Testing, Balancing, and Commissioning

Chapter Introduction

Commissioning a ventilation and air conditioning system is the final step that validates the design, installation, and operation of the entire system. For the journeyperson, this phase represents approximately 10 to 15% of the work hours on a commercial project. The Red Seal exam evaluates your ability to understand measurement principles, interpret results, and diagnose discrepancies. This chapter covers testing methods, measuring instruments, ventilation calculations, and applicable Canadian standards.

Fundamental Principles of Balancing

Objectives of Balancing

Balancing an air distribution system aims to adjust airflow rates at each diffuser, grille, or register to meet the specifications of the plans and specifications. A poorly balanced system results in overheated or undercooled zones, excessive energy consumption, and abnormal noise. Balancing is done in three steps: preparation, measurement, and adjustment.

Airflow: Volumetric flow rate (Q) is expressed in litres per second (L/s) or cubic metres per hour (m³/h). The fundamental relationship is:

Q = V × A

where V is the air velocity in metres per second (m/s) and A is the cross-sectional area of the duct in square metres (m²).

Types of Balancing

There are two main balancing methods:

Method	Principle	Advantages	Disadvantages
Proportional method	Adjust all dampers to the same proportion of opening, then measure and correct iteratively	Simple, fast for small systems	Less accurate for large networks
Ratio method	Measure the flow at each outlet, calculate the ratio of measured flow/required flow, adjust the most restrictive dampers first	Accurate, recommended for complex systems	More time-consuming, requires planning

The ratio method is the one recommended by the ASHRAE Handbook — HVAC Applications and is the most frequently tested on the exam.

Standard Balancing Procedure

15.Preliminary verification: Visually inspect all ducts, dampers, diffusers, and units. Ensure filters are clean and volume dampers are fully open.

16.Total flow measurement: Measure the flow at the air handling unit (AHU) outlet using a Pitot tube or anemometer.

17.Measurement at each outlet: Measure the flow at each diffuser or grille.

18.Calculate ratios: Divide the measured flow by the required flow for each outlet.

19.Adjustment: Partially close the dampers of outlets with a ratio greater than 1.0 (too much flow) to force air toward outlets with a ratio less than 1.0.

20.Repeat: Re-measure and adjust until all ratios are between 0.9 and 1.1 (±10% tolerance).

Measuring Instruments

Pitot Tube

The Pitot tube measures velocity pressure (Vp) which is the difference between total pressure (TP) and static pressure (SP). Air velocity is calculated by:

V = √(2 × Vp / ρ)

where ρ is the air density (approximately 1.204 kg/m³ at 20 °C and 101.325 kPa).

For standard air, the simplified formula is:

V = 1.291 × √Vp

with V in m/s and Vp in Pa.

Measurement procedure with the Pitot tube:

Insert the tube into the duct at a straight section of at least 7.5 diameters upstream and 2.5 diameters downstream of any disturbance.

Divide the duct cross-section into equal areas (traverse method). For a rectangular duct, divide into at least 16 equal areas. For a circular duct, use the concentric circle method (at least 10 points per diameter).

Measure the velocity pressure at each point and calculate the average.

Multiply the average velocity by the duct cross-sectional area to obtain the flow rate.

Vane Anemometer

The vane anemometer measures air velocity directly. It is used for measurements at diffuser and grille outlets. Accuracy is ±2 to ±5% depending on the model. The anemometer must be held perpendicular to the airflow and cover the entire outlet surface.

Manometer

The manometer (inclined tube, digital, or diaphragm type) measures static, total, and velocity pressures. Digital manometers are now the standard with an accuracy of ±0.5% of full scale.

Balometer (Flow Hood)

The balometer is a fabric cone that attaches to a diffuser or grille and channels the entire flow to an integrated anemometer. It provides a direct flow reading in L/s or m³/h. It is essential for accurate measurements at outlets.

Ventilation Calculations

Air Changes

The air change rate (ACH — Air Changes per Hour) is calculated:

ACH = (Q × 3600) / V

where Q is the airflow in m³/s and V is the room volume in m³.

Example: A classroom measuring 8 m × 6 m × 3 m (144 m³) requires an airflow of 400 L/s (0.4 m³/s). The air change rate is:

ACH = (0.4 × 3600) / 144 = 10 air changes per hour.

