NATIONAL COMFORT INSTITUTE (NCI) CERTIFICATION PRACTICE STUDY GUIDE - ORIGINAL
PRACTICE Q&A | STUDY GUIDE | NCI COMFORT + PERFORMANCE
NCI
COMFORT
2026/2027
NATIONAL COMFORT INSTITUTE (NCI) CERTIFICATION
PRACTICE STUDY GUIDE - 150 ORIGINAL QUESTIONS + DETAILED SOLUTIONS
BASED ON NCI PRINCIPLES | NOT ACTUAL EXAM | STUDY PURPOSE ONLY
150Q PRACTICE STUDY GUIDE DETAILED
ORIGINAL 2026-27 SOLUTIONS
INCLUDES:
• Airflow, Combustion, Carbon Monoxide Safety, System Performance, NCI
• Duct Diagnostics, Refrigeration, Psychrometrics, NCI Certifications
• 150 Original Practice Questions + Answers + Detailed Explanations
• Professional Study Guide | Borders + Page Numbers | 2026/2027 Edition
NCI Practice Guide | Not affiliated with NCI | Educational Only
Original Practice Questions - Not Actual Exam Content
,Airflow Combustion CO Safety System Performance NCI Principles
Description: National Comfort Institute NCI Certification Practice Study Guide core NCI principles performance-based contracting, NCI approach focuses on measured
performance not assumptions, airflow diagnostics total external static pressure TESP measurement supply plus return with digital manometer, rated TESP typically 0.5 inch
water column WC, high TESP indicates restrictive ductwork undersized filter grille coil dirty blower, static pressure budget component pressure drops, combustion analysis
combustion fundamentals fuel air mixture excess air, combustion analyzer measures O2 percentage 6-9 percent typical, CO carbon monoxide undiluted air-free max 100
ppm natural gas, draft pressure -0.02 to -0.04 inch WC, stack temperature, carbon monoxide safety CO safety NCI low-level CO monitoring personal CO monitor detects 1
ppm increments ambient CO limits 0-9 ppm normal 10-35 ppm investigate 36+ ppm action evacuate, flue CO testing air-free, appliance spillage test, worst-case
depressurization CAZ combustion appliance zone test all exhaust fans on doors closed measure CAZ pressure relative to outside max -5 Pa safe, duct diagnostics duct
leakage testing duct blaster pressurize duct to 25 Pa measure CFM25 leakage to outside, pressure pan test room to room, impact on comfort lost BTU pressure
imbalances infiltration, system performance delivered capacity BTU delivered formula airflow CFM times delta enthalpy times 4.5, target 350-400 CFM per ton cooling,
temperature split sensible 16-22F supply-return, refrigeration side NCI refrigeration diagnostics check airflow first before refrigerant, superheat TXV 8-12F fixed orifice
10-20F subcooling 8-12F per manufacturer, non-invasive.
Psychrometrics Duct Optimization Hydronics NCI Certifications Exam
Description: Psychrometrics psychrometric chart dry bulb temperature sensible, wet bulb evaporative, relative humidity RH, dew point, enthalpy total heat BTU per lb,
grains moisture, latent vs sensible capacity latent removal dehumidification, NCI uses return and supply wet bulb to calculate enthalpy delta delivered capacity, duct
optimization duct system optimization NCI redesign sealing mastic, sizing per Manual D friction rate, airflow balancing dampers, hydronics hydronic performance boiler
performance combustion efficiency, pump sizing, delta T 20F typical hydronic, primary secondary piping, NCI certifications National Comfort Institute offers certifications
Airflow Testing and Diagnostics Certification tests static pressure airflow, Combustion Performance and CO Safety Certification tests combustion analyzer CO safety CAZ,
System Performance Certification full system delivered BTU, Duct System Optimization Certification duct diagnostics sealing, Hydronic Performance Certification boiler
hydronics, Residential System Performance Certificate, Commercial System Performance, Air Balancing Certification, Refrigeration and System Diagnostics, NCI
membership High Performance HVAC, performance-based contracting selling comfort not boxes, exam process NCI training 2-4 days classroom field, certification exam
written 50-100 questions plus field certification, continuing education, methodology measure diagnose fix verify, tools digital manometer, combustion analyzer Testo
Bacharach, low-level CO monitor TPI, duct blaster Minneapolis, airflow hood, psychrometer, study materials NCI training manuals, NCI website, Modern Refrigeration,
Manual J D S, 2026/2027 original practice, 150 original practice questions answers detailed solutions for NCI candidates, NCI core airflow static combustion CO CAZ duct
leakage delivered BTU, NCI candidates exam preparation, National Comfort Institute Certification Examination Practice Guide, study guide borders page numbers
improved cover page educational purposes.
