When buying a conformal-coated power supply, ask what is coated, with which material and against which acceptance requirements. A phrase such as “high-level protection” is not enough to compare two offers. Do not infer a coating grade from a metal cover, a plastic housing or a photograph of the supply inside a cabinet.
Turn the word “level” into a defined requirement
Suppliers may use different descriptions for coating options. Before comparing those descriptions, establish whether they refer to a material, a coverage pattern, a process option or a tested product configuration. If a standard or test is cited, ask for its exact reference, edition where relevant, acceptance criteria and the offered model revision to which the evidence applies.
A useful purchase specification describes the operating environment first: expected moisture or condensation, dust, chemicals, temperature changes, ventilation and maintenance access. The supplier can then identify whether the proposed power supply and host protection are suitable or whether a different construction is required.
Keep coating, potting and the enclosure separate
| Item | Question to resolve |
|---|---|
| Conformal coating | Which board surfaces and components receive the specified protective film? |
| Potting or encapsulation | Which volume is filled, with what material and with which thermal or service implications? |
| Product enclosure | What openings, terminals and ventilation remain exposed? |
| Host cabinet | What environmental conditions reach the installed supply through doors, entries and ventilation? |
These are not successive grades on one universal scale. A requirement for one does not document the others. In particular, do not translate a coating description into an ingress-protection rating or assume that treatment of the PCB protects every connector and opening.
Coverage and process are part of the evidence
Ask for the coverage definition and any intentionally excluded areas. Connectors, adjustment features and other interfaces may impose requirements that cannot be answered by stating a material name alone. Also ask how the specified application and cure are controlled and how coverage is inspected.
Review selective application, cure and inspection of coating coverage as separate process questions. Request evidence for the actual material and process used on the ordered unit; a generic coating description does not establish what WEHO uses in the product shown here.
What the MDR-20-12 photograph can establish
The photographed WEHO MDR-20-12 is a 12 V, 1.67 A DIN-rail supply with a vented plastic case. Its original photograph and matching sheet establish its model and external construction. The supplied sheet does not state a conformal-coating material, coverage map or coating qualification for this sample.
We therefore do not describe this unit as coated, waterproof or suitable for direct exposure to a dusty or wet process. The application images show dry host compartments to explain the installation question; they are not environmental test evidence. Request the applicable offered configuration before specifying additional protection.
Write an RFQ that prevents an ambiguous answer
Include the full model, required output, site environment and host-cabinet design. State whether condensation, chemical exposure or frequent door opening is foreseeable. Ask the supplier to distinguish a standard feature from a special option and to identify any changed part number or revision.
Then request the relevant material and coverage description, exclusions, process evidence, environmental test scope and service limitations. Keep thermal performance, clearances and maintenance requirements in the review. Adding a protective treatment after delivery should not be treated as an informal workshop improvement: it can change the product and requires the manufacturer’s guidance.
Confirm the offered product before approving it
Use the MDR family information to identify the electrical product, then send WEHO the environmental requirement. Ask for a written response covering the delivered model and option rather than accepting a general statement about a product family.
Common buyer questions
Can I check coating from an external photograph?
Not reliably. A case photograph does not document internal coverage, material or process acceptance.
Does more coating always mean better protection?
Do not assume that. The specified material, application and product design must be considered together; request the defined process rather than a subjective thickness preference.
Can the cabinet alone settle the selection?
No. Review the environment reaching the supply and its documented limits as part of the completed equipment. A cabinet description does not automatically qualify the component inside it.
