In power distribution systems, dry-type transformers are widely preferred for their flame-retardant, environmentally friendly, and maintenance-free advantages in commercial buildings, industrial parks, data centers, and more. Choosing the right enclosure for a dry-type transformer not only improves operational safety but also effectively extends the transformer’s service life. The Ingress Protection (IP) rating is a key indicator of how well an enclosure protects against solid foreign objects and moisture. In this article, xinhong electrical will explain the differences between the two most common enclosure ratings for dry-type transformers – IP20 and IP40 – and provide professional recommendations for their typical application scenarios.
The IP rating consists of two digits: the first digit represents the level of protection against solid foreign objects (such as hands, tools, dust, etc.), and the second digit represents protection against water. For dry-type transformers, selecting the appropriate IP rating requires a balance between heat dissipation and safety protection. xinhong electrical has long focused on manufacturing high-quality dry-type transformers and matching enclosures. Below we break down the core differences between IP20 and IP40.
First digit “2” : Prevents ingress of solid objects larger than 12.5mm. It stops fingers or similar‑sized objects from accidentally touching live internal parts, but does not block fine dust or metal chips.
Second digit “0” : No water protection.
Characteristics:
An IP20 enclosure typically uses mesh or louvered openings, offering excellent ventilation and heat dissipation with a simple, cost‑effective structure. Since it provides no dust or water protection, it must be installed in dry, clean, conductive‑dust‑free indoor environments where unauthorised personnel cannot easily enter.
Recommended applications:
Dedicated electrical rooms (with access control, only for authorised personnel)
Indoor substations with dry conditions and no dripping risk
High‑capacity dry‑type transformers (e.g., above 2000kVA) that demand maximum heat dissipation
xinhong electrical advice: IP20 is the most cost‑effective basic solution. However, you must ensure the installation environment has no metal dust or water leakage hazards, otherwise insulation life may be reduced.
First digit “4” : Prevents ingress of solid objects larger than 1.0mm. It blocks most small tools, wires, metal chips or fibres.
Second digit “0” : No water protection.
Characteristics:
An IP40 enclosure has smaller openings than IP20, providing significantly better protection against fine solid particles while still lacking water protection. Like IP20, it is limited to dry indoor environments, but it offers improved isolation from small particles that may be present in the surroundings (e.g., dust, short fibres, metal debris).
Recommended applications:
General commercial building electrical rooms (basements of shopping malls, office buildings, hospitals)
Light industrial environments (e.g., textile mills, electronic assembly workshops) where small particles exist but no conductive dust
Locations where higher safety clearance is needed or where small tools/screws might accidentally fall into the transformer
xinhong electrical note: Because IP40 enclosures have smaller openings, their natural heat dissipation is slightly lower than that of IP20. When selecting IP40, you should evaluate the transformer load factor and consider adding assisted ventilation. We can provide customised temperature control and airflow design solutions.
| IP Rating | Solid Object Protection | Water Protection | Heat Dissipation | Typical Application Scenarios |
|---|---|---|---|---|
| IP20 | Objects >12.5mm (fingers) | None | Best | Dedicated electrical rooms, managed indoor substations |
| IP40 | Objects >1.0mm (small tools/particles) | None | Good | General indoor electrical rooms, light industrial workshops |
Evaluate the installation environment and access control
Separate electrical room, managed access, clean environment → IP20 is sufficient
Open‑access electrical room with frequent personnel activity or risk of small foreign objects → IP40 is safer
Balance heat dissipation and economy
Large transformer capacity and high load factor → prefer IP20 to avoid overheating
Medium capacity with higher requirements for particle protection → choose IP40
Do not ignore safety standards
According to GB/T 10228, IEC 60076‑11 and similar standards, when a dry‑type transformer is installed in a public area accessible to people, the minimum rating is IP20. If there is a risk of fine solid particles, upgrading to IP40 is recommended.
Some outdoor or humid environments may require higher ratings such as IP54. xinhong electricalcurrently offers IP20 and IP40 enclosures as standard products – both are designed for dry indoor conditions and provide optimal heat dissipation efficiency and economy. If your installation site is outdoors, dusty, or prone to water splashes, we recommend adding proper enclosure or dehumidification measures in the electrical room, or contact our team for custom solutions. We are always committed to providing the most reasonable and reliable dry‑type transformer enclosure option for your actual project conditions.
Precise matching – Both IP20 and IP40 enclosures have opening ratios precisely calculated based on transformer losses and temperature rise, avoiding overheating caused by over‑sealing.
High‑quality materials – Made of cold‑rolled steel or stainless steel with electrostatic powder coating for corrosion resistance and anti‑aging.
Safety details – All enclosures meet grounding protection requirements, with rounded edges on openings to prevent cable damage.
Flexible customisation – Options include fans, thermostats, door locks, inspection windows, and more to meet different project needs.
IP20 and IP40 are the most mature and reliable enclosure ratings for indoor dry‑type transformer applications. In short:
Maximum heat dissipation with a controlled environment → Choose IP20
Better protection against fine particles → Choose IP40
xinhong electrical recommends that you identify the risk level from solid foreign objects in your installation environment during the design phase, and then select the most appropriate enclosure. If you have any questions about enclosure selection, please visit our website or contact our technical team – we offer free temperature rise calculations and enclosure design consultations.
