A technical specification is an important document used to describe the required electrical item clearly before purchasing, requesting quotation, or issuing a purchase order.
In industrial maintenance, electrical items such as contactors, circuit breakers, cables, motors, soft starters, VFDs, relays, sensors, and panels must be specified correctly to avoid wrong supply, installation problems, and equipment failure.
A good technical specification helps maintenance, procurement, suppliers, and contractors understand the requirement clearly.
What Is a Technical Specification?
A technical specification is a document or description that defines the technical requirements of an item.
It may include:
- Item name
- Application
- Voltage rating
- Current rating
- Power rating
- Frequency
- Number of phases
- Number of poles
- Material
- Protection class
- Standard
- Brand or approved equivalent
- Accessories
- Testing requirements
- Documentation requirements
The purpose is to make sure the supplied item meets the required application.
Why Technical Specifications Are Important
Technical specifications are important because electrical items must match the system design and site requirements.
A poor specification can cause:
- Wrong item delivery
- Supplier confusion
- Installation delay
- Equipment incompatibility
- Safety risk
- Repeated failures
- Procurement delay
- Material rejection
- Extra cost
A clear specification reduces mistakes and improves purchasing quality.
When Is a Technical Specification Required?
A technical specification may be required for:
- Purchase requisitions
- RFQs
- Purchase orders
- New material codification
- Project work
- Replacement spare parts
- Equipment upgrades
- Contractor scope of work
- Technical bid evaluation
For critical items, a detailed specification is always recommended.
Main Sections of an Electrical Technical Specification
A good electrical technical specification may include:
- Scope
- Application
- System details
- Technical requirements
- Standards
- Environmental conditions
- Construction requirements
- Protection requirements
- Accessories
- Testing and inspection
- Documentation
- Warranty
- Delivery requirements
- Approval requirements
The level of detail depends on the item complexity.
Basic Template
A simple technical specification template can be:
| Section | Details |
|---|---|
| Item Name | Name of required item |
| Application | Where the item will be used |
| Voltage Rating | Operating voltage |
| Current Rating | Rated current |
| Power Rating | kW, HP, or kVA if applicable |
| Frequency | 50Hz or 60Hz |
| Phase | Single-phase or three-phase |
| Protection | IP rating, overload, short circuit, etc. |
| Standard | IEC, UL, NEMA, or site standard |
| Brand | Preferred brand or equivalent |
| Accessories | Required accessories |
| Documents | Datasheet, manual, test certificate |
| Remarks | Special requirements |
Electrical System Information
Before writing a specification, collect system information.
Check:
- Supply voltage
- Frequency
- Number of phases
- Earthing system
- Load type
- Motor rating if applicable
- Control voltage
- Panel type
- Installation location
- Indoor or outdoor use
- Ambient temperature
- Existing equipment brand
- Space limitation
- Cable size
- Protection coordination
This information helps avoid wrong item selection.
Specification for Contactors
For contactors, include:
- Number of poles
- Utilization category
- Rated operational current
- Rated voltage
- Coil voltage
- Frequency
- Auxiliary contacts
- Mounting type
- Compatible overload relay
- Brand or approved equivalent
- Standard
Example:
CONTACTOR, 3 POLE, AC-3 DUTY, RATED CURRENT 32A, RATED VOLTAGE 400VAC, COIL VOLTAGE 230VAC, 50/60HZ, AUX CONTACT 1NO+1NC, DIN RAIL/PANEL MOUNTING, IEC STANDARD, SCHNEIDER OR APPROVED EQUIVALENT.
Specification for Circuit Breakers
For circuit breakers, include:
- Type: MCB, MCCB, ACB
- Number of poles
- Rated current
- Rated voltage
- Breaking capacity
- Trip unit type
- Adjustable settings if required
- Mounting type
- Accessories
- Standard
- Brand or equivalent
Example:
MCCB, 3P, 100A, 415VAC, 50/60HZ, BREAKING CAPACITY 36KA, THERMAL MAGNETIC TRIP UNIT, PANEL MOUNTING, IEC 60947 STANDARD, ABB/SCHNEIDER/SIEMENS OR APPROVED EQUIVALENT.
