Engineering Estimating Guides
Practical, standards-based guides on estimating and takeoff — and how EngEst Pro automates each one.
20 guides · Electrical · EE Tools · Plumbing · Structural · Solar · Civil · FDAS · Painting · Estimating · Bidding
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#0 Welcome to The Estimator’s Edge — Meet EngEst Pro
What EngEst Pro is, who it’s for, and what this newsletter will send you.
Electrical
#1 Sizing THHN Conductors per PEC Table 3.10.1 — A Worked Example
Load current, the 125% continuous rule, correction factors, termination ratings, and a voltage-drop check — worked end to end.
#2 Voltage Drop Calculation for Branch Circuits and Feeders
The 3% and 5% rules, the single-phase and three-phase formulas, and how to find the conductor size that keeps you inside both.
#3 How to Build an Electrical Panel Schedule from a Load List
From a raw circuit list to a balanced panel schedule: phase balancing, connected vs demand load, spare ways, and main breaker sizing.
#4 Distribution Transformer Sizing for Buildings
kVA from demand load and power factor, standard sizes, load-growth allowance, and the impedance and vector-group details that matter for the BOQ.
#5 Standby Generator (Genset) Sizing for Commercial Buildings
Running kW is only half the job — motor starting kVA, step loading, and site derating decide the real generator size.
#6 Applying PEC Demand Factors to Lighting, Receptacle, and Appliance Loads
Why 30 kVA connected can legally be 14 kVA of demand — the PEC demand-factor tables, worked on a real house.
#7 Short-Circuit Current and Interrupting Capacity — Basics for Estimators
The infinite-bus method, transformer %Z, and why the wrong AIC rating turns a breaker into a bomb.
#8 Conduit and Raceway Fill Calculation per PEC
The 53 / 31 / 40 percent rule, conductor cross-sectional areas, and a worked EMT sizing example.
#9 Grounding and Bonding System Design per PEC Article 2.50
Grounding electrode vs equipment grounding vs bonding — three different jobs, three different sizing rules.
#10 Power Factor Correction — Sizing a Capacitor Bank
The kVAR formula from tan phi, step sizing, and why over-correction and harmonic resonance can cost more than the penalty you were fixing.
#11 Lighting Design by the Lumen Method — Fixtures and Circuits
Target lux, the lumen-method formula, room index, and how the fixture count becomes lighting circuits in the panel.
#12 Preparing an Electrical Riser / Single Line Diagram for Permit
What the SLD must show for a building permit — service entrance, protection, feeders, panels, and load summary on one sheet.
#13 Estimating an Electrical Bill of Materials from a Circuit Schedule
Turning a panel schedule into priced quantities — homerun logic, vertical drops, wastage, fittings ratios, and device counts.
#14 Motor Feeder and Branch Circuit Sizing per PEC
Use table FLC not nameplate, conductors at 125%, branch protection up to 250%, overloads at 115–125% — the four different multipliers explained.
EE Tools
#15 Wire Sizing by Ampacity vs Voltage Drop — Which Governs?
On short runs the ampacity table wins; past a crossover length, voltage drop takes over. Here is how to find that length.
#16 Reading PEC Table 3.10.2.6(B) — 60 °C Conductor Ampacities
Why small circuits are sized on the 60 °C column even when the wire is rated 90 °C — and how the temperature correction still uses the higher column.
#17 The 40% Conduit Fill Rule Explained (3 or More Conductors)
One wire 53%, two wires 31%, three or more 40% — the physical reason each number is what it is.
#18 Single-Phase vs Three-Phase Motor Circuits — FLA, Wire, and Breaker
Same horsepower, very different current: the root-3 factor, table FLC values, and how wire and breaker sizing diverge.
#19 Ampacity Correction Factors for Ambient Temperature and Bundling
Hot ceilings and crowded conduits both steal ampacity — and the two factors multiply.
#20 Sizing the Grounding Electrode Conductor and Ground Rods
GEC from the service size, the 14 mm² cap for rod connections, two rods 1.8 m apart, and the 25-ohm test.
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