Raspberry Pi 4 Thermal Management

Cooling solutions and thermal guidelines for RPi 4 routing platforms

Raspberry Pi 4 Thermal Management

The Raspberry Pi 4 requires active cooling for reliable 24/7 router operation. This guide covers thermal characteristics, cooling solutions, and best practices for your RPi4 deployment.

Why Cooling Matters for RPi4

Power Output

The RPi4 generates significantly more heat than earlier models:

Idle/Light Load: 3-5W (minimal cooling needed)
Typical Router Load: 12-15W (active cooling recommended)
Peak Performance: 18-20W with all features (active cooling required)
TDP: 15W thermal design power

This continuous heat generation demands active cooling for 24/7 operation.

Operating Temperature Range

Optimal Performance:

Target Range: 40-60°C
Characteristics: Maximum CPU speed, no throttling, silent operation
Result: Best routing performance and packet throughput

Acceptable Range:

Range: 60-75°C
Characteristics: Full performance, no throttling yet
Action: Monitor temperature, ensure adequate ventilation

Warning Range:

Range: 75-80°C
Characteristics: Approaching throttling point
Action: Improve cooling immediately, check fan operation

Critical Range:

Range: 80-85°C
Characteristics: Throttling active, reduced performance
Action: Stop normal operation, add/improve cooling

Emergency Shutdown:

At: 85°C
Effect: Automatic system shutdown to prevent damage
Result: Network goes offline until cooled

Thermal Characteristics of RPi4

Heat Sources

The BCM2711 SoC generates the majority of heat in four components:

CPU Cores (largest heat source - 60% of total)
- Draws 5-12W at full load
- Concentrated in small die area (~40mm²)
- Difficult to cool passively
GPU (secondary - 20% of heat)
- Draws 1-3W at typical load
- Lower power than CPU but always active
- Handles video output and offload operations
Memory (LPDDR4) (10% of heat)
- Draws 1-2W
- Distributed across two chips
- Less critical for cooling design
Voltage Regulators (10% of heat)
- Power conversion losses
- Typically <1W waste heat
- Minor contribution

Heatspreader

The RPi4 includes an integrated aluminum heatspreader:

Material: Aluminum passive interface
Direct Contact: Thermally bonded to CPU and memory
Effect: Improves passive heat dissipation by 5-10°C
Limitations: Without active cooling, still throttles under load

The heatspreader alone cannot sustain 24/7 routing. Additional cooling is necessary.

Passive Cooling (Not Recommended for RPi4)

Large Heatsink Configuration

Some users attempt passive cooling with large heatsinks:

Performance:

Idle: 35-40°C (excellent)
Light Load: 50-55°C (good)
Typical Routing: 70-80°C (throttling risk)
Peak Load: 80-85°C (definite throttling)

Verdict: Passive cooling is marginal for RPi4 router applications. May work in cool environments but cannot be relied upon for 24/7 operation.

Tower Coolers with Heat Pipes

Large tower coolers (60-80mm height) offer better passive performance:

Performance:

Idle: 35-45°C (very good)
Light Load: 50-60°C (good)
Typical Routing: 65-75°C (acceptable, edge of throttling)
Peak Load: 75-82°C (occasional throttling)

Verdict: Tower coolers can work but still pose throttling risk under continuous load.

When Passive Might Be Acceptable

Passive cooling can be considered only if:

Network is in cool climate (<20°C ambient)
Router load is light (< 8 devices, <50 Mbps)
No VPN or advanced features enabled
Willing to risk occasional throttling
Temperature monitoring in place

Better approach: Add a small 5V fan for reliability.

Active Cooling (Recommended)

Active cooling with a fan is the recommended solution for RPi4 routers.

Small 30mm Fan

Most Popular Configuration:

Size: 30mm x 30mm x 10mm
Voltage: 5V DC (powered via GPIO pins 2,4 GND)
Current: 150-300 mA
Air Flow: 2-3 CFM
Noise: 20-30 dB at full speed

Performance with 30mm Fan:

Idle: 30-35°C (excellent, fan may not run)
Light Load: 40-45°C (excellent)
Typical Routing: 50-60°C (optimal performance)
Peak Load: 60-70°C (comfortable range)
Sustained: No throttling

Benefits:

Compact form factor
Affordable ($5-15)
Can control speed via PWM
Fits in most cases
Minimal noise at low speeds

Limitations:

Limited air volume
Requires PWM control to minimize noise
Can be audible at full speed
May need additional heatsink

40mm Fan

Balanced Performance and Noise:

Size: 40mm x 40mm x 20mm
Voltage: 5V DC
Current: 200-400 mA
Air Flow: 5-8 CFM
Noise: 15-25 dB (larger fans run quieter)

Performance with 40mm Fan:

Idle: 28-33°C (excellent)
Light Load: 35-40°C (excellent)
Typical Routing: 45-55°C (optimal performance)
Peak Load: 55-65°C (comfortable)
Sustained: No throttling

Benefits:

Quieter operation (larger displacement)
Better heat transfer
Slower fan speeds possible
Professional appearance in case
More reliability

