“We asked two vendors to quote the same control panel, and one came back at nearly twice the price of the other. We have no idea which one is right.” That is almost always the opening line when a Japanese-owned plant in Thailand comes to us with a control panel design question. The cause is rarely that one supplier is overcharging. It is that the two quotations do not cover the same scope of work. This article is not a “what is a control panel” explainer. It is about how you decide whether to build the panel in Japan and ship it in or build it locally in Thailand, what information you have to hand over when you place the order, and where the arguments actually start.
Why control panel quotations are so hard to read
Cost lives in five separate layers
As long as you think of a control panel as a single lump-sum price, you cannot compare quotations at all. The cost of a control panel is made up of five layers that are completely different in nature, and each layer is moved by a different set of factors.
| Layer | What it covers | Main factors that move the price |
|---|---|---|
| 1. Design | Circuit diagrams, internal layout, bill of materials, nameplate list, panel drawing preparation | Level of detail in the specification, availability of a reusable base drawing, number of I/O points, number of approval-drawing revision rounds |
| 2. Materials | Breakers, contactors, PLCs, inverters, terminal blocks, enclosure, wire, wiring duct | Whether specific brands are mandated, where the parts are sourced, lead time, stock availability |
| 3. Manufacturing | Sheet metal work, cut-outs, device mounting, internal wiring, crimping, harness dressing, nameplate fitting | Number of wires, panel size, number of door-mounted devices, strictness of the workmanship standard |
| 4. Inspection | Continuity, insulation resistance, dielectric withstand, functional testing, preparation of the in-house test report | Number of test items, whether a witnessed inspection is required, the record format demanded |
| 5. Site installation | Delivery, setting, external wiring between panels and from panel to equipment, terminations, commissioning | Distance to site, whether a power shutdown is needed, number of cables, complexity of commissioning |
Of these five layers, the only ones guaranteed to appear in a quotation are 2 and 3. Layer 1 is sometimes broken out as a “design fee” and sometimes buried inside the manufacturing price. Layers 4 and 5 are very often outside the quoted scope entirely.
When vendor A’s number is double vendor B’s, what is usually happening is this. A has quoted layers 1 through 4, with 5 as a separate item. B has quoted only 2 and 3, on the assumption that it builds to drawings you supply, that inspection means a continuity check, and that installation is not included. Lining up the two grand totals tells you nothing.
Each layer can be owned by a different party
Splitting the cost into five layers does more than make quotations comparable. It also lets you decide, layer by layer, what you keep in-house and what you send outside.
| Layer | If you keep it in-house | Typical form when outsourced |
|---|---|---|
| 1. Design | Production engineering draws the circuit diagrams and produces the panel drawings to an internal standard | Electrical design outsourcing. You hand over the specification only and let the vendor start from the circuit diagram |
| 2. Materials | Your own purchasing department supplies free-issue parts (to keep to mandated brands) | The panel builder procures everything, using its purchasing power and stock |
| 3. Manufacturing | Your own maintenance workshop builds it (realistically only small modification panels) | Build contracted out to a panel manufacturer |
| 4. Inspection | Witnessed inspection against your own criteria | Panel builder’s in-house testing plus a submitted test report |
| 5. Site installation | Your own maintenance team sets and terminates | Local electrical contractor, or engineers dispatched by the panel builder |
A very common arrangement at Japanese-owned plants: layer 1 is held by the production engineering department at the parent company in Japan, layer 2 is held by in-house purchasing in the name of brand standardisation, layers 3 and 4 go to a panel builder in Thailand, and layer 5 goes to a local electrical contractor. It looks rational, but it creates three separate interfaces of responsibility. When something goes wrong, the reason everything stalls at “we built it exactly to the drawing” versus “the free-issue part was different” versus “the installer wired it incorrectly” is precisely this structure.
If you are going to split the work, the real battleground is not the split itself but how you document the interfaces. That leads directly into the section on the purchase specification below.
How many hours does the design layer actually take?
Requests to outsource the design only are increasing. People usually ask for a rule of thumb on man-hours, and this is exactly where we cannot give a straight number. Control panel design effort varies far more with the level of detail in the specification than with the physical size of the panel.
- A modification to an existing panel, where a reusable base drawing exists and only a handful of circuits are being added — design alone can be a few man-days.
