How to Choose Jumpers for Power Distribution Terminal Blocks
Choose the jumper as part of a documented terminal system—not by color, pole count or visual fit. Map the intended electrical node, then verify the exact host terminal, bridge channel and pitch, position pattern, segment current, voltage and insulation conditions, required accessories, and panel-level thermal and fault-current evidence.
Different terminal families use different interfaces, pitches and jumper channels. The image does not show a verified jumper installation. Photo: Dmitry G / Wikimedia Commons, CC BY-SA 3.0; display crop only.
Select the complete current path, not a loose accessory
A power-distribution jumper—also called a bridge, cross-connector or comb in some product systems—creates an intentional electrical connection between specified terminal positions. It is not a generic strip of conductive material. Its suitability depends on the exact terminal family, connection level, bridge channel, pitch, number and pattern of positions, electrical ratings for that configuration, and every required cover, partition or end accessory.
Start with the approved schematic and terminal plan. One jumper group should represent one intentional node: one phase, one DC polarity, one neutral group, one control voltage or another explicitly defined potential. Keep protection, disconnect, fuse, test, source and functional-earth boundaries visible. Only after that map is frozen should procurement compare part numbers. For the wider host-terminal decision, use SENTOP's terminal block selection checklist.
Compare the terminal, jumper, conductor, termination, accessories, ambient/enclosure conditions and assembly method. A terminal’s headline current or voltage does not automatically transfer to its bridge, and a physically compatible bridge does not prove panel approval.
A jumper group must equal one intentional electrical node
The safest selection drawing is a potential map. Mark what is deliberately common, what must remain isolated, where protective or switching functions occur, and which positions the bridge is allowed to occupy. Adjacency is not permission to connect.
Identify the source
Name the supply, upstream protective device and any normal/alternate or redundant-source relationship.
Never merge source A and source B merely because their terminals sit together.Name the potential
Assign L1/L2/L3, N, PE, +24 V, 0 V or the project’s approved circuit identifier.
Color supports identification; it does not create the electrical rule.Mark boundaries
Show fuses, disconnect/test functions, isolation, interlocks and separate protective branches.
A bridge must not silently bypass a safety or maintenance function.Map every load
Record branch current, operating combination, inrush/duty context and future reserved positions.
Use documented diversity; do not assume all loads share current evenly.Freeze the span
State the first and last terminal, adjacent or skipped positions, level and unused/open ends.
The released drawing should make an accidental extra common point obvious.
Calculate the duty of each bridge segment
With a single-end feed, the section nearest the source can carry the sum of every downstream branch current that is on at the same time. Current usually falls as branches leave the node. A center-fed arrangement creates two different paths; a multiple-feed arrangement adds source and protection questions. Do not assume two feeds or parallel bridges divide current equally unless the manufacturer and engineered design document that behavior.
- Use actual duty: list branch currents, operating combinations, load profile and any approved diversity or demand factor.
- Evaluate the worst segment: identify which bridge element carries the largest legitimate sum under normal service.
- Check the exact bridge data: a catalog value can change with the host modular terminal or configuration.
- Keep the thermal chain intact: conductor size/type, ferrule if permitted, terminal rating, enclosure temperature, grouping and assembly temperature rise still apply.
A bridge can fit mechanically and still fail the selection review
Pass every gate with the exact terminal and jumper documents. If one answer depends on visual similarity, a distributor description or a value copied from a neighboring product, hold the BOM.
Exact terminal identity
Record manufacturer, series, catalog number, terminal function, level and revision. Similar housings can have different bridge shafts or ratings.
Evidence: current datasheet and accessory table for the named terminal.Pitch, channel and pattern
Confirm pitch, bridge shaft, insertion direction, adjacent or skipped pattern, number of positions and any occupied conductor opening.
Evidence: dimensioned drawing plus permitted connection pattern.Published value for this host
Compare the worst segment current with the bridge value declared for the actual modular terminal and configuration.
Evidence: configuration-specific bridge current—not only terminal current.Insulation condition
Verify actual potential pairs, working voltage, declared insulation/impulse data, neighboring groups and any cover or partition condition. Include the documented pollution-degree condition.
