You are specifying a tray cable for a new industrial line. The cable will run through a wet chemical area, then into a dry control room. Your distributor offers two options: one with XHHW‑2 insulation, one with THHN. Both are TC‑ER rated. Both have black PVC jackets. But the price difference is noticeable. Which one lasts longer? Which is worth the extra cost?
This comparison guide walks you through the real differences between XHHW‑2 and THHN conductors in tray cable systems. You will learn how they perform in heat, moisture, oil, and cold – and how to choose the right one for your environment.
1. Quick Overview: XHHW-2 vs THHN
Before diving into details, here is the basic difference.
- XHHW-2 – Thermoset insulation (cross-linked polyethylene). Rated 90°C in both dry and wet locations. Excellent oil and chemical resistance. Stays flexible in extreme cold (-40°C). Higher cost.
- THHN – Thermoplastic insulation (PVC with nylon jacket). Rated 90°C dry, 75°C wet (as THWN-2). Moderate oil resistance. Nylon jacket resists abrasion. Lower cost.
The key takeaway: XHHW-2 keeps its 90°C rating in wet locations. THHN drops to 75°C when wet. That single difference determines lifespan in many industrial environments.
2. Why Insulation Type Affects Cable Lifespan
Insulation degrades faster when exposed to heat, moisture, chemicals, and electrical stress.
XHHW-2 (Thermoset)
XHHW‑2 is cross-linked polyethylene. The cross-linking process creates a three-dimensional molecular structure that resists deformation under heat. Once cross-linked, it cannot melt or flow. This gives XHHW‑2 higher thermal stability, excellent moisture resistance, superior chemical resistance, and stress crack resistance. In tray cable systems, XHHW‑2 often lasts 20+ years in harsh environments.
THHN (Thermoplastic)
THHN uses a PVC base insulation with a thin nylon jacket. Thermoplastics soften when heated and harden when cooled. Repeated heat cycles cause gradual embrittlement. Limitations include wet location derating to 75°C, higher water absorption, and lower chemical resistance compared to XLPE. However, THHN excels in dry, indoor, temperature-controlled environments. Its nylon jacket pulls easily through conduit and resists abrasion.
3. Three Common TC-ER Cable Specifications – XHHW-2 vs THHN
Here are three typical tray cable constructions with recommendations based on environment.
14 AWG 5/C Shielded TC-ER Cable – Control and Instrumentation
- Conductors – 5 conductors, 14 AWG, available in XHHW‑2 or THHN/THWN‑2.
- Shielding – Overall foil shield with drain wire.
- XHHW‑2 advantage – For wet or outdoor trays, chemical plants, or washdown areas.
- THHN advantage – For dry indoor control panels, assembly lines, or clean manufacturing.
- Typical application – Multi-sensor feedback in a packaging machine.
4 AWG 4/C Unshielded TC-ER Cable – Motor Feeders and Branch Power
- Conductors – 4 conductors (3 phase + ground), 4 AWG.
- Unshielded – Pure power; no sensitive electronics nearby.
- XHHW‑2 advantage – For pump houses, wastewater lift stations, or any location with persistent moisture.
- THHN advantage – For dry conveyor lines, HVAC units, or indoor motor control centers.
- Typical application – Feeder to a 15 HP motor in a dry assembly area (THHN) or a submersible pump (XHHW‑2).
2 AWG 3/C Unshielded TC-ER Cable – Heavy Branch Circuits
- Conductors – 3 conductors, 2 AWG (ground may be bare or separate).
- Unshielded – High current branch feeders.
- XHHW‑2 advantage – For outdoor cable trays, rooftop runs in hot climates, or chemical dosing areas.
- THHN advantage – For indoor power distribution in climate-controlled electrical rooms.
- Typical application – Feeding a 50 HP motor starter from an MCC in a dry factory (THHN) or a cooling tower fan (XHHW‑2 for outdoor heat and moisture).
When ordering, always specify the insulation type clearly. Do not assume "TC-ER" implies XHHW‑2 – many TC‑ER cables use THHN/THWN‑2.
4. Side-by-Side Performance in Real Environments
Let us compare how each insulation performs in typical industrial conditions.
- Hot and wet (e.g., wastewater plant, outdoor tray in summer rain)
XHHW‑2 maintains full 90°C rating. No derating. Lifespan long.
THHN derates to 75°C. If ambient is 40°C plus sun load, lifespan shortened.
Winner: XHHW‑2
- Dry and warm (e.g., indoor factory, electrical room)
XHHW‑2 works fine, but you pay extra for wet-rated performance you do not need.
THHN is fully adequate. 90°C dry rating matches XHHW‑2. Lower cost.
Winner: THHN (on cost)
- Oily environment (e.g., machine tool, hydraulic press area)
XHHW‑2 has excellent resistance to most oils and coolants.
THHN with nylon jacket provides moderate oil resistance, but prolonged exposure can soften PVC.
Winner: XHHW‑2
- Cold outdoor installation (e.g., winter in Canada)
XHHW‑2 remains flexible at -40°C. Easier to pull.
THHN can become stiff. Requires care or warming.