NCI Exam Domains Performance-Based Certification Study Guide 2026
Description: National Comfort Institute NCI Certification Practice Study Guide domains based on NCI principles, credential NCI Certified Technician multiple tracks Airflow
Combustion System Performance Duct Optimization Hydronic Residential, eligibility recommended field experience HVAC service installation, recommended NCI training
course attendance, exam blueprint Airflow Diagnostics 25 percent TESP supply return manometer static budget 0.5 inch WC filter grille coil blower CFM per ton 350-400
fan tables ECM, Combustion Performance and CO Safety 25 percent combustion fundamentals excess air O2 6-9 percent CO air-free max 100 ppm draft -0.02 to -0.04
stack temp analyzer operation CO safety ambient 0-9 normal 10-35 investigate 36+ action low-level monitor 1 ppm CAZ worst-case depressurization -5 Pa spillage, Duct
Diagnostics Optimization 15 percent duct blaster CFM25 pressure pan leakage to outside BTU loss pressure imbalances Manual D friction rate sealing mastic balancing,
System Performance Refrigeration 15 percent delivered BTU formula CFM delta enthalpy 4.5 temp split 16-22F airflow first then superheat 8-12F TXV subcooling 8-12F
psychrometrics dry wet bulb enthalpy grains latent sensible, Hydronics and Additional 10 percent boiler efficiency pump delta T 20F primary secondary piping, Business
Performance-Based 10 percent High Performance HVAC selling comfort measure diagnose, exam 50-100 questions per certification field certification required,
recertification every 2 years CE, study materials NCI manuals combustion analyzer, latest 2026/2027 original practice 150Q verified practice questions answers detailed
solutions for NCI candidates, NCI airflow static pressure combustion CO safety CAZ duct leakage delivered capacity psychrometrics, NCI candidates exam preparation,
National Comfort Institute Certification Examination Practice Guide, study guide borders page numbers improved cover page educational purposes.
Page 2 - NCI Practice 150Q 2026/2027
,Question 1: Q1: What is the NCI approach to airside diagnostics and total external static pressure? Measure TESP supply plus return
with manometer compare to rated 0.5 inch WC, high indicates restrictive duct dirty filter undersized
A. Incorrect: Uses rules of thumb without actual measurements violating NCI test-measure-diagnose approach for What
B. What is the NCI approach to airside diagnostics and total external static pressure? Measure TESP supply plus return with manometer compare to
rated 0.5 inch WC, high indicates restrictive duct dirty filter undersized - detailed per National Comfort Institute NCI principles and performance-based
methodology
C. Incorrect: Focuses only on equipment efficiency ignoring distribution and building pressures per NCI, wrong for is
D. Incorrect: Suggests guessing charge or airflow without manometer and combustion analyzer, unsafe per NCI CO safety standards
CORRECT ANSWER: B. What is the NCI approach to airside diagnostics and total external static pressure? Measure TESP supply plus return
with manometer compare to rated 0.5 inch WC, high indicates restrictive duct dirty filter undersized - detailed per National Comfort Institute
NCI principles and performance-based methodology
RATIONALE:
Rationale: What is the NCI approach to airside diagnostics and total external static pressure? Measure TESP supply plus return with manometer compare to rated 0.5
inch WC, high indicates restrictive duct dirty filter undersized - detailed per National Comfort Institute NCI principles and performance-based methodology. This aligns with
NCI performance-based contracting and air diagnostics methodology.
Question 2: Q2: How does NCI teach combustion analysis and what are acceptable CO levels? Use combustion analyzer O2 CO draft,
undiluted CO in flue max 100 ppm air-free, CO in ambient 0-9 ppm acceptable, action 35+ ppm
A. Incorrect: Uses rules of thumb without actual measurements violating NCI test-measure-diagnose approach for How
B. Incorrect: Focuses only on equipment efficiency ignoring distribution and building pressures per NCI, wrong for does
C. How does NCI teach combustion analysis and what are acceptable CO levels? Use combustion analyzer O2 CO draft, undiluted CO in flue max 100
ppm air-free, CO in ambient 0-9 ppm acceptable, action 35+ ppm - detailed per National Comfort Institute NCI principles and performance-based
methodology
D. Incorrect: Suggests guessing charge or airflow without manometer and combustion analyzer, unsafe per NCI CO safety standards
CORRECT ANSWER: C. How does NCI teach combustion analysis and what are acceptable CO levels? Use combustion analyzer O2 CO draft,
undiluted CO in flue max 100 ppm air-free, CO in ambient 0-9 ppm acceptable, action 35+ ppm - detailed per National Comfort Institute NCI
principles and performance-based methodology
RATIONALE:
Rationale: How does NCI teach combustion analysis and what are acceptable CO levels? Use combustion analyzer O2 CO draft, undiluted CO in flue max 100 ppm
air-free, CO in ambient 0-9 ppm acceptable, action 35+ ppm - detailed per National Comfort Institute NCI principles and performance-based methodology. This aligns with
NCI performance-based contracting and air diagnostics methodology.