Evidence: exact configuration row; do not borrow an Ex-only example.Protection and exposed ends
Check cover strips, end caps, separators, partition plates, end plates, markers and touch-protection requirements against the declared accessory range.
Evidence: complete line-up BOM, not a jumper alone.Assembly and service access
Confirm conductor space, tool access, retention, vibration conditions, bridge removal method and visibility for inspection.
Evidence: installed arrangement and manufacturer assembly instructions.Temperature and contamination
Apply product ambient limits, enclosure temperature, pollution/condensation assumptions, corrosion and required environmental accessories.
Evidence: project conditions matched to declared product conditions.Correct rating language
Keep continuous current, IEC short-time withstand, peak/dynamic evidence, UL SCCR and OCPD interrupting rating separate. For North American component review, see the UL 1059 terminal-block checks.
Evidence: the applicable component and assembly method with exact OCPD.Traceable release
Put first/last positions, potential ID, part numbers, accessory set and document revision into the drawing and BOM.
Evidence: substitution requires renewed technical approval.Adjacent, skipped, cut and wired bridges are different configurations
Do not convert one approved form into another by assumption. The product instructions decide whether a supplied bridge may be shortened, whether an open end needs insulation, whether a skipped pattern exists and whether a manufacturer-defined wire jumper is permitted.
| Configuration | Legitimate use | Evidence required | Stop condition |
|---|---|---|---|
| Adjacent plug-in bridge | Common pattern Connects a declared run of neighboring positions in the compatible bridge channel. | Exact terminal/bridge part pairing, pitch, positions, current/voltage data and end protection. | One position contains a fuse, disconnect, PE, different potential or incompatible terminal function. |
| Skipped or alternating bridge | Documented only Distributes a potential to a defined non-adjacent pattern when the manufacturer supplies that geometry. | Manufacturer pattern drawing, terminal level, excluded positions, insulation conditions and markers. | A field team intends to bend pins or leave accidental intermediate contacts. |
| Cut-to-length comb | System-specific Allowed only for a product designed to be cut and finished as instructed. | Approved cut location, exposed-end cover, maximum span, ratings and inspection criteria. | The bridge is not declared cuttable, or the proposed cut exposes an unprotected live end. |
| Manufacturer wire jumper | Possible exception A specified wire link can be valid when the terminal maker or approved design defines conductor and routing. | Wire type/size, ferrule or preparation, terminal occupancy, current path, routing and identification. | The link is improvised from scrap wire or bypasses a bridge-channel limitation without approval. |
| Stacked or parallel bridges | Do not assume Only a declared product arrangement may use more than one bridge in a coordinated way. | Explicit manufacturer data covering current sharing, insertion, insulation, heat and fault duty. | The design uses multiple pieces merely to claim a higher current. |
| Fabricated metal link | Engineered system only Belongs to a separately designed and approved busbar/link solution, not an accessory substitution. | Material, plating, section, supports, torque, spacing, temperature rise, fault forces and assembly approval. | It is a field-cut strip made to mimic a catalog jumper. |
Procurement rule: “10-pole jumper” is not a sufficient description. A usable line item includes the exact part number, host terminal, pitch/channel, level, position pattern, electrical conditions, accessory set and document revision.
Four numbers that answer four different questions
A robust release package preserves the manufacturer’s exact terminology. A high number on a breaker, terminal or distribution block cannot be copied onto the jumper group or the completed panel.
Know when the design has outgrown a terminal-row bridge
A bridge is effective when it creates a clear, documented common node within the electrical, thermal, mechanical and fault limits of its terminal system. It becomes the wrong architecture when aggregate current, incoming conductor size, branch count, expansion, fault-duty evidence or service clarity exceed what that system declares.
- Choose a declared bridge system for a modest, clearly bounded potential group with exact terminal and accessory evidence.
- Choose an internally commoned distribution terminal when the manufacturer offers a purpose-designed feed-in/out architecture and ratings for the required branches.
- Choose a power distribution block when large incoming/outgoing conductors, higher aggregate duty or more explicit branch architecture makes a PDB the cleaner component route.
