Engineer Building Facilities common mistakes
Engineer Building Facilities · Understand the traps and how to avoid them.
Calculates sensible cooling load as 1.08 x CFM x delta-T, then reports that value as the total coil load and sizes the chiller from it without adding latent or outdoor-air load.
The 1.08 shortcut is memorized as a general cooling-load formula; under time pressure the candidate treats the first airflow equation recalled as the total load and does not check units or the psychrometric chart.
What to do instead
Use a three-line template: sensible Btu/h = 1.08 x CFM x delta-T; latent Btu/h = 0.68 x CFM x delta-W in gr/lb; total = sensible + latent + outdoor-air/fan allowances. Verify CFM, degrees F, and grains are consistent, then compare total tons with a block-load estimate before selecting equipment.
Converts a balanced three-phase kVA load to amps with A = 1000 x kVA / V, then sizes the feeder and breaker from that inflated current.
The single-phase formula is overlearned; the candidate forgets the square root of 3 and mixes kVA with kW or omits power factor when the load is given in kW.
What to do instead
Write the formula with units every time: I = kVA x 1000 / (sqrt(3) x V line-to-line). For kW loads include power factor. Cross-check by converting the result back to kVA, and apply continuous-load and demand factors separately before choosing the breaker.
Computes occupant load from gross floor area for an assembly space that the code measures as net, then applies the stair egress-width factor to level corridors.
Code tables are memorized as a single occupant-load number; the candidate does not distinguish gross versus net area basis or component-specific egress capacity factors.
What to do instead
Build a one-line table per occupancy: area basis (gross or net), occupant-load factor, then the correct width per occupant for doors, corridors, and stairs. Identify the governing egress component and note the code section beside each figure.
Treats a sprinkler waterflow alarm and a manual fire alarm pull station as interchangeable initiating devices, or assumes sprinkler protection automatically allows the longest travel distance in every occupancy.
Life-safety systems are studied as a list of devices rather than a sequence; the candidate misses initiation, notification, elevator recall, and the conditions attached to code exceptions.
What to do instead
For each scenario, map the sequence: initiating device, alarm zone, occupant notification, elevator recall, suppression, and Fire Department response. Verify travel-distance exceptions against the specific occupancy and sprinkler condition instead of assuming a blanket increase.
Diagnoses a chilled-water coil with a 6 degrees F supply-to-return delta-T as low refrigerant charge and recommends adding refrigerant, without checking coil fouling, valve position, pump differential, or water flow.
Low delta-T is a familiar field symptom and refrigerant is a familiar fix; water-side checks are less visible in an exam scenario and get skipped.
What to do instead
Use a fixed diagnostic order: supply/return temperatures, coil approach, control-valve position, pump differential, and flow before touching charge. Low delta-T with normal approach points to flow, valve, or coil fouling; high approach points to heat-transfer fouling or air binding.
On a boiler short-cycling scenario, raises the operating setpoint or adjusts the low-water cutoff to stop nuisance trips instead of checking expansion tank charge, air elimination, feedwater, and limit settings.
Short cycling looks like a controls problem; the candidate chooses the fastest reset and confuses a safety device with an operating control.
What to do instead
Separate safety from control: never adjust the low-water cutoff or relief settings to cure cycling. Check load versus capacity, aquastat/limit differential, expansion tank charge, air elimination, feedwater, and steam traps; record cycle timing before and after any change.
When a senior technician is promoted to supervisor, answers that the new supervisor should personally perform the most difficult repairs to earn credibility rather than assign, brief, and follow up.
The candidate equates technical excellence with supervision and answers from the perspective of the best technician rather than the person accountable for crew output.
What to do instead
Apply a supervision cycle: define the task and standard, assign by skill and qualification, confirm understanding, provide resources, check progress at set points, and document completion. Reserve personal repair for coaching or emergencies.
Builds a shift roster that assigns the fire safety director and the elevator recall response to the same person, or schedules an uncertified technician alone on a shift requiring a licensed operator.
Scheduling is treated as filling slots; the candidate overlooks statutory qualifications, emergency response roles, and fatigue or coverage limits.
What to do instead
Create a coverage matrix for each shift: required license or certificate, minimum staffing, response role, and backup. Verify credentials and maximum hours before publishing the roster, and schedule relief for alarm response and elevator entrapment.
Compares competing maintenance contracts only on the base price and signs without checking unit rates for extra work, exclusions, bonds, insurance, and change-order markup.
Procurement is reduced to a bid number; the candidate does not normalize offers to a common scope or read the commercial terms that control later costs.
What to do instead
Prepare an evaluated-cost table covering base scope, unit rates, exclusions, mandatory documents, schedule, warranty, and markup. Clarify scope in writing before award, then incorporate the agreed scope and rates into the contract.
Sets all preventive maintenance on manufacturer calendar intervals and measures the program by the number of work orders closed rather than by asset criticality, failure history, backlog, and availability.
Calendar PM is easy to administer and work-order counts look productive; the candidate avoids criticality ranking and condition data.
What to do instead
Classify assets by criticality and failure consequence, then set PM and predictive intervals from OEM guidance plus failure history. Track backlog in work-hours, PM compliance, mean time between failures, and critical-asset availability, not just closure counts.