Center-Opening vs. Telescopic Side-Opening Elevator Doors

What Are Center-Opening and Telescopic Elevator Doors?

With a two-panel center-opening door, the leaves meet near the center when closed and move in opposite directions to open. Space is required for the moving panels on both sides of the passage.

With a two-panel telescopic side-opening door, both leaves open toward one side and overlap on separate tracks in the open position. The leaves travel different distances in the coordinated movement. This is often described as a two-speed side-opening arrangement.

Specify both panel count and opening direction. A single-panel side-sliding door and a two-panel telescopic door have different movement and parking requirements.

Center-opening arrangements can also use telescoping panel groups: a four-panel center-opening door combines the two concepts. The C2-versus-T2 comparison here concerns the two-panel versions.

Use the manufacturer’s actual arrangement code and drawing in the quotation. Define the viewing direction for left-hand or right-hand opening, because a description without a viewpoint can be read differently by the building and elevator teams.

Confirm the elevator’s applicable code basis alongside the geometry. EN 81-20 addresses new passenger and goods-passenger lifts within its stated scope. The project team should identify the relevant equipment category, locally applicable edition and replacement requirements before specifying entrance performance.

Where Do the Door Panels Park?

These unscaled diagrams show parking distribution. Obtain tracks, overlaps, brackets and required clearances from the selected assembly drawing.

TWO-PANEL CENTER OPENING — viewed from the landing

Opening movement:          ← [left leaf] | [right leaf] →

Fully open:
[left parking zone] |<------ clear opening ------>| [right parking zone]
        BOTH sides need room for the selected door assembly.

TWO-PANEL TELESCOPIC SIDE OPENING — opening toward the right

Opening movement:          [fast leaf] → [slow leaf] →

Fully open:
[closing jamb]      |<------ clear opening ------>| [overlapping leaves]
                                                  parking concentrated
                                                  on the opening side

This makes a telescopic arrangement worth evaluating when an obstruction lies close to one side and more space is available on the other. Compare the full width and depth to see whether that parking advantage helps the project.

Panel overlaps, frames, operating equipment and mounting details determine the actual dimensions. Use the supplier’s complete envelope to set the builder’s opening.

Door Leaf Travel and Speed Compared

An idealized movement model helps explain the tradeoff. Ignore overlaps and mechanism travel for a moment, and call the clear opening W. Each leaf of a two-panel center-opening arrangement travels approximately W/2. In a two-panel telescopic side-opening arrangement, the fast leaf travels approximately W while the slow leaf travels approximately W/2, so both can park on the same side.

For the example 900 mm opening completed in three seconds of panel movement:

On small screens, scroll the table to read every column.

The fast telescopic leaf covers twice the distance of a center-opening leaf in this model. Its longer travel brings both leaves into overlapping positions on one side, so compare movement as well as panel count.

The table illustrates geometry; actual movement includes overlaps and mechanism travel. For a given moving mass, higher speed increases kinetic energy, so closing performance must suit the moving mass and applicable safety requirements. Door-operator technical reference

Four Elevator Door Dimensions to Compare

On small screens, scroll the table to read every column.

Mark the sill and frame reference lines on both alternatives. One supplier may quote a component dimension while another quotes the complete package. Comparing those numbers without their endpoints creates a misleading result.

For an existing elevator, obtain both the car-side and landing-side drawings. Coordinate the replacement arrangement with the geometry of retained equipment. JAFITA’s modernization guidance helps define what will remain and what will change.

Do Telescopic Doors Need a Deeper Sill?

Overlapping leaves move on separate tracks, making entrance depth a key part of a telescopic-door comparison. Check the complete car-door and landing-door package, with the intervening gap and mounting geometry identified. A component sill width and a complete entrance-package depth describe different boundaries.

Compare both sections against the same shaft outline and landing reference. If one package is deeper, show where that difference is accommodated: cabin depth, entrance position or shaft depth. The layout makes that tradeoff visible.

The worked example below uses a 120 mm package for Proposal A and a 180 mm package for Proposal B. These illustrative values let the reader follow the decision while keeping the final product dimensions tied to the selected drawing.

Worked Example: Enough Total Width, Too Little on One Side

Assume a project requires a 900 mm clear opening at a fixed landing position. The plan shows 320 mm of available space to the left and 750 mm to the right, measured within the defined door-assembly zones.

AVAILABLE WIDTH AT THE FIXED OPENING POSITION

Left obstruction                                      Right obstruction
|<-- 320 -->|<---------- 900 clear ---------->|<-- 750 -->|

Total: 320 + 900 + 750 = 1,970 mm

Compare two layouts whose stated side requirements include the relevant frame, panel and dimensional allowances.

On small screens, scroll the table to read every column.

Proposal A needs 1,860 mm in total, less than the available 1,970 mm. It still conflicts with the left obstruction by 480 − 320 = 160 mm. Resolving that conflict requires a change to the entrance position or the left-side requirement.

Proposal B passes the side-space comparison with 220 mm remaining on the left and 70 mm on the right. Continue its assessment in the depth direction.

The coordinated entrance detail allows 160 mm for the package between agreed reference lines. Proposal A requires 120 mm; Proposal B requires 180 mm and is 20 mm too deep. The remaining problem is width for A and depth for B.

The appropriate response is to review a different package or a coordinated layout revision. Moving the opening, changing the entrance assembly or revising cabin geometry may be worth investigating, but each changes another project condition. The supplier and building designer must show what changes and which requirements are preserved.

