The delay-on timer (also known as an on-delay or delay-on-make timer) symbol represents a control relay whose output contacts change state only after a preset time interval following the application of voltage to its coil. Because industrial control panels are built globally, the exact schematic representation depends heavily on the regional standard used by the original equipment manufacturer (OEM). Below is the definitive reference for interpreting these symbols, mapping pinouts, and safely troubleshooting them in the field.

The Complete Delay-On Timer Symbol Reference Table

The following table maps the delay-on timer coil and contact symbols across the three major schematic standards you will encounter on machinery built between 1980 and 2026. Use this to identify the component type before tracing wires.

Component / Function IEC 60617 (Global / EU / Modern UK) ANSI/IEEE 315 (North America / UL508A) Legacy BS 3939 (Pre-1996 UK)
Timer Coil
(The trigger circuit)		 Rectangle with an 'X' inside, or a rectangle with two opposing internal arrows. Circle or rectangle containing 'TD' (Time Delay), 'TR' (Time Relay), or a clock face icon. Rectangle with a diagonal cross or semi-circle notation.
On-Delay NO Contact
(Closes after time delay)		 Standard NO contact symbol with an arrow on the moving blade pointing away from the actuating pivot line. Standard NO contact with a 'TD' label, or a specific delayed-make arrow notation. NO contact with a delayed slash or specific cross-hatch on the blade.
On-Delay NC Contact
(Opens after time delay)		 Standard NC contact symbol with an arrow on the moving blade pointing away from the actuating pivot line. Standard NC contact with a 'TD' label or delayed-break notation. NC contact with a delayed slash notation.
Instantaneous Contact
(Changes state immediately on coil energization, common on multi-function timers)		 Standard NO/NC contact with no timing arrow on the blade. Standard NO/NC contact, often labeled 'INST'. Standard NO/NC contact without timing modifiers.

Reference Note: For comprehensive symbol libraries, consult the Electrical Engineering Portal's IEC symbol guide or manufacturer datasheets like Macromatic's technical documents for North American ANSI implementations.

Rows People Get Wrong (and Faded Marking Protocols)

When reading schematics under poor lighting or troubleshooting legacy panels, two specific symbol misinterpretations lead to dangerous wiring errors or immediate machine faults.

The Arrow Direction Trap: On-Delay vs. Off-Delay

In the IEC 60617 standard, the direction of the arrow on the contact blade dictates the timing function. This is the most frequently misread symbol in industrial electrical work.

  • Arrow pointing AWAY from the pivot (actuating line): This is an On-Delay contact. The contact delays its transition when the coil is energized, but returns instantly when power is removed.
  • Arrow pointing TOWARDS the pivot: This is an Off-Delay (delay-on-break) contact. The contact transitions instantly when energized, but delays its return when power is removed.
SAFETY WARNING: If you wire an off-delay motor starter circuit using an on-delay timer because you misread the arrow direction, the motor will start immediately and coast to a stop on a delay. In applications like conveyor tensioning or pneumatic sequencing, this reversed logic can cause severe mechanical shock, product jams, or crush hazards.

Coil vs. Contact Confusion

Beginners often look at the timer coil symbol (the box with the 'X' or 'TD') and assume the wires connected to it are the load outputs. The coil (typically terminals A1 and A2, or pins 2 and 7 on an octal base) is strictly the input trigger. The actual load must be wired to the contact terminals (e.g., 15/16/18 for SPDT DIN-rail timers). Applying 120VAC load current to a 24VDC timer coil will instantly destroy the internal electronics or blow the control circuit fuse.

