DLO Cable Ampacity Chart: Free Air, Raceway and Derating

DLO Cable Ampacity: Start with the Installation Condition

A cable’s ampacity is the current it can carry continuously without exceeding the permitted conductor temperature under stated conditions of use. The phrase “under stated conditions” is the part that prevents a chart value from becoming a universal rating.

If the cable family or its markings are unfamiliar, begin with the companion guide explaining what DLO cable is, how it is constructed and where it is used.

A single conductor separated in free air can release heat more effectively than the same conductor enclosed with others in a raceway. A 90°C insulation system can be used for correction and adjustment calculations where the governing rules permit, while the connected equipment may still limit final loading to a 75°C or 60°C terminal basis. Higher insulation temperature does not automatically raise the temperature permitted at a lug.

DLO Cable Ampacity Chart

A 405 A number looks impressive; it is not a free pass. The installation column and terminal limit still have the final say.

This reference is a sizing starting point for the TEBAOFLEX 2 kV DLO range; the supplied construction uses EPR insulation and an XL-CPE jacket. Confirm the ordered size, marking and governing installation basis before final selection. Values assume the stated free-air or raceway basis at a 30°C ambient reference. They do not include every limitation for small conductors, continuous loads, motor circuits, ambient correction, more than three current-carrying conductors, terminal temperature, overcurrent devices, cable tray, parallel conductors or local rules.

Source basis: The common free-air values in this reference can be cross-checked against published DLO tables from Direct Wire and Mid America Wire & Cable. They are not universal values for every manufacturer: construction, conductor class, listing, spacing and thermal method can change the result. Southwire’s DLO CableTech page publishes construction-specific DLO tables, reinforcing that the exact marking and installation basis must be checked.

Important: these are base reference values, not a completed circuit design. The National Electrical Code is adopted and enforced by the applicable authority having jurisdiction, and the edition and local amendments must be confirmed for the project. Do not use a generic chart as a substitute for the approved calculation, equipment listing or manufacturer data.

For nominal outside diameter, mass, strand count and bending radius, use the TEBAOFLEX DLO cable ampacity and size table. If the project needs a non-standard kcmil size, request an approved data sheet and calculation rather than interpolating without engineering review.

Why DLO Ampacity Charts Show Different Numbers

Free air is a thermal condition, not simply “somewhere outdoors”.

Free Air Versus Raceway

“Free air” is not a synonym for any cable located outdoors or above ground. It describes an installation condition in which heat can dissipate around a conductor under the spacing and arrangement assumed by the applicable table or engineering method. A group of conductors touching in a tray, tied into a dense bundle or enclosed behind equipment may not behave like separated free-air conductors.

Raceway, cable and earth columns assume less favourable heat dissipation. That is why the same 4/0 copper DLO row can show 405 A at a 90°C free-air basis and 260 A at a 90°C raceway basis before other limitations are applied.

75°C Versus 90°C Columns

The TEBAOFLEX DLO insulation system is rated for 90°C wet or dry. That insulation rating establishes a thermal capability and may provide a basis for correction and adjustment where permitted. It does not mean every termination can operate at 90°C. Equipment terminals, connectors and devices often establish a lower permitted conductor-temperature basis.

The practical design check is therefore two-part: first use the permitted conductor temperature for correction and adjustment; then confirm that the corrected result does not exceed the ampacity allowed by the termination and equipment rules. The project engineer should document both steps.

Ambient Temperature

The table uses a 30°C ambient reference. Higher surrounding temperature leaves less thermal headroom between the environment and the maximum conductor temperature, so a correction factor may reduce allowable current. Lower ambient temperature does not automatically justify increasing the load unless the governing table and installation rules explicitly permit it.

Number of Current-Carrying Conductors

Multiple loaded conductors in a raceway or cable bundle heat one another. Adjustment factors can therefore apply when the number of current-carrying conductors exceeds the table’s base condition. Neutral and grounding conductors are not classified by guesswork; their treatment depends on circuit function and the governing rules.

