Choose a discipline
You can switch disciplines any time with the Home button below.
Air state — dry bulb + one other property
Chart is drawn from the same equations as the numbers above — it is a check on reasonableness, not a reading surface.
Coil / process load
Mix two airstreams
Duct friction
Size it for me
Governing constraint is whichever gives the larger duct. 0.08–0.10 in./100 ft is a common low-pressure design band; tighten it where fan energy or sound matters.
Fittings and components
Loss coefficients are typical values for a first pass. For a design of record use the ASHRAE Duct Fitting Database for the actual geometry.
Pipe friction — water
Valves and fittings
K values are typical. Confirm against the manufacturer's published Cv for balancing valves, control valves, and strainers — those three dominate a branch and vary widely by model.
Size selection
Affinity laws
Fan horsepower
Pump horsepower
Unit conversion
Temperature
Quick references — firm marina/electrical cheat sheet
Each card below is one reference "file." These are for a quick field check, not a design of record — confirm against the NEC edition and any local amendments adopted by the AHJ for the project before using a number from here on a drawing or calc package.
Conduit & tubing fill — NEC Ch.9 Table 1
| Number of conductors/cables | Cross-sectional area allowed |
|---|---|
| 1 | 53% |
| 2 | 31% |
| Over 2 | 40% |
Note 1: based on common conditions of proper cabling and alignment where pull length and bend count are within reasonable limits; certain conditions may call for a larger conduit or fewer conductors.
Note 2: pulling three conductors/cables into a raceway can jam if the raceway ID to conductor/cable OD ratio is between 2.8 and 3.2. Four or more can jam too, but the probability is very low.
Marina shore power receptacle demand factor — NEC 555.12(B)
| Number of shore power receptacles | Demand factor |
|---|---|
| 1–4 | 100% |
| 5–8 | 90% |
| 9–14 | 80% |
| 15–30 | 70% |
| 31–40 | 60% |
| 41–50 | 50% |
| 51–70 | 40% |
| ≥71 | 30% |
1. Where a slip has two receptacles at different voltages (e.g. one 30A/125V and one 50A/125-250V), only the receptacle with the larger kVA demand is counted.
2. A pedestal with an individual kWh submeter per slip, calculated per the criteria in Table 220.120, may have its total demand amperes multiplied by 0.9. (This app's Marina Load tool applies this.)
3. If a circuit feeds a boat hoist and shore power for the same slip, only the load with the larger kW demand is counted.
Single/three-phase amperage & voltage multipliers
| 1Φ | (kVA × 1000) ÷ Volts = Amps |
| 3Φ | (kVA × 1000) ÷ (Volts × 1.732) = Amps |
| 208V × 1.732 | 360.256 |
| 480V × 1.732 | 831.36 |
Service entrance conductor & conduit legend
Wire sized for THWN copper. Conduit sized for rigid PVC Schedule 40 — resize for a different conduit. Ampacity per NEC Table 310.16 at 75°C, ≤3 current-carrying conductors, 30°C ambient.
| Label | Grounding electrode | Conductors/conduit | Runs | Min. conduit | Ampacity 75°C | Φ | Voltage range |
|---|
Portable power cable & cord — marina/boatyard feeder legend
Wire sized using NEC 400.5(A)(1)/(A)(2), green insulated ground. All conductors copper; wet-listed, approved for marina use, suitable for continuous submersion. Conduit sized for rigid PVC Schedule 40. A feeder label with * on the plans indicates a neutral is not required.
| Label | Cable | Runs | Min. conduit | Ampacity 75°C | Φ | Voltage range |
|---|
Branch circuit & feeder legend with equipment ground
Wire sized for THWN copper. Conduit sized for rigid PVC Schedule 40 — resize for a different conduit. A feeder label with * on the plans indicates a neutral is not required.
| Label | Conductors per conduit | Runs | Min. conduit | Ampacity 75°C | Φ | Voltage range |
|---|
Voltage drop
Enter any two of wire size, distance, and amps — the third is solved for. Enter all three to check the actual drop for a known run.
Marina shore power load
Demand load for a marina/dock feeder or service — NEC 555.12(B) demand factor applied to shore power receptacles, plus general-use receptacle and pedestal lighting adders.
30A/125V receptacle connected load is counted at half its nameplate rating (15A) — see Basis tab for why. Confirm this matches the feeder configuration on this project before using the result.
Before you use a number from this app
Calculation basis
Psychrometrics
ASHRAE Handbook — Fundamentals, Ch. 1, Hyland & Wexler formulation. Saturation pressure by eq. 5 (over ice, below 32 °F) and eq. 6 (over water, 32–392 °F). Humidity ratio eq. 20/21, wet bulb eq. 33/34, dew point eq. 37/38, enthalpy eq. 30, specific volume eq. 26. Barometric pressure from the standard atmosphere, eq. 3.
Wet bulb reported is the thermodynamic wet bulb, solved iteratively. It differs slightly from a sling psychrometer reading.
Coil and process loads
Computed from actual mass flow — m = cfm / v using the
entering specific volume — not the 4.5 and 1.08
standard-air shortcuts. At 80 °F/67 °F entering at sea
level the true factors are 4.33 and 1.06, so the textbook shortcuts
overstate capacity by about 3.7%. The gap widens with altitude and with
entering temperature. The app shows the effective factors so you can see
how far from standard air you actually are.