Ventilation Requirements According to the Code

The Canadian Electrical Code, Part I (CSA C22.1-21) does not directly address ventilation, but ventilation requirements are covered by the National Building Code of Canada (NBC) and CSA F326 (Residential ventilation). For commercial buildings, ASHRAE 62.1 is the reference standard, adopted by reference in the NBC.

Occupancy Type	Minimum Flow (L/s per person)	Minimum Flow (L/s per m²)
Offices	2.5	0.3
Classrooms	5.0	0.9
Restaurants	3.5	1.2
Meeting rooms	2.5	0.3
Commercial kitchens	—	7.5 (hood)

Duct Balancing

The pressure loss method (or static pressure method) is used to size volume dampers. Each damper creates a local pressure loss (ΔP) expressed in pascals (Pa). The relationship between flow and pressure loss is:

Q = K × √ΔP

where K is the damper flow coefficient (provided by the manufacturer).

This relationship is crucial: to double the flow, you must quadruple the pressure loss. Conversely, reducing the pressure loss by 25% reduces the flow by approximately 13%.

Pressure Measurements in Ducts

Static Pressure (SP)

Static pressure is the pressure exerted by the air on the duct walls, independent of its velocity. It is measured perpendicular to the airflow. In a ventilation system, static pressure is positive on the supply side and negative on the return side.

Total Pressure (TP)

Total pressure is the sum of static pressure and velocity pressure:

TP = SP + VP

Velocity Pressure (VP)

Velocity pressure represents the kinetic energy of moving air. It is always positive and is measured with the Pitot tube oriented facing the flow.

Pressure Relationships

Parameter	Symbol	Relationship	Unit
Static pressure	SP	TP − VP	Pa
Velocity pressure	VP	TP − SP	Pa
Total pressure	TP	SP + VP	Pa

Exam point: Velocity pressure is always positive. Static pressure can be negative (suction side of the fan). Total pressure can be negative if the negative static pressure is greater in magnitude than the velocity pressure.

Fan Performance

Fan Laws

The fan laws (affinity laws) allow prediction of fan behaviour when speed, diameter, or air density changes:

Parameter	Speed variation (N)	Diameter variation (D)
Flow (Q)	Q ∝ N	Q ∝ D³
Pressure (P)	P ∝ N²	P ∝ D²
Power (W)	W ∝ N³	W ∝ D⁵

Example: If fan speed increases by 10%, flow increases by 10%, pressure increases by 21% (1.1² = 1.21), and power increases by 33% (1.1³ = 1.331).

Characteristic Curves

A fan curve shows the relationship between flow (Q) and total pressure (TP) at constant speed. The operating point is the intersection of the fan curve with the system curve (network pressure loss).

Exam trap: If a damper is partially closed, the system curve becomes steeper, and the operating point moves toward a lower flow and higher pressure. The fan consumes less power (fan laws), but the flow decreases.

Commissioning

Definition and Scope

Commissioning is the documented process that verifies all systems operate in accordance with the owner's specifications and design documents. It includes:

77.Equipment verification: Verify that all equipment is installed according to the plans and specifications.

78.Performance tests: Measure flows, pressures, temperatures, and sound levels.

79.Adjustments: Adjust dampers, valves, pulleys, and controllers.

80.Documentation: Produce a complete commissioning report.

Commissioning Steps

82.Planning: Establish a commissioning plan (Cx Plan) that defines responsibilities, procedures, and acceptance criteria.

83.Pre-functional verification: Inspect equipment before start-up (electrical connections, fastenings, filters, belts).

84.Functional tests: Operate each piece of equipment individually and verify its performance.

85.Integrated tests: Verify the interaction between systems (e.g., control sequences, alarms).

86.Final report: Document all results, discrepancies, and corrections made.

Roles and Responsibilities

Stakeholder	Responsibilities
Owner	Define requirements, approve the Cx plan, accept the system
Designer	Prepare design documents, verify compliance
Contractor	Install equipment, correct deficiencies
Commissioning agent	Plan, coordinate, test, document
Balancing technician	Measure and adjust air and water flows

Applicable Standards and Codes

Canadian Standards

Standard	Title	Application
CSA F326	Residential ventilation	Ventilation requirements for houses
CSA C22.1	Canadian Electrical Code, Part I	Electrical safety of equipment
CSA B149.1	Natural gas and propane installation code	Ventilation of rooms containing gas appliances
CAN/CSA Z317.1	Ventilation of health care facilities	Specific requirements for hospitals

ASHRAE Standards Adopted by Reference

ASHRAE 62.1: Ventilation for acceptable indoor air quality.

