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SAIL SWITCHES
# Sail Switches - Airflow Proving Switches for HVAC Systems
Shop replacement sail switches (airflow proving switches) for furnaces, air handlers, and HVAC equipment. We stock paddle-type air switches for all major brands at our Westland, Michigan warehouse. Ensure adequate airflow before heating or cooling operations.
## Why Buy Sail Switches From Technical Hot & Cold?
**Complete Switch Selection**
Sail switches for furnaces, air handlers, and custom applications in various sizes and configurations.
**Quality Components**
Reliable switches from White-Rodgers, Honeywell, and OEM manufacturers. Proven designs for critical airflow proving.
**Same-Day Shipping**
Airflow switches in stock ship today when ordered before 3PM EST from our Westland warehouse.
**Application Assistance**
Sail switches must match airflow requirements. Our team helps ensure proper sizing and installation.
## What is a Sail Switch?
A sail switch (also called paddle switch or airflow switch) is a safety device that:
- Proves adequate airflow before operation
- Detects blower motor operation
- Prevents operation without airflow
- Protects heating/cooling equipment
- Interlock for safe operation
**Located:** In airstream, usually in supply plenum or duct
**Function:** Airflow proving and safety interlock
## How Sail Switches Work
**Mechanical Operation:**
1. **Blower Starts**
- Air begins flowing
- Moves through ductwork
2. **Air Hits Sail/Paddle**
- Lightweight plastic paddle
- Mounted on pivot
- In airstream
3. **Paddle Deflects**
- Air pressure pushes paddle
- Paddle rotates on hinge
- Moves switch actuator
4. **Switch Closes**
- Electrical contacts close
- Proves airflow present
- Allows next sequence step
5. **Airflow Stops**
- Paddle returns to rest
- Spring returns paddle
- Switch opens
- Interrupts circuit
**Adjustable Sensitivity:**
- Some switches adjustable
- Set minimum airflow required
- Tension spring adjustment
- Match to application
## Types of Sail Switches
### Normally Open (N.O.) Sail Switches
Closes when airflow present - most common.
**Operation:**
- Contacts open at rest (no air)
- Contacts close with airflow
- Proves blower running
- Standard configuration
**Applications:**
- Prove blower before heating
- Interlock for electric heat
- Furnace airflow proving
- Air handler sequencing
### Normally Closed (N.C.) Sail Switches
Opens when airflow present - less common.
**Operation:**
- Contacts closed at rest
- Contacts open with airflow
- Opposite function
- Special applications
**Applications:**
- Alarm circuits
- Shutdown on airflow loss
- Custom control sequences
### SPDT Sail Switches
Single pole, double throw - both N.O. and N.C.
**Features:**
- Common, N.O., and N.C. terminals
- Can use either function
- More flexible
- Premium option
**Applications:**
- Complex control sequences
- Multiple circuit control
- Commercial systems
### Adjustable Sail Switches
Variable sensitivity setting.
