Glossary
The words the app uses, each in a sentence, with the section that says more.
DOAS — dedicated outside-air system
A machine whose only job is the ventilation air: 100 % outside air, recovered against the exhaust, dried once at the door and delivered neutral, the rooms' sensible load carried by other machines. Kinds of systems → Recovery unit and DOAS.
SZVAV — single-zone variable air volume
A machine serving one room that holds a supply-air setpoint, resets it upward as the load falls and slows its fan, so the room gets less air rather than warmer air. How a machine is run → Constant volume and SZVAV.
VAV terminal box
A room's own damper on a shared cold deck, metering its air between a minimum and a maximum and reheating at the minimum. Multi-zone VAV and terminal boxes.
Economiser
The outside-air damper opened past its minimum on a cooling hour when the outside air is cooler, or carries less heat, than the return: free cooling. Economiser and outside air.
Waterside economiser
A plate exchanger between the cooling-tower loop and the chilled-water loop: when the tower makes water colder than the chilled-water return, the exchanger carries the load and the chiller idles — free cooling on the water side, the way the airside economiser is free cooling on the air side. A building run gives a plant with one a free cooling stage ahead of its chiller stage. See the plate exchanger.
Demand-controlled ventilation
The outside-air minimum following how full the rooms are, down to the per-area share and no further. Economiser and outside air.
Face-and-bypass
A damper that sends part of the air across the coil and mixes the rest back; the coil dries the share it sees and the bypassed air is the reheat, for nothing. Humidity: ceilings and floors and the cleanroom case.
Head-pressure control
Condenser fans taken off on a cool day to hold a minimum condensing temperature — a constraint an expansion valve needs, not an economy. Head-pressure control.
Humidity ceiling and floor
A room's upper and lower bounds on moisture; the ceiling makes the machine over-cool and reheat (or bypass), the floor steers a humidifier. Humidity: ceilings and floors.
Cycling and modulation
How a stage with too much capacity unloads: a fixed-speed compressor runs flat out for part of the hour, an inverter or a valve turns down. Cycling and modulation.
Coupling
A join between two blocks at their open ports — water, air or refrigerant — carrying last hour's state across, one hour behind. Couplings between blocks.
Priority
The order machines serving one room take it in: the lead is offered the whole load and the latent, the next what the lead did not deliver. Several machines on one room.
Category
What a system is — rooftop, split, air handler, chiller, condensing unit, fan coil, evaporative, recovery, plant, unit cooler, or a label of your own. Kinds of systems.
Nested system
A saved or published system placed into a design as one block showing its open ports; the solver flattens it. Systems can contain systems.
Design point and TMY year
One set of entering conditions a system tab solves at; a typical meteorological year is the 8 760 hours a building tab runs against. A solve is one condition; a simulation is a year of them.
Superheat
How far the vapour leaving an evaporator is above its saturation (dew) temperature; a compressor map is published at one stated superheat and corrected to the operating one. The refrigerant charts carry the dew line it is measured from.
Subcooling
How far the liquid leaving a condenser is below its saturation temperature — the bubble temperature on a blend — and worth about a percent of capacity per two to three kelvin. The refrigerant charts carry the bubble line.
Sensible heat ratio (SHR)
The sensible share of a cooling duty, the rest being moisture condensed out; the slope of the process line on the chart. Draw one on the free chart.
Bypass factor
The fraction of the air a cooling coil leaves untouched; the rest leaves at the coil's surface temperature. The coil model computes it from the geometry.
Wet-bulb temperature
What a wetted thermometer reads in moving air — the limit of evaporative cooling and the floor under every cooling tower. Plot a state from it.
Dew point
The temperature at which cooled air begins to condense; a coil surface below it dries the air, one above it does not. The coil model solves the partly wet case in between.
COP and EER
Output over electrical input, dimensionless or in Btu/h per watt (EER is 3.412 × COP); SEER and SCOP weight a season, which a year's simulation measures instead.
Compressor map
A maker's ten-coefficient polynomial in evaporating and condensing temperature, valid inside its envelope. Read any of the catalog's at your conditions.
Evaporating and condensing temperature
The two saturation temperatures a circuit runs between, found where evaporator, compressor and condenser balance — the solver's two unknowns per circuit. What a solve returns.
Range and approach
A cooling tower's water temperature drop, and how close its cold water gets to the entering wet bulb; the approach can never be zero. The tower model is rated from one point.
Heat-recovery (three-pipe) VRF
Some indoor units cool while others heat on one outdoor unit, the heat moved between rooms rather than rejected. The clinic case measures it over a year.
Typical meteorological year (TMY)
8 760 hours of representative weather assembled from real years — for annual energy, not for sizing. Running a year.