Terms — 0-9 & symbols

66 field terms starting with 0-9 & symbols, 8 with a full reference page. Each links to the Anvilfield guides where the term is used on the job.

#15 / #30 felt

Asphalt-saturated felt by an old weight-per-square convention, #30 being the heavier, tougher rollIn: Roofing underlayment types

$/MW / $/kW

Cost per megawatt or kilowatt of IT capacity, the common way data center capital cost is benchmarkedIn: Data center buildout phases

% Gmm

In-place density as a percentage of Gmm; 100 percent minus % Gmm is roughly the air-void contentIn: Asphalt compaction window

% Gmm / air voids

In-place density as a percentage of the theoretical maximum specific gravity; the remainder is roughly the air-void contentIn: Cold-weather asphalt paving Asphalt compaction window

Transformer percent impedance from the nameplate, the percent of rated voltage that drives full-load current into a shorted secondaryIn: Available fault current study One-line diagram field guide

%Z (percent impedance)

Winding impedance as a percent of rated values; sets the downstream available fault currentIn: Padmount transformer energization

Fiber attenuation in dB per km, higher at shorter wavelengths, from the fiber data sheetIn: Fiber splice loss budget

ρ (rho)

Soil resistivity, in ohm-meters or ohm-centimetersIn: Ground resistance testing

-850 mV criterion / reference electrode

A polarized potential of -850 mV or more negative versus a copper/copper-sulfate electrode, the standard proof of protection in soilIn: Cathodic protection field guide

0-10V

Analog dimming over a low-voltage control pair, 10 V full to about 1 percent floor, polarity-sensitiveIn: Lighting controls and dimming

0-10V dimming

Low-voltage control pair that tells the LED driver how to dim, separate from the line voltageIn: LED lighting retrofit

0.083 h

Five minutes expressed in hours, the standard non-voice alarm duration; use 0.25 h for 15 min voiceIn: Fire alarm install and test

0U / vertical

A strip mounted in the rear channel that takes no rack-unit space from the 19 in fieldIn: Data center rack PDU types

0U PDU

Vertical rack power strip mounted in the side channel, taking no rack-unit spaceIn: Data center rack cable management Data center cabinet and rack types

1.25

Aging and derating margin applied to the summed ampere-hoursIn: Fire alarm install and test

1/0 AWG

The minimum conductor size the NEC permits to be paralleled for power, with narrow exceptionsIn: Parallel conductors, NEC

100 percent tie-off

Staying connected to an anchor at all times at height, including during transitions, the core of fall protectionIn: Cell tower and antenna install

11-month inspection

A full warranty walk before the one-year warranty expires, to catch defects while the contractor still owes the fixIn: Closeout and warranty management

13-week cash forecast

A rolling week-by-week projection of cash in against cash out for the next quarterIn: Cash flow and forecasting field guide

150 percent point

At 150 percent of rated flow the pump must produce at least 65 percent of its rated pressureIn: Fire pump and standpipe guide Fire pump acceptance test

19 in rack

The 482.6 mm rail-to-rail mounting width standardized in EIA-310 and IEC 60297In: Data center cabinet and rack types Rack readiness field guide

1:150 / 1:300 ratio

Square feet of attic floor per square foot of net free vent area required by codeIn: Roof attic ventilation

1:48 slope

About 2 percent, the maximum slope in all directions for accessible spaces and aislesIn: ADA accessible parking layout

2 AWG

The minimum bare copper conductor size for a ground ring, with heavier sizes common by designIn: Ground ring electrode field guide

2-pipe / 4-pipe

One coil on a seasonal changeover loop, versus separate heating and cooling coils available at onceIn: Fan coil unit field guide

2/10 net 30

A supplier term: 2 percent off for paying in 10 days, or the full amount due at 30In: Cash flow and forecasting field guide Accounts payable and supplier management

24/7 CFE

Carbon-free energy matched to consumption every hour, not averaged annuallyIn: Data center sustainability reporting

25 percent of LEL

The 1 percent hydrogen by volume ceiling the codes commonly hold the room belowIn: Battery room ventilation and hydrogen safety

25 percent rule

The trigger to pump when grease plus solids reach 25 percent of the liquid depthIn: Grease interceptor field guide

25 sync-check

ANSI device 25, the permissive relay that only allows a close when sync conditions are metIn: Generator paralleling switchgear

Cubic feet in one cubic yard, the divisor that takes the volume to orderable unitsIn: Concrete estimating and takeoff

2N / N+1

Redundancy levels on the critical power and cooling path, full duplicate versus one spare unitIn: AI GPU rack readiness

2N / system-plus-system / dual-bus

Two complete independent systems, each a full N, kept apartIn: UPS topology and redundancy design

3-2-1 rule

Three copies, two media, one offsite; extended to 3-2-1-1-0 with an immutable copy and tested restoresIn: Data center disaster recovery