**Features:**
- Adjust spring tension
- Set minimum CFM trigger
- Fine-tune for application
- Screw adjustment
**Applications:**
- Variable airflow systems
- Custom installations
- Precise control needs
## Sail Switch Applications
### Furnace Airflow Proving
**Function:**
- Proves blower is running
- Before enabling heat
- Prevents overheating
- Required for electric heat strips
**Sequence:**
1. Thermostat calls for heat
2. Blower starts (G signal)
3. Air begins flowing
4. Sail switch closes
5. Proves airflow adequate
6. Allows heat to energize
7. Safe heating operation
### Electric Heat Interlocks
**Critical Application:**
- Electric heat strips generate intense heat
- MUST have airflow or overheat
- Sail switch is safety interlock
- Required by electrical code
**Protection:**
- Prevents strip damage
- Fire prevention
- Equipment protection
- Code compliance
### Air Handler Sequencing
**Commercial Applications:**
- Multiple stages of heat/cool
- Verify airflow each stage
- Sequence dampers
- Interlock controls
### Humidifier Control
**Function:**
- Proves airflow before water flow
- Prevents water without air
- Protects ductwork
- Ensures distribution
### Economizer Control
**Commercial HVAC:**
- Proves outdoor air damper open
- Minimum position sensing
- Mixed air control
- Energy management
## Sail Switch Specifications
### Physical Specifications:
**Paddle Size:**
- 2" x 3" (small)
- 3" x 5" (standard)
- 4" x 6" (large)
- Custom sizes available
**Mounting:**
- Through-duct mounting
- Mounting plate included
- Gasket for seal
- Various orientations
**Material:**
- Plastic paddle (lightweight)
- Metal housing
- Stainless hardware
### Electrical Specifications:
**Contact Rating:**
- 24V AC (low voltage typical)
- 0.5-3 amps typical
- Some rated for 120V
- Pilot duty rating
**Switch Type:**
- SPST-NO (most common)
- SPST-NC
- SPDT (both)
**Terminal Type:**
- Screw terminals
- Quick-disconnect
- Wire leads
### Airflow Specifications:
**Actuation Velocity:**
- 100-500 FPM typical
- Depends on paddle size
- Larger paddle = less velocity needed
- Adjustable on some models
**Differential:**
- Close at X FPM
- Open at X minus 50 FPM
- Prevents chattering
- Built-in hysteresis
## Sail Switch Installation
**Proper Installation is Critical:**
### Location Selection:
**Best Practices:**
- Install in supply plenum
- After blower, before heat
- Straight duct section (no elbows nearby)
- Perpendicular to airflow
- Accessible for service
**Avoid:**
- Near turns or elbows (turbulent air)
- Dead spots or low velocity areas
- Where paddle can't move freely
- Inaccessible locations
### Installation Steps:
1. **Select Location**
- Straight duct section
- Good airflow pattern
- Accessible
- After blower
2. **Cut Mounting Hole**
- Trace mounting plate
- Cut sheet metal carefully
- Deburr edges
- Clean area
3. **Install Switch**
- Insert through hole
- Position paddle in airstream
- Secure mounting plate
- Install gasket/seal
4. **Verify Free Movement**
- Paddle should move freely
- No binding or sticking
- Spring returns paddle
- Test manually
5. **Wire Connections**
- Run low-voltage wire
- Connect to control circuit
- Secure connections
- Protect wiring
6. **Test Operation**
- Turn on blower
- Verify paddle deflects
- Test switch continuity
- Confirm airflow volume adequate
### Paddle Orientation:
**Critical for Proper Operation:**
**Correct:**
- Paddle perpendicular to airflow
- Air hits paddle broadside
- Full deflection with airflow
- Smooth operation
**Incorrect:**
- Paddle parallel to airflow
- Air flows past paddle
- Won't actuate
- System won't operate
## Troubleshooting Sail Switches
### System Won't Heat/Cool:
**Check Sail Switch:**
1. **Verify Blower Running**
- Is air flowing?
- Blower motor operating?
- Check at registers
2. **Check Paddle Movement**
- Turn on blower
- Watch paddle
- Should deflect with airflow
- Returns when blower stops
3. **Test Switch Electrically**
- Power off
- Remove one wire
- Test continuity
- Should close with paddle deflected
- Should open with paddle at rest
4. **Check Wiring**
- Connections tight?
- Wires damaged?
- Circuit complete?
