This article from the experts at NICEIC looks at electrical installations in medical locations, and will consider the scope of Section 710 of BS 7671 including some of the design requirements. Consideration will also be given to the use of system Grouping and how the classification of a safety service supply given in Section 560 is applied to such medical locations.
The intention of Section 710 is to provide enhanced reliability for the electrical installation, and greater electrical safety within the medical environment for both patients and medical staff.
The risk to a patient is greatly increased in a medical location due to:
• the threat from failure of the supply to medical equipment, especially that used for life support; and
• the natural reduction in body resistance inherent with open wounds, intrusive procedures and subsequent decline in patient defensive capacity either from induced medication or while anaesthetised.
As with all the special locations in Part 7, the requirements for Section 710 supplement or modify the general requirements of BS 7671 and are intended for those parts of the electrical installation in locations providing patient care, diagnosis, treatment, and monitoring. The requirements do not apply to items of medical electrical equipment.
The scope of Section 710 outlines particular requirements applicable to patient healthcare centres and facilities including:
• hospitals;
• private clinics;
• medical and dental practices;
• dedicated medical rooms in the workplace; and
• patient medical research establishments.
The requirements may also be applied to veterinary clinics, where applicable.
Healthcare-related construction contracts must also meet the requirements specified in the supporting information for healthcare premises outlined in the Health Technical Memorandum (HTM) 06-01 Electrical services supply and distribution, and 06-02 Electrical safety guidance for low voltage systems, published by the Department of Health.
Equivalent guidance documents are available for the devolved administrations: Scotland (SHTM), Wales (WHTM) and Northern Ireland (HTM) (Note 6 to regulation 710.1 refers).
Although, there are often subtle differences in the approach between BS 7671 and the specific HTM, the designer should always comply with the requirements of BS 7671. Where the standard does not provide sufficient information on a particular matter or detail, guidance in the relevant HTM should then be applied. However, such guidance should not contradict the requirements of BS 7671.
Assessment of general characteristics
Part 3 of BS 7671 outlines the characteristics that need to be assessed for all electrical installations.
The designer having responsibility of the electrical installation, within a medical location, is required to determine both the appropriate Group into which a particular medical location falls, and the classification that is to be applied to the electrical safety services in those locations.
The classification of a medical location is typically based on the:
• type of physical contact between the patient and the applied parts¹ of medical equipment (ME) or ME systems;
• threat to patient safety in the event of a loss of supply; and
• purpose for which the location is to be used.
To identify the appropriate level of classification that should be applied, based on the intended medical procedures likely to take place within the location, it is essential for the electrical installation designer to liaise with medical/clinical specialists (710.3).
To ensure safety in a medical location, where the location is to be used for multiple procedures or medical treatments, the requirements applicable to the most onerous usage should be applied.
Grouping
The guidance given in Table 1 highlights the definitions for Groups 0, 1 and 2 locations identified in Part 2 of BS 7671 and provides, based on Annex A710 of Section 710, some examples of rooms likely to be included in each Group.
It remains the responsibility of the designer in consultation with the relevant clinical staff to determine the appropriate Group for a particular location. It should also be borne in mind that the listing is not definitive.
Classification of a safety service
As described previously, the failure of an electrical supply in a medical location could cause danger to life. Appropriate safety services are therefore necessary to prevent such risk, and may typically include the provision for a standby supply for an operating theatre light.
Regulation 560.4.1 provides the classification of supplies for safety services. Section 710 requires such types of automatic supplies for safety services to be operational within a maximum changeover time designated for a particular area.
Table A710 of the annex to Section 710 provides guidance on the maximum permissible changeover times in typical medical locations.
For example, within bedrooms and massage rooms a changeover time greater than 0.5 s and not exceeding 15 s is recommended while a time not exceeding 0.5 s is recommended for supplies to luminaires and life-support equipment in locations such as operating theatres.
Further design considerations
The requirements for other sections in Part 7 of BS 7671 may also need to be considered, particularly where it is necessary to modify the electrical installation due to a change of utilization for the location. For example, where such intended work includes areas containing a bath or shower (701), or for mobile medical or transportable units (717).
Care should be taken to ensure that any such installations, or necessary work, do not influence or compromise the level of safety imposed by Section 710, including the effects from:
• fault current;
• electromagnetic interference EMI;
• electromagnetic compatibility EMC; or
• fire.
Although BS 7671 should not be applied retrospectively, when considering electrical work in an existing medical location, every intended alteration or addition should be preceded with a full analysis of risk to ensure that the intended work is appropriate and not liable to compromise the level of safety.
Summary
This article has outlined some of the considerations given in the scope of Section 710 of BS 7671 for various types of medical facilities. The requirements for specific Groups and safety service supply classifications utilised within a medical/healthcare environment have also been considered.
We would like to acknowledge and thank Brandon Medical for providing the image used within this article.
Get more details about NICEIC registration here
Find more industry technical articles here