Question 3: Q3: What is NCI carbon monoxide safety testing procedure? Test ambient CO with personal low-level CO monitor 1-10
ppm note, flue CO air-free, appliance spillage, worst-case depressurization CAZ
A. Incorrect: Uses rules of thumb without actual measurements violating NCI test-measure-diagnose approach for What
B. Incorrect: Focuses only on equipment efficiency ignoring distribution and building pressures per NCI, wrong for is
C. Incorrect: Suggests guessing charge or airflow without manometer and combustion analyzer, unsafe per NCI CO safety standards
D. What is NCI carbon monoxide safety testing procedure? Test ambient CO with personal low-level CO monitor 1-10 ppm note, flue CO air-free,
appliance spillage, worst-case depressurization CAZ - detailed per National Comfort Institute NCI principles and performance-based methodology
CORRECT ANSWER: D. What is NCI carbon monoxide safety testing procedure? Test ambient CO with personal low-level CO monitor 1-10
ppm note, flue CO air-free, appliance spillage, worst-case depressurization CAZ - detailed per National Comfort Institute NCI principles and
performance-based methodology
RATIONALE:
Rationale: What is NCI carbon monoxide safety testing procedure? Test ambient CO with personal low-level CO monitor 1-10 ppm note, flue CO air-free, appliance
spillage, worst-case depressurization CAZ - detailed per National Comfort Institute NCI principles and performance-based methodology. This aligns with NCI
performance-based contracting and air diagnostics methodology.
Question 4: Q4: Explain NCI duct leakage testing and impact on comfort. Pressure pan and duct blaster test leakage to outside,
leakage reduces delivered BTU and creates pressure imbalances leading to comfort complaints
A. Explain NCI duct leakage testing and impact on comfort. Pressure pan and duct blaster test leakage to outside, leakage reduces delivered BTU and
creates pressure imbalances leading to comfort complaints - detailed per National Comfort Institute NCI principles and performance-based methodology
B. Incorrect: Uses rules of thumb without actual measurements violating NCI test-measure-diagnose approach for Explain
C. Incorrect: Focuses only on equipment efficiency ignoring distribution and building pressures per NCI, wrong for NCI
D. Incorrect: Suggests guessing charge or airflow without manometer and combustion analyzer, unsafe per NCI CO safety standards
CORRECT ANSWER: A. Explain NCI duct leakage testing and impact on comfort. Pressure pan and duct blaster test leakage to outside,
leakage reduces delivered BTU and creates pressure imbalances leading to comfort complaints - detailed per National Comfort Institute NCI
principles and performance-based methodology
RATIONALE:
Rationale: Explain NCI duct leakage testing and impact on comfort. Pressure pan and duct blaster test leakage to outside, leakage reduces delivered BTU and creates
pressure imbalances leading to comfort complaints - detailed per National Comfort Institute NCI principles and performance-based methodology. This aligns with NCI
performance-based contracting and air diagnostics methodology.
Question 5: Q5: What is NCI system performance approach static pressure vs airflow? 350-400 CFM per ton target, measure static
pressure budget, fan airflow table, adjust speed tap ECM programming to achieve required CFM
A. Incorrect: Uses rules of thumb without actual measurements violating NCI test-measure-diagnose approach for What
B. What is NCI system performance approach static pressure vs airflow? 350-400 CFM per ton target, measure static pressure budget, fan airflow table,
adjust speed tap ECM programming to achieve required CFM - detailed per National Comfort Institute NCI principles and performance-based
methodology
C. Incorrect: Focuses only on equipment efficiency ignoring distribution and building pressures per NCI, wrong for is
D. Incorrect: Suggests guessing charge or airflow without manometer and combustion analyzer, unsafe per NCI CO safety standards
Page 3 - NCI Practice 150Q 2026/2027
, CORRECT ANSWER: B. What is NCI system performance approach static pressure vs airflow? 350-400 CFM per ton target, measure static
pressure budget, fan airflow table, adjust speed tap ECM programming to achieve required CFM - detailed per National Comfort Institute NCI
principles and performance-based methodology
RATIONALE:
Rationale: What is NCI system performance approach static pressure vs airflow? 350-400 CFM per ton target, measure static pressure budget, fan airflow table, adjust
speed tap ECM programming to achieve required CFM - detailed per National Comfort Institute NCI principles and performance-based methodology. This aligns with NCI
performance-based contracting and air diagnostics methodology.
Question 6: Q6: How does NCI refrigeration side diagnostics differ from standard? Check airflow first TESP before refrigerant, then
superheat subcooling per manufacturer, non-invasive approach ensures correct charge after airflow verified
A. Incorrect: Uses rules of thumb without actual measurements violating NCI test-measure-diagnose approach for How
B. Incorrect: Focuses only on equipment efficiency ignoring distribution and building pressures per NCI, wrong for does
C. How does NCI refrigeration side diagnostics differ from standard? Check airflow first TESP before refrigerant, then superheat subcooling per
manufacturer, non-invasive approach ensures correct charge after airflow verified - detailed per National Comfort Institute NCI principles and
performance-based methodology
D. Incorrect: Suggests guessing charge or airflow without manometer and combustion analyzer, unsafe per NCI CO safety standards
CORRECT ANSWER: C. How does NCI refrigeration side diagnostics differ from standard? Check airflow first TESP before refrigerant, then
superheat subcooling per manufacturer, non-invasive approach ensures correct charge after airflow verified - detailed per National Comfort
Institute NCI principles and performance-based methodology
RATIONALE:
Rationale: How does NCI refrigeration side diagnostics differ from standard? Check airflow first TESP before refrigerant, then superheat subcooling per manufacturer,
non-invasive approach ensures correct charge after airflow verified - detailed per National Comfort Institute NCI principles and performance-based methodology. This
aligns with NCI performance-based contracting and air diagnostics methodology.