- A new line, where you are also asked to select the equipment and the load list is not yet fixed — the back-and-forth needed to freeze the scope takes time, and depending on the scale the number changes by an order of magnitude.
Two projects can both be “a single-bay panel” while one needs a couple of approval-drawing rounds and the other needs more than twice that. The extra rounds are, almost without exception, caused by gaps in the information the customer handed over. If you want to bring the design cost down, tidying up the information you supply works better than negotiating the rate.
On the inspection layer, there is a published figure from Japan worth knowing: in-house testing (self-inspection) is put at 0.25 to 1 man-day, roughly JPY 10,000 to 40,000 (source: KTS-Lab). This is a Japan-domestic reference figure and cannot be translated into a labour rate for Thailand. It is described as varying with the size of the panel and the number of items checked, and demanding a witnessed inspection or a special record format takes you above that range. The point to take away is not the amount itself but the fact that inspection exists as an independent block of man-hours inside a quotation.
Build in Japan and ship it in, or build it in Thailand?
The cheaper unit price is not the deciding factor
If you decide this on unit price alone, you will almost certainly regret it later. A control panel is not something you deliver and forget; it is an asset that will be modified and maintained on a ten-year horizon. There are at least six axes to judge on.
| Axis | Built in Japan and imported | Built locally in Thailand |
|---|---|---|
| Materials procurement | Strong domestic stock and easy access to mandated brands. Easy to align with the parent company standard | Strong on locally distributed parts. Certain Japanese products become special-order items and lead times stretch |
| Transport | Sea freight days, packing cost, and protection against vibration and condensation are all needed. Large panels may have to be split for shipment | Road transport only. Depends on distance to the plant, but measured in days |
| Duties and BOI | Import formalities apply. Whether BOI privileges cover the item depends on the investment plan and the item classification, so confirm in advance | No import formalities at all |
| Speed of modification response | Fixes during commissioning take time. Engineers have to travel in | Easy to respond locally within a short window. Can keep up with changes during commissioning |
| Availability of spare parts | If the parts used are not distributed locally, a failure means ordering from Japan | Easy to build around a parts list that is obtainable locally |
| Language of drawings and nameplates | Tends to end up Japanese-dominant. You are left with drawings your local maintenance staff cannot read | Bilingual English/Thai marking can be designed in from the start |
A note on how to read this table. The two points that decide most cases are how much rework the commissioning phase will generate, and who will be maintaining the panel ten years from now. For mass-production equipment where the specification is fully frozen and rework is unlikely, building in Japan and importing as a single package can work in your favour. For projects where the specification is still being finalised on site during start-up, or for modifications to an existing line, the agility of local manufacturing wins.
Where each case usually lands
In practice this is rarely a binary choice. Most projects are solved with a combination.
| Case | Realistic combination | Reason |
|---|---|---|
| Rolling out equipment already proven in Japan to a Thai plant | Reuse the existing Japanese drawings for design, build in Thailand | Leverages the drawing assets while keeping rework and maintenance local |
| Starting up a new line locally | Design and build both in Thailand, parent company only approves the specification | Changes during start-up are frequent, and the cost of the back-and-forth dominates |
| Modifying or extending existing equipment | Design, build and install all in Thailand | Fitting to as-built conditions is unavoidable. Field measurement of the existing panel is mandatory |
| Equipment with unusually strict safety or quality requirements | Design in Japan, build wherever the requirements can be met | Decided by the level of standards compliance and inspection records demanded |
| Equipment producing goods for the North American market | Find a builder capable of UL 508A first | The standard narrows your choice of builder (see below) |
“Fitting to as-built conditions is unavoidable” is the heart of every modification project. The free space inside the existing panel, the spare terminals on the existing terminal blocks, the direction the existing cables enter from, the capacity of the existing supply — none of these can be confirmed from a drawing. You have to look at the real thing. Projects where a panel was designed in Japan from drawings alone, shipped in, and then would not fit are the direct result of skipping that check. For any modification-based project, write the pre-start field measurement into the schedule explicitly.