3-pole / 4-pole

Solid neutral switched through, or neutral switched with the phases, which sets the generator groundingIn: Standby generator install ATS commissioning field guide

3-pole vs 4-pole switch

3-pole switches the phases and leaves the neutral solid (not SDS); 4-pole switches the neutral too (SDS). The single-phase equivalent is 2-pole versus 3-poleIn: Generator grounding and bonding

32 reverse power

ANSI device 32, which trips a set that is motoring, drawing power from the bus instead of supplying itIn: Generator paralleling switchgear

4 to 1 ratio

Extension ladder base set out 1 ft for every 4 ft of working height, about a 75 degree angleIn: Portable ladder safety

4-bolt rule

1926.755 requirement that each column be anchored by a minimum of four anchor rods (anchor bolts), with a 300 lb eccentric-load strength criterionIn: Steel erection and connections

4-inch sphere rule

No opening in a required guard may pass a 4-inch sphere; 6-inch at the stair tread-riser triangleIn: Metal railing and guardrail fabrication

40 CFR 280

The federal EPA technical standards for underground storage tanks, adopted and enforced through state UST programsIn: Fuel storage tank field guide

40 percent depth

Where you drill on a slab drying from one side; 20 percent if it dries from two sidesIn: Slab moisture testing for flooring

400G / 800G ZR

OIF-defined coherent pluggables for amplified single-span DWDM, targeting roughly 80 to 120 km metro DCI; ZR+ variants extend the reachIn: Data center interconnect (DCI)

450.3

The NEC transformer overcurrent rule, sized off the transformer current, not the conductorIn: Dry-type transformer guide

4D / 5D

4D ties the model to the construction schedule for sequencing; 5D ties it to quantities and costIn: BIM VDC coordination

4PPoE

Four-pair PoE, the 802.3bt method that uses all four pairs for Type 3 and Type 4 powerIn: PoE voltage drop and heat

4X / corrosion-resistant

Type 4 plus a corrosion-rated material such as stainless, fiberglass, or polycarbonateIn: NEMA enclosure ratings

5 lb electrode (2.27 kg)

The defined-weight cylindrical probe STM7.1 uses; its contact pressure is part of the methodIn: ESD floor testing field guide

500

Constant for water, roughly 8.33 BTU/gal/degF times 60 minutes per hourIn: Hot water recirculation loops

500 psi (freeze threshold)

The commonly cited compressive strength fresh concrete should reach before it freezes, so ice no longer ruptures the pasteIn: Cold weather concreting

62 percent rule

The potential pin position, about 62 percent of the way to the current pin, where the reading is validIn: Grounding system testing field guide Ground resistance testing

70V distributed audio

Constant-voltage speaker distribution where transformer taps set each speaker's power, used for many speakers over long runsIn: Intercom and paging design field guide

8 in flashing height

The commonly cited NRCA minimum height base flashing turns up above the finished roof, higher in heavy snowIn: Roof penetration flashing

8.33

BTU to raise one gallon of water 1 degree F, since a gallon weighs 8.33 lb at a specific heat of 1.0In: Water heater sizing and selection

80 percent fill / OPD

Filling to 80 percent by liquid for expansion room, enforced by the overfill prevention deviceIn: Propane LP-gas system install guide

811 / one-call

The three-digit number and the center that notify utilities to mark their lines before you digIn: Utility locating and call before you dig

811 locate / damage prevention

The one-call system and the law requiring utilities to be located and marked before any digIn: OSP fiber and FTTH construction

90-day retention

Share of new hires still employed at 90 days; a read on whether onboarding worksIn: Hiring and onboarding techs

95 / 99 / 100

Particulate filter efficiency in percent; 100 is HEPA-grade at 99.97 percentIn: Respiratory protection program guide

96.25

The constant converting GPM over square feet to inches per hour; one GPM on one square foot is 96.25 in/hrIn: Irrigation audit field guide

Coefficient of thermal expansion for the material, from the manufacturerIn: Pipe thermal expansion

ΔL

Change in pipe length, the movement you have to absorbIn: Pipe thermal expansion

ΔT

Temperature rise, the setpoint minus the cold inlet, in degrees F, taken on the coldest-month inletIn: Hot water recirculation loops Pipe thermal expansion Water heater sizing and selection

εr

Relative dielectric of the concrete, roughly 6 to 8 dry, higher when wet; sets the pulse velocityIn: Concrete scanning before you drill

η (eta)

Thermal efficiency factor by process: SAW near 1.0, SMAW/GMAW/FCAW near 0.8, GTAW near 0.6In: Weld heat input and CWI acceptance

ρ (rho)

Soil resistivity in ohm-meters, or ohm-centimeters in older tablesIn: Grounding system testing field guide

All glossary terms

On the job

Crews log these terms against real jobs in FieldOS, then hand the customer a clean proof page. See how FieldOS works.