the Electrical Distribution Systems for Hospitals


In the previous topic, Electrical Design Requirements for Health Care Facilities – Part Two , We talk about Power sources in health care facilities, Health care Facilities voltage classification and mentioned that we will study the Electrical Distribution systems for the following health care facilities:
  1. Hospitals.
  2. Nursing homes and residential custodial care facilities.
  3. Other health care facilities (excluding hospitals, nursing homes, and residential custodial care facilities where the facility administers inhalation anesthetics or requires electromechanical life support devices).

You can review another previous topic; the Electrical Design Requirements for Health Care Facilities – Part One for more information and good following.

Today, we will begin studying the Electrical Distribution systems for Hospitals as follows.


General Electrical Distribution Systems for Health Care Facilities
Electrical Distribution Systems for Health Care Facilities is basically divided into two sub-systems as follows: (see fig.1)
  1. The normal electrical system (non-essential). 
  2. The essential electrical system. 
Fig (1):Electrical Distribution Systems for Health Care Facilities
 
Note: Both systems are supplied by the normal power source; however, the essential electrical system can be transferred to the alternate power supply whenever the normal power source experiences a power failure. 


1- Non-essential electrical system:


The non-essential electrical system consists of distribution equipment and circuits that supply electrical power from the normal power supply to loads that are not deemed essential to life safety, or the effective, and essential operation of the health care facility.

These non-essential or normal loads include things such as general lighting, general lab equipment, non-critical service equipment, patient care areas, etc. These loads are not required to be backed up with an alternate source of power.


2- Essential electrical system:


The essential electrical system consists of the alternate power supply (or supplies), transfer equipment, distribution equipment, and the circuits required to assure continuity of electrical service to those loads deemed as essential to life safety, critical patient care, and the effective operation of the health care facility.

Essential electrical system include three different types as follows:
  1. Essential Electrical System: Type 1-ESS.
  2. Essential Electrical System: Type 2-ESS.
  3. Essential Electrical System: Type 3-ESS 

We will know the differences between these types along our next discussion for the electrical distribution systems for different health care facilities.


First: Electrical Distribution Systems for Hospitals


In hospitals, usually the Essential Electrical System type will be Type 1-ESS.

Important considerations in design of Essential electrical system— Type 1:

  • Dual sources of normal power shall be considered but shall not constitute an alternate source of power 
  • Distribution system arrangements shall be designed to minimize interruptions to the electrical systems due to internal failures by the use of adequately rated equipment 
  • The following factors shall be considered in the design of the distribution system: 
  • Abnormal voltages such as single phasing of three-phase utilization equipment, switching and/or lightning surges, voltage reductions, and so forth 
  • Capability of achieving the fastest possible restoration of any given circuit(s) after clearing a fault 
  • Effects of future changes, such as increased loading and/or supply capacity 
  • Stability and power capability of the prime mover during and after abnormal conditions 
  • Sequence reconnection of loads to avoid large current inrushes that trip overcurrent devices or overload the generator(s) 
  • Bypass arrangements to permit testing and maintenance of system components that could not otherwise be maintained without disruption of important hospital functions 
  • Effects of any harmonic currents on neutral conductors and equipment 
  • Current-sensing devices, phase and ground, shall be selected to minimize the extent of interruption to the electrical system due to abnormal current caused by overload and/or short circuits 
  • Generator load-shed circuits designed for the purpose of load reduction or for load priority systems shall not shed life safety branch loads, critical branch loads serving critical care areas, medical air compressors, medical-surgical vacuum pumps, pressure maintenance (jockey) pump(s) for water-based fire protection systems, generator fuel pumps or other generator accessories 
  • Essential electrical systems shall have a minimum of two independent sources of power: a normal source generally supplying the entire electrical system and one or more alternate sources for use when the normal source is interrupted 
  • Where the normal source consists of generating units on the premises, the alternate source shall be either another generating set or an external utility service 

Essential electrical system branches:


Essential electrical system will include the following two sub-system:
1- Emergency system: which include the following two branches: (see fig.2) 
  • Life Safety Branch.
  • Critical Branch.
2- Equipment System/branch.

fig (2): Essential electrical system branches 

1-a Life Safety Branch


A subsystem of the emergency system consisting of feeders and branch circuits meeting the requirements of article 700 intended to provide adequate power needs to ensure safety to patients and personal, and which are automatically connected to alternate power sources during interruption of the normal power source

Shall supply power to loads per NFPA 70 and 99, including the following:
  • Alarm and alerting systems, such as Fire Alarm and Medical Gas Systems.
  • Automatic doors: Used for building egress.
  • Elevator cab lighting, control, communication, and signal systems.
  • Exit signs.
  • Generator set location: Task illumination, battery charger for emergency battery-powered lighting units and selected receptacles.
  • Illumination of means of egress.
  • Telecommunications Systems where used for issuing instructions during emergency conditions, including public address and Code One (Blue) systems and Disaster Control or Emergency Communication Centers.

1-b Critical Branch:


A subsystem of the emergency system consisting of feeders and branch circuits supplying energy to task illumination, special power circuits, and selected receptacles serving areas and functions related to patient care, and which are connected to alternate power sources by one or more transfer switches during interruption of the normal power source. The critical branch of the emergency system shall supply power for task illumination, fixed equipment, selected receptacles, and special power circuits serving the following areas and functions related to patient care:
  • Acute Nursing: Task illumination and selected receptacles.
  • Step-down Units: Task illumination and selected receptacles.
  • Anesthetizing Locations: Task illumination, selected receptacles and fixed equipment; task illumination includes battery back-up.
  • Angiographic Laboratories: Task illumination, selected receptacles and selected power circuits.
  • Blood, Bone, Eye and Tissue Banks: Task illumination, selected receptacles and refrigerators.
  • Cardiac Catheterization Laboratories and Rooms: Task illumination and X-ray unit.
  • Coronary Care Unit: Task illumination and PBPUs.
  • Emergency Room Treatment Areas and Life Support Rooms: Task illumination and PBPUs.
  • General Patient Bedrooms: Night lights, an alcove or a lavatory mirror light, one receptacle per bed wall, preferably in the PBPU, if available and a bathroom light.
  • Hemodialysis Rooms: Task illumination and one receptacle for each dialysis unit PBPU 
  • Human Physiology Labs: Task illumination, selected receptacles and selected circuits.
  • Intensive Care Units: Task illumination and PBPUs.
  • Medication Rooms and Medication Preparation Areas: Task illumination, selected receptacles and refrigerators.
  • Minor Operating Rooms: Task illumination and selected receptacles.
  • Nurse Call systems.
  • Nurses’ Stations: Task illumination and selected receptacles.
  • Pharmacy Dispensing Area (including Satellite Pharmacies): Power files, laminar flow hoods, refrigerators, copier for transmittal of physicians' orders, task illumination and selected receptacles.
  • Psychiatric Bedrooms: Task illumination (ceiling only).
  • Surgical Operating Rooms: Task illumination (50 percent of the general fluorescent fixtures above the surgery table including battery backup within two of these fixtures), each X-ray unit and one film processor per suite.
  • Surgical Recovery Rooms: Lighting fixture over each bed, one receptacle for each bed (or PBPU), night lights for each bed (or PBPU) and emergency alarm circuits.
  • Main Computer Room, Telephone Equipment Room, Telephone Console Room, Head End Room, and Telecommunications Rooms: All UPS equipment, lighting, and receptacles.
  • Ward Treatment Rooms: Task illumination and selected receptacles.


in the next topic, i will continue explaining the Electrical Distribution Systems for Hospitals. so, please keep following.




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