Furnace Field Guide

Select all that apply — each selection unlocks the relevant section below.

CONTROLS & SAFETY DEVICES

• Check Operation of Thermostat

  Set thermostat to HEAT, raise setpoint above current room temp. Verify system responds (inducer starts → ignition → blower). Check thermostat wiring (R, C, W, G) — confirm no loose/corroded terminals. Confirm FAN switch in AUTO. Advise customer on proper thermostat use.

  Thermostat Model

  ConditionGoodFairReplace
• Check Operation of Safety Limit Controls

  Test high limit switch continuity (must be closed at ambient temp). Test rollout switch(es) continuity. Test door interlock switch. Verify all safety devices are in-circuit — NEVER bypass. Review board fault history for any stored limit trips.

  High LimitPassedFailed — ReplacedFailed — Advise

  Rollout SwitchPassedFailed — ReplacedTripped — Reset

  Door InterlockPassedFailed — Replaced

BLOWER & MOTOR

• Remove and Clean Motor and Blower Assembly

  Remove blower assembly from furnace. Clean all blower wheel blades with brush and vacuum — buildup causes imbalance, noise, and reduced airflow. Inspect blades for damage or bending. Check setscrew on wheel hub — must be tight. Inspect motor bearings (spin freely, no grinding). Lubricate oil ports if accessible (3–5 drops SAE 10 non-detergent oil only). Inspect capacitor for bulging or leakage.

  Blower ConditionGood — CleanedDirty — CleanedDamaged — Advise

  Capacitor µF Rating

  Capacitor Tested µF

  Cap StatusWithin SpecLow — ReplacedFail — Replaced
• Check Motor Amperage — Blower Motor

  With blower running at heating speed, clamp ammeter around one motor lead. Compare to nameplate FLA (Full Load Amps). Reading above FLA = motor overloading (check capacitor, airflow, bearings). ECM motors: check module connector condition.

  Nameplate FLA (A)

  Measured Amps (A)

  Amperage StatusNormalHigh — InvestigateLow — Investigate
• Check Operation of Combustion Blower (Inducer)

  Observe inducer motor startup — should start within 30 sec of heat call. Listen for unusual noise (bearing squeal, rattling). Inspect inducer wheel through inlet — check for buildup or debris. Check pressure switch hose(s) for cracks, kinks, moisture. Check inducer capacitor if separate.

  Nameplate FLA (A)

  Measured Amps (A)

  Inducer ConditionGoodNoisy — AdviseFailed — Replaced

COMBUSTION SYSTEM

• Clean Burners and Visually Set for Proper Combustion and Ignition

  Remove burner assembly. Clean ports with compressed air and soft brush. Inspect for rust, cracks, or blocked orifices. Reinstall and align to manufacturer spec. Observe flame through sight glass — flames must be blue and steady. Yellow tips = insufficient air or dirty burners. Lifting/floating flame = too much air or low gas pressure. Inspect and clean flame sensor rod (use fine steel wool). Inspect ignitor — check for cracks (HSI). Check ignitor resistance.

  Burner ConditionGoodCleanedCorroded — Advise

  Flame ColourBlue / NormalYellow TipsOrange/Red

  Flame Sensor µA

  Ignitor ConditionGoodCracked — ReplacedWorn — Replaced
• Check Gas Pilot Safety System — Flame Sensor

  Verify flame sensor rod is properly positioned in the flame path. Measure µA signal during operation (2–6 µA normal; below 1 µA replace). Check sensor wire insulation — must not contact any metal panels. Confirm sensor mounting screw is tight. On older standing pilot units — inspect thermocouple or thermopile condition.

  Sensor µA (live)

  Sensor ActionCleaned OnlyCleaned + Reading OKReplaced

HEAT EXCHANGER (TSSA CRITICAL INSPECTION)

• Inspect Heat Exchanger — Visual + Operational Test

  Use flashlight and mirror or borescope — inspect all accessible heat exchanger surfaces for cracks, holes, rust-through, or unusual discoloration. While system is running with blower operating, hold a smoke pencil or lighted incense at the heat exchanger seams/joints — if the flame or smoke pulses, deflects toward, or is drawn in → CRACKED HEAT EXCHANGER. Also check for soot or CO around joints. ⚠️ TSSA REQUIREMENT: A cracked or failed heat exchanger must be red-tagged. The unit must NOT be returned to service — risk of carbon monoxide poisoning to occupants.