Capital investment in Thailand is expanding
For background, capital investment in Thailand itself is in an expansion phase. According to the Board of Investment (BOI), investment applications for January to June 2026 reached 1,299 projects worth THB 1.473 trillion, up 37% year on year. Of that, the electrical and electronics sector accounted for 179 projects worth THB 120.23 billion, the second largest by application value. The “Smart and Sustainable Industry” measure, which covers machinery replacement, energy saving, digitalisation and the introduction of automation and robots, accounted for 132 projects worth THB 17.158 billion (source: Nation Thailand).
Control panel demand tracks these numbers. New lines mean new panels; upgrades and automation retrofits of existing equipment mean modification panels. One caveat: we were not able to find a reliable figure for the market size of control panels themselves, so we treat the above only as circumstantial evidence of the investment trend. For a wider picture of FA investment in Thailand, see our article on factory automation in Thailand.
How to choose the standards your panel is built to
IEC 61439 is the foundation
The most fundamental international standard in the control panel and switchgear field is IEC 61439, covering low-voltage switchgear and controlgear assemblies. The current edition is IEC 61439-1:2020, and it is used as a harmonised standard for CE marking under the Low Voltage Directive (sources: IECEE, Siemens).
The key point is that it is a standard for the *assembly*. It requires the finished panel as a whole — not the individual components — to meet the requirements. That means the argument “all our components are from well-known brands, so we are fine” does not hold. Temperature rise, short-circuit withstand strength, insulation and degree of protection are all verified at the level of the assembled unit.
Related to this, IEC 62208 is the standard covering the empty enclosure for a panel; enclosure-only performance is assessed there. IEC 60529 (the IP code) defines degrees of protection against dust and water ingress, and IEC 62262 (the IK code) defines impact resistance ratings.
The difference between IEC 61439 and UL 508A
For panels fitted to machines destined for North America, UL 508A (the safety standard for industrial control panels) comes into play. A revised edition of UL 508A was issued on 26 June 2025.
In day-to-day practice, the difference between the two comes down to this.
| Aspect | IEC 61439 | UL 508A |
|---|---|---|
| Status | International standard. Used as a harmonised standard for CE marking under the Low Voltage Directive | A private-sector standard in the United States (UL) |
| Scope | Whole assemblies, including distribution boards | Individual industrial control panels |
| Requirements on components | Does not require UL components. Each component must comply with the corresponding IEC standard | Requires the components themselves to be UL Listed or Recognized |
| Impact at ordering | Relatively free choice of components | Choices are narrowed at the bill-of-materials stage, and the supply base is restricted too |
(Sources: Rittal, GT Engineering, IECEE)
Put in ordering terms: on a project where UL 508A applies, the standards conversation comes at the beginning of the design, not the end. Because the components themselves have to be UL Listed or Recognized, being told “make it UL compliant” after the bill of materials is frozen means starting over. As soon as you know the equipment will produce goods for North America, confirm with candidate builders whether they can work to UL 508A. That is a screening condition that comes before any price negotiation.
For equipment destined for Europe, or intended purely for use inside Thailand, taking IEC 61439 as the foundation is the standard starting point.
Internal temperature rise and cooling are decided together with the IP rating
One thing that gets overlooked in standards discussions is the trade-off between IP rating and internal panel temperature. The higher the degree of protection against dust and water, the closer the enclosure gets to fully sealed, and the less heat it can shed by natural dissipation. That drives you towards ventilation fans or a panel cooler, which in turn adds cost, power consumption and maintenance tasks (filter cleaning, condensate handling).
The order of decisions should be as follows.
- Determine the required IP rating from the conditions at the installation point (dust, oil mist, chemicals, wash-down water, direct sunlight, indoor or outdoor).
- Identify every heat-generating device inside the panel (mainly inverters, power supply units, transformers and resistors).
- Fix the maximum ambient temperature you have to design for (it varies enormously near the ceiling, next to machinery, or outdoors).
- Using 1 to 3, work with the builder to decide whether natural dissipation is enough, whether ventilation fans are enough, or whether a cooler is required.
What you as the customer should be handing over here is conditions 1 and 3, not an instruction that says “fit a cooler”. The cooling method is an output, not a requirement. Specifying the cooling method without supplying the conditions guarantees that it is either over-specified or inadequate.
Worth noting: in Thai plants the actual maximum temperature at the installation point is often higher than assumed. In buildings without air conditioning, on frames near the ceiling, or beside an outdoor cubicle, it is safer to take real daytime measurements before deciding. This is one of the classic cases where “same specification as the identical machine in Japan” simply does not carry over.