Question 7: Q7: What is NCI combustion safety CAZ worst-case testing? CAZ combustion appliance zone worst-case depressurization
all exhaust fans on doors closed, measure draft pressure and spillage, ensures safe venting
A. Incorrect: Uses rules of thumb without actual measurements violating NCI test-measure-diagnose approach for What
B. Incorrect: Focuses only on equipment efficiency ignoring distribution and building pressures per NCI, wrong for is
C. Incorrect: Suggests guessing charge or airflow without manometer and combustion analyzer, unsafe per NCI CO safety standards
D. What is NCI combustion safety CAZ worst-case testing? CAZ combustion appliance zone worst-case depressurization all exhaust fans on doors
closed, measure draft pressure and spillage, ensures safe venting - detailed per National Comfort Institute NCI principles and performance-based
methodology
CORRECT ANSWER: D. What is NCI combustion safety CAZ worst-case testing? CAZ combustion appliance zone worst-case depressurization
all exhaust fans on doors closed, measure draft pressure and spillage, ensures safe venting - detailed per National Comfort Institute NCI
principles and performance-based methodology
RATIONALE:
Rationale: What is NCI combustion safety CAZ worst-case testing? CAZ combustion appliance zone worst-case depressurization all exhaust fans on doors closed,
measure draft pressure and spillage, ensures safe venting - detailed per National Comfort Institute NCI principles and performance-based methodology. This aligns with
NCI performance-based contracting and air diagnostics methodology.
Question 8: Q8: Explain NCI psychrometrics and latent vs sensible capacity. Psychrometrics dry bulb wet bulb dew point relative
humidity, measure return and supply delta T 16-22F sensible, check latent removal via humidity drop
A. Explain NCI psychrometrics and latent vs sensible capacity. Psychrometrics dry bulb wet bulb dew point relative humidity, measure return and supply
delta T 16-22F sensible, check latent removal via humidity drop - detailed per National Comfort Institute NCI principles and performance-based
methodology
B. Incorrect: Uses rules of thumb without actual measurements violating NCI test-measure-diagnose approach for Explain
C. Incorrect: Focuses only on equipment efficiency ignoring distribution and building pressures per NCI, wrong for NCI
D. Incorrect: Suggests guessing charge or airflow without manometer and combustion analyzer, unsafe per NCI CO safety standards
CORRECT ANSWER: A. Explain NCI psychrometrics and latent vs sensible capacity. Psychrometrics dry bulb wet bulb dew point relative
humidity, measure return and supply delta T 16-22F sensible, check latent removal via humidity drop - detailed per National Comfort Institute
NCI principles and performance-based methodology
RATIONALE:
Rationale: Explain NCI psychrometrics and latent vs sensible capacity. Psychrometrics dry bulb wet bulb dew point relative humidity, measure return and supply delta T
16-22F sensible, check latent removal via humidity drop - detailed per National Comfort Institute NCI principles and performance-based methodology. This aligns with NCI
performance-based contracting and air diagnostics methodology.