Protocol for Faded or Missing Schematics

If the panel door schematic is sun-faded, oil-stained, or missing entirely, never guess the timer function based on a smudge. Follow this bench protocol:

  1. De-energize and Lockout: Shut off the main control breaker and verify zero energy with a Category III rated multimeter (e.g., Fluke 87V).
  2. Map the Pinout: Use the multimeter in continuity mode. Identify the Common (COM), Normally Open (NO), and Normally Closed (NC) terminals. On a standard Finder 80.01 DIN-rail timer, 15 is COM, 16 is NC, and 18 is NO.
  3. Verify the Coil Voltage: Read the physical text printed on the timer housing. Do not rely on the schematic. An Omron H3Y-2 might look identical whether it is a 24VDC or 120VAC model; the coil voltage is printed in small text near the A1/A2 terminals.
  4. Bench Test the Delay: Apply the verified rated voltage to the coil and use a stopwatch to confirm the physical contact transition matches the dial setting before putting the machine back online.

Regional Standards: Which Schematic Applies to You?

Understanding which standard your machine was built under saves hours of troubleshooting. The physical wiring might be identical, but the paper trail differs.

  • IEC 60617 (International Electrotechnical Commission): The dominant standard in Europe, Asia, Australia, and modern global OEMs. If your machine uses DIN-rail components, metric wire sizing (mm²), and IEC color codes (Brown/Blue/Green-Yellow), the schematic will use IEC symbols. The arrow-on-blade method is strictly enforced here.
  • ANSI/IEEE 315 (North America): Standard for US and Canadian industrial panels built to UL508A or CSA C22.2 No. 14. These schematics rely heavily on text labels ('TD', 'TR') and NEMA-style contactor representations rather than the minimalist IEC geometric arrows. Wire sizes will be in AWG, and control voltages are frequently 120VAC or 24VAC.
  • Legacy BS 3939 (United Kingdom): If you are maintaining British machinery built prior to the late 1990s, you will encounter BS 3939. The UK officially harmonized with the IEC (adopting BS EN 60617) in 1996. BS 3939 used distinct cross-hatching and semi-circles for timing relays. When retrofitting these panels, it is industry best practice to redraw the schematics in modern IEC format to prevent future confusion.

Delay On Timer Symbol FAQ

What does the arrow direction mean on a delay on timer symbol?

In IEC schematics, the arrow on the moving contact blade indicates the timing behavior relative to the pivot point (actuating line). An arrow pointing away from the pivot means the contact delays its action when the coil is energized (On-Delay). An arrow pointing towards the pivot means the contact delays its return when the coil is de-energized (Off-Delay). If there is no arrow, the contact is instantaneous.

How do I wire a delay-on timer if the schematic symbol is missing?

Without a schematic, you must rely on the physical terminal markings on the device. For standard DIN-rail timers (like Schneider Zelio or Finder 80 series), wire your control voltage to A1 (positive/line) and A2 (negative/neutral). Wire your load circuit to 15 (Common) and 18 (Normally Open). The load will remain off when A1/A2 are unpowered, and will turn on only after the preset dial time expires once A1/A2 receive voltage. For 8-pin octal plug-in timers (like Macromatic TR-60), the coil is typically on pins 2 and 7, with contacts on 1/3/4 and 5/6/8.

Is a delay-on-make the same as a delay-on-break timer symbol?

No. 'Delay-on-make' is simply another industry term for an On-Delay timer (the contacts make their transition after a delay upon energization). 'Delay-on-break' refers to an Off-Delay timer (the contacts break their state after a delay upon de-energization). They serve entirely different logical functions in a circuit and are represented by different symbols (arrows pointing away vs. towards the pivot in IEC, or different text labels in ANSI). Never substitute one for the other without rewriting the control logic.

Why does my schematic show a timer coil with an 'X' but the contacts have no arrows?

If the coil is identified as a timer (rectangle with an 'X' or clock symbol) but the associated contacts lack timing arrows, those specific contacts are instantaneous. Many modern multi-function timers (such as the Omron H3DT series) feature both timed contacts and instantaneous contacts on the same relay block. The instantaneous contacts change state the exact millisecond the coil receives voltage, bypassing the timing circuit, which is useful for providing immediate feedback to a PLC while the timed circuit sequences a motor.