Technical Notes: Selection, Drawing Reading and Standards Interpretation
Reading drawings
How to read and draw single-line diagrams, secondary wiring diagrams and terminal block diagrams.
How to read and draw a distribution box wiring diagram: symbol reference + standard sub-panel layout (with factory photos)
A distribution box wiring diagram is the backbone of an electrical assembly. This article breaks down three drawing types — single-line diagrams, control schematics and terminal layouts — against GB/T 7251.1, GB 50054 and JGJ 46, gives a 24-symbol reference, and maps four points from drawing to hardware using factory photos, with six FAQs.
Read → Reading drawingsHow to read a control cabinet wiring diagram: PLC control circuit vs main circuit
How to read a control cabinet wiring diagram: the 4 main sections — PLC control circuit, main circuit, secondary wiring, and terminal blocks — plus the drawing-to-physical-panel reading sequence, with 4 shop-floor photos for comparison.
Read → Reading drawingsPump VFD panel schematic: constant-pressure water supply with duty/standby rotation
Pump VFD panel schematic: PID constant-pressure control, automatic duty/standby rotation and multi-pump sequencing, with 4 workshop photos and 5 FAQs.
Read → Reading drawingsHow to read a main distribution board layout: incoming / metering / outgoing + configuration checklist
The primary distribution box is the "main switch" for temporary power on a construction site. Get the configuration wrong and every downstream secondary and tertiary box goes wrong with it. This article breaks down the standard configuration of a primary distribution box per GB 50054 (Code for Design of Low-Voltage Distribution) and JGJ 46-2005 (Technical Code for Safety of Temporary Electricity on Construction Sites): how to lay out the incoming disconnect switch, main ground fault protection, metering, and outgoing branch circuits, with a standard configuration
Read → Reading drawingsHow to read a distribution box system diagram: a 5-step method from incoming line to branch circuits
A distribution box system diagram is the "ID card" of an assembled cabinet — one drawing that lays out the incoming line, busbars, breakers, current transformers, and outgoing branch circuits in full. This article follows GB/T 6988.1 (Preparation of documents used in electrotechnology) to teach you a 5-step method for reading any distribution box system diagram, with a quick-reference table of graphical and letter symbols. Every cabinet from Zhejiang Golden Unicorn ships with 5 categories of as-built drawings plus inspection reports, ISO
Read → Reading drawingsHow should a three-level distribution box standard configuration diagram be laid out? End-of-line distribution · how to select ground fault protection + overload
The three-tier distribution box (switch box) is the last line of defense before equipment and the only tier that provides personnel protection (RCD ≤ 30mA). This article breaks down the standard configuration of a three-tier box per JGJ 46-2005: final-stage disconnect switch, 30mA RCD, and how to configure outgoing sockets/terminals, with a final-stage box selection table. Zhejiang Golden Unicorn produces 5,800+ units annually, MOQ 1 unit · 15
Read → Reading drawingsDistribution box system diagram reading guide: graphical symbols, text symbols, and circuit numbering rules
Reading system diagrams is a core skill for electrical engineers. This guide breaks down the three rule sets for distribution box system diagrams — graphical symbols, letter codes and circuit numbering — and includes a 32-item quick-reference table of high-frequency symbols. Written for newcomers in procurement, estimating, construction and switchgear assembly plants. Zhejiang Golden Unicorn is ISO 9001 certified and produces 5000+ units per year.
Read → Reading drawingsDistribution box system diagram symbols: a 32-item graphical symbol quick-reference table
System diagram symbols are the "alphabet" of reading electrical drawings. This article compiles 32 high-frequency graphical and letter symbols per GB/T 6988 and GB 4728, covering 4 categories: switching devices, protection, measurement, and busbars. Suitable for beginners as a quick reference. Zhejiang Golden Unicorn is ISO 9001 certified.
Read → Reading drawingsHow to Read a PLC Control Cabinet Wiring Diagram: A 4-Section Method for Power, Input, Output and Communication
A PLC control panel wiring diagram is the roadmap for commissioning and troubleshooting — if you can't read the drawing, you can't trace a fault. This article follows GB/T 6988.1 (Preparation of documents used in electrotechnology) to show you how to read a PLC control panel wiring diagram quickly using the 4-section method: power section, input section, output section, and communication section, with terminal block numbering rules and a checklist of common wiring errors. Every PLC panel from Zhejiang Golden Unicorn ships with a complete
Read → Reading drawingsHow do I read an electrical control cabinet wiring diagram? Reading the main circuit vs the control circuit
An electrical control cabinet wiring diagram has two parts: the main circuit and the control circuit. The main circuit handles power; the control circuit handles logic. The reading methods are completely different. This article follows GB/T 6988.1 to teach you the main-circuit-first, left-to-right, top-to-bottom reading method, with a motor forward/reverse wiring diagram example. Every cabinet from Zhejiang Golden Unicorn ships with a complete wiring diagram + terminal block diagram, ISO 9001:201
Read → Reading drawingsHow to read an electrical control box wiring diagram? Motor forward/reverse and star-delta starting explained
Motor forward/reverse and star-delta startup are the two most common control circuits in electrical control boxes. Understanding these two diagrams means you have mastered the core logic of electrical control. This article breaks down both wiring diagrams wire by wire per GB/T 6988.1, with a component code reference table. Zhejiang Golden Unicorn builds control boxes to drawing, ISO 9001:2015 certified, MOQ 1 unit · 15-25 days · 9
Read → Reading drawingsHow to read a VFD panel wiring diagram? Main circuit + control circuit + analog
A VFD panel wiring diagram has more to it than a standard control cabinet: the drive's main circuit, control terminals and analog signal wiring all add complexity. This article breaks down the VFD panel wiring diagram into 3 sections per GB/T 6988.1: main circuit (R/S/T → U/V/W), control circuit (start/stop + forward/reverse + fault), and analog signals (frequency reference 4-20mA / 0-10V). Zhejiang Golden Unicorn
Read → Reading drawingsHow do you read a high-voltage soft starter schematic? 6kV/10kV soft starter single-line diagram
High-voltage soft starters serve 6kV/10kV high-power motors (200kW to 20000kW), and the primary system diagram is far more complex than a low-voltage one — it involves vacuum circuit breakers, high-voltage thyristor valve groups, bypass disconnectors and more. This article breaks down how to read a high-voltage soft starter primary system diagram per GB/T 11022 (Common Specifications for High-Voltage Switchgear and Controlgear Standards).