Question 9: Q9: What NCI certifications exist? Airflow Testing and Diagnostics, Combustion Performance and CO Safety, System
Performance, Duct System Optimization, Hydronic Performance, Residential System Performance
A. Incorrect: Uses rules of thumb without actual measurements violating NCI test-measure-diagnose approach for What
B. What NCI certifications exist? Airflow Testing and Diagnostics, Combustion Performance and CO Safety, System Performance, Duct System
Optimization, Hydronic Performance, Residential System Performance - detailed per National Comfort Institute NCI principles and performance-based
methodology
C. Incorrect: Focuses only on equipment efficiency ignoring distribution and building pressures per NCI, wrong for NCI
D. Incorrect: Suggests guessing charge or airflow without manometer and combustion analyzer, unsafe per NCI CO safety standards
CORRECT ANSWER: B. What NCI certifications exist? Airflow Testing and Diagnostics, Combustion Performance and CO Safety, System
Performance, Duct System Optimization, Hydronic Performance, Residential System Performance - detailed per National Comfort Institute NCI
principles and performance-based methodology
RATIONALE:
Rationale: What NCI certifications exist? Airflow Testing and Diagnostics, Combustion Performance and CO Safety, System Performance, Duct System Optimization,
Hydronic Performance, Residential System Performance - detailed per National Comfort Institute NCI principles and performance-based methodology. This aligns with
Page 4 - NCI Practice 150Q 2026/2027
PRACTICE Q&A | STUDY GUIDE | NCI COMFORT + PERFORMANCE
NCI
COMFORT
2026/2027
NATIONAL COMFORT INSTITUTE (NCI) CERTIFICATION
PRACTICE STUDY GUIDE - 150 ORIGINAL QUESTIONS + DETAILED SOLUTIONS
BASED ON NCI PRINCIPLES | NOT ACTUAL EXAM | STUDY PURPOSE ONLY
150Q PRACTICE STUDY GUIDE DETAILED
ORIGINAL 2026-27 SOLUTIONS
INCLUDES:
• Airflow, Combustion, Carbon Monoxide Safety, System Performance, NCI
• Duct Diagnostics, Refrigeration, Psychrometrics, NCI Certifications
• 150 Original Practice Questions + Answers + Detailed Explanations
• Professional Study Guide | Borders + Page Numbers | 2026/2027 Edition
NCI Practice Guide | Not affiliated with NCI | Educational Only
Original Practice Questions - Not Actual Exam Content
,Airflow Combustion CO Safety System Performance NCI Principles
Description: National Comfort Institute NCI Certification Practice Study Guide core NCI principles performance-based contracting, NCI approach focuses on measured
performance not assumptions, airflow diagnostics total external static pressure TESP measurement supply plus return with digital manometer, rated TESP typically 0.5 inch
water column WC, high TESP indicates restrictive ductwork undersized filter grille coil dirty blower, static pressure budget component pressure drops, combustion analysis
combustion fundamentals fuel air mixture excess air, combustion analyzer measures O2 percentage 6-9 percent typical, CO carbon monoxide undiluted air-free max 100
ppm natural gas, draft pressure -0.02 to -0.04 inch WC, stack temperature, carbon monoxide safety CO safety NCI low-level CO monitoring personal CO monitor detects 1
ppm increments ambient CO limits 0-9 ppm normal 10-35 ppm investigate 36+ ppm action evacuate, flue CO testing air-free, appliance spillage test, worst-case
depressurization CAZ combustion appliance zone test all exhaust fans on doors closed measure CAZ pressure relative to outside max -5 Pa safe, duct diagnostics duct
leakage testing duct blaster pressurize duct to 25 Pa measure CFM25 leakage to outside, pressure pan test room to room, impact on comfort lost BTU pressure
imbalances infiltration, system performance delivered capacity BTU delivered formula airflow CFM times delta enthalpy times 4.5, target 350-400 CFM per ton cooling,
temperature split sensible 16-22F supply-return, refrigeration side NCI refrigeration diagnostics check airflow first before refrigerant, superheat TXV 8-12F fixed orifice
10-20F subcooling 8-12F per manufacturer, non-invasive.
Psychrometrics Duct Optimization Hydronics NCI Certifications Exam
Description: Psychrometrics psychrometric chart dry bulb temperature sensible, wet bulb evaporative, relative humidity RH, dew point, enthalpy total heat BTU per lb,
grains moisture, latent vs sensible capacity latent removal dehumidification, NCI uses return and supply wet bulb to calculate enthalpy delta delivered capacity, duct
optimization duct system optimization NCI redesign sealing mastic, sizing per Manual D friction rate, airflow balancing dampers, hydronics hydronic performance boiler
performance combustion efficiency, pump sizing, delta T 20F typical hydronic, primary secondary piping, NCI certifications National Comfort Institute offers certifications
Airflow Testing and Diagnostics Certification tests static pressure airflow, Combustion Performance and CO Safety Certification tests combustion analyzer CO safety CAZ,
System Performance Certification full system delivered BTU, Duct System Optimization Certification duct diagnostics sealing, Hydronic Performance Certification boiler
hydronics, Residential System Performance Certificate, Commercial System Performance, Air Balancing Certification, Refrigeration and System Diagnostics, NCI
membership High Performance HVAC, performance-based contracting selling comfort not boxes, exam process NCI training 2-4 days classroom field, certification exam
written 50-100 questions plus field certification, continuing education, methodology measure diagnose fix verify, tools digital manometer, combustion analyzer Testo
Bacharach, low-level CO monitor TPI, duct blaster Minneapolis, airflow hood, psychrometer, study materials NCI training manuals, NCI website, Modern Refrigeration,
Manual J D S, 2026/2027 original practice, 150 original practice questions answers detailed solutions for NCI candidates, NCI core airflow static combustion CO CAZ duct
leakage delivered BTU, NCI candidates exam preparation, National Comfort Institute Certification Examination Practice Guide, study guide borders page numbers
improved cover page educational purposes.
