16 Burns & McDonnell Hvac Engineer Interview Questions & Answers

I start by defining the project context, including occupancy, location, equipment, refrigerant, adopted code edition, authority having jurisdiction, and client criteria. I then identify the locally enforceable mechanical code, referenced standards such as ASHRAE Standard 15, ASHRAE Standard 34, and NFPA 90A when applicable, plus manufacturer instructions. I translate those requirements into design controls for refrigerant safety, machinery room implications, ventilation, pressure relief, combustion air, fire and smoke interfaces, service access, and other applicable hazards. I coordinate unclear requirements with the client, other disciplines, manufacturers, and the authority having jurisdiction when needed. Before issue or construction, I complete documented interdisciplinary reviews and resolve compliance comments rather than claiming compliance without applicable evidence.

I treat compliance as a traceable process from project context to applicable requirements, design controls, coordination, and documented verification. I do not begin by selecting an isolated requirement. I first determine which requirements actually govern the project.

1. What jurisdiction, adopted code edition, occupancy, and project type should I assume?
2. Is there a specific refrigerant system, fuel fired equipment, or fire and smoke interface that should be considered?
3. Are there client design criteria or manufacturer requirements beyond the adopted codes?

I first establish the project basis: occupancy and use, location, HVAC equipment, refrigerant, adopted code edition, authority having jurisdiction, and client criteria. This prevents applying requirements from the wrong jurisdiction or edition.

Next, I identify the requirement hierarchy. The locally adopted International Mechanical Code or other applicable mechanical code provides enforceable requirements. Referenced standards can include ASHRAE Standard 15 for refrigeration system safety, ASHRAE Standard 34 for refrigerant designation and safety classification, and NFPA 90A for applicable air distribution fire and smoke protection. Manufacturer installation and application instructions also need to be incorporated where applicable. Client criteria are tracked separately so they are not confused with statutory requirements.

I translate the governing requirements into physical design controls. For refrigeration systems, I identify the refrigerant classification and assess charge and concentration implications before determining whether machinery room provisions, ventilation, detection, pressure relief, discharge arrangements, or access restrictions apply. I also review combustion air for fuel fired equipment, electrical and stored energy hazards, service clearance, safe access, condensate disposal where applicable, and authorized isolation procedures such as lockout tagout during servicing or commissioning.

For air distribution systems, I coordinate fire damper, smoke damper, duct smoke detector, and smoke control interfaces with architectural, electrical, controls, and fire protection disciplines as applicable.

When a requirement is unclear or conflicting, I document the question and coordinate it with the appropriate discipline, client, equipment manufacturer, or authority having jurisdiction instead of making an unsupported assumption. Important decisions are incorporated into the design documents so the reasoning remains traceable.

Before issue or construction, I perform a documented code review and interdisciplinary design review. I confirm equipment selection, service access, fire and smoke interfaces, safety controls, and applicable requirements, then resolve comments. I only state that the design meets a requirement when the applicable basis and supporting design evidence are documented.

Common mistakes include selecting a requirement before confirming the jurisdiction and adopted edition, treating every standard as automatically enforceable, ignoring client criteria or manufacturer instructions, checking refrigerant charge without first identifying the refrigerant safety classification, overlooking machinery room or ventilation implications, missing fire and smoke interfaces between disciplines, failing to provide service clearance and safe access, and declaring compliance without documented evidence or resolved review comments.

Describe compliance as a traceable sequence: establish the project context, identify applicable requirements, convert them into design controls, coordinate unclear items, and document verification. Mention specific HVAC examples such as refrigerant classification, machinery room implications, fire and smoke interfaces, pressure relief, combustion air, ventilation, and service access, but avoid inventing numerical limits unless the jurisdiction, code edition, system, and refrigerant are known.

I start by defining the occupancy, location, equipment, adopted code edition, and authority having jurisdiction, then identify hazards and prioritize them by likelihood and consequence. Next, I determine the enforceable local code, applicable design standards, and manufacturer instructions. I apply preventive controls such as refrigerant detection and ventilation where applicable, pressure relief, fire and smoke coordination, combustion air provisions, preventive inspection, maintenance, and safe service access. I also plan authorized energy isolation, lockout tagout, emergency response, and appropriate contingency or backup provisions. Finally, I verify the controls with functional checks, document the evidence, and use root cause findings to strengthen preventive controls.