Read → Reading drawingsHow to read a soft starter control cabinet wiring diagram? Bypass contactor + start/stop logic
A soft starter cabinet wiring diagram comes down to three parts: the soft starter main circuit, the bypass contactor, and the start/stop logic. This article breaks down a soft starter cabinet wiring diagram per GB/T 14048.6 and walks through every terminal using a Schneider ATS480 as the example. Zhejiang Golden Unicorn soft starter cabinets ship with a wiring diagram and parameter setting table, ISO 9001:2015 certified, MOQ 1 unit · 15-25 days
Read → Reading drawingsHow to read the wiring diagram for a fan control cabinet? Star-delta / VFD / two-speed fan
Fan control cabinets come in three typical configurations — star-delta starting, VFD speed control, and two-speed motor switching — each with a different wiring diagram. This article breaks down all three fan control cabinet wiring diagrams per GB/T 6988.1. Zhejiang Golden Unicorn fan control cabinets cover the full 7.5kW to 250kW power range, ISO 9001:2015 certified, MOQ 1 unit · 15-25 days · 9
Read → Reading drawingsWhat is the working principle of a three-phase four-wire junction box? Star and delta connection diagrams
The three-phase four-wire system is the standard low-voltage distribution configuration in China — three phase conductors L1/L2/L3 plus a neutral. How are they arranged inside a junction box? This article uses GB/T 6988.1 to illustrate wye (Y) and delta (△) connections for three-phase four-wire junction boxes, with phase sequence arrangement and neutral grounding requirements. Zhejiang Golden Unicorn produces over 20,000 three-phase junction boxes annually, ISO 9001:2
Read → Reading drawingsHow do you read the wiring diagram of a three-phase four-wire junction box? L1/L2/L3/N/PE arrangement rules
The three-phase four-wire junction box wiring diagram is a foundational drawing in electrical construction — how are the five conductors L1/L2/L3/N/PE arranged, connected, and labeled? This article explains how to read the diagram per GB/T 6988.1, with phase sequence color codes and terminal arrangement rules. Zhejiang Golden Unicorn produces 20,000+ three-phase junction boxes per year, ISO 9001:2015 · MOQ 1 unit.
Read → Reading drawingsHow to read the physical wiring diagram of a meter junction box? Detailed explanation of current transformer secondary wiring
The metering junction box is the hub of the energy metering circuit — how do the CT secondary conductors run, how is the voltage circuit connected, and how is a test terminal block used? This article illustrates metering junction box field wiring per GB/T 17215 (electrical measuring equipment), with three-phase three-wire and three-phase four-wire metering wiring comparisons. Zhejiang Golden Unicorn produces 5,000+ meter boxes and metering cabinets per year.
Read → Reading drawingsHow to read a terminal box wiring diagram: single- and double-tier terminal block arrangement rules
A terminal box wiring diagram is the "connection map" of a control circuit — which wire lands on which terminal, how internal and external wiring correspond, and how single- and double-deck terminal blocks are laid out. This article explains how to read terminal block wiring diagrams per GB/T 6988.1, with terminal numbering rules. Zhejiang Golden Unicorn produces 20,000+ terminal boxes per year.
Read → Reading drawingsHow to read an equipotential bonding terminal box wiring diagram — MEB/LEB connections explained
The equipotential bonding terminal box is the last line of defense against electric shock — how do you wire MEB (main equipotential bonding) and LEB (local equipotential bonding)? This article illustrates equipotential bonding terminal box wiring per GB 50303 and GB 50057 (Code for Design of Lightning Protection of Buildings), with a bathroom LEB wiring example. Zhejiang Golden Unicorn produces 10,000+ equipotential bonding terminal boxes per year.
Read → Reading drawingsHow to Read a Solar Combiner Box Wiring Diagram: Positive/Negative, Surge Protective Device, and Monitoring Wiring — Primary and Secondary Drawing Reading
A combiner box wiring diagram reads in two halves: the DC primary circuit and the secondary monitoring circuit. One half runs PV+/PV- through the fuses to the output; the other covers the auxiliary wiring for the SPD and the monitoring module. This article follows GB/T 18479 to set out the reading sequence for the diagram and the key wiring points for polarity, surge protection and monitoring. Zhejiang Golden Unicorn builds combiner box enclosures and ships each unit with a cutout drawing and an enclosure inspection record, ISO 9001:2015 certified,
Read →Photo galleries
Shop-floor photo gallery of cabinet types: real units beat renderings.
Distribution cabinet gallery: GGD/GCS/MNS/power cabinets, 60+ workshop photos
A gallery of distribution cabinets — GGD, GCS, MNS, XL-21, power cabinets and changeover cabinets — with 60+ workshop photos, standard dimensions, typical configurations and selection notes.
Read → Photo galleriesDistribution box gallery: lighting, power and outdoor boxes
Distribution box photos: lighting distribution boxes, power distribution boxes, outdoor distribution boxes and stainless steel distribution boxes, with dimensions, typical applications and selection points.
Read → Photo galleriesControl cabinet gallery: PLC, VFD and soft starter cabinets from the workshop
Control cabinet photo gallery: 50+ shop-floor photos of PLC control cabinets, VFD panels, soft starter cabinets and MCC control cabinets, with dimensions, selection and wiring points.
Read → Photo galleriesJunction box gallery: waterproof, explosion-proof and stainless steel junction boxes
Junction Box Photo Gallery: 40+ photos of waterproof, explosion-proof, stainless steel, surface-mount and flush-mount junction boxes, with dimensions, IP ratings and a selection comparison table.