Conductor Spacing and Cable Tray Arrangement

Cable tray can provide useful ventilation, but tray installation is not automatically free air. The number of conductors, spacing, tray type, cable diameter and applicable cable marking affect both installation permission and thermal performance. In the current TEBAOFLEX range, CT-use and FT4/IEEE 1202 scope start at 1/0 AWG; verify the actual sheath marking. IEEE 1202 addresses flame-propagation testing, not ampacity calculation.

Terminal and Connector Temperature

A connector can become the controlling point because it adds contact resistance and may have a lower temperature rating than the insulation. DLO’s high strand count also means the lug must be identified for fine-stranded conductors. A connector that is the right nominal AWG but wrong strand range can invalidate an otherwise careful ampacity selection.

DLO Cable vs Welding Cable: Do Not Mix the Ampacity Charts

DLO and welding cable can both use fine-stranded copper, but their ampacity data is not automatically interchangeable. Compare the complete product marking, insulation and jacket, voltage rating, temperature rating, conductor class, listing and installation rule before carrying a value from one chart to another.

Some DLO constructions are dual-listed for applications such as RHH/RHW-2 or RW90, while other products are not. Confirm the ordered TEBAOFLEX marking and request a size-specific data sheet before using the ampacity value in a purchase or design package.

Five Steps for Selecting DLO Cable Ampacity

1. Confirm the delivered cable marking.

   Record DLO/HDFPC, RHH/RHW-2, RW90, voltage, conductor size, CT-use, flame and MSHA marks. A generic product name is not enough.

2. Classify the installation.

   Decide whether the conductor is genuinely in free air, in a raceway, grouped in a cable tray, inside equipment or governed by a tested assembly. Document spacing and the number of current-carrying conductors.

3. Select the permitted base ampacity.

   Use the adopted code table, equipment listing or approved engineering calculation that matches the installation. Do not mix the free-air value from one table with the correction factors from another method without justification.

4. Apply correction and adjustment factors.

   Account for ambient temperature, conductor grouping and any project-specific thermal conditions. Where several factors apply, follow the governing rule for how they combine.

5. Check the rest of the circuit.

   Confirm terminal temperature, connector strand range, overcurrent protection, continuous-load treatment, motor or generator rules, short-circuit withstand, voltage drop, parallel-conductor arrangement and authority approval.

The result of these five steps is the allowable circuit current for a defined installation—not a new permanent rating printed onto the cable.

Worked Example: Why 4/0 DLO Is Not Simply a 405 A Cable

Suppose a preliminary design calls for 4/0 AWG DLO. The chart offers four base references:

• 360 A at a 75°C free-air basis;
• 405 A at a 90°C free-air basis;
• 230 A at a 75°C raceway basis; and
• 260 A at a 90°C raceway basis.

If the conductor is installed with others in a raceway and the equipment terminals control at 75°C, choosing 405 A because the insulation is marked 90°C would use the wrong installation column and ignore the terminal basis. The 230 A raceway/75°C value is the relevant base reference before ambient, grouping, load and overcurrent rules are checked.

If the same size is part of an engineered, spaced free-air arrangement with equipment identified for the required temperature, a different base value may apply. The copper did not change; the heat path and equipment conditions did.

Non-Standard kcmil Sizes Need Extra Care

DLO catalogues commonly include intermediate sizes such as 262.6, 313.3, 373.7, 444.4, 535.3, 646.4 and 777.7 kcmil. These can fit equipment originally designed around locomotive or industrial conductor sizes, but they may not appear as standard rows in every installation-code table.

Do not round the size name to the nearest familiar conductor and assume identical resistance or ampacity. Obtain the manufacturer’s conductor resistance, strand count, outside diameter and thermal data, then confirm the accepted interpolation or engineering method. ASTM has an active work item addressing DLO-sized conductor coverage and DC-resistance discrepancies in B172, which is another reason to specify the exact standard edition and approved product data.

Parallel DLO Conductors, Voltage Drop and Fault Duty

High-current UPS, battery, data-centre, generator and industrial systems may use several DLO conductors in parallel. Parallel paths must be designed so conductors share current predictably. Size, material, length, termination, routing and electrical characteristics should be coordinated; a neat-looking group of flexible cables is not proof of equal current sharing.