What to verify if you build in Thailand (points we deliberately do not assert)
This section needs to be handled carefully. Thailand has its own industrial standards system, TIS (Thai Industrial Standards, administered by TISI), and some electrical TIS standards are based on IEC. However, which standard numbers apply to which scope, and how qualification requirements for electrical work are defined, could not be substantiated in the research behind this article. Please do not treat any of that as settled fact.
Instead, here is a list of items to verify before you place an order. The people to ask are the relevant authorities, your installation contractor, and where necessary a local specialist.
| Item to verify | Who to ask | Why it matters |
|---|---|---|
| Which standards apply to the equipment and panel (TIS / IEC / customer-mandated) | Customer quality department, installation contractor, relevant authority | You cannot write a specification until the applicable standard is fixed |
| Whether qualifications or notifications are required for electrical work locally | Installation contractor, relevant authority, local specialist if needed | Determines who is allowed to do the installation and termination work |
| Constraints on the plant’s incoming supply and power equipment | Facilities management, the utility side | Drives the primary-side conditions of the panel and protection coordination |
| Fire safety and insurance requirements | Insurer, facilities management | May impose constraints on electrical room conditions and materials |
| Scope and procedure if you intend to use BOI privileges | BOI, your internal application owner, local specialist | Affects the import-versus-local-build decision |
| Whether the end customer has its own panel specification | End customer’s production engineering and maintenance departments | In the automotive sector, the customer standard is effectively the specification |
The practical move is to run this table in parallel with the request for quotation. If the applicable standard is settled late, the bill of materials, the panel dimensions and the inspection scope all move.
The information you must hand over when ordering — where the arguments start
Missing information always pushes the quotation upward
It becomes obvious once you put yourself in the panel builder’s position. When they have to quote with incomplete information, they price in the risk. If the loads are not fixed, they size the assembly with margin. If the ambient temperature is unknown, they assume a cooler is needed. If no spare-space ratio is specified, they pick a larger enclosure. Missing information is loaded straight onto the price.
The corollary is that simply organising the information you hand over creates room for the quotation to come down. Below is the minimum set of items to supply when commissioning control panel manufacturing.
| Item | What to hand over specifically | What happens if you do not |
|---|---|---|
| Load list | List of motors, heaters, solenoids etc. with ratings, voltages, starting methods, and whether they run simultaneously | Capacity cannot be read, so the design ends up either oversized or short of capacity |
| Power capacity and supply conditions | Primary voltage, number of phases, frequency, expected current, upstream breaker specification, earthing system | Protection coordination cannot be established. The panel does not match the incoming supply at installation |
| Ambient temperature and environment | Maximum temperature at the installation point, direct sunlight, presence of dust, oil mist or chemicals, indoor or outdoor | Internal temperature rise cannot be calculated, so the cooling method cannot be fixed |
| Required IP rating | Rating specified per IEC 60529 (plus IK if needed) | You get incidents such as water ingress on a panel installed near a wash-down process |
| Basis for internal temperature rise | List of heat-generating devices and continuous operating conditions | There is no basis for selecting the cooler or ventilation fans |
| Spare space ratio | A numerical requirement such as “keep at least 20% of the interior free” | A future addition means rebuilding the whole panel |
| Cable entry direction | Top entry / bottom entry / rear, and the position of existing cable racks | On site the cables do not reach, or the bending radius cannot be achieved |
| Language of nameplates and markings | Which of Japanese, English or Thai goes where, and in what order | You are left with a panel your local maintenance staff cannot read |
| Mandated components | If certain brands are mandated, the exact scope (PLC only, etc.) | Spares do not match the maintenance inventory, and you end up managing two parallel stocks |
| Drawing submission format | CAD format, revision control method, approval flow and number of rounds | You are left with drawings that cannot be edited when you come to modify the panel |
The four items most often overlooked
Spare space ratio is rarely thought of as a cost item at design time, and it is the item that bites hardest later. If the panel is delivered packed full, adding a single extra signal means either an extension panel or a replacement. Specify it as a number.
Cable entry direction looks trivial on a drawing and causes more arguments on the installation site than anything else. If the existing cable rack runs at ceiling level and a bottom-entry panel arrives, the fix on site is additional trunking work. On modification projects in particular, freeze this together with the field measurement.