  Heat Exchanger StatusVisually IntactMinor Rust — MonitorCrack Suspected — TestCRACKED — RED TAG

  Inspection Method UsedFlashlight + MirrorBorescopeSmoke/Incense TestCO Test at HX

  🚨RED TAG REQUIRED — CRACKED HEAT EXCHANGER: Shut down the unit immediately. Do not return to service. Advise customer in writing. Issue a TSSA permanent red tag. CO poisoning risk to occupants is immediate. Document findings and notify customer of legal requirement to repair or replace before operation.

VENTING SYSTEM

• Examine Vent Connector

  Inspect all vent connector sections from furnace to chimney/wall penetration. All joints must be mechanically secure (screws or approved fasteners). Check for rust, corrosion, holes, or sagging. Verify slope is upward toward chimney (minimum ¼" per foot). No horizontal runs exceeding 75% of vertical rise. Type B double-wall must be used for Category I appliances — check classification on unit data plate.

  Vent Connector ConditionGoodRust — MonitorDamaged — ReplacedImproper — Corrected

  Vent TypeType B Double-WallSingle-Wall MetalPVC (High-Efficiency)CPVC
• Inspect Venting System (Full Flue Path)

  Trace entire venting path from furnace to termination. Check chimney liner condition (if applicable). For PVC high-efficiency: inspect both intake and exhaust pipes — no cracks, joints must be cemented. Confirm proper pitch on condensing exhaust (slope back toward furnace). Verify no vent pipe passes through living space without proper clearances (per B149.1 Natural Gas Code).

  Venting System StatusGoodMinor Issues — CorrectedBlocked — ClearedRequires Repair — Advise
• Check Vent Termination

  Inspect outdoor vent termination (or chimney cap). Must be free of debris, bird/insect nests, ice, or snow blockage. High-efficiency: check both intake and exhaust terminations — they must be separated per manufacturer spec (typically 12"+ apart, 12" minimum above expected snow line). Confirm no exhaust re-ingestion into intake. Verify termination clearances from windows, doors, meters, and grade (per B149.1 and manufacturer).

  Termination ConditionGood — ClearCleared of DebrisBlocked — ClearedImproper Location

GAS SYSTEM

• Visual Check of Gas Piping to Furnace

  Inspect all gas piping visible at the furnace — from the meter/supply to the gas valve. Look for corrosion, physical damage, improper joints, or flexible connectors passing through panels (not permitted per code). Confirm manual shutoff valve is accessible and operational. Apply approved leak detection solution to all joints — verify no bubbles. CSST (corrugated stainless) must be bonded per Ontario Electrical Safety Code.

  Gas Piping ConditionGood — No LeaksMinor Corrosion — MonitorLeak Found — RepairedImproper Install — Advise

  CSST Present?NoYes — BondedYes — Not Bonded — Advise
• Check Gas Pressure at Furnace — Manifold Pressure

  With furnace firing: connect manometer to gas valve test port (manifold side). Natural Gas manifold: typically 3.5" W.C. (±0.3" W.C.). Propane: typically 10" W.C. Incoming supply pressure (inlet tap): NG 7–10" W.C., LP 11"+ W.C. Low supply pressure = call gas company. High manifold pressure = adjust regulator. Document both readings. Consult unit data plate for model-specific pressures.

  Inlet Supply Pressure ("W.C.)

  Manifold Pressure ("W.C.)

  Spec Manifold Pressure

  Pressure StatusWithin SpecAdjusted — Now OKLow — Gas Company CalledHigh — Adjusted
• Check Pressure Switches and Power Vent System

  Test pressure switch function — briefly block hose during startup (with caution) to confirm inducer proves draft and switch closes. Check pressure switch hoses for cracks, moisture, or disconnection. Verify inducer amperage is within spec. On high-efficiency: test secondary condensate pressure switch if present.

  Pressure Switch TestPassedIntermittent — MonitorFailed — Replaced

AIR FILTER & CUSTOMER EDUCATION

• Check Air Filter — Inspect, Replace, and Educate Customer

  Inspect filter condition (record above in job info). Replace if dirty. Install with airflow arrows pointing toward furnace. Verify no air bypass around filter frame. TSSA/SAFETY INSTRUCTION TO CUSTOMER: The furnace MUST be turned off at the service switch (or thermostat to OFF) before changing the air filter. Explain location of service switch. Explain how to correctly size and install the filter. Recommend filter change every 1–3 months depending on use. Confirm customer understands this instruction.

