Definitions of the engineering, cost, and estimating terms used throughout MEPF Design Pro. Load figures and cost buildups are engineering aids; always verify against the governing codes and your project's Authority Having Jurisdiction.
General & Cost Terms
- MEPF
- Mechanical, Electrical, Plumbing (& Sanitary), and Fire Protection — the building services disciplines this tool estimates.
- Bill of QuantitiesBOQ
- An itemized schedule of materials and labor with quantities, unit rates, and extended costs, grouped by discipline.
- Occupancy Type
- The building's use classification (hospital, office, hotel, mall, etc.). It sets the engineering density factors used to derive loads and cost.
- Direct Cost
- The sum of direct material, direct labor, and tools/equipment before markups such as overhead, contingency, tax, and profit.
- General Requirements
- Project-wide indirect costs (site management, temporary works, supervision) applied as a percentage of direct cost.
- Bonds & Insurances
- Performance/payment bonds and construction insurance, applied as a percentage of direct cost.
- Contingency
- A reserve percentage added to cover estimating uncertainty and unforeseen conditions.
- Executable Bid Price
- The final tender figure after all direct costs, indirect markups, contingency, tax, and target profit are applied.
- Bromilow's Time-Cost Model
- An empirical relationship estimating construction duration from contract value: duration ≈ K × (bid value in $M) raised to a power B.
- Ambient Design Temperature
- The outdoor summer dry-bulb temperature (near the ASHRAE 0.4% cooling design condition) used for HVAC sizing and electrical cable thermal derating. Auto-filled from the project location.
Mechanical / HVAC
- HVAC
- Heating, Ventilation, and Air Conditioning.
- Refrigeration TonRT / TON
- A unit of cooling capacity equal to 12,000 BTU/h (≈3.517 kW) — the heat removal to freeze one short ton of water in 24 hours.
- Cubic Feet per MinuteCFM
- Volumetric airflow rate. Total supply airflow is estimated at roughly 400 CFM per refrigeration ton.
- Air Handling UnitAHU
- A central unit that conditions and distributes supply air via fans, coils, and filters.
- Fan Coil UnitFCU
- A localized terminal unit with a coil and fan serving a room or zone.
- Variable Air VolumeVAV
- A system that varies supply airflow to each zone to match its load, rather than varying temperature.
- Chilled Water System
- A hydronic loop where a chiller cools water that is pumped to AHUs/FCUs for space cooling.
- Darcy–Weisbach Equation
- The fundamental equation for pressure loss due to friction in a pipe, expressed via the friction factor, length/diameter ratio, and velocity head.
- Swamee–Jain Equation
- An explicit approximation of the Colebrook–White equation used to compute the turbulent friction factor without iteration.
- Reynolds NumberRe
- A dimensionless ratio of inertial to viscous forces that determines whether flow is laminar (Re < 2300) or turbulent.
- Testing, Adjusting & BalancingTAB
- The commissioning process of setting airflow and water flow to design values across the system.
Electrical
- Kilovolt-AmperekVA
- A unit of apparent electrical power (voltage × current). Connected demand density is estimated in VA per square meter by occupancy.
- Power FactorPF
- The ratio of real power (kW) to apparent power (kVA); a lower PF means more current for the same useful work.
- Design CurrentIb
- The load current a feeder must carry, derived from apparent power and system voltage for a three-phase circuit.
- Ampacity
- The maximum current a conductor can carry continuously without exceeding its temperature rating.
- Derating
- Reduction of a cable's rated ampacity for real conditions — ambient temperature (Ca) and grouping of circuits (Cg).
- Voltage Drop
- The reduction in voltage along a cable due to its impedance; typically limited to ≤3% for feeders.
- XLPE
- Cross-Linked Polyethylene insulation, rated to 90°C conductor temperature — common for LV/MV power cables.
- IEC 60364
- The international standard series for low-voltage electrical installations, including cable sizing and derating (Part 5-52).
- Main Distribution BoardMDB
- The primary LV switchboard that distributes power to sub-mains and final circuits.
- Extra-Low VoltageELV
- Low-energy systems such as data, CCTV, and access control, typically operating below 50 V AC.
Plumbing & Sanitary
- Water Supply Fixture UnitWSFU
- A dimensionless load value assigned to each plumbing fixture used to estimate probable peak demand.
- Hunter's Curve
- The probabilistic method (fixture units → peak flow) that accounts for the unlikelihood of all fixtures operating simultaneously.
- Liters per SecondL/s
- The SI unit of volumetric flow used for peak domestic water demand.
- Gallons per MinuteGPM
- A US flow unit; 1 GPM ≈ 0.0631 L/s.
- Flush Valve System
- A fixture type using a direct pressurized valve (higher instantaneous demand) versus a refilling tank system.
- Soil, Waste & VentSWV
- The drainage subsystems: soil (toilets), waste (basins/sinks), and vent (air balance) piping.
- PPR
- Polypropylene Random Copolymer pipe, common for domestic water due to low roughness and corrosion resistance.
- Booster Pump Set
- Pumps that raise supply pressure to serve upper floors or maintain fixture flow.
- Calorifier
- A vessel that stores and heats domestic hot water, often via a heat-exchange coil.
Fire Protection
- Sprinkler System
- An automatic water-based suppression system with heads that activate individually at rated temperatures.
- Standpipe
- A vertical fire main with landing valves/hose connections on each floor for firefighter use.
- Fire Pump
- A pump that boosts water pressure/flow to the fire network; often paired with a jockey pump for pressure maintenance.
- Jockey Pump
- A small pump that maintains system pressure to prevent unnecessary fire-pump starts.
- Fire Alarm Control PanelFACP
- The central controller that monitors detection devices and activates notification appliances.
- Clean Agent SuppressionFM-200
- A gaseous suppression system for spaces where water would damage contents (e.g. data centers).
- NFPA 13 / 14 / 20 / 72
- Key NFPA standards: sprinkler systems (13), standpipes (14), fire pumps (20), and fire alarm/signaling (72).
- Authority Having JurisdictionAHJ
- The local body (e.g. fire marshal, civil defense) empowered to approve equipment, installations, and procedures.