Language of nameplates and markings feeds directly into maintenance cost. A nameplate your Thai maintenance technicians cannot read makes first-line response to an abnormality impossible. Decide on Japanese plus English, or English plus Thai, at the nameplate-list stage. “We will re-label it later” essentially never happens.
Drawing submission format and revision control pays off ten years out. If all you receive is a PDF, then every modification means either redrawing from scratch or accumulating hand-written mark-ups. Make editable-format submission and the revision numbering scheme part of the purchase conditions.
Defining the interface when you outsource design only
If you are outsourcing electrical design alone — carving out just that layer — define the deliverables first.
| Deliverable | Points to state explicitly as included or excluded |
|---|---|
| Circuit diagrams (power and control) | Symbol conventions, wire numbering scheme, drawing frame format |
| Internal layout drawing | Device arrangement, duct and terminal block layout, door-face layout |
| Bill of materials (BOM) | Whether it goes down to manufacturer and model number, or specifies requirements only and leaves brand selection to the builder |
| Terminal block schedule and external wiring list | Whether it is detailed enough to be used for on-site cable procurement |
| Nameplate list | Language, character size, material |
| Panel drawing revision control | Whether native-format files can be submitted, how revision history is recorded |
| Relationship with the PLC software | Who is responsible for keeping the I/O list consistent |
That last row matters most in practice. If you place the panel hardware with one party and the PLC software with another, responsibility for I/O list consistency becomes ambiguous. The hardware side says “we wired it exactly as drawn”, the software side says “we built it exactly to the I/O list we were given”, and the signals do not line up on site. Settle in a single sentence, at order placement, who holds the master copy of the I/O list. For how to structure the software side of the outsourcing, we cover that separately in outsourcing PLC program development.
The maintenance perspective that pays off after start-up
A panel is not a delivered item, it is an asset you operate for ten years
Control panel failures surface not at handover but from year three onwards. A failed component that cannot be sourced, drawings that no longer match the physical panel, no record of who modified what and when — every one of these could have been headed off at the design and ordering stage.
| Maintenance concern | What to do at order placement | What happens if you leave it |
|---|---|---|
| Spare parts | Require a spare parts list for major components at handover, with the sourcing route (local / Japan) stated | Line downtime is extended by the time it takes to source parts after a failure |
| Local availability of components | Make “obtainable within Thailand” a selection criterion for components | Either your spares inventory balloons or line stoppages drag on |
| Panel drawing revision control | Native-format submission, revision numbering rules, storage location (who keeps it where) | Drawings fork with every modification and nobody knows which is the master |
| Modification history | Build in the practice of keeping a modification history sheet inside the panel door from day one | Nobody can answer “what was this wire added for?” |
| Language of nameplates and drawings | Bilingual marking in a language your Thai maintenance staff can read | Fault isolation requires calling in a Japanese expatriate every time |
| Standardised replacement procedures | Produce illustrated replacement procedures for major components | Knowledge stays with individuals, and maintenance stops when they leave |
Master drawing control is the most neglected of all
Here is the state of affairs we see most often on site. The as-delivered drawings exist as a PDF somewhere on a server; subsequent modifications were marked up by hand on paper that lives in a pocket on the panel door; and yet another modification was never recorded at all. Three years of that, and the only person who can safely touch the panel is the person who made the modification.
The remedy is not complicated. First, receive the drawings in native format. Second, always update the drawing before the modification is executed, not after. Third, put a modification history sheet inside the panel door and record date, content and the person responsible. You only need to set those three as operating rules at the outset. Starting them retroactively, however, is extremely hard — so decide them at the same time you order the panel.
If you are also considering assessing the condition of existing equipment or extracting data as part of the upgrade, it is worth combining this with the thinking in IoT retrofit for legacy equipment. Panel modification work and sensor or signal tapping work are much less disruptive when they are packed into the same power-shutdown window.
Process automation on the builder’s side affects lead time too
When comparing quotations, it is worth asking whether the builder has automated its manufacturing processes. Whether they operate automatic wire harness processing machines is said to affect both lead time and cost (source: KTS-Lab). The difference shows up particularly on panels with high wire counts. Asking “what is that delivery date based on?”, rather than only looking at the unit price, gives you a real picture of their production capability.
