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SEQUENCERS

# Sequencers - Electric Heat Time-Delay Sequencers

Shop replacement sequencers for electric furnaces, electric heat strips, and heat pump auxiliary heat. We stock time-delay sequencers in all configurations at our Westland, Michigan warehouse. Stage electric heating elements safely and efficiently.

## Why Buy Sequencers From Technical Hot & Cold?

**Complete Sequencer Selection**
Single-stage to multi-stage sequencers for residential and commercial electric heating systems.

**Quality Brands**
White-Rodgers, Mars, Packard, and OEM sequencers. Reliable operation for years of service.

**Same-Day Shipping**
Sequencers in stock ship today when ordered before 3PM EST from our Westland warehouse.

**Expert Sequencer Sizing**
Multiple configurations available. Our team helps match the right sequencer to your heating system.

## What is a Sequencer?

A sequencer is a time-delay control device that:
- Stages electric heating elements on/off
- Prevents all elements from starting simultaneously
- Reduces electrical demand and inrush current
- Protects breakers from tripping
- Extends contactor life
- Required for most electric heat applications

**Located:** Inside electric furnace or air handler control panel
**Function:** Timed staging of electric heat elements

## How Sequencers Work

**Mechanical-Thermal Operation:**

### Basic Operation:

1. **Thermostat Calls for Heat**
   - 24V signal to sequencer
   - Heat sequencer bimetal strip

2. **Bimetal Strip Heats**
   - Small heater element energized
   - Heats bimetal strip
   - Strip bends with heat

3. **First Contact Closes** (after time delay)
   - Usually 30-90 seconds
   - Energizes first heat strip
   - Heat begins

4. **Second Contact Closes** (if multi-stage)
   - Additional time delay
   - 30-90 seconds after first
   - Energizes second heat strip

5. **Additional Stages** (if equipped)
   - Continue in sequence
   - Each with time delay
   - Full heat achieved gradually

6. **Thermostat Satisfied**
   - Removes 24V signal
   - Heater cools
   - Bimetal strip cools
   - Contacts open in reverse order
   - Time delay on closing helps too

### Time Delay Benefits:

**Prevents:**
- Breaker trips from high inrush
- Voltage sag in building
- Rapid cycling
- Contactor wear
- Dimming lights

**Provides:**
- Smooth power draw
- Gradual heat-up
- Extended equipment life
- Code compliance

## Types of Sequencers

### Single-Stage Sequencers
Controls one heating element.

**Features:**
- One set of contacts (SPST)
- Simple time delay
- 30-90 second typical
- Basic applications

**Applications:**
- Small electric furnaces
- Single heat strip
- Supplemental heat
- Simple systems

**Common Uses:**
- 5-10 kW furnaces
- Heat pump auxiliary
- Space heaters

### Two-Stage Sequencers
Controls two heating elements independently.

**Features:**
- Two sets of contacts
- Each with own time delay
- Staggered closing
- Most common type

**Applications:**
- 10-20 kW electric furnaces
- Two heat strips
- Standard residential
- Heat pumps

**Typical Timing:**
- Stage 1: 30-45 seconds
- Stage 2: 60-90 seconds total
- Gradual heat-up

### Three-Stage Sequencers
Controls three heating elements.

**Features:**
- Three sets of contacts
- Individual time delays
- Sequential closing
- Larger systems

**Applications:**
- 15-25 kW furnaces
- Three heat strips
- Larger homes
- Commercial light

**Typical Timing:**
- Stage 1: 30 seconds
- Stage 2: 60 seconds
- Stage 3: 90-120 seconds

### Four-Stage Sequencers
Controls four heating elements - commercial applications.

**Features:**
- Four sets of contacts
- Independent delays
- Maximum staging
- Heavy-duty

**Applications:**
- 20+ kW systems
- Commercial buildings
- Large residences
- Custom applications

### Fan Control Sequencers
Include fan relay in addition to heat staging.

**Features:**
- Heat staging contacts
- Plus fan relay
- Integrated control
- Simplified wiring

**Function:**
- Start fan before heat
- Keep fan running after heat
- Single control device
- Convenient

## Sequencer Specifications

### Electrical Ratings:

**Heater Coil:**
- 24V AC (most common)
- Some 120V or 240V

**Contact Rating:**
- 20-30 amps per contact typical
- Must handle heat strip load
- Resistive load rating
- Pilot duty or full load

