Okay, this is a great question that highlights a common tension between design, longevity, and constructability. Let's break it down

Your Reasoning for XHHW-2:
Longevity

You've correctly identified that, in theory, XHHW-2 can offer a longer service life due to its cross-linked polyethylene (XLPE) insulation. XLPE is generally more resistant to heat, abrasion, and chemicals than the PVC insulation used in THWN-2. This is crucial for long-term, critical infrastructure projects.

Government/Long-Term Infrastructure

This is the key. You're designing for facilities intended to last decades. A slightly higher upfront cost can be justified if it significantly extends the lifespan and reduces maintenance over that period.

Contractor Complaints (and potential reasons)



Pulling Difficulty

XHHW-2 can be more difficult to pull than THWN-2. This is because: XLPE is generally a bit stiffer and less slippery than PVC. Larger conductor sizes, typical in infrastructure projects, exacerbate this.

Availability

While XHHW-2 is readily available, some suppliers might stock THWN-2 more heavily due to its wider use in general commercial and residential construction. This can lead to delays if the contractor isn't planning ahead or is using a supplier primarily focused on smaller projects.

Cost

XHHW-2 typically has a higher initial cost than THWN-2. This is a direct driver of contractor complaints.

Is Your Choice Reasonable?

It can be, but it requires a more nuanced approach. Here's a breakdown of when it's a good choice and when you might reconsider

Situations Where XHHW-2 is a Good Choice:

High-Temperature Environments

If the cable will be exposed to consistently high ambient temperatures (near the cable's rating), XHHW-2 is definitely preferred. For example, direct sunlight in conduit, areas near heating equipment, or hot process areas.

Chemical Exposure

If the cable might be exposed to oils, solvents, or other chemicals that can degrade PVC, XHHW-2 is the better choice.

Direct Burial

XHHW-2 is suitable for direct burial applications, whereas THWN-2 typically needs to be installed in conduit.

Long Lifespan Requirement

As you mentioned, if the facility is meant to last 50+ years and minimizing future replacement costs is paramount, XHHW-2 is a valid choice.

Situations Where You Might Reconsider



Mild Environments

If the cable is installed in a climate-controlled environment with no exposure to high temperatures or chemicals, THWN-2 might be sufficient.

Ease of Installation is Critical

If the project has very complex conduit runs with many bends, or if the contractor has limited experience with XHHW-2, the increased difficulty of pulling could lead to delays and cost overruns that outweigh the benefits of XHHW-2.

Budget Constraints

If the project has a very tight budget, the cost savings of THWN-2 might be necessary, but this should be carefully weighed against the potential for reduced lifespan and increased maintenance costs.

Recommendations and Mitigation Strategies


Document Your Reasoning

In your design specifications, clearly state why you're specifying XHHW-2. Explain the long-term benefits and the specific environmental factors that justify the choice. This will help contractors understand the rationale and be more accepting of the requirement.
2.

Consider Alternatives

Explore the possibility of using THHN/THWN-2 conductors inside conduit in less demanding environments, and using XHHW-2 in the more harsh locations of the project. This hybrid approach can balance cost and performance.3.

Specify Pulling Lubricant

Require the use of a high-quality pulling lubricant specifically designed for XLPE cables. This can significantly reduce friction and make pulling easier. Explicitly stating this in your specs can address the contractor's concerns.4.

Conduit Design

Consider the conduit layout. Minimizing bends and using larger conduit sizes will make pulling any type of cable easier.5.

Pre-Bid Meetings

Discuss the cable specification with potential bidders during pre-bid meetings. This gives them a chance to ask questions and understand the reasoning behind your choices. Also, you can then discuss options for cable supply and strategies to ensure easier installation.6.

Contractor Qualifications

In the bidding process, consider the contractor's experience with XHHW-2. You might want to give preference to contractors who have a proven track record of successfully installing it.
7.

Allow "Or Equal" Submissions (with Caveats)

You could allow contractors to propose alternative cables "or equal" to XHHW-2, but you need to be very specific about the performance criteria the alternative must meet (e.g., temperature rating, chemical resistance, abrasion resistance, listing for direct burial). Carefully scrutinize any proposed substitutions to ensure they truly meet the project's long-term needs. Don't just accept "it's cheaper."8.

Lifecycle Cost Analysis

Do a formal lifecycle cost analysis that compares the initial cost of THWN-2 versus XHHW-2, factoring in estimated replacement costs, downtime, and maintenance. This will provide concrete data to justify your choice.9.

Consider Cable Tray vs. Conduit

Depending on the application, consider utilizing cable tray instead of conduit, as the wire installation can be simpler in some instances.

In summary: Your desire to use XHHW-2 for long-term infrastructure projects is reasonable, but you need to be proactive in communicating your rationale to contractors and mitigating potential installation difficulties. By clearly specifying your requirements, considering alternatives for less demanding environments, and addressing contractor concerns, you can ensure that your projects are built to last without causing undue frustration. Flag for review