  Filter Replaced?YesNo — Still CleanCustomer Declined

  Customer Educated?Yes — ConfirmedNot Home — Left Note

CARBON MONOXIDE TEST — TSSA REQUIREMENT

• Perform Carbon Monoxide Test

  REQUIRED under G2 service standards: Test CO levels at two points: (1) At the duct/supply air plenum — insert probe into duct. (2) At the vent termination/flue. Normal CO in flue gases: <200 ppm air-free CO is generally acceptable in combustion gases. Supply duct CO above 10–35 ppm = serious concern (possible cracked heat exchanger). Ambient room CO above 35 ppm = DANGER — RED TAG and evacuate. Always cross-reference with Heat Exchanger inspection findings.

  CO — Supply Duct (ppm)

  CO — Vent Termination (ppm)

  CO — Ambient Room (ppm)

  CO StatusAll NormalElevated — MonitorHIGH — RED TAG REQUIRED

  🚨ELEVATED CO — IMMEDIATE ACTION: Shut down the furnace immediately. Ventilate the home. Advise occupants to leave if ambient CO is elevated. Issue a TSSA red tag. Do NOT restart the unit until the source is found and corrected. CO poisoning can be fatal. Call TSSA if required by regional protocol.

CONDENSATE SYSTEM (HIGH-EFFICIENCY UNITS)

• Check Condition of Condensate Line and Flush

  Inspect condensate drain line and trap for blockage, kinks, or algae growth. Disconnect and flush with clean water. Verify trap is installed correctly (maintains water seal). Confirm drain has a positive slope toward discharge. Check condensate pump (if present) — fill with water and verify pump activates. A blocked condensate drain causes pressure switch trips or flooding.

  Condensate Line StatusN/A — Standard Eff.Clear — FlushedBlocked — ClearedPump OKPump Failed — Replaced

TEMPERATURE RISE & ELECTRICAL MEASUREMENTS

• Record Temperature Rise, Voltage & Manifold Pressure

  Temperature Rise (Delta T) = Supply Air Temp minus Return Air Temp. Compare to nameplate range (typically 35°F–65°F / 20°C–36°C). HIGH Delta T = restricted airflow. LOW Delta T = combustion issue or excessive airflow. Check unit data plate for exact allowable range.

  Supply Air Temp (°C/°F)

  Return Air Temp (°C/°F)

  Δ T (Auto-Calculated)

  —

  Nameplate Δ T Range

  High Voltage (VAC)

  Low Voltage (VAC)

  Manifold Pressure ("W.C.)

FINAL SYSTEM TEST

• Complete Full System Operation Test — 2–3 Cycles

  Restore all panels (door switches must engage). Restore gas and power. Run system through 2–3 complete heating cycles. Verify: inducer starts → ignitor glows → burners ignite → flame proves → blower starts on schedule → system shuts off cleanly at setpoint → blower continues to post-purge then stops. Check board for any new fault codes after cycling. Confirm no unusual noises, odours, or CO alarms.

  Cycle Test ResultPassed — 2 CyclesPassed — 3 CyclesIssue Found — See Notes
• Verify CO Detector Present and Functional in Home

  Per TSSA requirements: confirm a working CO alarm is installed on every level of the home with a sleeping area, and within 5 metres of each sleeping area. If absent → advise customer in writing. This is a legal requirement in Ontario under the Fire Code. If CO alarm is expired (typical life: 5–7 years) → advise replacement.

  CO Detector Present?Yes — FunctioningYes — Expired — AdvisedNo — Customer Advised in Writing

PRE-INSTALLATION

• Verify unit is correct model, size (BTU), and fuel type for the application

  Confirm BTU output matches heat loss calculation or existing unit spec. Confirm voltage (120V single phase), fuel type, and efficiency rating are appropriate. Check clearances to combustibles are achievable at this location (from unit installation manual).
• Inspect and prepare installation location

  Verify floor or platform is level and rated for unit weight. Check existing ductwork condition — repair/seal any existing leaks before connecting. Confirm access space for future service is adequate.
• Combustion air supply confirmed

  Verify adequate combustion air supply to the mechanical room (per B149.1 — typically 1 sq in free area per 1,000 BTU/hr). For sealed combustion / direct vent: confirm dedicated intake piping to outdoors.

GAS PIPING

• Gas supply line size confirmed adequate for BTU load

  Verify pipe sizing per B149.1 pipe sizing tables. Size must account for total BTU load, pipe length, and number of fittings.
• All gas connections made with approved materials — leak tested

  Use only approved gas pipe, fittings, and thread sealant (rated for gas service). No flexible connectors passing through cabinet. Test ALL joints with approved leak detection solution — zero bubbles permitted. Conduct pressure test if required by AHJ.
• Manual shutoff valve installed and accessible within 1.8m of unit

  Confirm accessible shutoff valve is present on the gas supply within reach of the appliance. Valve must be upstream of the flex connector (if used). Confirm valve is operational.
• Gas pressure verified at unit — manifold pressure set and recorded

  Check supply and manifold pressures per maintenance checklist process. Adjust if required.

  Supply Pressure ("W.C.)

  Manifold Pressure ("W.C.)

VENTING (B149.1 COMPLIANCE)

• Vent material type confirmed correct for unit category

  Category I (≤83% AFUE, negative pressure): Type B double-wall vent. Category IV (90%+ AFUE, positive pressure, condensing): manufacturer-approved PVC or CPVC only. Never mix materials without engineering approval.
• Vent termination location compliant with B149.1

  Minimum clearances from: windows/doors (18" recommended, 12" minimum), gas meters (3 feet), electrical equipment, grade (12" minimum, 18"+ in snow regions), adjacent walls. Intake and exhaust separated per manufacturer spec. No termination in walkways, garages, or areas with vehicle exhaust.
• All vent joints secured and sealed per manufacturer specs

  PVC: primer and cement applied per manufacturer. Metal: minimum 3 screws per joint. All joints confirmed before startup — no loose connections inside or outside.
• Vent slope correct — condensate drain path confirmed

  Condensing unit exhaust vent must slope back toward furnace (or to condensate drain). Verify condensate trap is installed, connected, and drains freely to approved location.

ELECTRICAL & CONTROLS

• Dedicated 120V/15A circuit confirmed — correct polarity verified

  Measure voltage at furnace disconnect: should be 120V AC ±10%. Verify polarity with multimeter (hot/neutral/ground). REVERSED POLARITY causes flame sensor faults and board faults. Confirm proper grounding — essential for flame sensing function.

  Supply Voltage (VAC)

  Polarity OK?Yes — CorrectNo — Corrected
• Thermostat wiring connected and tested

  Connect R, C, W, G, Y wires per thermostat wiring diagram. Verify 24V AC across R–C terminals. Test each function (heat, fan, cool if applicable). Confirm C-wire is connected for smart thermostat compatibility.
• Service switch installed within sight of unit

  A service disconnect switch must be within sight of the appliance (typically the gray SSU switch on or near the unit). Confirm proper labelling.

DUCTWORK & AIRFLOW

• Supply and return duct connections sealed — no air leaks

  Seal all duct connections at furnace with HVAC foil tape and/or mastic. Check for air bypass around air handler cabinet. Verify return air path is adequate for the unit's airflow rating.
• Filter in place — correct size and MERV rating

  Install appropriately sized filter. MERV 8–11 recommended for most residential applications. Higher MERV filters can restrict airflow — confirm blower performance is acceptable.

COMMISSIONING & SAFETY VERIFICATION

• Complete startup — verify full sequence of operations

  Run through complete startup sequence: inducer → pressure switch proving → ignition → flame proving → blower. Run 3 complete cycles. Monitor for any fault codes, unusual noises, or combustion issues.
• Temperature rise within nameplate range — recorded

  Measure and record supply and return temps after 5+ minutes of operation.

  Supply Air Temp

  Return Air Temp

  Delta T
• CO test performed — readings within safe levels

  Perform CO test as per maintenance checklist. Document all readings.

  CO Duct (ppm)

  CO Vent Term. (ppm)

  CO Ambient (ppm)
• Customer walkthrough — filter, thermostat, shutoff valve, emergency steps

  Show customer: (1) How to change the filter safely (unit OFF). (2) How to operate the thermostat. (3) Location of the gas shutoff valve. (4) What to do if they smell gas (leave, call gas company, do not use electrical switches). (5) Confirm CO detector location. Provide owner's manual.

STEP 1 — THERMOSTAT

Select the noise type:

Which safety tripped? (Check board LED flash code — compare to Section 02 error code table):

TSSA SAFETY TAG — UNIT STATUS