**Contacts:**
- SPST per stage
- Normally open
- Close with heat/time
- Heavy-duty silver

### Timing Specifications:

**On-Delay:**
- 30-90 seconds typical
- Fixed or adjustable
- Cumulative for multiple stages
- Consistent timing

**Off-Delay:**
- Usually faster than on
- Immediate to 30 seconds
- Heat removal
- System dependent

**Differential:**
- Prevents rapid cycling
- Built-in hysteresis
- Smooth operation

### Physical Specifications:

**Mounting:**
- Screw mount to panel
- Standard hole spacing
- Vertical or horizontal
- Temperature considerations

**Terminals:**
- Screw terminals typical
- 1/4" quick-disconnect
- Clearly labeled
- Easy wiring

## Selecting the Right Sequencer

### Determine Requirements:

1. **Number of Heat Strips**
   - Count heating elements
   - One contact per strip
   - Match sequencer stages

2. **Heat Strip Amperage**
   - Each strip amp rating
   - Contact must handle load
   - Add safety margin
   - Usually 20-30A contacts sufficient

3. **Control Voltage**
   - Usually 24V
   - Match thermostat voltage
   - Verify system voltage

4. **Timing Needs**
   - Standard timing usually fine
   - Adjustable if specific needs
   - Consider system size

5. **Fan Control**
   - Integrated fan relay?
   - Or separate fan control?
   - Check wiring diagram

### Replacement Selection:

**OEM Replacement:**
- Exact match to original
- Same configuration
- Guaranteed fit
- Part number match

**Universal Replacement:**
- Multi-stage adjustable
- Flexible configuration
- May need wiring changes
- Cost-effective

## Common Sequencer Problems

### Heat Strips Don't Come On:

**Check Sequencer:**

1. **Power to Coil**
   - Verify 24V at heater terminals
   - No voltage = wiring problem
   - Has voltage = test sequencer

2. **Coil Continuity**
   - Power off
   - Test heater coil resistance
   - Should show 100-500 ohms typical
   - Infinite = open coil, bad sequencer

3. **Contacts**
   - Apply 24V to coil
   - Wait for time delay
   - Test contacts for closure
   - No closure = bad sequencer

### Only Some Heat Strips Work:

**Possible Causes:**
- Some sequencer contacts bad
- Wiring to strips
- Breakers tripped
- Failed heat strips themselves

**Test Each Stage:**
- Apply power
- Wait for each delay period
- Test each contact set
- Identify failed stage

### Breaker Trips Immediately:

**Not Sequencer Issue:**
- Shorted heat strip
- Shorted wiring
- Wrong breaker size
- Damaged component

**But Check:**
- Sequencer staging properly?
- Time delays working?
- All at once would trip breaker
- Sequencer may be stuck

### Heat Won't Turn Off:

**Stuck Sequencer:**
- Contacts welded closed
- Overheated bimetal
- Mechanical failure
- Replace sequencer

**Other Causes:**
- Thermostat stuck calling
- Wiring short
- Control board issue

## Sequencer Installation

**Safety First:**
1. Turn off all power - BOTH 24V and high voltage
2. Verify no voltage at sequencer and heat strips  
3. Use proper electrical safety procedures

**Replacement Steps:**

1. **Document Existing Wiring**
   - Photo all connections
   - Label every wire
   - Note wire colors
   - Draw diagram if helpful

2. **Disconnect Power**
   - Turn off breakers
   - 24V and high voltage
   - Verify no voltage
   - Wait 5 minutes

3. **Remove Old Sequencer**
   - Disconnect low-voltage wires (24V)
   - Disconnect line voltage wires (careful!)
   - Remove mounting screws
   - Extract sequencer

4. **Compare New to Old**
   - Same number of stages?
   - Same terminal configuration?
   - Physical size fits?
   - Mounting holes align?

5. **Install New Sequencer**
   - Mount in same location
   - Secure with screws
   - Proper orientation
   - Good ventilation

6. **Connect Low Voltage (24V)**
   - Match wire positions
   - Heater coil terminals
   - Usually two wires
   - Polarity doesn't matter

7. **Connect Line Voltage**
   - EXTREME CAUTION - high voltage!
   - Match each heat strip circuit
   - Line in/load out per stage
   - Secure all connections
   - Use wire nuts
   - Double-check

8. **Verify All Connections**
   - All wires secure
   - Proper terminals
   - No bare wire exposed
   - Compare to photos

9. **Test Operation**
   - Restore power
   - Call for heat
   - Time each stage
   - Verify all strips energize
   - Check amp draw
   - Monitor several cycles

## Wiring Basics

### Typical Sequencer Wiring:

**Low Voltage Side:**
- R - 24V hot from transformer
- W - Heating call from thermostat
- (Sometimes labeled H1, H2, etc.)