Read → Photo galleriesOperator console photos: custom build shop floor photos of non-standard operator consoles / sloped consoles / desk-style consoles
Operator Console Photo Gallery: 30+ Shop-Floor Photos of Custom Non-Standard Consoles, Sloped Operator Consoles, Piano-Style Control Consoles, Two-Tier Consoles and Monitoring Consoles — with Dimensions + Configurations + Selection Guide.
Read → Photo galleriesHow to read GGD distribution cabinet photos? Illustrated guide to frame / busbar / drawer / instrument photos
GGD is the most widely used fixed-type low-voltage distribution cabinet type in China. This article uses workshop photos to walk through 4 things to look at in a GGD cabinet: frame structure, busbar layout, outgoing breakers and meter configuration, plus a GGD selection and dimension table. Zhejiang Golden Unicorn produces 5,800+ assembled cabinets per year across GGD/GCS/MNS and other types. MOQ 1 unit · exported to 10+ countries
Read → Photo galleriesHow to read secondary distribution box photos? Photo guide to internal layout / circuits / labeling standards
The secondary distribution box is the distribution hub on a construction site — it receives power from the primary box and feeds each final-stage switch box. This article uses on-site photos to explain the internal layout, circuit arrangement and labeling standards of a secondary box, with a secondary box selection table. Zhejiang Golden Unicorn produces 5,800+ units per year, MOQ 1 unit · 15–25 days.
Read → Photo galleriesHow should distribution box signage images be read? Warning signs / circuit labels / nameplate requirements
Distribution box labels are not just stickers — GB 2894 and JGJ 46 make them mandatory. This guide illustrates the three label types on a distribution box: warning signs, circuit labels and nameplates, with a full label checklist. Every cabinet from Zhejiang Golden Unicorn ships with a complete label set; ISO 9001:2015 certified.
Read → Photo galleriesHow to Read Package Substation Photos: European / American / Pre-assembled Photo Gallery
A package substation photo tells you a lot. This article breaks down enclosure features, the 3-compartment layout and incoming/outgoing line methods, with a comparison gallery of European, American and prefabricated units. Zhejiang Golden Unicorn produces 300+ package substation enclosures per year.
Read → Photo galleriesHow to read PLC control cabinet photos: enclosure layout, wiring, and touchscreen photo gallery
Photos are the fastest way to understand how a PLC control panel is built. This article uses a set of shop-floor photos to break down the build details of a PLC panel from 4 angles: cabinet layout, wiring practice, HMI configuration and component labeling. Zhejiang Golden Unicorn builds 2,000+ PLC control panels per year, is ISO 9001:2015 certified, and exports to 10+ countries with 300+ customers.
Read → Photo galleriesHow to read electrical control cabinet photos: control cabinet / VFD panel / soft starter cabinet photo gallery
There are many types of electrical control cabinets, and photos are more direct than text. This article uses a shop-floor photo gallery to show the internal structure, component layout and workmanship details of 3 common control cabinets — standard electrical control cabinets, VFD panels and soft starter cabinets — with visual inspection criteria. Zhejiang Golden Unicorn produces 5000+ assembled control cabinets per year, is ISO 9001:2015 certified, and exports to 10+ countries · 300
Read → Photo galleriesHow to read a VFD panel photo: actual shots of the internal layout, braking unit, and cooling fan
Photos of a VFD panel show exactly how the drive is mounted, where the braking unit sits, and how the cooling system is laid out. This article uses real workshop photo sets to walk through 4 things to look for in VFD panel photos. Zhejiang Golden Unicorn builds 1,500+ VFD panels a year, holds ISO 9001:2015 certification, and exports to 10+ countries with 300+ customers.
Read → Photo galleriesHow to read pump control cabinet photos: real shots of duty/standby and two-duty/one-standby configurations
Pump control cabinet photos show the internal layout, pump rotation control circuits, and constant pressure water supply system configuration at a glance. This photo gallery breaks down the structural differences between the two typical pump control cabinet configurations: one-duty/one-standby and two-duty/one-standby. Zhejiang Golden Unicorn builds 800+ pump control cabinets per year, is ISO 9001:2015 certified, and exports to 10+ countries with 300+ customers.
Read → Photo galleriesHow to read fire control panel photos? Real shots of dual-power, inspection, and pump-start panels
The fire pump control panel is the core equipment of a fire protection system — dual power source transfer, automatic inspection, and start/stop control of hydrant and sprinkler pumps. This article uses on-site photos to explain the structure of fire pump control panels per GB 50016 (Code for Fire Protection Design of Buildings) and GB 50116 (Code for Design of Automatic Fire Alarm Systems). Zhejiang Golden Unicorn fire pump control panels meet the requirements for dual power source transfer + automatic inspection + multi-pump rotation
Read → Photo galleriesFlush-mounted junction box photo gallery: Type 86 / Type 146 dimensions and installation photos
A flush-mount junction box is a hidden component embedded in the wall during the finishing stage — where do 86-type, 146-type and octagonal boxes each go? This article uses spec drawings and installation photos to illustrate the 5 main types of flush-mount junction boxes, with a size comparison table. Zhejiang Golden Unicorn produces 50,000+ flush-mount boxes per year. MOQ 1 unit · 15–25 days.
Read → Photo galleriesSurface-mounted junction box photo gallery — waterproof surface-mount boxes / PVC surface-mount box size comparison
A surface-mounted junction box is the visible component mounted on the wall surface — used for post-renovation additions, outdoor waterproofing, and industrial exposed wiring. This article uses specification drawings and on-site photos to explain the 3 main types: waterproof surface-mounted boxes, PVC surface-mounted boxes, and stainless steel surface-mounted boxes, with an ingress protection (IP) rating comparison. Zhejiang Golden Unicorn produces over 30,000 surface-mounted boxes annually.