ASHRAE 111: Practices for measurement, balancing, and adjustment of air distribution systems.

ASHRAE 55: Thermal environmental conditions for human occupancy.

Relevant Canadian Electrical Code Rules

The Canadian Electrical Code, Part I (C22.1-21) contains rules applicable to ventilation systems:

Rule 8-200: General requirements for motor circuits — each motor must have an overload protection device.

Rule 26-250: Motor overload protection — the device must be set at 125% of the full-load current for continuous-duty motors.

Rule 26-252: Motor overcurrent protection devices.

Exam point: During commissioning tests, verify that electrical protections match motor nameplate ratings. A fan motor drawing more current than its nameplate rating indicates a mechanical problem (over-tightened belt, defective bearing).

Temperature and Humidity Measurements

Psychrometrics

Psychrometrics is the study of the thermodynamic properties of moist air. The psychrometric chart is an essential tool for air conditioning system analysis.

Property	Symbol	Unit	Description
Dry-bulb temperature	DB	°C	Temperature measured by an ordinary thermometer
Wet-bulb temperature	WB	°C	Temperature measured by a thermometer whose bulb is wrapped in a wet wick
Relative humidity	RH	%	Ratio of water vapour pressure to saturation pressure
Absolute humidity	W	g/kg	Mass of water vapour per kilogram of dry air
Enthalpy	h	kJ/kg	Total heat content of moist air

Temperature Measurement

For commissioning tests, temperatures are measured with:

Thermocouples (types K, J, T): accurate to ±0.5 °C.

RTDs (resistance temperature detectors): accurate to ±0.1 °C.

Infrared thermometers: for surface measurements, accurate to ±1 °C.

Humidity Measurement

Relative humidity is measured with a psychrometer (two thermometers, dry and wet) or a capacitive hygrometer. The conversion formula is:

RH = (Pv / Psat) × 100

where Pv is the partial pressure of water vapour and Psat is the saturation pressure at the dry-bulb temperature.

Specific Performance Tests

Duct Leakage Test

The duct leakage test verifies that air leaks in ducts are within acceptable limits. The SMACNA (Sheet Metal and Air Conditioning Contractors' National Association) standard defines leakage classes:

Class	Maximum leakage (L/s per m² of duct surface)	Application
A	0.5	High-pressure ducts (> 1000 Pa)
B	1.5	Medium-pressure ducts (500-1000 Pa)
C	3.0	Low-pressure ducts (< 500 Pa)

Procedure: Seal all duct ends, pressurize to the service pressure, measure the leakage with a calibrated flow meter.

Terminal Velocity Test

Terminal velocity is the air velocity at a given distance from a diffuser. It is measured with a hot-wire anemometer. The recommended terminal velocity in the occupied zone is 0.15 to 0.25 m/s for comfort.

Noise Test

The sound level of a ventilation system is measured with a sound level meter in A-weighted decibels (dBA). Typical values:

Space Type	Maximum Level (dBA)
Hospital patient room	35
Private office	40
Classroom	40
Restaurant	50
Workshop	65

Power and Energy Calculations

Fan Power

The power absorbed by a fan is calculated:

P = (Q × TP) / (η × 1000)

where P is the power in kW, Q is the flow in m³/s, TP is the total pressure in Pa, and η is the overall fan efficiency (typically 0.5 to 0.7).

Example: A fan delivers 2.5 m³/s at a total pressure of 800 Pa with an efficiency of 0.6.

P = (2.5 × 800) / (0.6 × 1000) = 3.33 kW

Heating Power

The heating power required to raise the temperature of an airflow:

P = Q × ρ × cp × ΔT

where cp is the specific heat of air (1.006 kJ/kg·K) and ΔT is the temperature difference in K.

For standard air, the simplified formula:

P (kW) = Q (m³/s) × 1.21 × ΔT (°C)

Example: Heating 1.5 m³/s of air from −10 °C to 20 °C (ΔT = 30 °C):

P = 1.5 × 1.21 × 30 = 54.45 kW

Cooling Power

The cooling power of a cooling coil:

P (kW) = Q (m³/s) × 1.21 × ΔT (°C) + Q × 2500 × ΔW

where ΔW is the change in absolute humidity in kg/kg.

Pitfalls to Avoid

Measurement Errors

146.Measuring velocity less than 7.5 diameters from an elbow: Turbulence distorts readings. Always choose a straight section.