Limitations:

Larger form factor
Slightly higher cost ($8-20)
More power draw
Requires suitable case

Case with Integrated Cooler

Purpose-Built Solutions:

Several cases include built-in fan systems:

Argon ONE M.2 ($40-60):

Integrated 92mm fan
M.2 SSD slot
Professional aluminum construction
PWM fan with thermal control
Power button and safe shutdown
Performance: 40-50°C at typical load

GeeekPi ICE Tower Cooler ($20-30):

Dual-fan tower design
RGB lighting (optional)
Large heatsink surface
Excellent cooling capacity
Performance: 35-45°C at typical load

Official Raspberry Pi Case (if available):

Factory-optimized design
Proper ventilation ports
Fan mounting points
Recommended compatibility
Performance: 50-60°C depending on model

Cooling Solution Recommendations

For Small Home Networks

Configuration: RPi 4 2GB, <100 devices, <500 Mbps

Recommendation: 30mm fan + moderate heatsink

Setup: Case with fan mounting, aluminum heatsink
Cost: $15-25 total
Temperature: 50-60°C typical
Performance: Reliable, no throttling
Noise: Minimal (PWM controlled)

For Advanced Home Networks

Configuration: RPi 4 4GB, 100-300 devices, 500+ Mbps

Recommendation: 40mm fan or case with cooler

Setup: Quality case with integrated fan
Cost: $25-40 (case with cooler)
Temperature: 45-55°C typical
Performance: Excellent, full gigabit
Noise: 15-20 dB at typical speed

For Small Business Deployments

Configuration: RPi 4 4GB or 8GB, 200-500 devices, gigabit

Recommendation: Professional cooler with temperature monitoring

Setup: Argon ONE M.2 or equivalent with monitoring
Cost: $40-70
Temperature: 40-50°C typical
Performance: Optimal, room for growth
Monitoring: Temperature alerts and logging
Scalability: Can handle sustained peak loads

Installation and Setup

30mm Fan Installation

Materials Needed:

30mm PWM fan
Thermal paste (small amount)
Double-sided thermal tape or hot glue
GPIO jumper wires (optional, if PWM control desired)

Steps:

Clean the heatspreader:
```
# Power off the Pi
sudo shutdown -h now
```
- Remove any dust or old thermal material
- Use isopropyl alcohol (90%+) and lint-free cloth
- Let dry completely (1-2 minutes)
Apply thermal interface:
- Place small amount of thermal paste on CPU
- Spread thin, even layer (~0.5mm)
- Cover entire exposed CPU area
- Avoid excess (can impede heat transfer)
Mount heatsink (optional):
- Paste aluminum heatsink over CPU
- Firm, even pressure
- Secure with thermal tape or mounting bracket
- Ensure good contact
Mount fan:
- Position above/near heatspreader
- Direct airflow across heatsink
- Secure with double-sided thermal tape or zip ties
- Ensure fan blades clear of obstructions
Connect fan power (if PWM control):
- Red wire → Pin 2 or 4 (5V)
- Black wire → Pin 6, 9, 14, 20, or 25 (GND)
- Yellow wire → GPIO pin (PWM pin 12, 13, 18, or 19)
- Verify polarity before power-on

Test:

# After booting, check temperature
vcgencmd measure_temp
# Should read lower than before

Case with Integrated Cooler Installation

Steps vary by case, but general process:

Power down the Pi:
```
sudo shutdown -h now
```
Prepare Pi:
- Remove microSD if case design requires it
- Ensure GPIO header is unobstructed
Install according to case instructions:
- Usually involves sliding Pi into internal mounting bracket
- Screw down retention points
- Ensure thermal pads contact CPU
Connect fan power (if required):
- Follow case instructions for fan connector
- Typical: JST or similar micro-connector
- Verify correct polarity
Install HAT/cooling module:
- Align with GPIO header
- Press down firmly
- Secure with provided screws if needed
Close case:
- Ensure ventilation ports are unobstructed
- Power on and test

Temperature Monitoring

Check Current Temperature

From Command Line:

# Single measurement
vcgencmd measure_temp

# Output example:
# temp=52.3'C

Continuous Monitoring:

# Update every second
watch -n 1 vcgencmd measure_temp

# Press Ctrl+C to stop

Via Web UI:

Most router management interfaces display current temperature
Check Pimeleon dashboard or system monitoring page

Temperature Ranges

Normal Operation:

35-50°C: Excellent - optimal performance
50-65°C: Normal - good operating range
65-75°C: Warm - acceptable but monitor

Action Required:

75-80°C: Hot - improve cooling soon
80°C+: Critical - throttling active, stop non-critical services

Long-Term Monitoring

Script for Logging:

#!/bin/bash
# Save to /root/temp-monitor.sh

while true; do
    TEMP=$(vcgencmd measure_temp | cut -d '=' -f 2)
    TIMESTAMP=$(date '+%Y-%m-%d %H:%M:%S')
    echo "$TIMESTAMP: $TEMP" >> /var/log/rpi-temperature.log
    sleep 60
done

Add to cron for automatic logging:

# As root, edit crontab
sudo crontab -e

# Add this line:
@reboot /root/temp-monitor.sh > /dev/null 2>&1 &

Environmental Factors

Location Selection

Good Locations:

Well-ventilated area
Cool room (ambient <25°C)
Away from heat sources
Adequate airflow around router
Not enclosed (or with ventilation)

Poor Locations:

Enclosed cabinets without airflow
Near heating vents or radiators
Direct sunlight (especially south-facing)
On top of other hot equipment (modems, switches)
Poorly ventilated closets

Seasonal Considerations

Summer/Hot Weather (Ambient 25-35°C):

Temperatures rise 10-15°C compared to typical
May require upgraded cooling
Monitor more frequently
Consider active cooling if using passive

Winter/Cold Weather (Ambient 5-15°C):

Temperatures naturally lower
Passive cooling more effective
Can reduce fan speed if PWM controlled
Optimal conditions for performance testing

Ventilation

Case Ventilation:

Ensure intake and exhaust ports are open
Keep dust filters clean
Remove intake obstructions
Allow 2-3 inches clearance on all sides

Room Air Flow:

Router should not be in dead air pocket
Place away from room corners
Avoid stacking equipment on top
Keep area free of clutter

Troubleshooting Overheating

Symptoms of Excessive Heat

Performance Issues:

Slower web browsing (throttled CPU)
Increased latency in ping
Dropped connections
Service timeouts or crashes
VPN throughput reduced

System Behavior:

Random reboots
Kernel panics in logs
High CPU usage from thermal throttling
Shutdown without warning (emergency thermal shutdown)

Diagnostic Steps

Check current temperature:
```
vcgencmd measure_temp
```
- If > 80°C, throttling is likely active
- If > 85°C, emergency shutdown will trigger

Check temperature history:

# View log if you're logging temperatures
tail -20 /var/log/rpi-temperature.log

# Check kernel logs for throttling
journalctl -u thermald | tail -20

Verify fan operation (if applicable):

# Check if fan GPIO is being controlled
# Example for GPIO pin 12 (PWM):
cat /sys/class/pwm/pwmchip0/pwm0/duty_cycle

Check CPU frequency (if throttled):

# View current CPU frequency
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq

# Compare to max frequency
cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq

# If significantly lower, throttling is active

Immediate Cooling Solutions

Quick Fixes (for emergency):

Add desk fan: Point room fan at router
Remove case: Expose heatspreader to room air
Reduce load: Stop non-critical services
Move location: To cooler room or area
Open ventilation: If in cabinet, open doors

Short-Term Solutions:

Add room air conditioning
Install temporary 5V fan
Reduce ambient temperature
Limit concurrent connections
Disable advanced features

Permanent Solutions:

Install proper heatsink
Add or upgrade fan
Replace case with ventilated model
Upgrade to case with integrated cooler
Move to cooler location
Improve room ventilation

Performance Impact of Temperature

Clock Speed Throttling

When temperature reaches 80°C:

CPU Clock Reduction: Decreases from 1.5-1.8 GHz to ~1.0 GHz
Performance Loss: 40-50% reduction
Routing Throughput: Drops from 900+ Mbps to 400-500 Mbps
VPN Performance: Severely reduced
Recovery: Returns to full speed when cooled below 75°C

Throttling Prevention

Maintain temperature below 75°C to:

Prevent thermal throttling
Maintain full performance
Ensure reliable 24/7 operation
Extend hardware lifespan

Best Practices

Immediate Setup

When first deploying:

Install cooling solution immediately (don't wait)
Monitor temperature for first week
Verify no throttling under normal load
Document baseline temperatures
Plan for upgrades if needed

Ongoing Maintenance

Monthly:

Check temperature readings
Clean dust from heatsink/fan
Verify fan operation (if applicable)
Check for obstructions

Quarterly (every 3 months):

Deep clean cooling components
Check thermal paste condition (if using one)
Verify fan bearings (if applicable)
Test under peak load

Annually:

Replace fan if bearing noise detected
Inspect for corrosion or damage
Reapply thermal paste if temperatures rising
Update cooling firmware if applicable

Performance Optimization

To maintain cool operation:

Run 64-bit OS (better compiler optimizations)
Update to latest firmware
Use optimized router software
Enable CPU frequency scaling
Limit non-essential services

Cooling Solution Comparison

Solution	Cost	Performance	Noise	Space	Maintenance
No cooling	$0	Poor (throttles)	N/A	Minimal	None
Heatsink only	$5-10	Marginal	None	Small	Dust cleaning
30mm fan	$15-25	Good	20-30dB	Compact	Fan cleaning
40mm fan	$25-35	Very Good	15-20dB	Moderate	Fan cleaning
Tower cooler	$30-40	Excellent	18-25dB	Large	Fan cleaning
Case w/ cooler	$35-60	Excellent	15-20dB	Moderate	Intake filter

RPi 4 Hardware Platform - Full hardware overview
RPi 4 Specifications - Detailed technical specs
Cooling Solutions - How cooling works
Cases - Cooling-compatible case options