Planning the panel work that comes with automation investment
On automation projects, the panel bites you late
In labour-saving and automation investment, attention naturally concentrates on the machine side — robots, conveying equipment, inspection systems. But as the project progresses, the panel conversation always arrives. Where does the added equipment draw its power from? How does it interlock with the control of the existing line? How is emergency stop integrated? Every one of those involves extending or modifying a panel.
The problem is that this discussion starts only after machine selection is complete. By then the installation location and the timing are already fixed, so there is no time left for panel design. The result is either an expensive rush-order build or temporary, improvised wiring.
Avoiding it is simple: at the concept stage of the automation project, confirm just these three things in advance.
| Item to verify | When to verify it | What happens if you do not |
|---|---|---|
| Whether the existing incoming supply has spare capacity | Before machine selection | The equipment arrives but there is not enough power, and work on the incoming supply becomes an add-on |
| Whether the existing panel has spare space and spare I/O points | At the same time as machine selection | An extension panel becomes necessary, and you go back to square one on installation space |
| The approach to integrating safety circuits with the existing line | At the same time as machine selection | The safety circuit has to be rebuilt, extending total line downtime |
These three are not normally included in the machine supplier’s quotation. They are yours to verify. For the wider approach to automation investment, our article on labour-saving and factory automation examples is also worth reading.
Consolidate your shutdown windows
The other practical point is the shutdown window for the work. Thai plants tend to concentrate construction work into long holidays (Songkran, year-end and New Year), and those windows are heavily contested.
Panel modification, sensor additions, rewiring, work on the incoming supply — split these across different periods and each one costs you a line stoppage. If you design the capital investment plan so that everything touching the panel falls into a single shutdown window, the total downtime changes dramatically. Conversely, leaving panel design until last makes that consolidation impossible.
Request-for-quotation template (a checklist you can use as-is)
You can copy the following straight into a request for quotation. Any field you cannot fill in is exactly where the variance in the quotation is coming from.
A. Project background
- Purpose: new line / modification of existing equipment / panel replacement (end-of-life renewal)
- Installation location: plant name, building, indoor or outdoor, floor level
- Required delivery date, and the reason for it (equipment delivery date, dates the line can be stopped)
- Whether power shutdown work is possible, and in which time slots (weekends / nights / long holidays)
- Standards to be applied: IEC 61439 series / UL 508A / customer standard / undecided
- Preferred place of manufacture: Japan / Thailand / no preference (want a comparison)
B. Electrical specification
- Primary supply: voltage, number of phases, frequency, expected current, earthing system
- Specification of upstream protective devices (basis for protection coordination)
- Load list (device name, rating, voltage, starting method, whether operated simultaneously)
- Control power specification (AC or DC, whether isolation is required)
- Required level for emergency stop and safety circuits (attach the customer requirement if there is one)
- I/O count (DI / DO / AI / AO) and the required number of spare points
- Whether the PLC and HMI are mandated (specific model, or performance specification)
C. Construction and environment
- Installation environment: maximum ambient temperature, direct sunlight, presence of dust, oil mist or chemicals
- Required IP rating (IEC 60529), plus IK rating if needed (IEC 62262)
- Mounting form: free-standing / wall-mounted / machine-mounted
- Maximum permissible dimensions (including constraints on the delivery route into the building)
- Cable entry direction: top / bottom / rear, and the position of existing racks
- Required spare space ratio (e.g. at least 20% of the interior)
- Preferred cooling method: natural dissipation / ventilation fans / cooler / no preference
- Paint colour and material requirements (if you have an internal standard)
D. Drawings, nameplates and language
- Whether drawings are supplied (reuse of existing drawings, or starting from scratch)
- Drawing submission format (whether native format is acceptable) and number of copies
- Required symbol conventions and wire numbering rules
- Timing of approval drawing submission and the expected number of revision rounds
- Nameplate language (Japanese / English / Thai, and the order when bilingual)
- Language for operation and warning markings
- Language of the operating manual
E. Inspection and witnessing
- Scope of in-house testing (self-inspection) and the format of the test report
- Whether a witnessed inspection is required, where, and who attends
- Specified conditions for insulation resistance and dielectric withstand tests
- Scope of functional testing (stand-alone operation / simulated inputs / connected to the actual machine)
- Required retention period for inspection records (where the end customer requires it)
F. Installation and post-handover
- Scope of site installation: how far it goes — delivery, setting, external wiring, terminations, commissioning
- Distance to site and access conditions
- Requirement to submit a spare parts list, with the sourcing route stated
- Warranty period and warranty scope (parts / labour / travel costs)
- Point of contact for post-handover modifications, and the expected response time
- Who holds the master copy of the drawings
G. Interfaces of responsibility (essential if the work is split)
- Who is responsible for each of design, materials, manufacturing, inspection and installation
- If parts are free-issued, the list of items and when they will be supplied
- Who holds the master copy of the I/O list (hardware side or software side)
- Who performs the field measurement, and when
- How the cost of rework during commissioning is treated
The last line of section G is a frequent source of disputes. Whether a change made during commissioning counts as “rework” or as “a specification change” determines who pays for it. Writing down even a single sentence on the range of changes you anticipate and how they will be treated makes the later negotiation much shorter.
