Figure 2 CCA conductivity vs temperature relationship
4. Insulation Options
4.1 Insulation Materials
Insulation
Max Temp
Application
PVC
105°C
Low-temp zones
XLPE
125°C
Standard underhood
TPE
125°C
Flexible
Silicone
150°C
High-temp
ETFE
150°C
Premium
FEP
200°C
Extreme
4.2 Insulation Selection
Zone
Recommended Insulation
Away from heat
XLPE, TPE
Standard underhood
XLPE, ETFE
Near exhaust
Silicone, FEP
4.3 Wire Standards
Standard
Temp Rating
ISO 6722 Class B
100°C
ISO 6722 Class C
125°C
ISO 6722 Class D
150°C
5. Design Guidelines
5.1 Routing
Guideline
Purpose
Route away from heat
Reduce exposure
Use heat shields
Protect wiring
Allow air flow
Cooling
Avoid contact with hot surfaces
Prevent damage
5.2 Protection
Method
Application
Heat sleeves
Near exhaust
Conduit
Physical protection
Looms
Organization, some protection
Tape
Heat reflection
5.3 Connection Design
Factor
Guideline
Connector rating
Match temperature
Sealed connectors
Prevent contamination
Strain relief
Prevent vibration damage
5.4 Sizing
For high-temperature zones:
Apply temperature derating
Consider peak temperatures
Include safety margin
Diagram placeholder
MEDIA TODO
Figure 3 Underhood wiring routing best practices
6. Conclusion
6.1 Summary
Factor
Recommendation
Conductor
CCA with appropriate sizing
Insulation
Match to temperature zone
Routing
Minimize heat exposure
Protection
Shields and sleeves
6.2 Design Checklist
Map temperature zones
Select insulation per zone
Size for temperature derating
Route away from heat
Provide protection
7. References
ISO 6722. (2022). Road Vehicles - 60V and 600V Single-Core Cables.
SAE J1128. (2020). Low Tension Primary Cable.
Frequently Asked Questions
What insulation is needed for engine bay wiring?
For standard underhood locations (105-125°C), use XLPE or TPE insulation. Near exhaust components (125°C+), use silicone or FEP insulation. Always match insulation temperature rating to the specific zone.
How does temperature affect CCA ampacity?
At 125°C ambient, CCA ampacity is reduced to approximately 36% of the 60°C rating. Apply appropriate derating factors and size conductors for worst-case temperature conditions.
Can CCA be used near the exhaust manifold?
CCA can be used near exhaust with proper insulation (silicone or FEP rated for 150°C+) and physical protection (heat sleeves). Consider routing away from extreme heat sources when possible.
What protection methods work for underhood wiring?
Use heat sleeves near exhaust, conduit for physical protection, heat-reflective tape, and proper routing with air gap from hot surfaces. Ensure connectors are sealed and rated for the temperature zone.