Read → Photo galleriesTerminal box photo gallery — terminal box / signal terminal box, actual site photos
A terminal box is the transfer point between control circuits and signal circuits — rows of terminal blocks inside the box land each incoming and outgoing wire one-to-one. This article uses shop-floor photos to break down three types: wiring terminal boxes, signal terminal boxes, and explosion-proof terminal boxes, with a terminal block specification comparison. Zhejiang Golden Unicorn produces 20,000+ terminal boxes per year.
Read →Standards & codes
How GB/T 7251.1, JGJ 46 and Ex explosion-proof ratings apply to a specific cabinet.
Sub-distribution board standard layout: how primary, secondary and tertiary distribution are tiered, and how they are configured
Sub-distribution board standard layout: how primary, secondary and tertiary distribution are tiered, how outgoing circuits are defined. JGJ 46 / GB 50054 explained, with a typical GGJ sub-panel scheme.
Read → Standards & codesExplosion-proof requirements for mining control cabinets: Ex d I, flameproof joints and cable entry standards
Before a mining-duty control cabinet goes underground it has to clear two gates: the explosion-proof construction gate (GB 3836) and the coal mine safety certification gate (MA). The core requirements concentrate in two areas — the parameters and maintenance of flameproof joints, and the sealing rules for cable entry devices (cable glands). This article breaks down GB 3836.1 and MT 818 clause by clause. Zhejiang Golden Unicorn offers joint supply with an Ex-qualified manufacturer, I
Read → Standards & codesHow to read explosion-proof distribution box standards: understanding Ex d IIB T4
How to read explosion-proof distribution box standards? How do you break down an Ex d IIB T4 rating? GB 3836 and IEC 60079 series explained across 3 dimensions: protection type, gas group and temperature class.
Read → Standards & codesHow to calculate distribution box half-perimeter: GB 50054 worked example
The half-perimeter of a distribution box is a high-frequency concept in electrical budgeting and quota pricing. This article provides the half-perimeter calculation formula and worked examples per GB 50054, along with quota application methods. Suitable for cost estimators and switchgear assembly plants.
Read → Standards & codesInterpretation of key clauses of GB/T 17467, the technical specification for package substations
The core of package substation specifications is GB/T 17467 (high-voltage/low-voltage prefabricated substations). This article interprets the key clauses: temperature rise, ingress protection, grounding, and insulation level. Zhejiang Golden Unicorn produces 300+ package substation enclosures annually and holds ISO 9001:2015 certification.
Read → Standards & codesWhat are the installation requirements for control cabinets? Foundation, mounting, grounding, and incoming/outgoing cable requirements
Improper control cabinet installation is one of the main causes of later failures — an uneven foundation deforms the cabinet, poor grounding causes interference, and disorganized cable entry makes maintenance difficult. This article summarizes the 6 major control cabinet installation requirements per GB 50054 (Code for Design of Low-Voltage Distribution) and GB 50303 (Code for Acceptance of Construction Quality of Building Electrical Engineering). Zhejiang Golden Unicorn provides an installation guide manual, I
Read → Standards & codesJunction box installation requirements: GB 50303 spacing, mounting and sealing
Improper junction box installation is the most common deduction item in electrical acceptance inspections. This article breaks down the 5 major requirements for junction box installation per GB 50303 (Code for Acceptance of Construction Quality of Building Electrical Engineering): location, mounting, sealing, grounding and labeling, with an acceptance inspection checklist. Zhejiang Golden Unicorn builds to drawing, ISO 9001:2015 · MOQ 1 unit · 15–25 days.
Read → Standards & codesJunction box compliance quick reference: material / ingress protection (IP) rating / flame-retardant requirements
What codes apply to junction box selection? Material, ingress protection, and flame retardancy — all three matter. This article compiles a quick-reference table of junction box code requirements per GB/T 7251.1 and GB 8613, with selection comparisons for various environments. Zhejiang Golden Unicorn produces 30,000+ junction boxes per year. ISO 9001:2015 · MOQ 1 unit.
Read → Standards & codesEquipotential bonding terminal box installation: location, height, and connection requirements
Wrong location, undersized bonding conductors, wrong wire color — and the whole installation fails inspection. This article breaks down the 5 code requirements for equipotential bonding terminal box installation per GB 50303, with an inspection checklist. Zhejiang Golden Unicorn produces 10,000+ equipotential boxes per year, ISO 9001:2015 · MOQ 1 unit.
Read → Standards & codesHow to read explosion-proof distribution box ratings? Gas group IIA/IIB/IIC + temperature class T1-T6 — a full guide to explosion-proof markings
The explosion-proof rating is the "identity code" of an explosion-proof distribution box: the gas group (IIA/IIB/IIC) determines how severe a flame propagation it can contain, and the temperature class (T1–T6) determines the maximum surface temperature allowed. This article breaks down each segment of the explosion-proof marking per GB 3836.1 (Explosive Atmospheres — Part 1: General Requirements), with a group-temperature reference for common hazardous gases
Read → Standards & codesHow to wire an explosion-proof distribution box: cable entry devices / cable glands / sealing rings — installation code
80% of explosion-proof distribution box failures start at the incoming cable connection: a gland not tightened down, a sealing ring cut open, a spare entry left unplugged — any one of these voids the explosion-proof rating of the entire enclosure. This article breaks down the correct practice for cable entry devices (glands) and sealing rings per GB 3836.1 and GB 3836.2, with a 5-step installation sequence and a checklist of common violations. Zhejiang Golden Unicorn provides
Read → Standards & codesHow is fire protection configured for a BESS cabinet? GB/T 42288 fire system configuration: detection, suppression, ventilation
Lithium battery thermal runaway is the number one risk in a BESS cabinet. Fire protection is not an option — it is a life-safety requirement. GB/T 42288, the Safety Code for Electrochemical Energy Storage Stations, sets out system-level requirements for fire detection, suppression, ventilation and pressure relief. Zhejiang Golden Unicorn handles BESS cabinet enclosure fabrication — detector mounting positions, suppression piping pass-throughs, pressure relief structures and thermal insulation installation are completed by us to drawing. Battery clusters, BMS and fire control panels are supplied by partners.
