calculations under one select. Lighting by the lumen method: the room cavity ratios, the effective reflectances of the ceiling and floor cavities, the direct ratio of the luminaire array integrated from the entered candela distribution, the coefficient of utilization by flux transfer between the three cavities (the zonal-cavity derivation written out with exact view factors), the maintained average illuminance E = N Φ CU LLF / A, the luminaires needed for a target, the spacing criterion of the distribution against the layout, a point-by-point illuminance map by the inverse-square cosine law with the uniformity ratios, lighting power density and efficacy. Branch circuit: load current from power or current and power factor, conductor resistance from the NBS copper and aluminum wire tables at the operating temperature, reactance entered or estimated from the conductor spacing, voltage drop by phasors with the approximate and resistive forms beside it against the 3 percent branch-circuit limit, the smallest size that meets the limit, the ampacity check with the 125 percent continuous-load rule and the temperature and bundling factors, the standard breaker rating, conduit fill by areas, and a point-to-point short-circuit estimate from the transformer impedance. The default is an illustrative 40 by 30 by 10 ft office with twenty 4,000 lm cosine-distribution luminaires in a 5 by 4 array (LLF 0.8, reflectances 80/50/20, the UFC 3-530-01 office criterion of 30 fc as the target) and a 16 A continuous 120 V load on 100 ft of 12 AWG copper; the Navy roadway lumen-method example and the Army 3 percent voltage-drop table are reproduced by the test script.

1 worked example reproduced, listed on the tool page.

Voltage Drop and Short Circuit

Three building-electrical calculations under one select. Voltage drop of a single-phase or three-phase feeder or branch circuit: conductor resistance from the NBS copper and aluminum wire tables at the operating temperature, reactance entered or estimated from the spacing with a raceway factor, parallel conductors, the exact phasor drop with the receiving end held and with the sending end held beside the IEEE Std 141 approximate form I (R cos + X sin) and the resistive form, the percent drop against the entered limit (3 percent branch / 5 percent total, the NEC informational note; 2 percent feeder, UFC 3-501-01), the smallest size that meets it, the ampacity check against the entered table value with the temperature and bundling factors, and the drop at motor starting. Short-circuit current of a radial low-voltage system by the ohmic (complex) method: utility available MVA or an infinite bus, transformer kVA, percent impedance and X/R, motor contribution, the conductor impedance of every run, the bolted three-phase and line-to-ground fault at every bus with the X/R, the half-cycle peak and rms asymmetry factors from the closed forms, the per-unit values on the transformer base, the point-to-point f / M form for comparison, the device interrupting rating with the X/R derating, the conductor withstand, a fault-current profile along the feeder and a one-line sketch. Transformer and motor currents: full-load currents from kVA and voltage, inrush, motor full-load current from horsepower, efficiency and power factor, locked-rotor current from the code-letter kVA per hp. The default is an illustrative 480 V, 1,500 kVA, 5.75 percent transformer on a 500 MVA utility feeding a 400 A, 200 ft feeder of two 3/0 copper conductors per phase; the Army TM 5-811-14 fault and motor examples and the TM 5-811-1 voltage-drop example are reproduced by the test script. Arc-flash incident energy (IEEE 1584) is not computed.

1 worked example reproduced, listed on the tool page.

Generator and UPS Sizing

Three sizing calculations of a building's backup power under one select. Generator sizing from a load schedule: running kW and kVA of resistive, motor, UPS, lighting, HVAC and medical loads with a demand factor and growth, the step-loading sequence with the starting kVA of each step (across-the-line, soft-start or drive-started motors), the voltage dip at each step from the entered transient reactance against the allowable dip, the alternator kVA the dip requires, the nonlinear-load share with the UFC 3-540-01 subtransient-reactance rule and an entered alternator multiplier, the site derating for altitude and ambient from the maker's curve entered as rates, the kW and kVA the set must carry, the check of an entered set rating, its full-load current, the transfer-switch and conductor currents, fuel rate from an entered specific-consumption curve at 25 to 100 percent load, the tank for the required runtime, the runtime of an existing tank and the day tank, the NFPA 110 class, type and level restated from the entered values, and a chart of the load through the start sequence. UPS sizing from the critical-load schedule: kVA and kW with growth against the module rating and power factor, N+1 redundancy, inverter and rectifier efficiencies, the input kVA the generator sees with and without battery charging, heat to the room, the battery string (cell count from the dc voltage, end-of-discharge voltage), runtime by the constant-power discharge of a Peukert cell with the IEEE 485 temperature, aging and design-margin factors, the number of parallel strings for the required runtime, the constant-current form beside it, the recharge current and charger power for the entered recharge time, and charts of runtime against load and of the string voltage during the discharge. Plant unit capacity by the MIL-HDBK-1003/11 procedure: firm capacity at 125 percent of the maximum demand, the unit size range from the minimum demand, the number of units and loading for each candidate size and the spares by duty; the handbook's Table 8 example is reproduced by the test script. The default is an illustrative 480 V facility with 30 kW of lighting, 30 kW of HVAC, a 100 hp chiller on a soft starter and a 50 kVA UPS; the NEC, NFPA 110, IEEE 485, ISO 8528 and NEMA MG 1 are cited only.

1 worked example reproduced, listed on the tool page.

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HVAC Loads · Ducts and Airflow · Psychrometrics · HVAC Equipment · Ventilation and Air Quality · Energy · Plumbing · Fire Protection · Controls and Commissioning · Codes and Compliance