- Choose an engineered busbar system when scale, future expansion, short-circuit forces, heat, protective coordination or service requirements demand a designed assembly.
Use the terminal block specification checklist to keep conductor, voltage, current, insulation and environmental fields visible. Where the row mixes ordinary and protected branches, review the feed-through versus fuse-terminal boundary before defining the span.
Turn the potential map into a traceable BOM
Use this workflow for engineering, supplier review and QA. Each step closes a distinct evidence gap; none authorizes live work or undocumented modification.
Freeze the node
Mark source, potential, branches, protection and every position that must remain separate.
Output: approved potential map.Name the host
Record terminal manufacturer, exact catalog number, function, level and certification category.
Output: host-terminal identity.Name the bridge
Specify part number, pitch, shaft, positions and adjacent/skipped/cut configuration.
Output: configuration-specific accessory.Map current
Calculate the worst legitimate current through every segment using documented load combinations.
Output: segment-duty schedule.Verify thermal duty
Check conductors, terminations, ambient, grouping, enclosure and product derating data.
Output: thermal evidence chain.Verify insulation
Check voltage pairs, spacing declarations, neighboring groups, covers and partitions.
Output: approved line-up condition.Verify fault method
Record available fault current, panel target, OCPD model/settings and conditional evidence.
Output: SCCR/withstand review input.Confirm in writing
Have the supplier identify the current document covering the exact terminal, bridge and pattern.
Output: traceable supplier evidence.Release the BOM
State first/last terminals, potential ID, accessories, revision and no-substitution rule.
Output: buildable controlled package.Verify as built
Qualified personnel compare accessible hardware and records under the approved QA process.
Output: documented handover state.Ask for a documented distribution system—not “jumper, 10 pole”
Send the supplier enough information to reject a visually similar but unapproved substitute. The same package should let engineering, purchasing, QA and commissioning trace why the configuration was released.
Do not release the selection when the evidence breaks
A procurement deadline is not a technical basis. Escalate to the terminal manufacturer, panel designer or a different distribution architecture when any of these conditions appears.
The part only “looks right”
No current manufacturer document links the bridge to the exact host terminal, level and pattern. Do not use a cross-brand dimensional match as electrical or compliance evidence.
The node crosses a boundary
A proposed span includes different phases, sources, polarities, neutral/PE functions, fuse/disconnect positions or separately protected branches without an approved special-function design.
Aggregate current or heat is unclear
The team is relying on terminal current, a universal percentage, assumed diversity or equal current sharing instead of a documented worst-segment calculation and assembly thermal review.
A nearby kA value is doing the work
The claim depends on a breaker AIR, another component’s SCCR, a generic current-limiting statement or an IEC short-time value used as a different rating.
The plan needs cutting, drilling or stacking
The exact product is not documented for the proposed cut, wire link, parallel bridge, open end or fabricated part. Redesign rather than modifying hardware in the field.
The bridge obscures distribution
Incoming conductor size, branch count, expansion, serviceability, fault forces or thermal duty points toward a purpose-designed PDB or busbar system.
Verify the as-built node before energization
Panel QA should compare the installed terminal and bridge part numbers, first/last positions, potential markers, covers and partitions with the released drawing and BOM. Under the site's approved de-energized procedure, qualified personnel may perform specified continuity and isolation checks to confirm that the jumper connects only the intended node. SENTOP's control-cabinet wiring components guide provides the broader panel context.
A continuity result does not prove current rating, insulation coordination, fault duty, torque, conductor preparation or final panel approval. It only answers the limited test question under the specified setup. Any undocumented bridge, missing insulating part, uncertain circuit identity, heat/discoloration, damage or previous protective-device operation requires controlled isolation and technical assessment—not repeated resetting or improvised rework.
Retain the as-built terminal plan, exact parts, supplier evidence, inspection result, protection data, deviations and approval owner. Future service teams should be able to reconstruct the node without guessing from a continuous row of hardware.
Related SENTOP engineering guides
These pages cover adjacent decisions without replacing the exact manufacturer evidence required for a jumper configuration.
Power distribution jumper FAQs
These answers preserve the product-system and assembly boundary. The exact manufacturer documents and adopted panel method remain decisive.
