What makes an enclosure for an electrical switchboard weatherproof and suitable for outdoor use? There are number of requirements which are not as clear cut as you might think. IP Ratings, corrosion resistance and UV stability should all be considered when veryfying if an enclosure is suitable. These areas and their relevance to enclosure selection for weatherproof outdoor applications will be explored further.
IP Rating for a Weatherproof Switchboard
The IP rating refers to the ingress protection of the enclosure. Here the two digits after IP refer to the ingress protection for solid materials and liquids respectively.
Normally an IP rating of IP42 is sufficient for indoor purposes. This represents:
- First numeral 4 (solid materials): The access probe of 1.0 mm diameter is not to penetrate
- Second numeral 2 (liquids): Protected against vertically falling drops of water with enclosure tilted 15° from the vertical. Limited ingress permitted
For outdoor applications, IP55 is normally the minimum that would be used. This represents:
- First numeral 4 (solid materials): Limited ingress of dust permitted (no harmful deposits)
- Second numeral 2 (liquids): Protected against jets of water. Limited ingress permitted. When hosing jets of water at all angles.
So if there is a enclosure rated IP55 or higher, is this suitable for outdoor applications? No. Before it can be used in outdoor applications it must also be verified for corrosion resistance and UV stability.
Corrosion resistance in electrical switchboard enclosures
There are different classifications of tests for corrosion resistance required and also exemptions.
Which electrical enclosures are exempt from corrosion resistance verification?
All enclosures which are not made of a ferrous metal. This means that aluminium enclosures, stainless steel enclosures and polycarbonate enclosures are exempt. Mild steel enclosures must be verified.
There are two different classifications of corrosion resistance testing under AS/NZS 61439.
- Severity test A: This is for indoor enclosures. The test includes a salt spray testing and damp environment testing for 8 days.
- Severity test B: This is for outdoor enclosures. Similar to the above test however it is carried out over 24 days.
To use an enclosure outdoors it must be tested to Severity test B under 61439.
UV Stability for Weatherproof Switchboards
The powder coating or surface of the electrical switchboard enclosure must be verified for UV stability.
It must be tested against ISO 4892-2 Method A which is a 500 hour UV test.
While there are many other requirements for electrical switchboard enclosures depending on the material and use case, these are the main requirements for general use of enclosure and the minimum requirements for using an electrical switchboard enclosure outdoors.