Essential Electrical System — Who is to say?

No, really — who is to say? Where is such entity defined or described? The answer could be found in two following documents:

  1. In the CSA standard Z32, which is actually called Electrical safety and essential electrical systems in health care facilities; and
  2. In Section 24 of the Canadian Electrical Code which covers installation of electrical equipment in patient care areas.

Photo 1. An essential electrical system consists of loads and branches listed in Table 7, and such loads represent a combination of the electrical equipment comprising “life safety systems” defined and described in Section 46, CE Code, and electrical equipment essential for care of the patients for effective operations of the health care facility (i.e., electrical equipment that in addition to life safety systems is also supplied by vital, delayed-vital or conditional branches).

CSA standard Z32 offers the following definition of essential electrical system: “Essential electrical system — an electrical system that has the capability of restoring and sustaining a supply of electrical energy to specified loads if the normal supply of energy is lost.”

Clause 6 of Z32 is dedicated to all aspects of an essential electrical system including normal and emergency power supply arrangements and redundancy of power sources, requirements for transfer of power and for the maintenance and repair of transfer switches. Table 7 of Z32 lists types of the essential electrical system loads and branches and subdivides these branches for the purpose of life/public safety and patient care as vital, delayed vital and conditional branches.

Section 24 of the CE Code also offers almost identical definition of an essential electrical system and provides a clear description of the circuits comprising the essential electrical system and the requirements for wiring to these circuits.

However, let’s find out what these two documents are about. Scope of CSA standard Z32 states the following: This Standard is not intended to apply to veterinary facilities, although its electrical safety principles could prove useful in the design, construction, and operation of such facilities.
The scope of this standard also describes the relationship with the applicable provisions of the Canadian Electrical Code as follows:
1.1.3 Provisions of this Standard are supplementary to the installation requirements specified in Sections 24 and 52 of the Canadian Electrical Code, Part I.
So far, so good. But how far is the scope of this standard intended to apply in a typical hospital? Would it cover such areas as a parking garage, offices, cafeterias, etc.?The answer is provided in Clause 1.2.1 as follows:

1.2.1 This Standard applies to (a) patient care areas of Class A, Class B, and Class C health care facilities; and (b) areas outside health care facilities that are intended for patient diagnosis, treatment, or care involving intentional electrical contact of any kind between patients and medical electrical equipment.
Let’s take a look at the definition of health care facility and at the types of such facilities under the scope of this standard. This could help us in understanding whether a typical chiropractor’s office, dental hygiene office or a massage/physiotherapy office in a strip mall would fall under the scope of this standard.Z32 offers the following definitions of health care facility and of specific classes of a health care facility:

Health care facility (HCF) — a set of physical infrastructure elements supporting the delivery of specific health-related services.
HCF, Class A — a facility, designated as a hospital by the government of Canada or the government of a Canadian province or territory, where patients are accommodated on the basis of medical need and are provided with continuing medical care and supporting diagnostic and therapeutic services. Note: Class A facilities include acute and complex care.
HCF, Class B — a facility whose residents cannot function independently because of a physical or mental disability and are accommodated because they require daily care by health care professionals.
Administrator — the person responsible for operating the health care facility (or his or her designee).
6.1.1 The requirements of Clause 6 shall apply to electrical systems that are considered essential for life and fire safety as specified in Article of the National Building Code of Canada, for effective and safe patient care, and for the effective operation of the HCF during an interruption of the normal electrical supply for any reason.
6.1.2 The requirements of Clause 6 shall also apply to those portions of an HCF in which the interruption of the normal supply of power to the essential electrical system loads described in Table 7 would produce unacceptable risk to the effective and safe care of patients.
(1) Essential electrical systems should not be automatically deemed necessary for areas where the risk to patient safety is not dependent on the availability of the electrical supply. It is intended by Clause 6 that the administrator of an HCF may determine a need to comply with provisions of Clause 6 for the specific areas of the HCF.
First of all, let’s dissect the scope of Clause 6.
24-302 Circuits in essential electrical systems (see Appendix B)
(1) An essential electrical system shall comprise circuits that supply loads designated by the health care facility administration as being essential for the life, safety, and care of the patient and the effective operation of the health care facility.
(2) An essential electrical system shall comprise at the minimum a vital branch and may also include a delayed vital branch or a conditional branch, or both.
(3) The wiring of the essential electrical system shall be kept entirely independent of all other wiring and equipment and shall not enter a luminaire, raceway, box, or cabinet occupied by other wiring except where necessary
(a) in transfer switches; and
(b) in emergency lights supplied from two sources.
Subrule (1) clearly explains to the Code users that it is up to the health care facility administration to designate loads of the essential electrical system. There are numerous installations where a health care facility administrator chooses to select the loads of the facility entire distribution system as “essential electrical system.” In this case, an electrical designer may (in consultation with the administrator) elect to supply all loads of the health care facility from an emergency generator, and except for a fire pump, all these loads could be supplied via a single transfer switch. Some electrical safety regulators have a tendency to reject such design arrangements, stating that the electrical equipment comprising “life safety systems” described by Section 46 of the CE Code must be wired via a separate transfer switch. Some electrical safety regulators often mandate that conditional or delayed-vital loads must be connected via a transfer switch separate from the transfer switch dedicated to the vital loads. However, such decisions by the regulators who misinterpret codes and standards officially adopted for regulatory purpose could be legally challenged, unless the provisions of Z32 and Rule 24-302(2) are formally amended in their respective jurisdictions.There are other situations where administrators of jails, colleges or airports would like to consider all loads of those facilities to be designated as essential electrical systems and being supplied with an emergency generator via a single transfer switch. In these cases, electrical designers and the proponents of such approach should communicate their intent with the electrical safety regulators and to demonstrate to the electrical safety authorities that the safety objectives by the relevant codes and standards are not compromised by such proposed distribution arrangements, as the CE Code intent to invoke application of essential electrical system is limited only to health care facilities in conjunction with application of the CSA standard Z32.

So, hopefully, the question raised in the title of this article has been answered.

Ark Tsisserev
Ark Tsisserev is president of EFS Engineering Solutions, Ltd., an electrical and fire safety consulting company, and is a registered professional engineer with a master’s degree in Electrical Engineering. Prior to becoming a consultant, Ark was an electrical safety regulator for the city of Vancouver. He is currently the chair of the Technical Committee for the Canadian Electrical Code and represents the CE Code Committee on the CMP-1 of the National Electrical Code. Ark can be reached by e-mail at: His company web site is: