FAQ Coverage Gaps¶
Concepts from the learning graph whose exact label (allowing plurals and hyphen/space variants) does not appear in any FAQ question or answer. 291 of 581 concepts are listed here; 290 (49.9%) are covered. Priority uses the Concept Impact Score (CIS) from learning-graph.json: High is CIS 20 or more, Medium is 5 to 19, Low is under 5. Every listed concept is taught in the chapter shown.
Concepts marked (variant wording) are already answered in the FAQ under different words (for example "Top Horizontal" rather than "Top Horizontal Discharge"); they need only a terminology touch, not a new question.
Critical Gaps (High Priority)¶
| # | Concept | CIS | Direct dependents | Chapter | Suggested question |
|---|---|---|---|---|---|
| 1 | Viewed From Drive Side (variant wording) | 111 | 3 | Chapter 12 | — |
| 2 | Reading a Performance Table (variant wording) | 58 | 3 | Chapter 26 | — |
| 3 | Stuffing Box Seal (variant wording) | 48 | 1 | Chapter 16 | — |
| 4 | Motor Base | 43 | 7 | Chapter 14 | How is a motor base chosen for a belt-driven fan? |
| 5 | Impeller Blade (variant wording) | 26 | 8 | Chapter 8 | — |
| 6 | Motor Efficiency Class | 26 | 1 | Chapter 14 | What do TCF's Standard and Premium motor efficiency classes mean? |
| 7 | Catalog Structure | 26 | 3 | Chapter 26 | How is a Twin City Fan product catalog organized? |
| 8 | ODP Motor (variant wording) | 25 | 1 | Chapter 14 | — |
| 9 | TEFC Motor (variant wording) | 25 | 1 | Chapter 14 | — |
| 10 | Severe Duty Motor (variant wording) | 25 | 1 | Chapter 15 | — |
| 11 | Hazardous Location Motor | 25 | 1 | Chapter 15 | When does a fan need a hazardous location motor? |
| 12 | Premium Efficiency Motor (variant wording) | 25 | 1 | Chapter 15 | — |
| 13 | Fan Pedestal | 24 | 7 | Chapter 17 | What does a fan pedestal do, and when is a separated or bolt-on pedestal used? |
| 14 | Arrangement 8 | 23 | 1 | Chapter 24 | When is Arrangement 8 chosen over Arrangement 1 or 4? |
| 15 | Arrangement 1P Plug | 23 | 1 | Chapter 24 | When should a plug fan be pedestal mounted (1P, 4P, 8P or 9P)? |
| 16 | Arrangement 4P Plug | 22 | 1 | Chapter 24 | (same question as 1P) |
| 17 | Lab Exhaust Arrangements | 22 | 1 | Chapter 11 | Which arrangements are used for laboratory exhaust fans? |
| 18 | Bearings Out of Airstream (variant wording) | 22 | 1 | Chapter 11 | — |
| 19 | Up Blast Discharge Position (variant wording) | 22 | 1 | Chapter 12 | — |
| 20 | Top Horizontal Discharge (variant wording) | 22 | 1 | Chapter 12 | — |
| 21 | Bottom Horizontal Discharge (variant wording) | 22 | 1 | Chapter 12 | — |
| 22 | Down Blast Discharge Position (variant wording) | 22 | 1 | Chapter 12 | — |
| 23 | Arrangement 8P and 9P Plug | 22 | 1 | Chapter 24 | (same question as 1P) |
| 24 | Fan Family Selection | 21 | 2 | Chapter 26 | How do I choose the fan family before the size? |
| 25 | Motor Positions W X Y Z (variant wording) | 20 | 1 | Chapter 12 | — |
| 26 | Class Shading in Tables (variant wording) | 20 | 1 | Chapter 26 | — |
Medium Priority Gaps¶
| # | Concept | CIS | Chapter | Category |
|---|---|---|---|---|
| 1 | Motor Position Restrictions | 19 | 13 | ROT |
| 2 | Housing Drain | 17 | 20 | SPEC |
| 3 | Product Options | 17 | 26 | CAT |
| 4 | Bearing Vibration Sensor | 16 | 16 | BRG |
| 5 | Inlet Silencer | 16 | 18 | INOUT |
| 6 | Outlet Silencer | 16 | 18 | INOUT |
| 7 | Axial and Inline Arrangements | 15 | 11 | ARR |
| 8 | Spark Resistant Type A | 15 | 21 | SPEC |
| 9 | Spark Resistant Type B | 14 | 21 | SPEC |
| 10 | RTO Service Conditions | 14 | 21 | SPEC |
| 11 | Material Specifications Table | 13 | 26 | CAT |
| 12 | AMCA Certified Ratings | 12 | 26 | CAT |
| 13 | Impeller Hub | 9 | 8 | IMP |
| 14 | Fan Selector Software | 8 | 26 | CAT |
| 15 | Dimensional Data Table | 8 | 27 | CAT |
| 16 | Bearing Lubrication | 7 | 16 | BRG |
| 17 | Detached Inlet Box | 7 | 18 | INOUT |
| 18 | Companion Flange | 7 | 18 | INOUT |
| 19 | Speed Change Calculation | 7 | 25 | PERF |
| 20 | Octave Band Sound Data | 7 | 27 | CAT |
| 21 | Swingout Fan | 6 | 24 | ARR |
| 22 | Bearing Seal | 6 | 16 | BRG |
| 23 | Altitude Correction | 6 | 10 | PERF |
| 24 | Pressure Blower | 5 | 6 | FAM |
| 25 | Impeller Orientation | 5 | 8 | IMP |
| 26 | Plenum Fan Arrangements | 5 | 11 | ARR |
| 27 | Angular Discharge | 5 | 12 | ROT |
| 28 | Inline Configuration | 5 | 12 | ROT |
| 29 | NEMA Frame Size | 5 | 14 | MOT |
| 30 | Motor Positioner | 5 | 15 | MOT |
| 31 | Pillow Block Bearing | 5 | 16 | BRG |
Low Priority Gaps¶
234 leaf or near-leaf concepts (CIS under 5), listed by chapter. Most are specific parts, product lines or arrangement variants that a reader reaches through the chapter rather than a FAQ.
- Chapter 2: Airflow Continuity Equation, Pressure Rise, Velocity Pressure Equation
- Chapter 3: Bolted Housing, Stack Cap, Welded Housing
- Chapter 4: Panel Fan, Ring Fan, Roof Mounted Axial Fan, Wall Mounted Fan, Weatherhood
- Chapter 5: Cabinet Ventilator, Centrifugal Wall Exhauster, Fiberglass Fan, Gravity Relief Ventilator, Hooded Roof Exhauster, Kitchen Exhaust Fan, Louvered Roof Exhauster, Low Profile Roof Ventilator, Mancooler, Smoke and Heat Exhaust Fan, Square Inline Centrifugal Fan
- Chapter 6: Air Kit, Filtered Supply Fan, Inline Lab Exhaust Fan, Lab Exhaust Total Flow, Paint Booth Exhaust Fan, Plume Dilution, Roof Mounted Panel Fan
- Chapter 7: Belt Guard, Belt Tube, Cast Housing, Curb Cap, Discharge Cone, Horizontal Split Housing, Housing Access Panel, Housing Framing, Insulation Plug, Nozzle and Windband, Pie Split Housing, Roof Exhauster Shroud, Three-Way Split Housing
- Chapter 8: Back Plate Fins, Blade Leading Edge, Fiberglass Axial Impeller, Fixed Pitch Impeller, Impeller Back Plate, Impeller Shroud
- Chapter 9: Axial Blade Count, Axial Blade Tip, Blade Pitch Angle, Fiberglass Hub, Impeller Airflow Path, Impeller End Ring, Impeller Gusset, Impeller Tie Rod, Impeller Width, Material Handling Impeller, Open Radial Paddle Impeller, Paper Handling Impeller, Setback Outlet Flange
- Chapter 10: Blade Pass Frequency, Fan Outlet Area, Sone Rating
- Chapter 11: Arrangement 2, Arrangement 3 SI and DI, Arrangement 7, Motor Support Base, Vertical Arrangement
- Chapter 12: Axial Motor Positions, Bottom Angular Up Discharge, Top Angular Down Discharge, Top Angular Up Discharge
- Chapter 13: Axial Fan Configuration, Axial Rotation Convention, Bottom Angular Down Discharge, DWDI Discharge Limits, Inline Horizontal Configuration, Inline Vertical Configuration, Plenum Motor Positions, Vertical Inline Motor Location
- Chapter 14: C-Face Motor Mount, Foot Mounted Motor, K Mount Motor, Motor Base Saddle, TEAO Motor, TENV Motor
- Chapter 15: Bi-Directional Positioner, Motor Temperature Rise, Motor Thermal Protection, Motor Voltage and Phase, Motor Winding RTD, Pivot Motor Base, Post Mount Motor Base, Synchronous Motor Speed, Tri-Directional Positioner, Vertical Jack Screws
- Chapter 16: Bearing Positioner, Bearing RTD and Thermocouple, Clad Shaft, Flange Mount Bearing, Friction Shaft Seal, Lip Shaft Seal, Restrained Bearing, Set Screw Mount, Shaft Locking Collar, Shaft Turndown, Two-Bearing Housing
- Chapter 17: Adapter Sleeve Mount, Bearing Dowel Pins, Bearing Seal Speed Limit, Bolt-On Pedestal, Concentric Bearing Mount, Grease Fitting, Keystock, L-50 Bearing Life, Labyrinth Seal, Non-Drive End Bearing, Oil Mist Lubrication, Shaft and Coupling Guards, Solid Pillow Block Bearing, Split Pillow Block Bearing, Static Oil Lubrication, Taconite Seal, Totally Split Roller Bearing, Two and Four Hole Mount
- Chapter 18: Butterfly Gravity Damper, Damper and Vane Bearings, External Inlet Vanes, Transition Piece, Wiper Bar
- Chapter 19: ASA Pipe Flange Bolt Pattern, Airfoil Blade Damper, Blast Gate, Bolt-On Inlet Box, Bolted Flange Connection, Ceiling Type Gravity Damper, Damper Throttling, Flat Blade Damper, Flexible Connector, Free-Standing Inlet Box, Inlet Box Horn, Inlet Venturi, Lab Exhaust Bypass Damper, Lab Exhaust Isolation Damper, Nested Inlet Vanes, Slide Gate Damper, Slip Connection, Tube Adapter and Sleeve, Wall Type Gravity Damper
- Chapter 20: Corten Steel, Fan Grounding Device, Forged Shaft, Insulated Inlet Box, Insulated Jacket, Shaft Material Grades, Spark Resistant Type C, Stainless Steel Construction
- Chapter 21: Aluminum Clad Construction, Axial High Temperature Package, Buffer Strip, Continuous Seal Weld, Fan Leakage, High Expansion Bearing, Insulation Pins, Recess Cone, Thermal Expansion
- Chapter 22: Inlet Box Mounting Planes, Isolator Mounting Method, Neoprene Isolation Pad, Seismic Restraint, Weather Cover, Zero Speed Switch
- Chapter 23: Airflow Measurement, Ceiling Hung Isolation, Direct Mounted Isolators, Floor Mounted Isolation, Housed Spring Isolator, Isolation Rails, Isolator Mounting Angle, Open Spring Isolator, Pressure Transmitter, Restrained Spring Isolator, Seismic Spring Isolator, Shaft and Coupling Alignment, Snubber, Thrust Restraint
- Chapter 24: Arrangement 3F, Arrangement 4CS and 9CS, Arrangement 4S Swingout, Arrangement 4SO and 9SO, Arrangement 4VI and 4HI, Arrangement 7SI and 7DI, Arrangement 9H, Arrangement 9ST and 9SS, Clamshell Fan, Double Door Clamshell, Inline Motor Positions A to H, Motor Positions L and R, Plenum Arrangement 3SM, Plenum Arrangement 4V, Plenum Arrangements 3HS and 3HA, Plenum Arrangements 3VA and 3VS, Standard Motor Position Rule, Swingout Door Assembly, Swingout Motor Position Rule
- Chapter 25: Fan Power Equation, Flow Control Efficiency, Inlet System Effect, Outlet System Effect, Pressure Varies as Speed Squared, Shutoff Pressure, Size Change Calculation, System Effect Curve
- Chapter 26: AMCA 204 Balance Grade, Air Change Method, Appurtenance Effects, Catalog Operating Limits, FanPedia vs Current Catalog, First Critical Speed, Minimum Conveying Velocity, Performance Table Header, Technical Description
- Chapter 27: Annotated Fan Drawing, Application Requirements, Capstone Fan Specification, Cold Start Motor Sizing, Efficiency Requirements, Noise Limits, Selection Trade-Offs, Space Constraints, Specification Performance Clause, Specification Review, Submittal Data
Recommendations¶
- Add questions for the 11 high-priority gaps not already answered under variant wording, starting with the motor topics (motor base, motor efficiency class, hazardous location motor), catalog structure, fan family selection and the pedestal plug arrangements.
- Touch up wording in existing answers for the high-priority (variant wording) concepts so their exact glossary labels appear; this alone moves strict coverage above 50%.
- Consider questions for the 31 medium-priority concepts in a later revision, grouped by chapter so each new question covers several.
- Leave the low-priority concepts to the chapters and the glossary unless learner questions show demand.