Flammability of Electrical Enclosures
Are our standards still fit for purpose?
As part of the electrification drive in South Africa for low-cost housing and dwellings in informal settlements, standards were developed for compact electrical installations consisting of SANS 1619: Small Power Distribution Units (SPDU’s or “Ready Boards”) and NRS 035: Pole Top Boxes for electricity reticulation.
A SPDU comprises a plastic electrical enclosure in the form of a basic distribution board containing circuit breakers, an earth leakage protection unit, socket outlets, and in some instances a bulkhead type luminaire.
These compact electrical installations can be extended to include electricity metering and additional circuitry for lighting and socket outlets. Such extensions are often conducted by unskilled persons and are seldomly subject to inspection by qualified electricians to ensure the safety of their installations
Risk Assessment and Action
The increased prevalence of fires occurring in informal settlements have serious consequences. Although it is difficult to establish the exact cause of a fire, we can safely attribute many to the illegal electrical connections and adverse environmental conditions to which these SPDU’s and electrical enclosures are exposed.
Additional investigation and risk assessment are required to evaluate the effectiveness and relevance of flammability requirements in these standards. While many informal dwellings are made of flammable material and offer restricted space for cooking, heating and occupancy, they pose a higher risk to the incidence of fire breakouts. An aggravating factor impacting the fire risk is that occupants including children and elderly people are exposed to these electrical installations. While SPDUs are exposed to harsh conditions, and many uncontrolled modifications and additions are made to these basic electrical installations, it is essential that stricter flammability requirements are applied to prevent spreading of fires in the event of electrical overloading or fault conditions.
At the turn of the twentieth century, the United States also experienced a significant increase in fire loss due to the increasing use of electricity in homes which posed a serious threat to property and human life. This led to the founding of Underwriters Laboratories which since has become a leader in developing standards such as UL 94.
The international standard IEC 60695 series also encompasses the most commonly applied flammability and fire resistance tests for plastic enclosures and other components, including conduit systems. These cover various test methods including glow wire tests at different temperatures, ranging from 550°C to 960°C, depending on the likelihood of contact between the enclosure and hot wire. Additionally, there are needle flame tests to determine the degree of flame propagation and the risk of setting adjacent materials alight due to molten plastic material drops. The time taken for the flame to self-extinguish is specified giving an indication of the flammability rating of the enclosure material.
Recent tests conducted on a SPDU by three different accredited laboratories comprising glow wire and needle flame tests showed failures with the specified requirements. The tests also confirmed that the flame propagation characteristics of plastic materials used in the manufacture poses fire risk. These risks can be lessened by considering an amendment to the applicable SANS and NRS standards, and specifying plastics that are inherently non-flammable.
While SPDU’s are not effectively regulated, it is strongly recommended that specifiers, housing project developers, local authorities and ESKOM add references to tender specifications that the following requirements must be met:
- Eskom’s tender specification added a reference to UL94 V1 separately which requires that an open flame be used to ignite the material instead of a glow wire. (There is overwhelming international precedent for this needle flame test to be done as certain materials do not always ignite with a glow wire test in the IEC requirements).
- Alternatively, consideration should be given to a glow wire test conducted at 850°C which will ensure the use of self-extinguishing plastic housings, which will also satisfy the UL94 requirements.
- Eskom’s tender specification added a reference to UL94 V1 separately which requires that an open flame be used to ignite the material instead of a glow wire. (There is overwhelming international precedent for this needle flame test to be done as certain materials do not always ignite with a glow wire test in the IEC requirements).
A side note worth mentioning is that international norms almost always require V0 performance and not V1. The difference is that V0 requires self-extinguishing in 10 seconds and not 60 seconds.
To mitigate the fire risk specifically in informal settlement housing, Safehouse has reached out to the SABS technical committee. We requested that SABS TC 067 is reviewed and amended to the applicable standards.