Read → Standards & codesHow is rain testing performed on containerized BESS cabinets? IPX5/IPX6 ingress protection verification per GB/T 4208
Outdoor containerized BESS cabinets must withstand 20 years of driving rain — the ingress protection (IPX5/IPX6) rain test on the enclosure is a key pre-shipment verification. GB/T 4208 (IP code for enclosure ingress protection) specifies the nozzle, water flow rate, duration and pass criteria. Zhejiang Golden Unicorn performs enclosure fabrication for BESS containers; the sealing structure is designed and manufactured in-house, and third-party IP testing can be arranged at the factory.
Read →Selection & principles
Selection by operating conditions and principle breakdowns: how to calculate capacity, how to configure circuits, how to settle on a scheme.
Power factor correction cabinet: what it does and how to size it, from 0.7 to 0.95
What a power factor correction cabinet does and how to size it: from 0.7 to 0.95, how much capacitance do you need? GB/T 15576 and GB 50054 explained, with a quick sizing table.
Read → Selection & principlesWhat is an MCC panel? How it differs from a distribution cabinet and a motor control circuit
What is an MCC panel? MCC = Motor Control Center — a drawer-type assembly that combines starting, protection and control for multiple motors. Common in large plants, chemical works, power stations and water treatment.
Read → Selection & principlesFire pump control panel: duty/standby, manual/auto and periodic testing
Fire pump control panel: duty/standby, manual/auto, mechanical emergency start, inspection function (GB 50974-2014). 3 workshop photos + 5 FAQs.
Read → Selection & principlesWhat is an equipotential bonding terminal box? Where it goes and how to wire it
What does an equipotential bonding terminal box do? Shock protection for bathrooms, washrooms and swimming pools — where to install it, how to wire it, and how it differs from supplementary grounding.
Read → Selection & principlesHow to determine equipotential bonding terminal box dimensions: surface-mount / flush-mount specs and installation height
How to size an equipotential bonding terminal box: surface-mount / flush-mount specs, terminal count selection, mounting height, wiring space allowance. Quick-reference table + 5 FAQs.
Read → Selection & principlesRittal-style enclosures vs the original brand: the 9-fold profile process and where the price difference comes from
Rittal-style Enclosures vs. the original brand: 9-fold profile, TS 8 frame, 9-fold vs 12-fold, IP rating, price gap, selection comparison table.
Read → Selection & principlesWhat a solar combiner box does: how DC-side PV strings are combined and how surge protection is configured
What a Solar Combiner Box Does: How PV DC-Side Combining and Surge Protection Work, and How a Combiner Box Differs from a DC Distribution Cabinet. A Guide to GB/T 34933 and GB/T 18802.31.
Read → Selection & principlesBESS cabinet structure: how battery clusters / PCS / BMS / fire suppression are arranged by layer
BESS cabinet layout: how battery clusters, the battery management system (BMS), the PCS converter, the fire suppression system and HVAC/liquid cooling are arranged by layer. Interpretation of GB/T 36276 and GB/T 36558.
Read → Selection & principlesHow to select a distribution cabinet for EV charging stations: capacity calculation, dual power supply, metering scheme
How to select a distribution cabinet for EV charging stations: capacity calculation formula, dual power transfer, active / reactive metering, surge protection. Interpretation of GB/T 51313 and NB/T 33002.
Read → Selection & principlesWhat a grid-tied PV cabinet does: grid-connection conditions, anti-islanding, acceptance checkpoints
Role of the grid-tied PV combiner cabinet: interconnection conditions, anti-islanding protection, frequency / voltage / harmonic monitoring, energy metering, and commissioning checklist. Interpretation of GB/T 50866 and GB/T 19939.
Read → Selection & principlesHow do you read distribution box specs and model codes? PZ30/XL/JP/power cabinet model code comparison
A distribution box model number is a string of letters and digits — once you can read it, you know what cabinet you are looking at. This article breaks down the meaning of mainstream codes including PZ30, XL-21, JP, GGD, GCS and MNS, with a model comparison table. Zhejiang Golden Unicorn produces 5,800+ assembled cabinets per year. MOQ 1 unit · build to drawing.
Read → Selection & principlesDistribution Box Specifications & Model Guide: Lighting, Power, JP and Meter Boxes in One Table
Too many distribution box models to remember? One table covers it. This guide consolidates mainstream models and specs for lighting boxes, power boxes, JP cabinets, meter boxes, GGD/GCS/MNS and more, grouped by application with a selection cross-reference. Zhejiang Golden Unicorn produces 5,800+ units per year. MOQ 1 unit · build to drawing.
Read → Selection & principlesHow do you size a distribution box? Circuit count → enclosure size cross-reference table + installation clearances
Distribution box dimensions are not arbitrary — circuit count, breaker rating, heat dissipation clearance, and mounting height all follow code. This article provides a circuit count → enclosure size table and mounting clearance requirements. Zhejiang Golden Unicorn produces 5,800+ units annually, MOQ 1 unit · build to drawing.
Read → Selection & principlesPZ30 distribution box size chart: surface-mounted / flush-mounted / number of circuits
PZ30 is the most widely used terminal distribution box for homes and offices. This article provides a complete PZ30 size chart: surface mount vs. flush mount, circuit counts, and DIN rail positions, with selection advice. Zhejiang Golden Unicorn produces 2,000+ terminal boxes per year, MOQ 1 unit.
Read → Selection & principlesWhat is a JP cabinet? Composition, function and selection of a combined distribution box
The JP cabinet is the "three-in-one" distribution box for rural grid distribution areas — metering, compensation and distribution combined in one unit. This article breaks down the JP cabinet's components, functions and selection points. Zhejiang Golden Unicorn produces 500+ JP cabinets per year, MOQ 1 unit · build to drawing.