The process should move from understanding the risk to proving that the selected controls work. I would not start by assuming a specific code requirement or declaring a system compliant. I would first establish the application and jurisdiction, prioritize credible hazards, determine the governing requirements, apply preventive controls, prepare for failure response, and then verify and improve the system.

1. What type of HVAC equipment, occupancy, location, and operating environment should I assume?
2. Which adopted code edition and authority having jurisdiction apply?
3. Is the main concern refrigerant, combustion, pressure, electrical, stored energy, or a combination of these hazards?

Compliance Basis: First, I identify the occupancy and use, location and environment, equipment and systems, adopted code edition, and authority having jurisdiction. I identify credible failure hazards and prioritize them by likelihood and consequence. I then separate enforceable local code requirements from design standards and manufacturer instructions. Relevant references can include ASHRAE 34 for refrigerant designations, safety classifications, and concentration limits, ASHRAE 15 for refrigeration system safety provisions, including applicable machinery room and detection requirements, the International Mechanical Code, and NFPA 90A where applicable.

Safety Checks: Next, I apply controls appropriate to the identified hazards and governing requirements. Depending on the application, these can include refrigerant detection and required ventilation, pressure relief, fire and smoke interface coordination with dampers and smoke control where required, combustion air provisions, preventive inspection and maintenance, and safe service access. I also verify that access and clearances support safe servicing.

For servicing or a failure event, I use authorized energy isolation, lockout tagout, and verification of deenergization where applicable. I also establish emergency response actions and contingency or backup provisions that are appropriate to the consequence of the failure.

Code Reasoning: Finally, I verify the controls with functional checks and document the evidence needed for review by the responsible parties and authority having jurisdiction. If an incident occurs, I investigate the root cause and feed those findings back into inspection, maintenance, design controls, procedures, or contingency planning. I would only describe the system as compliant after the applicable requirements and supporting evidence have been confirmed.

Common mistakes include selecting a requirement before identifying the governing code and jurisdiction, treating a design standard as automatically enforceable, failing to prioritize hazards by likelihood and consequence, overlooking manufacturer instructions, ignoring stored energy or service access hazards, omitting contingency planning, bypassing or defeating safety controls, assuming inspection alone proves compliance, and correcting an incident without feeding root cause findings back into preventive controls.

Present the answer as a five step flow: identify the context and prioritize hazards, determine governing requirements, apply preventive controls, prepare safe isolation and emergency response, then verify and improve. Mention ASHRAE 15, ASHRAE 34, the International Mechanical Code, and NFPA 90A as applicable references, while making clear that the adopted edition, jurisdiction, equipment, occupancy, refrigerant, manufacturer instructions, and authority having jurisdiction determine the actual requirements.

I begin with a measured annual energy baseline using utility data, weather, occupancy, and schedules. Then I look for operational waste such as poor scheduling, inefficient part load operation, economizer issues, excessive fan energy, weak temperature or static pressure reset strategies, and simultaneous heating and cooling. I evaluate controls improvements before equipment replacement. For each major option, I compare annual energy, peak demand, carbon emissions, life cycle cost, comfort, equipment limits, applicable ASHRAE 90.1 requirements, and renewable energy opportunities. I keep ventilation and safety requirements intact, then use measurement and verification with stated assumptions, weather and occupancy adjustments, and uncertainty to confirm actual performance.

My approach is to treat energy optimization as a measured engineering process. I establish how the building currently uses energy, identify avoidable HVAC waste, compare practical improvement options, and then verify the result. I do not use design peak load as a substitute for annual consumption, and I do not assume that nameplate efficiency represents actual part load performance.

1. Is the project an existing building optimization effort, a new design, or both?
2. What utility, interval, BAS, occupancy, schedule, and weather data are available for establishing the baseline?
3. Is the main client objective lower annual energy, lower peak demand, lower carbon emissions, lower life cycle cost, improved comfort, or a combination?

I start by defining a measured annual energy baseline from utility data and relating it to weather, occupancy, and operating schedules. That gives me a defensible reference before estimating savings.