Frequently asked questions
Can I outsource just the control panel design?
Yes, provided you define the deliverables first. State explicitly how far the deliverables go across circuit diagrams, internal layout drawings, bill of materials, terminal block schedule, external wiring list and nameplate list. In particular, whether the bill of materials goes down to manufacturer and model number, or specifies requirements only and leaves brand selection to the builder, changes how much freedom you have downstream. And if you are placing the PLC software with a different party, you must decide at order placement who holds the master copy of the I/O list — otherwise, when the signals do not line up on site, nobody owns the problem.
If we build the panel in Thailand, can we use our Japanese drawings as they are?
You can reuse them, but they will not be sufficient on their own. Four things need checking. First, whether the primary supply conditions (voltage, number of phases, frequency) match the local incoming supply. Second, whether the components used are obtainable within Thailand, which feeds directly into spare parts availability. Third, whether the ambient temperature at the installation point differs from the Japanese assumption. Fourth, whether your local maintenance staff can read the language of the nameplates and drawings. The second and fourth cause no trouble at handover and bite from year three onwards. On modification projects, you also need to measure the existing panel on site — free space, spare terminals, cable entry direction — or the build will not fit as drawn.
What determines the cost of a control panel?
Cost divides into five layers — design, materials, manufacturing, inspection and site installation — and each layer is moved by different factors. Design is driven by the level of detail in the specification and the number of approval-drawing rounds; materials by whether specific brands are mandated and where they are sourced; manufacturing by wire count and panel size; inspection by the number of test items and whether witnessing is required; installation by distance to site, whether a power shutdown is needed, the number of cables and the complexity of commissioning. The single biggest reason quotations cannot be compared is that different vendors include different layers. Ask for a price against each of the five layers and they become comparable. Note that a published figure exists for in-house testing effort — 0.25 to 1 man-day, roughly JPY 10,000 to 40,000 (source: KTS-Lab) — but this is a Japan-domestic reference figure and cannot be converted into a labour rate for Thailand. Treat it only as confirmation that inspection exists as an independent block of man-hours.
Should we work to IEC 61439 or UL 508A?
It depends on where the equipment or product carrying the panel will be used. For machines destined for North America, UL 508A applies, and because that standard requires the components themselves to be UL Listed or Recognized, your choices are narrowed at the bill-of-materials stage. That means you have to confirm a builder’s capability before design starts. For Europe, IEC 61439 is used as the harmonised standard for CE marking under the Low Voltage Directive. For equipment used only inside Thailand, taking IEC 61439 as the foundation is the standard starting point. There is also a difference in scope: IEC 61439 covers whole assemblies including distribution boards, while UL 508A covers individual industrial control panels.
What qualifications or notifications are needed to install a control panel in Thailand?
The research behind this article could not obtain reliable confirmation of the details of qualification requirements or notification procedures for electrical work in Thailand, so we deliberately state nothing definitive. Before ordering, confirm with the relevant authorities, the local contractor who will perform the installation, and a local specialist where necessary. Alongside that, confirm which standards apply (TIS, IEC or customer-mandated), the constraints on the plant’s incoming supply, fire safety and insurance requirements, and whether the end customer has its own panel specification. It is most efficient to pursue these checks in parallel with the request for quotation, because if the applicable standard is settled late, the bill of materials, panel dimensions and inspection scope all move.