Read → Selection & principlesPT cabinet vs metering cabinet — voltage transformer cabinet vs electrical energy metering cabinet
PT cabinets and metering cabinets are often confused, but their functions are completely different. This article breaks down the 5 differences between a PT cabinet (voltage transformer cabinet) and a metering cabinet (energy metering cabinet). Zhejiang Golden Unicorn holds ISO 9001:2015 certification and produces 5,800+ assembled cabinets per year.
Read → Selection & principlesWhat is a package substation? European vs. American-style package substations — differences and selection
A package substation integrates a transformer, medium voltage switchgear and low-voltage distribution cabinet into a single enclosure. This article breaks down its composition, the European vs. American differences, and selection points. Zhejiang Golden Unicorn produces 300+ package substation enclosures per year, MOQ 1 unit · build to drawing.
Read → Selection & principlesAutomatic transfer switch cabinet (ATS) principle: main/backup transfer + time delay + auto restore
The automatic transfer switch (ATS) cabinet is what keeps power flowing at fire protection, hospital and data center sites. This article breaks down how an ATS works, the transfer methods and time delay settings. Zhejiang Golden Unicorn builds 300+ ATS cabinets a year, MOQ 1 unit.
Read → Selection & principlesLow-Voltage Distribution Cabinet Model Guide: GGD / GCS / MNS / GCK / XL-21 Compared
Too many low-voltage distribution cabinet models to remember? One table makes it clear. This guide covers mainstream low-voltage cabinet models including GGD, GCS, MNS, GCK and XL-21, sorted by mounting type, current rating and application. Zhejiang Golden Unicorn produces 5,000+ low-voltage cabinets per year.
Read → Selection & principlesWhat is a PLC control cabinet, and how does it differ from a standard control cabinet? PLC cabinet vs. power cabinet vs. distribution cabinet
A PLC control cabinet is an automated control assembly built around a programmable logic controller (PLC). Unlike a standard distribution cabinet that only distributes power, a PLC panel can acquire signals, execute logic and output control commands to automate a process. Following GB/T 7251.1 (low-voltage switchgear assemblies), this article breaks down the 6 core differences between a PLC control cabinet and a standard control cabinet or distribution cabinet. Zhejiang Golden Unicorn
Read → Selection & principlesWhat are the components of a PLC control cabinet? A full breakdown of CPU / IO / power supply / relays / terminals
A PLC control cabinet looks complex, but it breaks down into 6 major modules — CPU, I/O, power supply, relays, terminals and communications. This article walks through each module per GB/T 7251.1, covering selection criteria and wiring practice, with a bill-of-materials template. Zhejiang Golden Unicorn PLC panels integrate mainstream brands such as Siemens and Schneider, are ISO 9001:2015 certified, and start at 1 unit.
Read → Selection & principlesWhat are the common faults of a VFD panel? How are they handled? 12 cases of overcurrent / overvoltage / overheating
Troubleshooting VFD panel faults is a routine job for maintenance electricians. This article follows GB/T 12668 (Adjustable speed electrical power drive systems) to break down the causes and fixes for the 12 most common VFD panel faults, with a fault code reference table. Zhejiang Golden Unicorn VFD panels ship with a fault code table and commissioning manual, ISO 9001:2015 certified, MOQ 1 unit · 15-25 days.
Read → Selection & principlesHow does a soft starter cabinet work? Thyristor voltage reduction vs autotransformer voltage reduction
The soft starter cabinet is the mainstream solution for reduced-voltage starting of large motors. Compared with direct-on-line starting, it cuts starting current by 60%–70%; compared with star-delta starting, it provides continuous voltage regulation and smooth acceleration. This article breaks down the two working principles of soft starter cabinets — thyristor voltage ramp and autotransformer step-down — per GB/T 14048.6 (Low-voltage electromechanical contactors and motor-starters). Zhejiang Golden Unicorn soft starter cabinets integrate Schneider/Le
Read → Selection & principlesHow do you troubleshoot an online soft starter cabinet? Thyristor breakdown / phase loss / overheating
Online soft starter cabinets (no bypass) running under continuous load have a higher failure rate than bypass-type units. This article analyzes 3 major fault categories in online soft starter cabinets per GB/T 14048.6: SCR breakdown, phase loss operation, and overheating protection, with fault tree analysis and troubleshooting procedures. Zhejiang Golden Unicorn soft starter cabinets ship with a fault code table and maintenance manual, ISO 9001:2015 certified, MOQ 1 unit
Read → Selection & principlesHow do you repair a pump control cabinet? An 8-step troubleshooting method for constant pressure water supply faults
The constant pressure water supply pump control cabinet is a high-failure-rate control device — long-term damp environments, frequent start/stop cycling, and improper PID parameters can all cause pump shutdown. This article lays out an 8-step troubleshooting method for constant pressure water supply control cabinets per GB 50054 (Code for Design of Low-Voltage Power Distribution). Zhejiang Golden Unicorn pump control cabinets ship with a commissioning manual + fault code table, ISO 9001:2015 certified, MOQ 1 unit
Read → Selection & principlesHow do you commission a VFD pump control cabinet? PID parameters + pressure setting steps
The core of variable-frequency constant-pressure water supply commissioning is PID parameter tuning and pressure setting. Get it wrong and either the pressure won't come up or the system short-cycles and oscillates. This article follows GB/T 12668 (Adjustable speed electrical power drive systems) to walk through the 7-step commissioning procedure for a VFD pump control cabinet. Zhejiang Golden Unicorn's variable-frequency constant-pressure water supply cabinets are PID pre-tuned before shipment, so only minor on-site adjustment is needed. ISO 9001:2015 certified,
Read → Selection & principlesWhat is the purpose of a junction box? Why use one? Three main functions: splitting, transition and protection
A junction box is the least conspicuous but most indispensable small part in an electrical installation. This article breaks down the three main functions of a junction box per GB/T 7251.1 and GB 50303: branching, transition, and protection, with a material and IP rating selection table. Zhejiang Golden Unicorn produces 30,000+ junction boxes / terminal boxes per year, ISO 9001:2015 · MOQ 1 unit · 15–2
Read → Selection & principlesHow Do You Wire a Junction Box? Crimping vs. Twisting vs. Soldering — 3 Methods Compared
How do you make compliant splices inside a junction box? Crimp, twist and solder each suit different situations. This article works through the operating points and acceptance criteria for all three methods per GB/T 9330 (plastic-insulated control cable), with a crimping tool selection table. Zhejiang Golden Unicorn ships 100% crimped + bolted terminations, ISO 9001:2015 certified.