Next, I investigate actual HVAC operation, especially at part load. I review economizer behavior, VFD operation, temperature and static pressure reset strategies, operating schedules, equipment staging, and signs of simultaneous heating and cooling. I normally examine controls changes before recommending equipment replacement because operational corrections can reduce waste with less capital cost and disruption.

For proposed energy conservation measures, I use an appropriate energy model or engineering analysis to compare annual energy and peak demand rather than relying only on design load. I evaluate equipment performance under expected operating conditions and consider renewable energy options where practical.

I compare alternatives using annual energy, peak demand, applicable utility tariffs, carbon factors, life cycle cost, equipment limits, and comfort consequences. Simple payback can help with screening, but I do not use it as the only economic measure because it does not represent the full life of an investment.

I also check the applicable jurisdiction and the relevant ASHRAE 90.1 requirements. Throughout optimization, I retain required ventilation, indoor environmental quality, equipment protection, and safety functions.

Finally, I define measurement and verification before implementation. I document the baseline, expected operating conditions, adjustment methods for weather or occupancy changes, metering needs, uncertainty, and the evidence required to confirm performance. After implementation, I compare measured post use performance with the adjusted baseline and investigate meaningful differences between predicted and measured results. Where appropriate, ASHRAE Guideline 14 can inform the measurement and verification approach.

Common mistakes include estimating savings before establishing a measured baseline, treating design peak load as annual energy use, comparing equipment only by nameplate efficiency, ignoring part load behavior, overlooking schedules and simultaneous heating and cooling, replacing equipment before investigating controls, evaluating renewable energy without project specific technical and economic context, using simple payback as the only financial test, ignoring tariff and carbon assumptions, and reducing airflow or operating hours without checking ventilation, comfort, equipment protection, and safety requirements.

Describe the work as a sequence from measured baseline to waste reduction to option comparison to verification. Mention specific operational checks such as economizer behavior, VFD operation, temperature and static pressure resets, schedules, and simultaneous heating and cooling. Then show professional judgment by explaining how you compare annual energy, peak demand, carbon emissions, life cycle cost, comfort, equipment limits, applicable ASHRAE 90.1 requirements, renewable energy options, and measurement and verification assumptions.

My approach is to start with the building load, operating schedule, utility data, and site conditions, then reduce unnecessary demand before sizing renewable generation. For rooftop solar PV, I would confirm solar access, shading, roof and structural capacity, electrical capacity, protection, and utility interconnection requirements. The PV array produces DC power, the inverter converts it to AC, and the building electrical bus serves loads such as HVAC while the bidirectional meter connects the building with the utility grid. I would compare annual energy, peak demand, carbon impact, and life cycle cost, then verify actual building use and PV production after installation.

Renewable energy should be integrated as part of the building energy strategy, not treated as a separate addition. I would first understand the measured energy baseline, weather, occupancy, operating schedules, HVAC performance, and the project objective. I would also look for efficiency opportunities such as controls improvements, better scheduling, reset strategies, reduced simultaneous heating and cooling, and stronger part load performance before increasing renewable capacity.

1. Is the goal mainly lower annual energy use, lower peak demand, lower carbon emissions, lower operating cost, or a combination of these?
2. What site constraints apply, such as roof area, shading, structural capacity, electrical service capacity, or utility interconnection limits?
3. Is there existing utility interval data or an energy model that can be used to establish the baseline and evaluate renewable production?

I would describe the process as five connected decisions.

First, I establish the site and load conditions. I review utility data, occupancy, schedules, weather context, and annual energy use. I do not use design peak load as a substitute for annual consumption.

Second, I reduce demand where practical. For HVAC, that can include controls optimization, reset strategies, VFD operation, economizer performance, heat recovery, demand control ventilation where appropriate, and correcting simultaneous heating and cooling. Ventilation, comfort, and safety requirements remain in place.

Third, I integrate the renewable source. For rooftop solar PV, I check solar access, shading, usable roof area, and structural capability. Electrically, the PV array produces DC power. An inverter converts that power to AC, which connects to the building electrical bus. The building can use the solar power for loads such as HVAC, while a bidirectional meter supports energy exchange with the utility grid. I also confirm electrical capacity, protection, and interconnection requirements.