Can I use a jumper from another terminal-block manufacturer?
Do not assume so. Terminal geometry, bridge channel, pitch, insulation, current path and recognition conditions can differ even when parts appear alike. Use an accessory the host-terminal manufacturer expressly identifies for the exact system, unless a separately engineered and approved panel solution provides another documented basis.
Does the terminal block current rating also apply to its jumper?
Not automatically. The jumper is a separate current path and may have its own published value or a value that changes with the host terminal. Compare the exact bridge data with the worst current in every bridge segment, then verify conductor, ambient, grouping and assembly temperature-rise conditions.
How many terminal blocks can one jumper connect?
Only the compatible positions permitted by the exact jumper and terminal documentation. The answer depends on part number, pitch, bridge channel, pole count, adjacent or skipped pattern, terminal level, electrical conditions and required end protection. Visual row length is not a specification.
Can I cut a terminal-block jumper to length?
Only when the manufacturer expressly designs that product to be cut and states the cutting, exposed-end protection, maximum span, ratings and inspection requirements. Do not cut, drill, bend or notch an undocumented bridge to make it fit.
Are wire jumpers always prohibited?
No. Some manufacturers define wire-jumper solutions for particular terminal systems. The prohibited practice is an improvised or undocumented link. A valid wire jumper still needs declared conductor, preparation, terminal occupancy, current path, routing, identification and approval conditions.
Can a jumper connect different phases or separate power sources?
Not as an ordinary convenience bridge. One jumper group should represent one intentional node. A manufacturer-designed star/delta bridge or another documented special circuit may connect positions in a defined way, but it requires the approved schematic, dedicated accessory and engineering/panel review.
When should I use a power distribution block instead of a bridge?
Escalate when aggregate current, incoming conductor size, branch count, expansion, fault evidence or service clarity exceeds the declared terminal-bridge system. Verify whether the proposed North American product is evaluated as a UL 1059 terminal block or a UL 1953 power distribution block; the commercial name alone does not decide.
Does a jumper change the panel SCCR?
It can change the current path the panel evaluation must consider, but it does not automatically raise SCCR. The completed panel rating comes from the applicable method, exact components, voltage, available fault current, protective-device conditions and restrictions. A breaker interrupting rating or another component's high kA value cannot be borrowed.
Can I parallel two jumpers to carry more current?
Do not assume current will divide evenly. Parallel or stacked bridges are acceptable only where the manufacturer explicitly documents that arrangement, including current sharing, insertion, heat, insulation and fault duty. Otherwise select a larger declared distribution system, PDB or engineered busbar.
What belongs on the jumper RFQ and BOM?
Include exact host and jumper part numbers; potential ID; first/last positions; pitch, level and pattern; published electrical conditions; source/OCPD and worst segment current; conductors and environment; covers, partitions, ends and markers; market/compliance and SCCR inputs; document revision; and a controlled substitution rule.
Standards and manufacturer evidence
Standards define scopes and evaluation routes. Product pages illustrate configuration-specific data; they are not universal ratings for other terminal or jumper systems.
- IEC 60947-7-1:2025 — terminal blocks for copper conductors, component scope.
- IEC 60947-7-2 — protective-conductor terminal blocks and their specific current path.
- IEC 61439-1:2020 and IEC 61439-2:2020 — assembly-level framework and power switchgear/controlgear assemblies.
- UL 1059, Edition 6 — terminal-block component scope and end-product suitability boundary.
- UL 1953 — power distribution block category boundary.
- UL 508A Supplement SA and UL SCCR guidance — industrial-control-panel component and SCCR context.
- UL Component Recognition — Conditions of Acceptability and finished-product boundary.
- WAGO interconnection FAQ and rail-terminal application tips — compatibility, bridge current and cumulative-current cautions.
- Phoenix Contact FBS 10-3.5 BU — exact bridge example whose actual current depends on the modular host terminal.
- Weidmüller power distribution blocks — purpose-designed PDB/flat-bridge system example.
- OSHA 29 CFR 1910.333 — U.S. electrical-work safety boundary; local rules and employer procedures still control.