NCI Exam Domains Performance-Based Certification Study Guide 2026
Description: National Comfort Institute NCI Certification Practice Study Guide domains based on NCI principles, credential NCI Certified Technician multiple tracks Airflow
Combustion System Performance Duct Optimization Hydronic Residential, eligibility recommended field experience HVAC service installation, recommended NCI training
course attendance, exam blueprint Airflow Diagnostics 25 percent TESP supply return manometer static budget 0.5 inch WC filter grille coil blower CFM per ton 350-400
fan tables ECM, Combustion Performance and CO Safety 25 percent combustion fundamentals excess air O2 6-9 percent CO air-free max 100 ppm draft -0.02 to -0.04
stack temp analyzer operation CO safety ambient 0-9 normal 10-35 investigate 36+ action low-level monitor 1 ppm CAZ worst-case depressurization -5 Pa spillage, Duct
Diagnostics Optimization 15 percent duct blaster CFM25 pressure pan leakage to outside BTU loss pressure imbalances Manual D friction rate sealing mastic balancing,
System Performance Refrigeration 15 percent delivered BTU formula CFM delta enthalpy 4.5 temp split 16-22F airflow first then superheat 8-12F TXV subcooling 8-12F
psychrometrics dry wet bulb enthalpy grains latent sensible, Hydronics and Additional 10 percent boiler efficiency pump delta T 20F primary secondary piping, Business
Performance-Based 10 percent High Performance HVAC selling comfort measure diagnose, exam 50-100 questions per certification field certification required,
recertification every 2 years CE, study materials NCI manuals combustion analyzer, latest 2026/2027 original practice 150Q verified practice questions answers detailed
solutions for NCI candidates, NCI airflow static pressure combustion CO safety CAZ duct leakage delivered capacity psychrometrics, NCI candidates exam preparation,
National Comfort Institute Certification Examination Practice Guide, study guide borders page numbers improved cover page educational purposes.
Page 2 - NCI Practice 150Q 2026/2027
,Question 1: Q1: What is the NCI approach to airside diagnostics and total external static pressure? Measure TESP supply plus return
with manometer compare to rated 0.5 inch WC, high indicates restrictive duct dirty filter undersized
A. Incorrect: Uses rules of thumb without actual measurements violating NCI test-measure-diagnose approach for What
B. What is the NCI approach to airside diagnostics and total external static pressure? Measure TESP supply plus return with manometer compare to
rated 0.5 inch WC, high indicates restrictive duct dirty filter undersized - detailed per National Comfort Institute NCI principles and performance-based
methodology
C. Incorrect: Focuses only on equipment efficiency ignoring distribution and building pressures per NCI, wrong for is
D. Incorrect: Suggests guessing charge or airflow without manometer and combustion analyzer, unsafe per NCI CO safety standards
CORRECT ANSWER: B. What is the NCI approach to airside diagnostics and total external static pressure? Measure TESP supply plus return
with manometer compare to rated 0.5 inch WC, high indicates restrictive duct dirty filter undersized - detailed per National Comfort Institute
NCI principles and performance-based methodology
RATIONALE:
Rationale: What is the NCI approach to airside diagnostics and total external static pressure? Measure TESP supply plus return with manometer compare to rated 0.5
inch WC, high indicates restrictive duct dirty filter undersized - detailed per National Comfort Institute NCI principles and performance-based methodology. This aligns with
NCI performance-based contracting and air diagnostics methodology.
Question 2: Q2: How does NCI teach combustion analysis and what are acceptable CO levels? Use combustion analyzer O2 CO draft,
undiluted CO in flue max 100 ppm air-free, CO in ambient 0-9 ppm acceptable, action 35+ ppm
A. Incorrect: Uses rules of thumb without actual measurements violating NCI test-measure-diagnose approach for How
B. Incorrect: Focuses only on equipment efficiency ignoring distribution and building pressures per NCI, wrong for does
C. How does NCI teach combustion analysis and what are acceptable CO levels? Use combustion analyzer O2 CO draft, undiluted CO in flue max 100
ppm air-free, CO in ambient 0-9 ppm acceptable, action 35+ ppm - detailed per National Comfort Institute NCI principles and performance-based
methodology
D. Incorrect: Suggests guessing charge or airflow without manometer and combustion analyzer, unsafe per NCI CO safety standards
CORRECT ANSWER: C. How does NCI teach combustion analysis and what are acceptable CO levels? Use combustion analyzer O2 CO draft,
undiluted CO in flue max 100 ppm air-free, CO in ambient 0-9 ppm acceptable, action 35+ ppm - detailed per National Comfort Institute NCI
principles and performance-based methodology
RATIONALE:
Rationale: How does NCI teach combustion analysis and what are acceptable CO levels? Use combustion analyzer O2 CO draft, undiluted CO in flue max 100 ppm
air-free, CO in ambient 0-9 ppm acceptable, action 35+ ppm - detailed per National Comfort Institute NCI principles and performance-based methodology. This aligns with
NCI performance-based contracting and air diagnostics methodology.