Ampacity is only one sizing test. Long runs can require a larger conductor to control voltage drop. Available fault current and protective-device clearing time can create a short-circuit thermal requirement. Large DLO conductors also impose substantial pulling weight and bending forces on cable tray, supports and terminals.

For a quotation, provide the one-way route length, circuit voltage, load profile, number of parallel conductors per phase or pole, installation arrangement, ambient temperature, terminal details and required short-circuit data. TEBAOFLEX can then issue a size-specific data sheet rather than treating a generic chart as the project calculation.

Common DLO Ampacity Mistakes

1. Quoting a free-air value without stating conductor spacing. “Open tray” may still be a grouped installation.
2. Using the 90°C column as the final equipment load. Terminal and device temperature can control.
3. Skipping ambient correction. Engine rooms, equipment enclosures, rooftops and industrial plants may exceed the table reference temperature.
4. Ignoring other current-carrying conductors. A dense raceway or bundle changes heat dissipation.
5. Assuming cable-tray marking sets ampacity. CT use addresses installation qualification; it does not choose the thermal column by itself.
6. Using a standard-strand lug. Fine DLO strands need a connector and tooling identified for the strand class.
7. Forgetting overcurrent and circuit-specific rules. Small conductors, continuous loads, motors and other circuits may have additional limitations.
8. Ignoring voltage drop or short-circuit duty. A conductor can pass an ampacity check and still be unsuitable for the system.

Information Needed for an Ampacity Review

• Cable type, complete sheath marking and requested conductor size.
• Circuit voltage, AC or DC system and continuous/non-continuous load profile.
• Free-air spacing, raceway size, tray arrangement or equipment enclosure details.
• Number of current-carrying conductors and parallel conductors.
• Maximum ambient temperature and nearby heat sources.
• Terminal, lug and equipment temperature ratings.
• Run length, acceptable voltage drop and available fault current.
• Adopted code edition, authority requirements and project approval documents.

DLO Cable Ampacity FAQ

How do I choose a DLO cable size from this chart?

Start with continuous load and installation method, select the applicable temperature column, apply ambient and conductor-grouping corrections, then check terminal temperature, overcurrent protection, voltage drop and fault duty. After the electrical basis is confirmed, compare dimensions, markings and available sizes on the TEBAOFLEX 2 kV DLO cable product page. Send the route, load and terminal details for a size-specific data sheet and quotation.

What is 4/0 DLO ampacity?

The reference values range from 230 A for a 75°C raceway basis to 405 A for a 90°C free-air basis. The usable value depends on installation, terminal temperature, ambient conditions, conductor grouping and circuit rules.

What is 2/0 DLO ampacity?

Reference values are 265 A at 75°C free air, 300 A at 90°C free air, 175 A at 75°C in raceway and 195 A at 90°C in raceway. Apply all project corrections and limits before selecting the conductor.

What is the ampacity of 535.3 kcmil DLO?

Reference values are 644 A at 75°C free air, 730 A at 90°C free air, 394 A at 75°C in raceway and 446 A at 90°C in raceway. Because 535.3 kcmil is a non-standard table size in some codes, confirm the accepted calculation method.

Can I use the 90°C ampacity when the cable is rated 90°C?

Not automatically as the final load value. The 90°C column may be used for correction or adjustment where permitted, but the corrected result must also comply with terminal, equipment, overcurrent and circuit-specific limitations.

Does cable tray count as free air?

Not by default. Tray type, conductor spacing, number of conductors, cable diameter, installation rule and product marking all matter. Treating every tray route as free air can significantly overstate allowable current.

Why can two DLO charts disagree?

They may use different conductor temperatures, ambient temperatures, installation methods, spacing, code editions or interpolation rules. Compare the table notes before comparing the numbers.

Use the Chart as a Starting Point, Not the Final Answer

DLO cable ampacity is a thermal result tied to a specific route and equipment system. Start with the correct table, apply ambient and grouping rules, respect the terminal temperature and then check overcurrent protection, voltage drop and fault duty. For product dimensions and available markings, review the 2 kV DLO cable product page. To obtain a project-specific quotation and data sheet, send TEBAOFLEX the circuit and installation details.