Duct
ASHRAE Handbook — Fundamentals, Ch. 21. Friction factor from the
Colebrook-White implicit equation solved by bisection (not an explicit
approximation). Absolute roughness values from Ch. 21 Table 1. Velocity
pressure Pv = ρ(V/1097)², which reduces to
(V/4005)² at 0.075 lb/ft³. Rectangular duct
friction uses the circular equivalent diameter
De = 1.30(ab)^0.625/(a+b)^0.25 with velocity taken from the
actual cross-section.
Air density is computed for dry air at the entered temperature and elevation — the ASHRAE standard-air basis, which returns 0.0749 lb/ft³ at 70 °F and sea level. Humidity moves density only a few tenths of a percent across the normal supply-air range, and assuming a humidity would be an unstated guess, so the app does not. The density actually used is always displayed.
Fitting loss coefficients are typical values only. They are adequate for sizing a run in the field. They are not adequate for a design of record — use the ASHRAE Duct Fitting Database entry for the specific geometry.
Pipe
Darcy-Weisbach with Colebrook friction factor, water properties (density, kinematic viscosity, vapor pressure) interpolated against temperature from standard steam-table values. Hazen-Williams is offered as a cross-check and is only valid for water near 60 °F in the turbulent range — it will mislead you on hot water, glycol, and low-flow branches. Inside diameters are catalog nominal values; confirm against the specified product. Valve and fitting K values are typical; confirm against published Cv for balancing, control, and strainer components.
Fans and pumps
Affinity laws with speed exponents 1/2/3. Impeller trim uses exponents 1/2/3; a geometrically similar fan wheel family uses 3/2/5. Both degrade outside roughly 80–115% of the reference point, and the app says so.
Electrical — voltage drop
DC conductor resistance from NEC Chapter 9, Table 8 (uncoated
and coated copper, aluminum; solid conductors only through 8 AWG,
matching field practice under 310.106(A)). Ampacity from NEC Table
310.16 at the selected 60/75/90 °C column, 30 °C
ambient, ≤3 current-carrying conductors — no 310.15(B)/(C) correction
or adjustment factors are applied; apply those separately if they govern
the actual installation. Voltage drop is
Vdrop = R/ft × A × ft × multiplier,
multiplier 1 for single phase or √3 for three phase, matching the
firm's SuperiorVDCalc workbook. Provide any two of wire size, distance,
and amps and the third is solved for; providing all three checks the
actual drop for a known run.
Electrical — marina shore power load
Demand factor by total receptacle count per NEC 555.12(B). Connected load: a 50A/125-250V receptacle counts at its full 50A nameplate rating. A 30A/125V single-pole receptacle counts at 15A, half its nameplate rating — a firm convention, confirmed for this app: the 50A receptacles are two-pole 240V loads that draw on both ungrounded conductors of the shared feeder, while a 30A/125V receptacle is single-pole and loads only one of the two conductors, so on a balanced multiwire feeder carrying both load types its contribution to either conductor is taken as half of nameplate. This assumption is specific to a shared 120/240V multiwire feeder mixing both receptacle types — confirm it still applies to the feeder configuration on the project before using the result. A metered installation (individual kWh submeter per slip, NEC 220.120 criteria) gets the 0.9 multiplier per the firm cheat sheet's note 2. General-use 20A/125V duplex receptacles are counted at 180 VA each (Table 220.14(I)) with the Table 220.44 demand factor (first 10 kVA at 100%, remainder at 50%). Pedestal lights are counted at 9 VA each ×1.25 continuous-load factor (210.19(A)/215.2). All electrical amp figures assume a 240V basis for the duplex/pedestal-light adders, matching the source workbook.
Not included by design: AIC/available fault current rating and standard breaker-size selection are not implemented as calculators here — use the reference legends for conductor/conduit selection and confirm fault current and breaker selection against the project's actual utility/transformer data and the panel schedule.
Reference legends (service entrance, portable cable, and branch circuit/feeder tables) are transcribed from the firm's cheat sheet and cross-checked row by row against this app's own Table 310.16 data — see the validation suite, section 25. They are quick-reference only; the project's issued conductor/conduit schedule governs.
Validation
The calculation engine ships with a test suite of 146 assertions checked against published reference values — ASHRAE psychrometric tables, the ASHRAE duct friction chart and equivalent-diameter tables, the Moody diagram, AHRI rating conditions, steam tables, copper tube and Schedule 40 friction tables, NEC Chapter 9 Table 8 and Table 310.16, and NIST unit factors. Pipe results are cross-validated between Darcy-Weisbach and Hazen-Williams, which share no code; electrical reference legends are cross-validated against the app's own ampacity table.
Run it with node validation.test.mjs. Every assertion
names its source. Treat a failing suite as a stop-work condition on this
app, and re-run it after any change to engine.js.
Known limitations, stated plainly: no glycol or steam properties; no duct or pipe insulation heat gain; no acoustics; SMACNA pressure-class and gauge selection is not implemented; the psychrometric chart is drawn for the entered elevation only; electrical calculators assume the 2023 NEC article/table numbers cited above and do not check 310.15(B)/(C) correction/adjustment factors, conduit fill, or AIC/breaker sizing.