Read → Selection & principlesWhat is a terminal box? Differences from a junction box / distribution box
Terminal box, junction box, distribution box — these three "boxes" are often confused. This article breaks down their definitions, functions and differences per GB/T 7251.1, with a selection comparison table. Zhejiang Golden Unicorn produces 50,000+ terminal boxes, junction boxes and distribution boxes combined per year. MOQ 1 unit · 15–25 days.
Read → Selection & principlesWhat is the purpose of a terminal box? Why does a control circuit need its own terminal box?
Why can't a control loop be wired directly into a distribution box? Why does it need its own terminal box? Because the functions differ, the maintenance requirements differ, and the interference protection differs. This article breaks down the 4 main functions of a terminal box per GB 50054 (Code for Design of Low-Voltage Power Distribution), with control loop wiring guidelines. Zhejiang Golden Unicorn produces 20,000+ terminal boxes per year.
Read → Selection & principlesWhat is the purpose of an equipotential bonding terminal box? How is it set up in bathrooms / equipment rooms?
That inconspicuous little box in the bathroom could save a life — the purpose of an equipotential bonding terminal box is to bond metal parts in a local area to the same potential, eliminating electric shock hazards. This article explains the working principle and installation requirements of equipotential bonding terminal boxes per GB 50303, with installation examples for bathrooms and equipment rooms. Zhejiang Golden Unicorn produces over 10,000 equipotential boxes annually.
Read → Selection & principlesWhat size is a local equipotential bonding terminal box? LEB box specifications and mounting height
Pick the wrong size for a local equipotential bonding (LEB) terminal box and you either run out of terminals or can't fit the box in. This article summarizes common LEB terminal box sizes, terminal counts, mounting heights and enclosure materials per GB 50303, with a selection comparison table for bathrooms and equipment rooms. Zhejiang Golden Unicorn produces 10,000+ LEB boxes per year.
Read → Selection & principlesWhat is the role of a fire alarm terminal box? How do fire interlock and signal transmission work?
A fire alarm terminal box is the signal hub of a fire interlock system — how do smoke detectors, heat detectors, manual call points and fire hydrant buttons feed their signals back to the fire alarm control panel? This article explains the function and wiring of the fire alarm terminal box per GB 50116 (Code for Design of Automatic Fire Alarm Systems). Zhejiang Golden Unicorn produces 5,000+ fire alarm terminal boxes per year.
Read → Selection & principlesStainless steel distribution box vs. carbon steel: 304/316/galvanized sheet material comparison
Pick the wrong enclosure material and it rusts through in two years — so which one do you actually specify: 304 stainless steel, 316 stainless steel, or powder-coated galvanized sheet? This article compares corrosion resistance, strength and price across all three per GB/T 7251.1, with an environment-based selection table. Zhejiang Golden Unicorn builds 5,000+ stainless steel distribution boxes a year. MOQ 1 unit · 15–25 days.
Read → Selection & principlesHow to choose the ingress protection rating for an outdoor distribution box? IP54/IP65/IP66 comparison
Pick too low an IP rating for an outdoor distribution box and rain shorts out your equipment; pick too high and you pay for protection you don't need. What actually separates IP54, IP65 and IP66? This guide walks through outdoor distribution box IP rating selection per GB/T 4208 (Degrees of protection provided by enclosures — IP code), with a test-condition comparison table. Zhejiang Golden Unicorn builds 5,000+ outdoor boxes a year. MOQ 1 unit.
Read → Selection & principlesHow do you select an explosion-proof distribution box? How to read Ex d IIB T4 ratings: gas group + temperature class + protection type
The first step in selecting an explosion-proof distribution box is reading the Ex marking. Break down Ex d IIB T4: Ex = explosion-proof, d = flameproof, IIB = gas group, T4 = temperature class. This article walks through explosion-proof distribution box selection item by item per GB 3836.1 (general requirements) and GB 3836.2 (flameproof), with a selection comparison table. Zhejiang Golden Unicorn
Read → Selection & principlesWhat is the difference between an explosion-proof distribution cabinet and a standard distribution cabinet? 5 structural differences: enclosure / flameproof joint surface / cable entry device / components / marking
An explosion-proof distribution cabinet is not simply a heavier-gauge version of a standard cabinet. The two differ in every respect — enclosure strength, flameproof joint, cable entry, internal components and factory marking — and that is also why the price gap runs 2–5x. This article compares the 5 structural differences one by one per GB 3836.1 (General requirements for explosive atmospheres) to help you judge when an explosion-proof cabinet is mandatory. Zhejiang Golden Unicorn works with an Ex-qualified manufacturer
Read → Selection & principlesWhat is an explosion-proof control cabinet? Comparison of Ex e / Ex d / Ex p — principle, zone and cabinet characteristics
An explosion-proof control cabinet is the command station for motor start/stop, process interlocking and signal indication in hazardous areas. It is widely used in petrochemical, chemical, pharmaceutical, and oil & gas storage and transport. There are three mainstream routes to explosion protection: Ex d flameproof (GB 3836.2), Ex e increased safety (GB 3836.3), and Ex p pressurized (GB 3836.5). Cabinet construction, applicable zone
Read → Selection & principlesHow do I select an explosion-proof junction box? Flameproof / increased safety / intrinsically safe — how to choose the type, number of entries, and material
An explosion-proof junction box is the smallest unit for cable branching and transition splicing in a hazardous area, and it is used in far greater quantities than explosion-proof distribution boxes. Three selection questions: which protection type (Ex d / Ex e / Ex i), how many cable entries and what size, and what enclosure material. This article covers GB 3836.1 (general), GB 3836.3 (increased safety), and GB 3836.4 (intrinsic safety).