Question 3: Q3: What is NCI carbon monoxide safety testing procedure? Test ambient CO with personal low-level CO monitor 1-10
ppm note, flue CO air-free, appliance spillage, worst-case depressurization CAZ
A. Incorrect: Uses rules of thumb without actual measurements violating NCI test-measure-diagnose approach for What
B. Incorrect: Focuses only on equipment efficiency ignoring distribution and building pressures per NCI, wrong for is
C. Incorrect: Suggests guessing charge or airflow without manometer and combustion analyzer, unsafe per NCI CO safety standards
D. What is NCI carbon monoxide safety testing procedure? Test ambient CO with personal low-level CO monitor 1-10 ppm note, flue CO air-free,
appliance spillage, worst-case depressurization CAZ - detailed per National Comfort Institute NCI principles and performance-based methodology
CORRECT ANSWER: D. What is NCI carbon monoxide safety testing procedure? Test ambient CO with personal low-level CO monitor 1-10
ppm note, flue CO air-free, appliance spillage, worst-case depressurization CAZ - detailed per National Comfort Institute NCI principles and
performance-based methodology
RATIONALE:
Rationale: What is NCI carbon monoxide safety testing procedure? Test ambient CO with personal low-level CO monitor 1-10 ppm note, flue CO air-free, appliance
spillage, worst-case depressurization CAZ - detailed per National Comfort Institute NCI principles and performance-based methodology. This aligns with NCI
performance-based contracting and air diagnostics methodology.
Question 4: Q4: Explain NCI duct leakage testing and impact on comfort. Pressure pan and duct blaster test leakage to outside,
leakage reduces delivered BTU and creates pressure imbalances leading to comfort complaints
A. Explain NCI duct leakage testing and impact on comfort. Pressure pan and duct blaster test leakage to outside, leakage reduces delivered BTU and
creates pressure imbalances leading to comfort complaints - detailed per National Comfort Institute NCI principles and performance-based methodology
B. Incorrect: Uses rules of thumb without actual measurements violating NCI test-measure-diagnose approach for Explain
C. Incorrect: Focuses only on equipment efficiency ignoring distribution and building pressures per NCI, wrong for NCI
D. Incorrect: Suggests guessing charge or airflow without manometer and combustion analyzer, unsafe per NCI CO safety standards
CORRECT ANSWER: A. Explain NCI duct leakage testing and impact on comfort. Pressure pan and duct blaster test leakage to outside,
leakage reduces delivered BTU and creates pressure imbalances leading to comfort complaints - detailed per National Comfort Institute NCI
principles and performance-based methodology
RATIONALE:
Rationale: Explain NCI duct leakage testing and impact on comfort. Pressure pan and duct blaster test leakage to outside, leakage reduces delivered BTU and creates
pressure imbalances leading to comfort complaints - detailed per National Comfort Institute NCI principles and performance-based methodology. This aligns with NCI
performance-based contracting and air diagnostics methodology.
Question 5: Q5: What is NCI system performance approach static pressure vs airflow? 350-400 CFM per ton target, measure static
pressure budget, fan airflow table, adjust speed tap ECM programming to achieve required CFM
A. Incorrect: Uses rules of thumb without actual measurements violating NCI test-measure-diagnose approach for What
B. What is NCI system performance approach static pressure vs airflow? 350-400 CFM per ton target, measure static pressure budget, fan airflow table,
adjust speed tap ECM programming to achieve required CFM - detailed per National Comfort Institute NCI principles and performance-based
methodology
C. Incorrect: Focuses only on equipment efficiency ignoring distribution and building pressures per NCI, wrong for is
D. Incorrect: Suggests guessing charge or airflow without manometer and combustion analyzer, unsafe per NCI CO safety standards
Page 3 - NCI Practice 150Q 2026/2027
, CORRECT ANSWER: B. What is NCI system performance approach static pressure vs airflow? 350-400 CFM per ton target, measure static
pressure budget, fan airflow table, adjust speed tap ECM programming to achieve required CFM - detailed per National Comfort Institute NCI
principles and performance-based methodology
RATIONALE:
Rationale: What is NCI system performance approach static pressure vs airflow? 350-400 CFM per ton target, measure static pressure budget, fan airflow table, adjust
speed tap ECM programming to achieve required CFM - detailed per National Comfort Institute NCI principles and performance-based methodology. This aligns with NCI
performance-based contracting and air diagnostics methodology.
Question 6: Q6: How does NCI refrigeration side diagnostics differ from standard? Check airflow first TESP before refrigerant, then
superheat subcooling per manufacturer, non-invasive approach ensures correct charge after airflow verified
A. Incorrect: Uses rules of thumb without actual measurements violating NCI test-measure-diagnose approach for How
B. Incorrect: Focuses only on equipment efficiency ignoring distribution and building pressures per NCI, wrong for does
C. How does NCI refrigeration side diagnostics differ from standard? Check airflow first TESP before refrigerant, then superheat subcooling per
manufacturer, non-invasive approach ensures correct charge after airflow verified - detailed per National Comfort Institute NCI principles and
performance-based methodology
D. Incorrect: Suggests guessing charge or airflow without manometer and combustion analyzer, unsafe per NCI CO safety standards
CORRECT ANSWER: C. How does NCI refrigeration side diagnostics differ from standard? Check airflow first TESP before refrigerant, then
superheat subcooling per manufacturer, non-invasive approach ensures correct charge after airflow verified - detailed per National Comfort
Institute NCI principles and performance-based methodology
RATIONALE:
Rationale: How does NCI refrigeration side diagnostics differ from standard? Check airflow first TESP before refrigerant, then superheat subcooling per manufacturer,
non-invasive approach ensures correct charge after airflow verified - detailed per National Comfort Institute NCI principles and performance-based methodology. This
aligns with NCI performance-based contracting and air diagnostics methodology.
