Health Technical Memorandum 06-01: Electrical services supply and distribution 2017 Edition
Health Technical Memorandum 06-01 (HTM 06-01), titled Electrical services supply and distribution, is the definitive guidance issued by the Department of Health in the United Kingdom regarding the electrical infrastructure of healthcare premises. This 2017 edition consolidates and supersedes both parts of the 2007 edition, providing a single source for design, installation, operation, and maintenance. It functions within the wider legal framework of the Health and Safety at Work etc. Act and the Electricity at Work Regulations, acting as best-practice guidance for fulfilling statutory duties of care.
The document governs the entire electrical technical infrastructure, from primary intake points to final circuit connections at the point of use. It establishes a robust governance model through the introduction of the Electrical Safety Group, a multidisciplinary body responsible for monitoring and recording all electrical safety issues. Structurally, the memorandum is divided into 17 chapters and 4 appendices, covering topics such as clinical and business continuity risk grading, distribution strategies for resilience, power quality, and specialised systems like Medical IT (isolated terra) and Uninterruptible Power Supplies (UPS).
This guidance categorises risks into specific grades to help designers select proportionate distribution strategies. It aligns with contemporary standards including BS 7671 (IET Wiring Regulations) and BS 5266 (Emergency lighting), ensuring that healthcare facilities maintain maximum reliability and supply integrity for patient safety.
Governance and the Electrical Safety Group
Chapter 3 introduces the Electrical Safety Group (ESG), a multidisciplinary body formed to oversee all aspects of electrical safety and resilience within a healthcare organisation. The group reports to a designated person at Board level and is typically led by a person with appropriate management responsibility, such as the head of estates operations.
- Remit: The ESG informs the design process for new builds and modifications, oversees commissioning, and manages operational maintenance and decommissioning.
- Composition: Typical members include estates staff, an Authorising Engineer, Authorised Persons (HV/LV), clinicians, and specialist users of medical electrical equipment.
- Risk Management: The group is responsible for maintaining the organisation's risk register regarding electrical failures and ensuring that all tasks indicated by risk assessments are accepted and allocated.
- Decision Authority: Critical decisions affecting the resilience or integrity of supply systems must be agreed upon by the ESG before implementation.
Clinical and Business Risk Grading
Chapter 4 establishes a grading system to assess the consequence of power failure based on patient risk and business continuity. These grades assist designers in determining the required level of supply integrity and resilience for specific hospital departments.
- Clinical Risk Grade A: Highest risk areas where supply failure represents a threat to life, such as operating theatres and critical care units. Requires a tertiary supply available within 0.5 s or a no-break supply.
- Clinical Risk Grade E: Low risk areas where loss of supply does not have an immediate effect on clinical treatment, such as circulation spaces and offices.
- Business Risk Grade I: High risk to medical support services, including laboratories and medical records, where interruption compromises patient welfare.
- Business Risk Grade IV: Lower risk business support services like finance or laundries, where single-conversion UPS may be sufficient for safe shutdown.
Distribution Strategy and Resilience
Resilience in healthcare electrical systems is often expressed through the N+1 principle. Chapter 7 details the topology of distribution networks required to minimise single points of failure as close to the final circuits as practical.
- Primary Electrical Supply (PES): Large acute hospitals typically require 11 kV connections, while smaller facilities may be supplied at 0.4 kV.
- N+1 Definition: The normal total requirement plus one resilient unit (e.g., two 1000 kVA transformers sharing a 1000 kVA load at 50% each).
- Diverse Routing: Where dual primary and secondary circuits are installed, they should follow diverse cable routes to prevent a single incident from damaging both supplies.
- HV Networks: Larger sites (AMD above 3.5 MVA) should utilize HV ring networks to restore resilience quickly following a distribution fault.
Secondary and Tertiary Power Supplies
Chapters 9 and 11 address backup power sources, including standby generators, Combined Heat and Power (CHP) plant, and UPS systems. These are essential for maintaining services during a primary supply outage.
- Standby Generators: Must be capable of reaching operational status and connecting to supported circuits within 15 s of a cold start.
- Fuel Storage: A main reserve of fuel oil sufficient for 200 h of full-load running for each generator should be available on-site.
- UPS Autonomy: For Group 2 Medical Locations, a battery autonomy of 3 h is standard, which may be reduced to 1 h if an alternative secondary supply is available within 15 s.
- VRLA Batteries: The use of valve-regulated lead-acid batteries is preferred due to near-zero-gassing and low maintenance requirements.
Specialist Systems and Final Circuits
Chapter 15 details requirements for final circuits, particularly in Medical Locations categorized as Group 0, 1, or 2 under BS 7671.
- Medical IT Systems: Used in Group 2 locations to ensure that a first fault to earth does not cause a supply interruption. They require insulation-monitoring devices (IMD).
- Socket-Outlets: In Group 2 areas, outlets must be unswitched, blue in colour, and identified as "Medical Equipment Only".
- Residual Current Devices (RCDs): Type AC RCDs are not permitted in Group 1 or Group 2 Medical Locations; Type A or Type B must be used.
- Emergency Lighting: Updated to include "emergency safety lighting" for premises where occupants are not immediately evacuated during a supply failure.
Frequently Asked Questions
What is the primary role of the Electrical Safety Group (ESG) in hospitals?
The ESG is a multidisciplinary group responsible for governance, risk assessment, and oversight of the design, operation, and maintenance of electrical infrastructure to protect patients and staff from electrical failures.
How does HTM 06-01 define N+1 resilience?
N+1 resilience means the system has the capacity to meet the normal total requirement plus one additional resilient unit, such as two transformers each rated at 100% of the required load but typically carrying 50% each.
What are the requirements for standby generator fuel storage?
Healthcare organisations must maintain an on-site fuel oil main reserve capable of supporting 200 hours of full-load running for each standby generator set.
What is the maximum supply restoration time for life-support equipment in Risk Grade A areas?
Disconnection of the supply to critical medical electrical equipment in Risk Grade A areas requires an alternative source (tertiary power supply) to be available within 0.5 seconds or as a no-break supply.
Can standard 13 A extension leads be used in clinical areas?
Trailing multi-outlet extension leads should not be used in Medical Locations Group 1 and Group 2; they require a full risk assessment by a competent person before use with any medical electrical equipment.
What are the specific socket-outlet requirements for Group 2 Medical Locations?
Socket-outlets connected to the Medical IT system must be unswitched, coloured blue, and permanently identified with the label "Medical Equipment Only".
What is the difference between Clinical Risk Grade A and Grade E?
Grade A applies to life-support and complex surgery areas where failure is a threat to life, while Grade E applies to support services and circulation spaces where failure has no immediate effect on patient safety.
What standards govern the testing and validation of healthcare electrical systems?
Systems must be tested and validated according to BS 7671, BS EN 60601-1, and specific HTM 06-01 procedures, with records held in the building logbook and risk register.