Fourth, I compare alternatives using annual energy, peak demand, carbon factors, installed cost, life cycle cost, equipment limits, and expected operating conditions. I would not claim savings without a measured or modeled baseline and documented assumptions. ASHRAE Standard 90.1 can inform the building efficiency context when the applicable jurisdiction and edition are confirmed.

Fifth, I verify performance. I compare actual building energy use and PV production with the baseline and design assumptions through measurement and verification. I document weather, occupancy, tariff assumptions, uncertainty, and any operational changes that affect the comparison.

The key point is that renewable generation works best when site feasibility, building efficiency, electrical integration, economics, and verification are considered together.

Common mistakes include sizing renewable generation before understanding annual building energy use, using design peak load as annual consumption, ignoring shading or roof limitations, overlooking electrical capacity and utility interconnection requirements, assuming nameplate HVAC efficiency represents part load performance, ignoring simultaneous heating and cooling, estimating savings without a defensible baseline, and relying only on simple payback without considering life cycle cost, carbon impact, equipment limits, comfort, ventilation, and measurement uncertainty.

Keep the answer focused on engineering decisions rather than only naming renewable technologies. Walk through site and load assessment, reducing demand, renewable integration, energy and cost evaluation, and performance verification. If you do not have a specific completed renewable project to discuss, do not invent one. Explain the method you would use and clearly separate known facts, assumptions, and information you would need from the project team.

I start by defining the basis of design, including occupancy, climate, indoor conditions, zoning, operating hours, reliability, and service constraints. I then compare only feasible HVAC alternatives using validated load and ventilation results. I evaluate cost, schedule, performance, maintainability, reliability, and space together, then align the tradeoffs with owner and stakeholder priorities. I select the option that best satisfies the required criteria and validate it against the design requirements. If validation fails, I revisit the alternatives or priorities rather than forcing the original choice.

I treat cost, schedule, and performance as competing design criteria rather than allowing one of them to control the decision automatically. The process starts with the basis of design because an option that cannot satisfy required conditions is not a valid alternative, even if it is cheaper or faster.

1. Which requirements are mandatory, and which priorities can be traded against each other?
2. Are first cost, operating cost, schedule, reliability, maintainability, or space the strongest owner priorities?
3. Are there known site, equipment availability, service, or construction constraints that could remove an option from consideration?

First, I define the project constraints before selecting equipment. I confirm occupancy, climate, indoor conditions, outdoor design conditions, operating hours, zoning, reliability expectations, service access, space limitations, and applicable ventilation requirements. I also use validated zone and block load information so the system comparison starts from credible demand data.

Next, I screen feasible alternatives. Depending on the project, that could include air systems, heat pumps, VRF, DOAS, or a central plant. I compare each viable option using the same criteria rather than choosing a preferred technology first.

The main tradeoff criteria are first cost, schedule, performance, maintainability, reliability, and space. I also consider operating efficiency, humidity control, acoustics, redundancy, refrigerant implications, equipment access, and constructability when they materially affect the project. For cost, I look beyond initial price and consider expected operating implications over the useful life of the design.

For example, a DOAS with heat pumps could be a viable integrated solution when dedicated outdoor air and zone heating and cooling fit the project requirements. That example is not automatically the best system. It still has to be compared with the other feasible choices.

I then review the tradeoffs with the owner, design team, operations staff, and other key stakeholders. A lower first cost may create higher operating cost. A faster delivery option may reduce equipment flexibility. A higher performance option may require more space or maintenance. I make those consequences explicit so the decision reflects both engineering requirements and stakeholder priorities.

Finally, I validate the selected integrated HVAC system against the basis of design and current equipment performance data. I check that the selected airside and equipment approach can satisfy required conditions, ventilation, reliability, maintainability, space, constructability, and project constraints. If the requirements are not met, I return to the alternatives or reconsider the priority weighting. The goal is a traceable decision that protects required engineering quality while balancing cost, schedule, and performance.

I start by aligning project requirements, design criteria, responsibilities, deliverables, and revision status with the other disciplines. Then I share current models and documents, review physical interfaces such as structural framing, HVAC ductwork, chilled water piping, fire protection piping, penetrations, and service access, and resolve issues with documented decisions. After changes are made, I verify that the model, drawings, schedules, specifications, and related documents remain consistent. My goal is not only to remove clashes, but also to protect HVAC design intent, maintenance access, and constructability before construction.

