Glossary

Field service, plainly

42 HVAC, refrigeration, compliance and finance terms — defined the way engineers and planners actually use them.

HVAC

AHU: Air Handling Unit — central unit that conditions and circulates air as part of a ducted ventilation system.
BMS: Building Management System — controls and monitors HVAC, lighting and energy across a building. Work App integrates BMS alarms into job dispatch.
Commissioning Pack: Structured handover documentation for a newly installed system covering electrical readings, refrigerant charge, airflows, pressures, controls strategy and witness sign-off — typically required before final payment.
EER / SEER: Energy Efficiency Ratio / Seasonal EER — ratio of cooling output to electrical input. Higher numbers mean a more efficient system.
FCU: Fan Coil Unit — local terminal device with a fan and coil, supplied with hot or chilled water from a central plant.
VRF / VRV: Variable Refrigerant Flow / Volume — multi-split system with one outdoor unit serving many indoor units, each independently controlled.

Refrigeration

Pump Down: Procedure that isolates the refrigerant in the condenser/receiver so the rest of the system can be opened for service without venting gas.
Refrigerant Recovery: Capturing refrigerant from a system into a certified recovery cylinder for reuse, recycling or destruction. Required by F-Gas before opening any sealed circuit.
Subcooling: Difference between liquid-line temperature and saturated condensing temperature. Used to verify correct charge on a TXV system.
Superheat: Difference between suction-line temperature and saturated evaporating temperature. Used to verify correct charge on a fixed-orifice system.

Compliance

Calibration Certificate: Proof that a measuring instrument (gauges, scales, anemometer) has been verified against a traceable standard within the last 12 months.
CO₂-equivalent (CO₂e): Refrigerant charge expressed as the global-warming-potential equivalent of CO₂. Determines mandatory leak-check frequency (5t, 50t, 500t CO₂e thresholds) under F-Gas.
Driver CPC: Certificate of Professional Competence — 35 hours of periodic training every 5 years required for drivers of vehicles over 3.5t.
DVSA Walkaround Check: Pre-use vehicle inspection mandated by the UK Driver & Vehicle Standards Agency covering lights, tyres, brakes, fluids and load security.
F-Gas: EU/UK regulation governing fluorinated greenhouse gases. Requires certified engineers, leak checks at intervals based on CO₂-equivalent charge, and a full register of refrigerant added, recovered and reclaimed for every system.
Lone Worker: Engineer working without direct supervision or colleagues nearby. Requires check-in procedures, SOS capability and risk assessment.
LOTO: Lockout/Tagout — physically isolating an energy source and tagging it so it cannot be re-energised while an engineer is working on the system.
MOT: UK annual roadworthiness test required for vehicles over 3 years old. Work App tracks expiry dates and alerts ahead of due date.
Permit to Work: Formal authorisation required before high-risk tasks (hot work, work at height, confined space, electrical isolation) can begin on site.
PPE: Personal Protective Equipment — issued items (gloves, harness, hard hat) that must be tracked with issue date and inspection cycle.
RAMS: Risk Assessment and Method Statement — site-specific safety documentation engineers must read and sign before starting work.
Tachograph: Device fitted to commercial vehicles that records driving time, breaks and rest periods for EU drivers' hours compliance.
TM44: UK statutory inspection of air-conditioning systems over 12kW, repeated every 5 years and lodged with the Landmark register.
Toolbox Talk: Short safety briefing delivered to engineers (often weekly) covering a single topic — e.g. ladder safety, F-Gas leak response — with a recorded attendance list.

Field Service

Asset Register: Central record of every plant item under management — make, model, serial, location, install date, refrigerant, service history and attached documents.
Defect Report: Daily vehicle or asset check that records faults found before use. Required by DVSA for commercial vehicles and best practice for plant.
Dispatcher: The planner who allocates jobs to engineers based on skill, location, SLA and availability. Often the role Work App's scheduler replaces.
First-Time Fix Rate: Percentage of jobs resolved on the first visit without a return trip. The single biggest driver of field-service profitability.
Job Card: The on-site work record an engineer completes — covering work done, parts used, time on site, photos and customer signature.
Photo Evidence: Time-stamped, GPS-tagged photos captured during a job — proof of completion, condition on arrival and parts fitted.
PPM: Planned Preventative Maintenance — recurring service visits scheduled in advance (monthly, quarterly, annually) to keep assets in warranty and prevent reactive breakdowns.
Reactive Call-out: An unplanned visit triggered by a customer report of fault or breakdown, usually billed at a higher rate than PPM with a target response SLA.
Service Report: Branded PDF emailed to the customer after each visit, summarising work done, readings taken, photos and recommended remedials.
SLA: Service Level Agreement — the contractual response and fix times agreed with a customer, often broken down by priority (P1 4hr response, P2 next day, etc.).
Worksheet: Synonym for job card in many UK trades. Often dual-purpose: engineer completion record plus customer sign-off.
Wrench Time: Proportion of an engineer's paid hours actually spent on productive tool-on work versus travel, admin and waiting.

Finance

Aged Debtors: Report grouping unpaid invoices by how overdue they are (0-30, 31-60, 61-90, 90+ days). The KPI Accounts Receivable teams live by.
Application for Payment: Periodic claim submitted under a JCT/NEC contract showing value of work completed to date, less previous payments and retention.
DSO: Days Sales Outstanding — average number of days it takes to collect payment after an invoice is raised. Lower is better.
Quote / Estimate: Priced proposal sent to a customer before work begins. A quote is typically binding; an estimate is indicative.
Retention: Percentage (typically 5%) of a contract value held back by the customer until the defects-liability period ends, then released in two halves.
Variation Order: Authorised change to scope or price of an in-flight job, captured against the original quote so the final invoice reconciles.