OBC Building Services flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Building services scope

The mechanical, electrical, plumbing, fire protection and vertical transport systems that make a building safe, comfortable and functional, plus the coordination needed among them.

Occupancy classification

The code category assigned to a building or portion based on its use, which sets egress, fire protection, ventilation and plumbing fixture requirements.

Sensible heat ratio

Sensible load divided by total load (sensible plus latent). The cooling coil must be selected to match the space ratio or humidity control will drift.

Airflow sensible heat formula

Cfm equals Btu per hour divided by 1.08 times the temperature difference. The constant 1.08 accounts for air density, specific heat and 60 minutes per hour.

Equal friction duct sizing

A duct design method that selects sizes so pressure loss per unit length is constant along the run, simplifying fan calculation and balancing.

Static pressure per foot

Water exerts about 0.433 psi per foot of vertical rise, so pump pressure must cover elevation plus friction losses in the piping.

Fixture units

A code-weighted value assigned to plumbing fixtures reflecting probable simultaneous demand, used to size water supply and drainage piping.

Three-phase power formula

Power in watts equals the square root of three times voltage times current times power factor for a balanced three-phase load.

Voltage drop limits

Common design targets cap branch circuit drop near 3 percent and total feeder plus branch near 5 percent to keep equipment voltage within tolerance.

Ground fault circuit interrupter

A device that trips when current leaks to ground, required in wet, outdoor and other specified locations to reduce electric shock hazard.

Means of egress components

Exit access, the exit itself, and exit discharge. Each component has its own width, travel distance and protection requirements under the code.

Egress width calculation

Required width equals occupant load multiplied by the code width factor per occupant, with stairways typically using a different factor than level corridors.

Travel distance limit

The maximum permitted distance from the most remote point to an exit, varying with occupancy and whether the building is sprinklered.

Fire-resistance rating

The time in hours a building assembly resists fire, applied to structure, shaft enclosures and separations between different occupancies.

Sprinkler design density

The water flow rate in gallons per minute per square foot applied over a defined remote area, selected according to the occupancy hazard classification.

Standpipe system

Piping with hose connections at specified locations that gives firefighters a pressurized water supply within the building during an incident.

Stair pressurization

A smoke control approach that supplies air to stairwells to maintain positive pressure and keep escape stairs free of smoke.

Firefighter elevator service

A control mode, activated by a key switch or alarm signal, that recalls elevators and allows trained use during a fire emergency.

Elevator pit and overhead

The pit depth, buffer space and overhead clearance required by elevator code so the car, counterweight and safety devices operate safely.

Commissioning

A documented quality process that verifies installed systems meet design intent through functional performance testing before acceptance and handover.

As-built drawings

Record documents showing actual installed locations and sizes of systems, used as the baseline for maintenance and future alterations.

Concealed work inspection

In-process code inspection of work that will be hidden by finishes, such as piping in walls or ductwork above ceilings, before it is covered.

Heating load calculation

A room-by-room estimate of heat loss through envelope surfaces plus infiltration and ventilation, used to size heating equipment.

Cooling load calculation

An estimate of sensible and latent heat gains from envelope, occupants, lighting and equipment at design conditions, used to size cooling equipment.

Ventilation rate procedure

A code method that sets minimum outdoor air per person and per floor area, adjusted for zone population and system ventilation efficiency.

Duct velocity and noise

Air speed limits in ducts and at diffusers control regenerated noise; main trunks commonly stay near 1,200 to 1,500 feet per minute.

Domestic water recirculation

A pumped or gravity loop that keeps hot water near fixtures, reducing wait time, water waste and scald risk at points of use.

Panel schedule load balance

Distribution of branch circuits across phases so that phase currents and neutral current stay within limits and breakers are not overloaded.

Fire alarm sequence of operations

The documented cause-and-effect matrix describing what happens when each initiating device activates, including recall, notification and suppression actions.

Smoke compartmentation

Dividing a building with smoke-resistant barriers and closures so smoke spread is limited, supporting both egress and firefighting operations.

Mixed-use building services

A building with multiple occupancy classifications must satisfy the most restrictive applicable requirements and provide required separations between uses.

Equipment service clearance

The code-required working space and access around mechanical and electrical equipment so it can be inspected, maintained and replaced safely.