What should we compare when selecting a control panel manufacturer?
Beyond price, line up the following. First, which layers the quotation covers (how far it goes across design, materials, manufacturing, inspection and installation). Second, which standards they can work to, especially whether UL 508A is possible. Third, the drawing submission format and whether native-format files are available. Fourth, the languages they can support on nameplates and drawings. Fifth, whether they will submit a spare parts list with the sourcing route stated. Sixth, the point of contact and response time for post-handover modifications. Seventh, the basis for their quoted lead time, including the state of automation in their production process. The sixth in particular pays off over the following decade. A control panel is not a delivered item but an asset you operate long term, so select on whether you can work with the builder afterwards, not only on whether they can build it.
Is it better to modify an existing control panel or build a new one?
There is no universal answer, but the deciding factors can be laid out. Modification is favourable when there is ample spare space inside the panel, the existing drawings still exist and are editable, and the circuits being added fit within the capacity of the existing supply. You should consider a rebuild when the panel is packed full and no devices can be added, when the drawings have diverged from the physical panel so far that investigation eats significant man-hours, or when existing components are discontinued and spare parts cannot be sourced. That last one matters most: modifying the panel will not stop the same problem recurring in the near future. Compare the modification cost together with the additional maintenance effort you will incur afterwards.
Summary
With control panel design and manufacturing, the outcome is largely decided well before you get to comparing prices. To recap the essentials:
- Break the cost into five layers: design, materials, manufacturing, inspection, site installation. Each is moved by different factors, and different vendors include different layers. Ask for a price on all five and quotations become comparable.
- Judge Japan-built versus Thailand-built on six axes: materials procurement, transport, duties and BOI, speed of modification response, spare parts availability, and the language of drawings and nameplates. Unit price does not decide it.
- In practice you solve it with a combination: for a roll-out, reuse existing Japanese drawings for design and build locally; for a modification project, field measurement is mandatory, so run design locally too.
- Fix the standards at the start of design: IEC 61439 is the foundation. For North America, UL 508A requires components themselves to be UL Listed or Recognized, so choices narrow at the bill-of-materials stage. IP and IK ratings should also be fixed from the installation environment first.
- Verify Thailand-specific regulations and qualification requirements yourself: ask the relevant authorities, your installation contractor and a local specialist about the scope of applicable standards, qualifications and notifications, constraints on the incoming supply, and fire and insurance requirements. Run it in parallel with the request for quotation.
- Missing information is loaded straight onto the price: load list, supply conditions, ambient temperature, IP rating, basis for internal temperature rise, spare space ratio, cable entry direction, nameplate language. Organising the information you supply works better than negotiating the rate.
- Order it as an asset you will run for ten years: spare parts list, local availability of components, native-format drawing submission and revision control, a modification history sheet, and nameplates your Thai maintenance staff can read.
Capital investment in Thailand is in an expansion phase, with BOI investment applications in the first half of 2026 reported as up 37% year on year. As both new lines and modifications increase, control panel demand moves with them. But how well you place the order is not something the investment climate can compensate for. What decides it is whether you have determined who owns which of the five layers, assembled the information you need to hand over, and built ten years of maintenance into the order.
TOMAS TECH is a systems integrator based in Bangkok, Thailand, working across factory IT, OT and FA for Japanese-owned manufacturers. We are happy to talk even before your specification is finalised — questions like “should we draw this modification up in Japan, or start from field measurement locally?” are a perfectly good starting point. If you send over your panel drawings and load list, we can work through which of the five layers to keep in-house and which to send outside. Even if you are only at the stage of assembling the facts you need to decide, feel free to get in touch via our contact page.
References
- BOI says first-half investment tops B1.47tn | Nation Thailand
- International standards for control panels and enclosure selection (in Japanese) | Rittal
- Basics of IEC 61439 and UL for control panels built for export (in Japanese) | Rittal
- IEC 61439-1:2020 | IECEE
- IEC standards and European directives for panel building (in Japanese) | Siemens
- What kind of standard is the new IEC 61439? (in Japanese) | Overseas-specification control design
- Breakdown of control panel cost and quotations (in Japanese) | KTS-Lab
- UL 508A Standard for Industrial Control Panels | GT Engineering