Question 7: Q7: What is NCI combustion safety CAZ worst-case testing? CAZ combustion appliance zone worst-case depressurization
all exhaust fans on doors closed, measure draft pressure and spillage, ensures safe venting
A. Incorrect: Uses rules of thumb without actual measurements violating NCI test-measure-diagnose approach for What
B. Incorrect: Focuses only on equipment efficiency ignoring distribution and building pressures per NCI, wrong for is
C. Incorrect: Suggests guessing charge or airflow without manometer and combustion analyzer, unsafe per NCI CO safety standards
D. What is NCI combustion safety CAZ worst-case testing? CAZ combustion appliance zone worst-case depressurization all exhaust fans on doors
closed, measure draft pressure and spillage, ensures safe venting - detailed per National Comfort Institute NCI principles and performance-based
methodology
CORRECT ANSWER: D. What is NCI combustion safety CAZ worst-case testing? CAZ combustion appliance zone worst-case depressurization
all exhaust fans on doors closed, measure draft pressure and spillage, ensures safe venting - detailed per National Comfort Institute NCI
principles and performance-based methodology
RATIONALE:
Rationale: What is NCI combustion safety CAZ worst-case testing? CAZ combustion appliance zone worst-case depressurization all exhaust fans on doors closed,
measure draft pressure and spillage, ensures safe venting - detailed per National Comfort Institute NCI principles and performance-based methodology. This aligns with
NCI performance-based contracting and air diagnostics methodology.
Question 8: Q8: Explain NCI psychrometrics and latent vs sensible capacity. Psychrometrics dry bulb wet bulb dew point relative
humidity, measure return and supply delta T 16-22F sensible, check latent removal via humidity drop
A. Explain NCI psychrometrics and latent vs sensible capacity. Psychrometrics dry bulb wet bulb dew point relative humidity, measure return and supply
delta T 16-22F sensible, check latent removal via humidity drop - detailed per National Comfort Institute NCI principles and performance-based
methodology
B. Incorrect: Uses rules of thumb without actual measurements violating NCI test-measure-diagnose approach for Explain
C. Incorrect: Focuses only on equipment efficiency ignoring distribution and building pressures per NCI, wrong for NCI
D. Incorrect: Suggests guessing charge or airflow without manometer and combustion analyzer, unsafe per NCI CO safety standards
CORRECT ANSWER: A. Explain NCI psychrometrics and latent vs sensible capacity. Psychrometrics dry bulb wet bulb dew point relative
humidity, measure return and supply delta T 16-22F sensible, check latent removal via humidity drop - detailed per National Comfort Institute
NCI principles and performance-based methodology
RATIONALE:
Rationale: Explain NCI psychrometrics and latent vs sensible capacity. Psychrometrics dry bulb wet bulb dew point relative humidity, measure return and supply delta T
16-22F sensible, check latent removal via humidity drop - detailed per National Comfort Institute NCI principles and performance-based methodology. This aligns with NCI
performance-based contracting and air diagnostics methodology.
Question 9: Q9: What NCI certifications exist? Airflow Testing and Diagnostics, Combustion Performance and CO Safety, System
Performance, Duct System Optimization, Hydronic Performance, Residential System Performance
A. Incorrect: Uses rules of thumb without actual measurements violating NCI test-measure-diagnose approach for What
B. What NCI certifications exist? Airflow Testing and Diagnostics, Combustion Performance and CO Safety, System Performance, Duct System
Optimization, Hydronic Performance, Residential System Performance - detailed per National Comfort Institute NCI principles and performance-based
methodology
C. Incorrect: Focuses only on equipment efficiency ignoring distribution and building pressures per NCI, wrong for NCI
D. Incorrect: Suggests guessing charge or airflow without manometer and combustion analyzer, unsafe per NCI CO safety standards
CORRECT ANSWER: B. What NCI certifications exist? Airflow Testing and Diagnostics, Combustion Performance and CO Safety, System
Performance, Duct System Optimization, Hydronic Performance, Residential System Performance - detailed per National Comfort Institute NCI
principles and performance-based methodology
RATIONALE:
Rationale: What NCI certifications exist? Airflow Testing and Diagnostics, Combustion Performance and CO Safety, System Performance, Duct System Optimization,
Hydronic Performance, Residential System Performance - detailed per National Comfort Institute NCI principles and performance-based methodology. This aligns with
Page 4 - NCI Practice 150Q 2026/2027