**Line Voltage Side (per stage):**
- L1 in - Line voltage in
- T1 out - Load (heat strip) out
- Repeats for each stage

**Color Codes:**
- Red - Hot (line)
- White - Heat strip load
- Black - Hot
- Blue - Common (sometimes)

**⚠️ VERIFY with wiring diagram!**
- Every system different
- Follow manufacturer diagram
- Take photos before disconnecting

## Common Installation Mistakes

❌ **Wrong Voltage Connections**
- Mixing 24V and 120V/240V
- Can destroy sequencer
- Can cause short circuit
- Verify all connections

❌ **Incorrect Staging**
- Strips wired to wrong stage
- Timing sequence wrong
- May overload single stage
- Follow diagram

❌ **Undersized Contacts**
- Sequencer amp rating too low
- Contacts can't handle load
- Premature failure
- Check ratings

❌ **Poor Ventilation**
- Sequencer needs air circulation
- Gets hot during operation
- Enclosed = overheating
- Shorten life

❌ **Loose Connections**
- High current connections critical
- Arcing can occur
- Heat and failure
- Tighten all connections

## Sequencer Maintenance

**Annual Inspection:**
- Visual inspection for heat damage
- Check all connections tight
- Listen for proper operation
- Time the staging
- Check for arcing/burning

**Signs of Failure:**
- Burned/discolored housing
- Smell of burning
- Erratic operation
- Failed stages
- Excessive noise

**Preventive Replacement:**
- Every 10-15 years
- During heat strip replacement
- If showing signs of wear
- Inexpensive vs. downtime

## Adjustable Sequencers

**Some Sequencers Adjustable:**

**Adjustment Features:**
- Variable time delay
- Turn screw to adjust
- Increase or decrease delay
- Match to application

**When to Adjust:**
- Breaker trips on startup
- Need longer staging delay
- Short cycling issues
- Custom applications

**How to Adjust:**
- Usually small screw adjustment
- Turn clockwise = longer delay
- Turn counter-clockwise = shorter delay
- Test and fine-tune

## Sequencer FAQs

**Q: What does a sequencer do?**
A: Stages electric heating elements on/off with time delays. Prevents all elements from starting at once, reducing electrical demand and preventing breaker trips.

**Q: How long should sequencer delays be?**
A: Typically 30-90 seconds between stages. Exact timing depends on system size and electrical service.

**Q: Can I bypass a sequencer?**
A: Not recommended. Would cause:
- Breaker trips
- Voltage sag
- Reduced equipment life
- Code violations
Sequencers are required for staged electric heat.

**Q: Why does my sequencer click?**
A: Normal. You hear contacts closing as bimetal heats and bends. Should hear sequential clicking as each stage energizes.

**Q: How do I test a sequencer?**
A: 
1. Apply 24V to coil
2. Wait for time delay
3. Test each contact for closure
4. Should close in sequence
5. Remove voltage, contacts should open

**Q: Why won't my sequencer close?**
A: Possible causes:
- No 24V to coil
- Bad heater coil
- Mechanical failure
- Stuck bimetal
- Replace sequencer

**Q: Can I use a 2-stage sequencer for 3 heat strips?**
A: Not ideal. Last strip wouldn't be controlled. Need 3-stage sequencer for 3 strips.

**Q: What causes sequencers to fail?**
A: Common causes:
- Age (10-15 years typical life)
- Overheating from poor ventilation
- Excessive cycling
- High current through contacts
- Manufacturing defect

**Q: Do sequencers work on gas furnaces?**
A: No. Sequencers are for electric heat only. Gas furnaces use different controls.

**Q: Can a bad sequencer trip my breaker?**
A: If contacts stick closed on all stages, multiple heat strips energize at once, potentially tripping breaker.

## Troubleshooting Quick Reference

| Symptom | Possible Cause | Solution |
|---------|---------------|----------|
| No heat | No power to sequencer | Check 24V supply |
| Only one stage works | Failed contact | Replace sequencer |
| All stages on at once | Stuck contacts | Replace sequencer |
| Breaker trips | All strips on together | Check sequencer timing |
| Delayed heat | Normal operation | No action if timing OK |
| Won't turn off | Welded contacts | Replace sequencer |

## For HVAC Contractors

**Stock Common Configs:**
- 2-stage sequencers (most common)
- 3-stage sequencers
- Fan-controlled sequencers
- Universal adjustable

**Installation Tips:**
- Photo everything first
- Label all wires clearly
- Test before closing panel
- Document timing
- Educate customer on delays

**Upsell Opportunity:**
- Replace during heat strip replacement
- Preventive replacement at 10+ years
- Upgrade to fan-controlled

## Need Help Selecting a Sequencer?

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

**Provide: Number of heat strips, amp rating of each, and control voltage. We'll match you with the perfect sequencer!**

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.

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