I treat interdisciplinary coordination as a controlled design process rather than only a clash detection exercise. The main objective is to identify conflicts, responsibilities, and document inconsistencies while changes are still inexpensive to resolve.

1. What design stage and deliverables are being coordinated?
2. Which disciplines and interfaces create the greatest coordination risk on this project?
3. What process is used to document decisions, revisions, RFIs, submittals, and approvals?

I use four main steps.

First, I align goals and responsibilities. I confirm project requirements, HVAC design criteria, discipline boundaries, expected deliverables, coordination responsibilities, and the current revision status. This establishes who owns each interface and what information everyone should be using.

Second, I share current design information. The coordination set should include the applicable models, drawings, schedules, specifications, and other design information. Everyone needs to work from compatible revisions so that an old structural layout or outdated mechanical routing does not create unnecessary rework.

Third, I review interfaces and access. I check HVAC ductwork and piping against structural framing, fire protection, chilled water piping, electrical, plumbing, architectural constraints, penetrations, and other affected systems. I also check service access and constructability. For example, an HVAC supply duct can be geometrically clear of a structural beam, fire protection pipe, and chilled water pipe but still create a problem if the arrangement blocks the service access zone needed for maintenance. For civil coordination, I apply the same principle to site connection points, routing constraints, elevations, and other interfaces that affect the HVAC scope.

Fourth, I resolve, update, and verify. Each significant issue should have a documented decision and responsible party. After revisions, I verify that affected models, drawings, schedules, specifications, calculations, and control information remain consistent. RFIs, submittals, substitutions, and shop drawings should be reviewed against the approved HVAC design intent rather than accepted simply because they fit geometrically.

A useful rule is that clash free is not enough. The final coordinated design should also support service access, constructability, design intent, and document consistency. Before issuing documents for construction, I confirm that identified issues have been addressed and that the coordinated information tells the same engineering story across the project documents.

Common mistakes include treating clash detection as the complete coordination process, using outdated discipline information, checking physical interference without checking service access, failing to define responsibility for an interface, changing a model without updating related drawings or schedules, and accepting a substitution or shop drawing without verifying the original HVAC design intent.

Explain coordination as a repeatable engineering process: align requirements, share current information, review interfaces and access, then resolve and verify. Give one practical example, such as coordinating an HVAC supply duct around a structural beam, fire protection pipe, and chilled water pipe while maintaining the required service access zone.

My construction administration approach starts with the contract drawings, equipment schedules, specifications, and basis of design. For submittals, I compare shop drawings and product data against those requirements, including performance, interfaces, service access, and proposed substitutions. For RFIs, I check the drawings, specifications, and actual field condition, then provide a documented clarification or design revision when needed and identify schedule implications when relevant. During site visits, I observe installation and workmanship, compare the work with the design documents, check access and coordination with other disciplines, and document deficiencies or required corrective action. I also keep the record information current so the final documentation reflects approved decisions.

Construction administration is the process of maintaining HVAC design intent as the project moves from issued documents into procurement and construction. I treat drawings, equipment schedules, specifications, calculations, and approved decisions as one coordinated set. A model that is free of geometric clashes is useful, but it does not by itself prove that performance, accessibility, constructability, or contract requirements have been satisfied.

1. What level of authority does the HVAC engineer have for submittal review, RFI responses, and approval of substitutions?
2. How are field observations, deficiencies, and design revisions documented and communicated on your projects?
3. Which disciplines and construction team members are normally involved when an HVAC issue affects access, safety, or schedule?

I use a four step construction administration workflow.

First, I establish the design intent and review basis. I check the coordinated HVAC drawings, equipment schedules, specifications, basis of design, and relevant revision status so I know what the contractor is required to provide.

Second, I review submittals such as shop drawings and product data against the contract requirements. I confirm required HVAC performance and key characteristics, then check interfaces with architectural, structural, electrical, plumbing, and fire systems. I also check service clearance and maintainability. If a substitution is proposed, I verify its technical impact rather than assuming that similar geometry makes it acceptable. Any exception or deviation should be clearly documented and handled through the proper approval process.

Third, I address RFIs by identifying the exact field question, then checking the drawings, specifications, and actual field condition that caused it. I determine whether the issue can be answered by clarification or whether a design revision is needed. I document the engineering response and note schedule impact when the issue could affect sequencing, procurement, or installation.