Specification for Cables
For power cables, include:
- Conductor material
- Number of cores
- Cable size
- Insulation type
- Sheath type
- Voltage grade
- Armoured or unarmoured
- Fire resistance requirement if applicable
- Standard
- Application
- Color if required
Example:
POWER CABLE, COPPER CONDUCTOR, 4 CORE, 25 SQMM, XLPE INSULATED, PVC SHEATHED, ARMOURED, VOLTAGE GRADE 0.6/1KV, SUITABLE FOR INDUSTRIAL INSTALLATION, IEC STANDARD.
Specification for Control Cables
For control cables, include:
- Number of cores
- Core size
- Conductor material
- Insulation
- Shielding if required
- Armouring if required
- Voltage grade
- Application
- Standard
Example:
CONTROL CABLE, COPPER, 12 CORE, 1.5 SQMM, PVC INSULATED, PVC SHEATHED, 300/500V, NUMBERED CORES, SUITABLE FOR INDUSTRIAL CONTROL CIRCUITS.
Specification for Electric Motors
For motors, include:
- Power rating
- Voltage
- Phase
- Frequency
- Speed
- Mounting type
- Frame size
- IP rating
- Insulation class
- Efficiency class
- Duty type
- Bearing type if required
- Application
- Standard
Example:
ELECTRIC MOTOR, 15KW, 3PH, 400VAC, 50HZ, 1450RPM, FOOT MOUNTED, IP55, INSULATION CLASS F, IE3 EFFICIENCY, S1 DUTY, SUITABLE FOR CENTRIFUGAL PUMP APPLICATION.
Specification for Soft Starters
For soft starters, include:
- Motor power rating
- Rated current
- Voltage range
- Control supply voltage
- Starting duty
- Bypass contactor requirement
- Protection features
- Communication if required
- Mounting type
- Brand or equivalent
- Standard
Example:
SOFT STARTER, SUITABLE FOR 75KW THREE-PHASE MOTOR, RATED CURRENT AS PER MOTOR APPLICATION, OPERATING VOLTAGE 380-415VAC, CONTROL SUPPLY 110-230VAC, WITH MOTOR PROTECTION FUNCTIONS, SUITABLE FOR INDUSTRIAL MOTOR STARTING APPLICATION, SIEMENS/SCHNEIDER OR APPROVED EQUIVALENT.
Specification for VFDs
For VFDs, include:
- Motor power rating
- Rated output current
- Input voltage
- Output voltage
- Frequency range
- Overload capacity
- Control mode
- Communication protocol
- IP rating
- Braking option if required
- EMC filter if required
- Application
- Brand or equivalent
Example:
VARIABLE FREQUENCY DRIVE, SUITABLE FOR 30KW THREE-PHASE MOTOR, INPUT 380-415VAC, 50HZ, OUTPUT CURRENT SUITABLE FOR MOTOR NAMEPLATE CURRENT, WITH V/F AND VECTOR CONTROL, MODBUS COMMUNICATION, IP20 PANEL MOUNTING, SUITABLE FOR PUMP APPLICATION.
Specification for Relays
For relays, include:
- Relay type
- Coil voltage
- Contact configuration
- Contact rating
- Mounting type
- Base requirement
- Indication LED if required
- Brand or equivalent
Example:
CONTROL RELAY, 24VDC COIL, 2CO CONTACTS, 5A CONTACT RATING, PLUG-IN TYPE, WITH BASE AND LED INDICATION, SUITABLE FOR INDUSTRIAL CONTROL PANEL.
Specification for Sensors
For sensors, include:
- Sensor type
- Supply voltage
- Output type
- Contact logic
- Sensing distance
- Body size
- Connector type
- IP rating
- Material
- Application
Example:
PROXIMITY SENSOR, INDUCTIVE TYPE, 24VDC, PNP NO OUTPUT, M12 CONNECTOR, SENSING DISTANCE 8MM, CYLINDRICAL BODY, IP67, SUITABLE FOR INDUSTRIAL MACHINE APPLICATION.