### Intermittent Operation:
**Possible Causes:**
- Insufficient airflow
- Dirty filter restricting
- Weak blower motor
- Paddle binding
- Loose connections
- Switch contacts dirty
### Paddle Won't Move:
**Inspect For:**
- Debris blocking paddle
- Frozen/stuck pivot
- Bent paddle
- Wrong orientation
- Insufficient airflow
### Switch Won't Close:
**Check:**
- Adequate airflow velocity
- Paddle deflecting fully
- Switch adjustment (if adjustable)
- Bad switch mechanism
- Corroded contacts
## Sail Switch Maintenance
**Annual Inspection:**
- Check paddle for damage
- Verify free movement
- Test switch operation
- Clean if needed
- Check wire connections
**Preventive:**
- Keep ductwork clean
- Change filters regularly
- Ensure adequate airflow
- Address issues promptly
**Cleaning:**
- Power off first
- Remove dust from paddle
- Don't use lubricants
- Check pivot for freedom
- Test after cleaning
## Common Problems & Solutions
**Problem: Electric heat won't come on**
- Check sail switch operation
- Verify airflow adequate
- Test switch continuity
- Check wiring
**Problem: Paddle stuck**
- Debris blocking movement
- Frozen pivot
- Bent paddle
- Clean or replace
**Problem: Paddle moves but switch doesn't close**
- Bad switch contacts
- Adjustment needed (if adjustable)
- Switch worn out
- Replace switch
**Problem: Nuisance trips (opens during operation)**
- Insufficient airflow
- Dirty filter
- Weak blower
- Check system restrictions
## Sail Switch FAQs
**Q: What is a sail switch used for?**
A: Proves adequate airflow before allowing heating or cooling. Safety interlock that protects equipment and ensures proper operation.
**Q: Can I bypass the sail switch?**
A: Not recommended. Sail switches are safety devices. Bypassing can cause:
- Overheating
- Equipment damage
- Fire hazard (especially with electric heat)
- Code violations
**Q: How much airflow triggers a sail switch?**
A: Typically 100-500 FPM (feet per minute) depending on paddle size. Larger paddles need less velocity to actuate.
**Q: Why won't my sail switch close?**
A: Common causes:
- Insufficient airflow
- Dirty filter
- Weak blower
- Paddle stuck or binding
- Bad switch
- Wrong installation orientation
**Q: Can I adjust a sail switch?**
A: Some models are adjustable. Can set spring tension to require more or less airflow. Not all switches adjustable.
**Q: What size paddle do I need?**
A: Depends on duct size and airflow:
- Small ducts/high velocity: Small paddle
- Large ducts/low velocity: Large paddle
- Match to application
**Q: How do I test a sail switch?**
A:
1. Turn on blower
2. Verify paddle deflects
3. Test continuity with meter
4. Should show closed circuit with airflow
5. Should open when blower stops
**Q: Can sail switches fail?**
A: Yes. Common failures:
- Worn contacts
- Broken paddle
- Stuck pivot
- Corroded housing
- Typically last 10-15 years
**Q: Do I need a sail switch?**
A: Required for:
- Electric heat applications
- Many furnace sequences
- Code compliance in some areas
- Safety interlocks
**Q: Where should I install a sail switch?**
A:
- Supply plenum preferred
- Straight duct section
- After blower, before heat
- Perpendicular to airflow
- Accessible location
## Selecting the Right Sail Switch
**Considerations:**
1. **Duct Size**
- Larger ducts need larger paddles
- Or need more sensitive switch
2. **Airflow Velocity**
- Calculate CFM / duct area = FPM
- Match switch to velocity
3. **Application**
- Heat interlock = normally open
- Alarm circuit = normally closed
- Complex = SPDT
4. **Adjustability**
- Fixed switches are cheaper
- Adjustable more flexible
- Match to needs
5. **Quality**
- OEM switches for exact replacement
- Quality aftermarket for reliability
- Avoid cheap imports
## For HVAC Contractors
**Stock Common Types:**
- Standard 3"x5" N.O. switches
- Adjustable switches
- Various paddle sizes
- SPDT for flexibility
**Installation Tips:**
- Straight duct mandatory
- Test before final connection
- Educate customers on function
- Document installation
## Need Help Selecting a Sail Switch?
Our HVAC parts specialists are here to help! Contact us:
- **Phone:** [Your phone number]
- **Email:** [Your email]
- **Hours:** [Your business hours]
- **Location:** Westland, MI - Local pickup available
**Let us help you select the right sail switch for your application. Provide duct size and airflow information for best recommendation!**
Can't find what you're looking for?
If you don't see your model or part, call us! Our friendly technicians are standing by. We can help you find the part you need with guaranteed fitment. Speak with us today at (734) 326-3900.
