The words on the invoice, explained on one page.

Sorted by how often we use the term, not alphabetically. The first eight cover ninety percent of the conversations.

200A service

The capacity of a residential or small-farm utility connection — 200 amps at 240 V, single-phase. The minimum we'd put on a small dairy or sugarhouse today; smaller services are unsafe to overload and a frequent reason for a rewire. See J-01 farm service.

NEC Article 547

The chapter of the National Electrical Code that covers agricultural buildings. Adds equipotential-plane, dust-tight enclosure, and corrosion-resistant material requirements on top of standard residential and commercial code.

Equipotential plane

A bonded conductive grid (typically #4 bare copper at 12-inch centers) embedded in the concrete or under matting in livestock confinement areas, tied to the building's grounding electrode system. The point is to keep step-potential between a cow's feet to under 0.5 V. See the safety reference.

Stray voltage

Steady-state potential difference (typically 0.2–2.0 V AC) between two conductive surfaces a cow contacts simultaneously. Not a fault — the normal residual current of a properly grounded utility neutral. UW Dairy publishes the canonical methodology.

Knob-and-tube (K&T)

The wiring method used in American buildings roughly 1880 to 1940: separate hot and neutral conductors run through ceramic knobs and porcelain tubes, no ground. Usually safe in original condition; usually unsafe in five-times-modified condition. See J-04 heritage rewire.

AFCI / GFCI

Arc-Fault Circuit Interrupter / Ground-Fault Circuit Interrupter. AFCI detects the signature of an arcing fault and trips before the arc starts a fire. GFCI detects current flowing to ground (e.g. through a person) and trips at 5 mA. Modern code requires both on most circuits.

Vacuum tubing system

The plastic-and-stainless tube network that conveys sap from tap to sugarhouse under negative pressure (typically −24 to −27 in Hg). The vacuum is supplied by a 2 to 10 HP electric pump in the sugarhouse and is the single largest electrical load during the run. See J-03 sugarhouse.

RO (reverse osmosis)

A membrane-based concentration step that pre-concentrates raw sap from ~2% sugar to 8–18% before evaporation, cutting evaporator fuel by roughly 75%. Electrically: a high-pressure feed pump (5–15 HP) plus auxiliary booster pumps and a control panel.

Head tank

The elevated stainless tank in a sugarhouse that gravity-feeds concentrated sap into the evaporator's flue pan. A float switch on the head tank controls the upstream feed pump; if the float wiring fails, you flood the evaporator or starve it.

Pelton wheel

An impulse turbine for high-head, low-flow microhydro: a wheel of bucket-shaped vanes struck by one or more water jets. Efficient (≈80%) for heads of 100 ft and up. Common on Vermont hill farms with a brook above the house. See J-05 microhydro.

Turgo turbine

An impulse turbine similar to the Pelton but accepting water at an angle, allowing higher rotational speeds for the same head. Useful when direct-drive generator RPM matters.

LFP (lithium iron phosphate)

A lithium-ion battery chemistry (LiFePO₄) that trades energy density for thermal stability and cycle life. Standard for off-grid systems. DOE explainer.

MPPT (Maximum Power Point Tracking)

A solar charge-controller algorithm that continuously adjusts the load impedance to extract the maximum possible power from the PV array under varying irradiance. Standard since ~2010. Victron sets the consumer-grade benchmark.

Type-1 SPD

A surge protective device installed at the service entrance, ahead of the main breaker. Tested to 10 kA per UL 1449. The first line of defense against transients from utility events and indirect lightning. See J-06 lightning.

Type-2 SPD

A surge device on a panel or load side, downstream of the main breaker. Faster, lower-energy, narrower window than Type-1; meant to handle transients that get past the Type-1 or originate inside the building.

NM-B

"Romex." Non-metallic-sheathed cable for residential and small-commercial wiring. Cheap, fast to pull, and what most American houses are wired with after roughly 1970. Replaces K&T in heritage rewires.

EMT

Electrical Metallic Tubing — thin-wall steel conduit. Standard for exposed wiring in agricultural buildings because it survives barn coats, pitchforks, and a 1,200-pound cow's left shoulder. Bent with a Greenlee 555 in our shop.

Wireway / cable tray

Open or semi-enclosed metal channels used to route many circuits along a barn wall. Lets us re-route a feeder in 20 minutes instead of repulling the EMT.

Megger (insulation resistance test)

A 500 V or 1,000 V DC test that measures the insulation resistance between conductors and ground. Above 100 MΩ is acceptable; below 1 MΩ is failing. We megger every K&T circuit before we energize a remediated heritage panel.

Service drop

The utility's overhead wire from the pole to your meter. Past the meter is yours; up to the meter is the utility's. We coordinate with Green Mountain Power or Washington Electric Co-op on every service upgrade.

Soft-start

A motor controller that ramps voltage to a 3-phase motor over 5–30 seconds, reducing inrush current from ~6× to ~2× full-load amps. Required by us on any vacuum-pump > 5 HP, because the inrush of five sugarhouses starting in the same hour will sag the local feeder. See March almanac.

Class S license (Vermont)

The Vermont electrician's specialty license category. Master EM is the unrestricted journeyman/supervisor license. Class S permits limited specialty work. The shop carries master EM and Class S because some of our work overlaps low-voltage controls. VT OPR.

VT Division of Fire Safety

The state agency that issues electrical permits and conducts inspections in Vermont. Almost every job we do over $5,000 gets a permit. firesafety.vermont.gov.

Patronage distribution

The cooperative-specific term for surplus paid to worker-owners at year-end, distributed by hours worked rather than shares held. Reported on IRS Form 1099-PATR.