Specification for Lighting Items
For industrial lighting, include:
- Lamp type
- Wattage
- Voltage
- Color temperature
- Lumen output if required
- IP rating
- Mounting type
- Indoor or outdoor use
- Body material
- Application
Example:
LED HIGH BAY LIGHT, 150W, 220-240VAC, 50HZ, 6500K COOL WHITE, IP65, ALUMINUM BODY, SUSPENDED MOUNTING, SUITABLE FOR INDUSTRIAL WORKSHOP APPLICATION.
Environmental Conditions
Electrical items should be suitable for site conditions.
Mention if applicable:
- Indoor or outdoor installation
- Ambient temperature
- Dusty area
- Humidity
- Corrosive area
- Vibration
- Hazardous area
- High temperature area
- Washdown area
Example:
The item shall be suitable for indoor industrial installation in dusty environment with ambient temperature up to 45°C.
Standards and Compliance
Mention required standards if known.
Common standards include:
- IEC
- IEEE
- NEMA
- UL
- CE
- ISO
- Local electrical regulations
- Company standards
For industrial electrical items, IEC standards are commonly used.
Documentation Requirements
Ask suppliers to provide documents such as:
- Datasheet
- User manual
- Wiring diagram
- Test certificate
- Calibration certificate if applicable
- Compliance certificate
- Warranty certificate
- Country of origin
- Installation instructions
Documentation helps technical review and future maintenance.
Inspection and Testing Requirements
For critical items, mention inspection and testing requirements.
Examples:
- Visual inspection
- Functional test
- Factory test report
- Insulation resistance test
- Calibration certificate
- Load test
- FAT if required
- Site acceptance test
Testing requirements depend on the item type and criticality.
Equivalent Items
If equivalent items are acceptable, write:
“Approved equivalent is acceptable subject to technical review.”
If equivalent is not acceptable, write:
“Equivalent is not acceptable. Exact part number and brand are required.”
This avoids confusion during procurement.
Technical Specification Checklist
| Check Point | What to Verify |
|---|---|
| Item name | Clear and correct |
| Application | Mentioned if required |
| Voltage | Correct voltage rating |
| Current | Correct current rating |
| Power | Correct kW, HP, or kVA |
| Frequency | 50Hz or 60Hz |
| Phase | Single or three phase |
| Protection | IP rating and protection features |
| Size | Correct physical size |
| Standard | IEC/UL/NEMA if required |
| Accessories | Included if needed |
| Documents | Datasheet and manual requested |
| Equivalent | Allowed or not allowed |
| Environment | Suitable for site condition |
Common Specification Mistakes
Common mistakes include:
- Missing voltage rating
- Missing coil voltage
- Missing current rating
- Missing breaking capacity
- Missing cable type
- Missing IP rating
- Missing application
- Not mentioning accessories
- Not mentioning standard
- Accepting equivalent without technical review
- Writing description too generally
- Copying old specifications without checking
Practical Example
A maintenance engineer needs to order a contactor for an 11 kW motor starter.
Weak specification:
“Contactor for motor, 230V.”
Professional specification:
“CONTACTOR, 3P, AC-3 DUTY, RATED CURRENT 25A OR SUITABLE FOR 11KW MOTOR AT 400VAC, COIL VOLTAGE 230VAC, 50/60HZ, AUX CONTACT 1NO+1NC, DIN RAIL/PANEL MOUNTING, IEC STANDARD, SCHNEIDER OR APPROVED EQUIVALENT.”
The professional specification gives procurement and supplier enough information to quote correctly.
Safety and Quality Notes
Electrical items must be selected carefully because wrong items can create safety hazards.
For protection devices, motor control equipment, panels, and critical systems, technical approval is required before purchase.
Do not approve alternatives only based on price.
Always verify voltage, current, protection rating, compatibility, and application.
Conclusion
A technical specification is essential for purchasing electrical items correctly.
A good specification should include item name, application, voltage, current, power, frequency, phase, protection, standard, brand, accessories, documents, and equivalent requirements.
Clear technical specifications reduce wrong supply, improve procurement quality, and support safe industrial maintenance.
