You've correctly identified the challenges: THHN gets unwieldy at larger gauges, MTW is too finely stranded for some terminations, and finding a flexible Class C 4/0 wire that's also THHN/MTW rated is proving difficult. Here's a breakdown of suggestions and things to consider

1. Understanding Class B vs. Class C Stranding:
Class B

Typically 19 strands for 4/0 AWG. This is the standard for THHN. It offers a good balance of flexibility and ruggedness.

Class C

Higher strand count than Class B, making it more flexible. The exact number of strands depends on the wire standard.

Class K

Extremely fine strands, often used for welding cable and highly flexible applications. Not designed for standard terminations.

2. Finding Class C 4/0 Options (and why they are hard to find with THHN/MTW)



The Challenge

THHN and MTW are primarily insulation types and do not dictate the stranding Class. THHN (Thermoplastic High Heat Nylon) is generally paired with Class B stranding for general-purpose wiring. MTW (Machine Tool Wire) is typically Class K. It's difficult to find Class C conductors with both THHN and MTW insulation.

3. Potential Solutions (Prioritized)



Search for "Extra Flexible THHN" or "Flexible Stranded THHN"

These terms might lead you to manufacturers who offer THHN insulation with Class C or a more flexible stranding configuration that still meets THHN specifications. Be very careful to verify the exact stranding Class and UL listings before ordering.

Example search terms

"Flexible 4/0 AWG THHN Class C," "Extra Flexible 4/0 THHN Cable," "High Strand Count 4/0 THHN."

Look at manufacturers like

Southwire, Cerro Wire, General Cable (Prysmian), Encore Wire. Check their catalogs carefully and contact their technical support.

Consider Industrial Control Cable with THHN/MTW Insulation

Some manufacturers offer control cables with multiple conductors that use THHN/MTW insulation and Class C stranding. You might be able to repurpose individual conductors from such a cable. This can be a more expensive option.

Accept Class B with careful installation



Loosen the termination point

Ensure the power distribution block termination is fully opened before inserting the wire.

Bend strategically

Pre-bend the wire carefully to match the shape of the termination point before insertion. Avoid sharp bends.

Use a proper wire bender

A hand-operated wire bender can help create smooth, controlled bends in larger gauge wire.

Use a wire pull lubricant

Lubricant can reduce friction when pulling the wire through tight spaces.

Check the power distribution block specs again

Some power distribution blocks may accept Class K stranding with the correct lugs installed. It's worth re-checking the specifications and contacting the manufacturer to confirm if this is the case.

4. Important Considerations



UL Listings

Always ensure that the wire you choose has the correct UL listings (or other relevant certifications) for your application. Using the wrong type of wire can violate electrical codes and create safety hazards.

Ampacity

Verify that the wire you select has the appropriate ampacity rating for your circuit. The ampacity is determined by the wire gauge, insulation type, and installation method.

Termination Compatibility

Confirm that the wire termination method (lugs, connectors, etc.) is compatible with both the wire type and the power distribution block. Use the correct crimping tools and dies.

Minimum Bend Radius

Pay attention to the minimum bend radius specified by the wire manufacturer. Exceeding the minimum bend radius can damage the wire's insulation and conductors.

5. Contact Wire Manufacturers and Distributors

The best way to find the right wire is to contact major wire manufacturers and distributors directly. Explain your requirements and ask for their recommendations. They may have products that are not widely advertised. Bring the power distribution block specs to the conversation so the manufacturer can consider termination requirements.

Example Search Strategy:1. Start with broad searches on Google or your preferred search engine: "flexible 4/0 THHN cable"2. Visit the websites of major wire manufacturers (Southwire, Cerro, Prysmian, Encore) and search their product catalogs.
3. Use the manufacturer's website to contact their technical support team.By following these steps, you should be able to find a suitable 4/0 wire that meets your flexibility requirements while also complying with all relevant codes and standards. Good luck! Flag for review