If the opening can move, redraw both side spaces and review the passenger approach, landing entrance and car layout. Follow the width and depth checks with the header, mounting and retained-interface checks.

Can Shifting the Door Opening Solve the Conflict?

The failed comparison becomes useful when the team tests a defined change. Suppose the architect permits the opening to shift to the right without changing the two outer obstructions. Let the shift be x millimetres. The new available left space is 320 + x; the new right space is 750 − x.

For Proposal A’s 480 mm requirement on both sides:

Left condition: 320 + x ≥ 480, so x ≥ 160 mm.

Right condition: 750 − x ≥ 480, so x ≤ 270 mm.

There is therefore a geometrically feasible shift range of 160–270 mm for this simplified width check. A shift of 200 mm gives 520 mm on the left and 550 mm on the right, leaving 40 mm and 70 mm against the stated side requirements. Proposal A’s assumed 120 mm package also fits the 160 mm depth allocation, with 40 mm remaining.

The calculation identifies a specific design option. Proposal A becomes a candidate if the 200 mm entrance shift is compatible with the landing approach, cabin entrance, structure and other equipment. If the architecture permits only a 100 mm shift, the left-side conflict remains.

Proposal B needs a different depth arrangement or a change to the relevant car/shaft geometry. Keep the width remedy for A and the depth remedy for B separate when requesting revised layouts.

At either end of the 160–270 mm range, one side has zero margin against the hypothetical requirement. The project still has to account for any excluded uncertainty or construction variation. Choosing an interior point gives geometric room in this example, but the supplier’s actual drawing basis determines whether additional allowances are needed.

For a shaft serving several floors, also check the common-width method across floors. The entrance position must work with the usable shaft space through the full travel.

Clear Opening for Wheelchairs, Luggage and Carts

Door geometry is useful only if the resulting entrance serves the intended task. Define that task before asking the supplier to maximize the opening within a small shaft.

For a home elevator, identify the actual user, mobility aid and approach direction, then review how to measure a home elevator shaft. For a passenger elevator, include recurring luggage, strollers or service carts. Check the turn outside the door as well as the passage through it.

Keep clear opening and cabin dimensions unchanged in the first comparison where possible. If an alternative needs a smaller opening or usable cabin, show that reduction explicitly as a changed requirement.

Compare opening and closing behavior, moving mass, duty and protection arrangement for the offered equipment. Door operation interacts with the controller, users and the rest of the elevator.

Which Door Type Is Faster? Compare the Full Stop Cycle

Opening time matters, but the buyer experiences the full stop: door preparation and coupling, opening, passenger transfer and dwell, closing, and confirmation that the elevator can continue. Record which interval a supplier’s quoted time covers. A motor’s peak speed and an entrance’s complete operating cycle are different measurements.

In a simplified timing example, assume sequential intervals with no overlap. Proposal A opens in 2.5 seconds, dwells for 4.0 seconds and closes in 3.0 seconds: 2.5 + 4.0 + 3.0 = 9.5 seconds. Proposal B opens in 3.0 seconds with the same dwell and closing time: 3.0 + 4.0 + 3.0 = 10.0 seconds. The opening advantage is half a second within this roughly ten-second interval.

A real evaluation adds controller sequencing, coupling/unlocking, door protection, reopening events and the passenger task. Keep dwell, endpoints and conditions consistent between offers so the comparison isolates the difference being assessed. Select operating settings through the equipment’s approved commissioning process.

Panel construction also affects moving mass, operator selection and achievable performance. Keep the panel specification attached to the timing offer, and update both when the construction changes.

Replacing Door Operators in Elevator Modernization

In a replacement project, the car-door operator may work with retained landing doors at several floors. Check their condition, alignment and repair history floor by floor, documenting exceptions alongside the common arrangement.

Distinguish the layers of compatibility:

On small screens, scroll the table to read every column.

Review how the door controller and main lift controller exchange commands, limit indications and reversing signals. The replacement operator must participate in the intended sequence with the retained devices.

The acceptance record should identify retained components and their condition, cover the installed floor interfaces and required protection/locking functions, and record performance under the approved procedure.

Which Door Type Needs More Maintenance?

Compare the selected components and duty. Identify surfaces that collect debris, items requiring adjustment and the access available after cladding and finishes are installed.

The maintenance schedule should identify the applicable tracks, guides, transmission parts and connections, with the access needed for inspection and replacement. Use that schedule to compare maintainability on the actual configuration.

For a quotation, separate scheduled maintenance, replacement-part identification and access to remove major components. Compare reliability data only when the configuration, usage and observation period are stated.

Elevator Door Comparison Worksheet

Give both suppliers the same measured plan and required passage. Ask them to fill the same fields and mark any changed assumption.

On small screens, scroll the table to read every column.

Read each completed column as one configuration. If the proposed door, frame, finish or panel construction changes, obtain the corresponding revision rather than retaining an old dimension that happens to be favorable.

For modernization, attach the floor-by-floor interface assessment to this comparison sheet so the selected layout and the retained-equipment scope remain part of the same decision.

When to Choose Center-Opening vs Telescopic Doors

Evaluate C2 when both sides provide suitable parking space. Evaluate T2 when concentrating parking on one side helps the layout. In both cases, preserve the user’s opening and cabin requirements while checking depth, operator space and interfaces.

If both fit, compare timing, duty, maintenance access and installed scope. If a conflict remains, revise a defined constraint and show its effect on the complete layout.