Read → Selection & principlesWhat is an explosion-proof lighting distribution box? Integrated solution: luminaires + switches + fuses — configuration, circuits, installation
An explosion-proof lighting distribution box houses the switches, fuses, and indicator lights for lighting circuits inside a flameproof enclosure. It is the main disconnect for lighting systems in petrochemical plants, fuel depots, pharmaceutical facilities, and dust-laden workshops. Compared with an explosion-proof power distribution box, it carries more circuits at lower current per circuit, and it must also handle luminaire control and safe maintenance. This article breaks down the configuration, circuit calculations, and installation requirements per GB 3836.2 (flameproof type). Zhejiang Golden Unicorn
Read → Selection & principlesHow to choose an explosion-proof distribution box manufacturer? 6-point verification guide for qualifications, certificates and testing
When selecting an explosion-proof distribution box manufacturer, verify qualifications first, then discuss price. Certificate authenticity, nameplate consistency, and inspection reports are all essential — low-price uncertified products, borrowed certificates with OEM labeling, and assembled or modified units are the three biggest traps in this industry. This article outlines 6 verification steps per GB 3836.1 to help you screen out unqualified suppliers before signing. Zhejiang Golden Unicorn is an enclosure manufacturer; explosion-proof products are supplied in
Read → Selection & principlesHow to select a dust explosion-proof distribution box? Ex tD + designed for Zone 20/21/22 dust environments
Flour, wood dust, metal powder, plastic dust — all of them can explode. Dust explosion protection and gas explosion protection are two separate systems: zones are classified 20/21/22, the rating uses Ex tD, and the ingress protection and temperature assessment methods are completely different. This article breaks down the selection logic for dust explosion-proof distribution boxes per GB 12476 (Electrical Apparatus for Use in the Presence of Combustible Dust). Zhejiang Golden Unicorn holds Ex qualifications
Read → Selection & principlesHow to select a mining-duty explosion-proof distribution box? Ex d I mining-duty + MA coal mine safety certification, for underground coal mine use only
An explosion-proof distribution box for underground coal mines has to clear two more hurdles than one for above-ground chemical plants: first, it must be designed for Group I (methane atmospheres), marked Ex d I; second, it must hold a Mining Product Safety Mark (MA coal mine safety certification), and the cable must be MT 818 mining flame-retardant cable. This article breaks down the selection and verification of mining-duty explosion-proof distribution boxes per GB 3836.1 and MT 818
Read → Selection & principlesHow to select an explosion-proof VFD panel? Pressurized vs flameproof — heat dissipation, power, and cost
The VFD is the hardest component to handle in an explosion-proof cabinet — the higher the power, the harder it is to make explosion-proof. In practice, high-power explosion-proof VFD panels use Ex p pressurized enclosures (GB 3836.5), while only low-power units use Ex d flameproof enclosures. This article compares the principles, power limits, cost and maintenance of the two approaches and provides a selection decision table. Zhejiang Golden Unicorn provides joint supply with an Ex-qualified manufacturer
Read → Selection & principlesWhat is an explosion-proof pressurized control cabinet? Continuous ventilation + loss-of-pressure protection principle, GB 3836.5 pressurized principle
A pressurized control cabinet achieves explosion protection by "purging": clean protective gas is continuously fed into the cabinet so that internal pressure stays above the surrounding hazardous atmosphere — combustible gas simply cannot get in, which means ordinary PLCs, contactors and VFDs can be used inside. This article breaks down the three mechanisms — continuous ventilation, purge interlock and loss-of-pressure protection — per GB 3836.5 (pressurized type "p"). Zhejiang Golden Unicorn holds Ex qualification
Read → Selection & principlesHow to select an explosion-proof electrical control box? Explosion-proof selection of push buttons, indicator lights, and switches — explosion-proof operation elements
Every push of a button and every lit indicator is a potential ignition source — an explosion-proof electrical control box (operator station / pushbutton box) puts an explosion-proof enclosure around these small components. Small as they are, they are the most frequently operated and most frequently damaged explosion-proof devices on site. This article covers the selection points for explosion-proof pushbuttons, indicator lights and selector switches per GB 3836.1. Zhejiang Golden Unicorn supplies in joint supply with an Ex-qualified manufacturer
Read → Selection & principlesHow to select marine distribution boards? CCS/EC certification + corrosion and water ingress protection specific to the marine environment
A marine distribution board must deliver reliable power for decades under the triple assault of motion, vibration, and salt: list and trim, main engine vibration, and salt spray corrosion — none of them can be allowed to bring it down. Classification society certification (CCS/EC) and the IEC 60092 series impose structural, ingress protection, and material requirements far stricter than those for land-based cabinets. Zhejiang Golden Unicorn handles marine distribution board enclosure fabrication — bending, welding, marine-grade coating, and sealed structures
Read → Selection & principlesHow to select a solar combiner box: DC input strings, surge protection and fuse configuration on the PV DC side
Get one parameter wrong on a combiner box and an entire string is wasted: DC input count, system voltage, fuse rating, SPD surge protection class — each one directly affects power yield and safety. This article covers the key selection points per GB/T 18479 (Photovoltaic power generation system overview and guidelines) with reference to GB/T 34933 (Technical requirements for combiner boxes). Zhejiang Golden Unicorn provides solar combiner box enclosure fabrication —
Read → Selection & principlesHow is metering handled in an EV charging station distribution cabinet? AC/DC charger metering options and trade settlement configurations
Every kilowatt-hour at an EV charging station is money — pick the wrong metering scheme and the operator and the driver end up arguing every day. AC chargers and DC chargers meter power in completely different ways: one relies on a watt-hour meter, the other on a DC meter plus a shunt. This article breaks down AC/DC EV charger metering schemes and how they work with the distribution cabinet, per GB/T 28569 and metrological verification regulations. Zhejiang Golden Unicorn builds charging-station-matched distribution cabinet enclosures and
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