Fourth, during site visits I observe installed work and workmanship and compare what I see with the drawings, specifications, and approved submittals. I check equipment access, service clearances, constructability, and coordination with architectural, structural, electrical, plumbing, and fire systems. I also look for visible conditions that could create a safety concern and route those concerns through the appropriate project process. Site observation is not a substitute for the contractor's own quality control or responsibility for construction means and methods.

When I find a deficiency, I document the location, condition, applicable requirement, and required follow up. Approved changes are carried into the project records and final record information as appropriate. The goal is to maintain consistent design intent from the original documents through construction and closeout.

Common mistakes include reviewing only equipment dimensions instead of performance and contract requirements, treating a clash free model as proof of a valid design, overlooking service clearance, accepting substitutions without checking system impacts, answering an RFI without confirming the governing drawings and specifications, failing to coordinate with other disciplines, and documenting field issues without a clear required action or follow up.

Describe construction administration as a continuous design intent and documentation process. Give a clear sequence from contract requirements to submittal review, RFI resolution, field observation, and final documentation. Emphasize engineering judgment, interdisciplinary coordination, service access, documented decisions, and verification rather than software commands.

My approach is to first define the commissioning objective or confirm the reported problem, then establish the acceptance criteria from the OPR, design intent, project specifications, and applicable requirements. Before testing, I verify safe test conditions, instrument calibration, operating conditions, baseline readings, and commanded versus actual equipment states. I then run the appropriate functional tests and TAB measurements, such as airflow, water flow, temperature, pressure, and control response. I compare the results with the acceptance criteria. If something fails, I investigate the root cause, correct the issue, retest the affected function, confirm safe and intended operation, and document the final verified condition.

I treat equipment testing as an evidence based process rather than simply taking readings. The test must begin with a clear objective, defined acceptance criteria, known operating conditions, and measurements that directly prove whether the equipment is safe and performing as intended. I also distinguish planned commissioning from troubleshooting an existing fault. Commissioning verifies performance against the required intent, while troubleshooting starts by confirming the complaint and then isolating the cause.

1. Are we discussing planned commissioning of new equipment or troubleshooting an existing performance problem?
2. What project specifications, OPR, design intent, or acceptance requirements should govern the test?
3. Which equipment functions or operating conditions are most important to verify?

I would describe the work as a five stage process.

First, I define the objective and acceptance criteria. For planned commissioning, I review the OPR, design intent, project specifications, sequences, and applicable requirements. For an existing problem, I first confirm the complaint and define exactly what condition needs to be tested.

Second, I prepare and establish a baseline. I confirm that testing can be performed safely, verify instrument calibration, document operating conditions, and record baseline readings. I also compare commanded and actual equipment states so I know whether a control command is actually being carried out.

Third, I execute the test using measurements that match the function being evaluated. Depending on the equipment, that can include functional testing and TAB measurements for airflow, water flow, temperature, pressure, or control response. I check basic flow conditions before concluding that a capacity problem exists.

Fourth, I compare the measured results directly with the defined acceptance criteria. If the results do not meet the criteria, I investigate the root cause using measured evidence. For example, I might separate an airflow problem from a thermal or control problem rather than changing settings without confirming the cause.

Finally, after corrective action, I repeat the affected tests and record the post correction condition. I confirm safe and intended operation, document the results and any unresolved issues, and complete the required handover. This provides a traceable record from objective, to measurement, to acceptance decision, to correction, and finally to verified performance.

Common mistakes include starting adjustments before confirming the complaint, testing without defined acceptance criteria, using instruments without checking calibration, recording measurements without the operating conditions, relying only on commanded control values instead of checking actual equipment response, blaming equipment capacity before verifying airflow or water flow, changing several variables at once, and stopping after a correction without repeating the affected test and documenting the final condition.

Explain the sequence from objective to acceptance criteria, baseline, measurement, evaluation, corrective action, retest, and documentation. Mention specific HVAC measurements such as airflow, water flow, temperature, pressure, and control response, but avoid inventing test values or employer specific procedures. Emphasize that you compare measured evidence with defined criteria before deciding whether equipment is safe and performing as intended.