Corrugated Loom Fill Guide: How Much Wire Fits in Split and Non-Split Loom?
Links to wire loom HellermannTyton Wire Loom – PV Cables Inc.
Links to wire loom clamps Loom Clamps (P-Clips) – PV Cables Inc.
If you’re building a custom wiring harness for your solar system, choosing the correct wire loom size is critical. Corrugated loom protects wires from abrasion, vibration, moisture, and heat, but simply fitting wires into the loom isn’t enough. Overfilling loom can reduce flexibility. Consequently, installation becomes difficult and wire insulation wears down faster.
A good rule of thumb is to limit loom fill to approximately 80% of its internal capacity. This provides enough room for the wire bundle to flex naturally, improves routing around bends, and helps maintain the protective qualities of the loom.
Why You Shouldn’t Fill Loom Beyond 80%
Many installers choose loom based on how the wires physically fit inside. While that may work initially, a tightly packed loom often creates problems later.
Overfilled loom can:
- Reduce flexibility when routing through tight spaces
- Increase friction and abrasion between conductors
- Make future wire additions nearly impossible
- Create installation challenges around connectors and terminals
- Cause split loom to separate under stress
An 80% fill ratio ensures wires slide through easily. Furthermore, it leaves vital room for future circuit expansion.
Benefits of an 80% Fill Ratio
| Benefit | Why it Matters |
|---|---|
| Easier Installation | Wires slide through the loom more easily |
| Better Flexibility | Harnesses bend and route more naturally |
| Reduced Abrasion | Less conductor-to-conductor contact |
| Room for Expansion | Additional circuits can be added later |
| Cleaner Appearance | Professional-looking wire routing |
Wire Gauge Doesn’t Tell the Whole Story
Many installers assume all 10 AWG wire takes up the same amount of space. In reality, PV wire insulation thickness is greater than most other wire types and has a significant impact on overall wire diameter.
The copper conductor inside the wire may be identical, but the outside diameter varies considerably depending on the insulation type.
This difference may seem small, but when bundling multiple conductors together inside loom, the total space required increases dramatically.
When Should You Choose the Next Larger Loom Size?
Consider upsizing when:
- Loom fill exceeds 80%
- Future circuits may be added
- The harness includes large terminals or connectors
- Routing requires multiple bends
The additional space improves installation and reduces long-term wear on the wiring system.
Common Loom Sizing Mistakes
Choosing Based on Wire Gauge Alone
- Choosing Based on Wire Gauge Alone – Always consider wire outside diameter, not just conductor size.
- Ignoring Future Expansion – Leave room for additional circuits whenever possible.
- Overfilling the Loom – Just because the wires fit doesn’t mean the loom is properly sized.
Proper loom sizing starts with understanding wire diameter, not simply wire gauge.
By selecting the correct split loom and limiting fill to approximately 80% of capacity, you’ll create cleaner, more flexible, and more serviceable wiring installations for your solar system. Taking the time to size loom correctly will improve both performance and long-term reliability.