147.Using a vane anemometer in a high-velocity duct: The vane has inertia that distorts measurements above 15 m/s.

148.Ignoring air temperature: Air density varies with temperature and altitude. Correct measurements if the temperature deviates by more than 5 °C from 20 °C.

149.Not calibrating instruments: Instruments must be calibrated annually. An uncalibrated instrument gives false results with deceptive confidence.

Calculation Errors

151.Confusing static pressure and total pressure: Velocity pressure is always positive and adds to static pressure on the supply side.

152.Forgetting unit conversions: Flows are often given in L/s on plans, but power calculations require m³/s. 1 m³/s = 1000 L/s.

153.Applying fan laws without verifying conditions: The laws only apply if the system remains identical (same duct network).

154.Calculating flow with maximum velocity instead of average velocity: Always use the average of the traverse measurements.

Procedure Errors

156.Balancing before checking filters: Dirty filters reduce total flow and distort balancing.

157.Adjusting dampers without re-measuring: Each adjustment changes the flows at other outlets. Always re-measure after each adjustment.

158.Ignoring existing volume dampers: Do not fully close a volume damper without checking the downstream static pressure.

159.Not documenting final settings: Final damper positions must be marked and documented for future service work.

Exam-Specific Pitfalls

161.Question on the flow/pressure relationship: For a damper, if the flow must be reduced by 50%, the pressure loss must be reduced by 75% (because Q ∝ √ΔP).

162.Question on fan laws: If speed increases by 20%, power increases by 72.8% (1.2³ = 1.728).

163.Question on velocity pressure: Velocity pressure is measured with the Pitot tube oriented facing the flow, never perpendicular.

164.Question on balancing tolerance: The standard tolerance is ±10% of design flow for comfort systems.

Summary

Balancing ventilation systems is done using the ratio method, with a ±10% tolerance on flows.

The Pitot tube measures velocity pressure, which is converted to velocity by the formula V = 1.291 × √Vp.

Duct traverses must cover at least 16 points for rectangular ducts and 10 points per diameter for circular ducts.

Fan laws: flow ∝ N, pressure ∝ N², power ∝ N³.

Total pressure = static pressure + velocity pressure. Velocity pressure is always positive.

Commissioning includes pre-functional verification, functional tests, integrated tests, and documentation.

Applicable Canadian standards: CSA F326 (residential ventilation), CSA C22.1 (electrical), CSA B149.1 (gas).

Duct leakage testing uses SMACNA classes A, B, and C with maximum leakages of 0.5, 1.5, and 3.0 L/s per m².

Heating power is calculated: P (kW) = Q (m³/s) × 1.21 × ΔT (°C).

Instruments must be calibrated and measurements corrected for air temperature.

Pitfalls to Avoid (Reminder)

Pitfall	Consequence	Prevention
Measuring near an elbow	Reading distorted by turbulence	Choose a straight section (7.5 D upstream, 2.5 D downstream)
Using maximum velocity instead of average	Flow overestimated	Always calculate the average of traverses
Forgetting density correction	3 to 5% error per 10 °C deviation	Correct with the formula ρ = 1.204 × (293 / (273 + T))
Closing a damper without re-measuring	Imbalance at other outlets	Re-measure after each adjustment
Confusing L/s and m³/s units	Error by a factor of 1000	Verify units before any calculation
Applying fan laws to a modified system	Erroneous prediction	The laws only apply to an unchanged system
Ignoring negative static pressure on the suction side	Damage to flexible ducts	Check static pressure before securing flexible ducts

Final Exam Tips

179.Memorize the key formulas: Q = V × A, V = 1.291 × √Vp, P = Q × 1.21 × ΔT.

180.Understand the physical relationships: Don't just memorize formulas, understand why pressure varies with the square of velocity.

181.Know the reference values: Standard air density (1.204 kg/m³), specific heat (1.006 kJ/kg·K), balancing tolerance (±10%).

182.Identify keywords in questions: "proportional to the square," "directly proportional," "inversely proportional" — these terms indicate the expected mathematical relationship.

183.Practice unit conversions: L/s → m³/s (÷1000), Pa → kPa (÷1000), kW → W (×1000).

Mastery of balancing and commissioning distinguishes the competent journeyperson from the simple installer. These skills are directly assessed on the Red Seal exam and are essential in the daily practice of the pipefitting trade.

Testing, Balancing, and Commissioning