Winner: XHHW‑2
- Abrasion during pulling (e.g., long conduit or tray with rough edges)
XHHW‑2 has good abrasion resistance.
THHN has very good abrasion resistance due to slippery nylon jacket.
Winner: THHN (slight edge)
5. Customer Pain Point – When THHN Failed Too Soon
A food processing plant used THHN/THWN‑2 TC‑ER cable for motor feeders in a washdown area. The cables were in cable trays above the production floor. Daily high-pressure hot water cleaning (70°C) created a wet, warm environment. Within 18 months, several cables developed ground faults. Inspection showed the THHN insulation had become brittle and cracked.
The plant switched to XHHW‑2 TC‑ER cable for the replacement. Three years later, no insulation failures. The lesson: in environments with wet heat above 75°C, XHHW‑2 is not optional – it is necessary.
Customer pain point: "We tried to save money with THHN, but the replacement labor cost more than the initial savings. Now we only use XHHW‑2 in wet areas."
6. Selection Reminder – How to Choose
Follow this simple decision tree.
- Is the cable in a wet location for extended periods?
Yes – Choose XHHW‑2 (90°C wet rating). No – Go to next question.
- Is the cable in a dry, climate-controlled indoor space?
Yes – THHN/THWN‑2 is cost-effective. No (outdoor, unheated, or damp) – Consider XHHW‑2 for margin.
- Will the cable see oil, chemicals, or extreme cold?
Yes – XHHW‑2. No – THHN may suffice.
- Budget is tight and environment is dry?
THHN is the answer.
Selection reminder from our sales team: Do not overspecify XHHW‑2 for every job. Dry indoor trays do not need its wet rating. But do not underspecify THHN for hot wet areas – the replacement cost will hurt. Match the insulation to the real operating environment.
7. Installation Tips for Both Insulation Types
Regardless of which insulation you choose, follow these tips.
- Check the jacket marking – Verify "TC-ER" for exposed run installation without conduit.
- Support spacing – Follow local code. Typical: 4.5 ft vertical, 6 ft horizontal.
- Bending radius – Do not exceed recommended minimum. For both types, 5× cable diameter is a safe rule for unshielded.
- Shield grounding (if shielded) – Ground at one end to avoid circulating currents.
- Separation from VFD cables – Maintain 6 inches or use shielded cable.
For THHN specifically, avoid pulling in very cold weather without warming the cable. For XHHW‑2, the nylon‑free surface is slightly less slippery, so use appropriate pulling lubricant.
8. UL Certifications – What You Should Know
Our TC-ER cables are manufactured under strict quality controls. Cables with XHHW‑2 conductors comply with UL 44 (Thermoset-Insulated Wires and Cables). Cables with THHN/THWN‑2 conductors comply with UL 83 (Thermoplastic-Insulated Wires and Cables). The complete tray cable assembly is UL 1277 listed for Tray Cable with Exposed Run rating. These certifications ensure compliance with North American safety standards. For specific UL file numbers or to request our certificate, contact our technical team.
FAQ
Q1: Is XHHW-2 always better than THHN for tray cable?
No. XHHW‑2 is better in wet, hot, oily, or cold outdoor environments. In dry, indoor, temperature-controlled spaces, THHN provides equivalent performance at lower cost. Choose based on your actual conditions.
Q2: Can I use THHN/THWN-2 TC-ER cable outdoors?
Yes, if the cable jacket is marked "Sunlight Resistant" or "UV Resistant". However, remember that THHN's wet rating is 75°C. On a hot sunny day with high ambient temperature, you may be close to that limit. For outdoor use in hot climates, XHHW‑2 gives more margin.
Q3: How long does XHHW-2 typically last in a wet industrial environment?
With proper installation, XHHW‑2 often exceeds 20 years in wet, 90°C rated conditions. Actual lifespan depends on specific chemicals, mechanical stress, and UV exposure.
Q4: Does Greater Wire supply both XHHW-2 and THHN TC-ER cables?
Yes. We manufacture UL 1277 listed TC-ER cables with either XHHW‑2 or THHN/THWN‑2 conductors. Available gauges include 14 AWG 5/C, 4 AWG 4/C, 2 AWG 3/C, and many others. Shielding and custom lengths available. Contact us with your specifications.
Q5: Can I mix XHHW-2 and THHN in the same cable tray?
Yes, physically they can be run together. However, be aware that the ampacity and temperature ratings may differ. Do not exceed the lower rating of the two when derating for ambient temperature.
Need a Quote for Your Industrial Tray Cable Project?
Tell us your conductor count, gauge (14 AWG, 4 AWG, 2 AWG, or others), insulation type (XHHW‑2 or THHN), shielding requirement, environment (wet, dry, outdoor, indoor), and total length. We will recommend the right TC-ER cable and provide a competitive quote.
Contact us
Dongguan Greater Wire & Cable Co., Ltd.
Tel/WhatsApp/Wechat: +86 136 6257 9592
Tel/WhatsApp/Wechat: +86 135 1078 4550
Email: manager01@greaterwire.com
Website: www.greaterwire.com