The “Mystery” Surrounding Electric Vehicle Energy Management Systems (EVEMS)
Ark Tsisserev, Principal
This article is to address concerns and questions received from the readers on the subject at hand.
First, a bit of history: Let’s acknowledge that this new defined terminology – (EVEMS) and relaxations allowed by Section 8 of the Canadian Electrical Code, Part I (CE Code) in conjunction with this definition – has been introduced to Section 8 of the CE Code when the 24th edition of the CE Code was published by the CSA in 2018.
The Code Committee has recognized that with proliferation of the electric vehicle supply (EVSE) loads, calculated load for services and feeders in building would increase drastically, if the EVSE loads are not adequately managed, as any electric vehicle supply equipment loads must be calculated with a demand factor of 100%. As such, the following changes have been introduced into Section 8.
1. EVEMS has been defined as follows:
Electric vehicle energy management system – a means used to control electric vehicle supply equipment loads through the process of connecting, disconnecting, increasing, or reducing electric power to the loads and consisting of any of the following: a monitor(s), communications equipment, a controller(s), a timer(s), and other applicable device(s).
2. Two new Subrules 8-106(10) and 8-106(11) were added to Rule 8-106, to allow relaxation for demand load of the EVSE, under specific conditions as follows:
(10) Where electric vehicle supply equipment loads are controlled by an electric vehicle energy management system, the demand load for the electric vehicle supply equipment shall be equal to the maximum load allowed by the electric vehicle energy management system.
(11) For the purposes of Rules 8-200(1)(a)(vi), 8-202(3)(d), 8-204(1)(d), 8-206(1)(d), 8-208(1)(d), and 8-210(c), where an electric vehicle energy management system as described in Subrule 10 monitors the consumer’s service and feeders and controls the electric vehicle supply equipment loads in accordance with Rule 8-500, the demand load for the electric vehicle supply equipment shall not be required to be considered in the determination of the calculated load.
3. New Rule 8-500 has been added to Section 8 – to recognize criteria under which EVEMS is permitted to monitor electrical loads in services, feeders and branch circuits for the purpose of controlling EVSE loads, as follows:
Rule 8-500 Electric Vehicle Energy Management Systems
(1) Electric vehicle energy management systems shall be permitted to monitor electrical loads and to control electric vehicle supply equipment loads.
(2) An electric vehicle energy management system shall not cause the load of a branch circuit, feeder, or service to exceed the requirements of Rule 8-104 5) or 6).
(3) An electric vehicle energy management system shall be permitted to control electrical power by remote means.
New Table 38 was introduced in conjunction with Rules 8- 202 – 8-210, to recognize permitted use of additional demand factors, specified in this Table, when more than four EVSE loads are connected to the building distribution system (see below):
Table 38: Electric vehicle supply equipment demand factors (See Rules 8-202 to 8-210)
Secondly, let’s discuss the impact of these new provisions in Section 8 of the CE Code on the Code users.
It should be noted that Table 38 created lots of inconsistency and confusion among the Code users, as it was not clear from this table whether it applies to EVSE loads connected to a feeder only or to a branch circuit as well, since Rule 86-300 allows more than one EVSE load to be supplied by a single branch circuit.
In addition, the Code users were confused, whether demand factors listed in Table 38 could be used in conjunction with relaxations permitted under conditions specified by Rule 8-106(10).
As such, the S/C on Section 8 of the CE Code, has recommended to delete Table 38, and hopefully, Table 38 will be deleted from the 2024 edition of the CE Code. So, in respect to the EVSE loads, Section 8 considers 3 following options:
1. Use of a fixed rating type EVEMS under relaxations allowed by Rule 8-106(10)
It means that if a fixed rating type EVEMS is installed to control all EVSE loads connected to it (let’s say for example, if this EVEMS is rated at 400 A), then for the purpose of EVSE load calculations in accordance with Section 8, all EV loads controlled by this type of the EVEMS would be considered to be 400 A, regardless whether 10 or 20 pieces of EVSE are connected to such fixed rating type EVEMS, as in this example, the fixed rating type EVEMS rated at 400 A, will not allow to supply more that 400 A of connected EVSE loads, if fused switch or circuit breaker protecting the feeder supplying this EVEMS, is marked for continuous operation at 100% of the ampere rating of its overcurrent devices.
If, however, the fused switch or circuit breaker protecting the feeder supplying this EVEMS, is marked for continuous operation at 80% of the ampere rating of its overcurrent devices, then this fixed rating type EVEMS rated at 400 A, will not allow to supply EVSE loads rated at more than 80% of the rating of the O/C device (in this example – will not allow to supply more than 320 A of EVSE loads), connected to it, and it will control the total demand of connected pieces of the EVSE accordingly (will perform load shedding). This fixed rating type EVEMS could be specified by the electrical consultants and installed by the electrical contractors, as such fixed rating type EVEMS would have to represent an “approved” equipment in accordance with Rule 2-024 of the CE Code, and this type of the EVEMS would have to be certified to the applicable CSA Part II safety standard for the EVEMS equipment.
It should be noted that in conjunction with relaxations, allowed by Subrule 8-106(10), total EVSE load connected to this fixed rating type EVEMS cannot exceed the rating of this EVEMS equipment under these Code provisions, and individual EVSE loads must be counted in the load calculations to the extent of the rating of the EVEMS, to which such EVSE loads are connected.
2. Use of an integrated, interconnected-in-the-field, complete system under relaxations allowed by Rule 8-106(11)
It means that if a sophisticated (interconnected and integrated) energy management system is installed in the field – to monitor loads in the consumer’s service, feeders and branch circuits and to control the electric vehicle supply equipment loads under specific relaxations allowed by Rule 8-106(11), then all EVSE loads controlled by the EVEMS, are permitted to be completely disregarded, as such monitoring and control is intended to ensure that the loading of the service, distribution feeders and branch circuits is in full compliance with Rules 8-104(5) or (6) regardless whether the EVSE loads are connected to the EVEMS or not.
The objective of relaxation allowed by Subrule 8-106(11) is to ascertain that all EVSE loads, controlled by such sophisticated EVEMS would be only connected to the building distribution system, if provisions of Rules 8-104(5) or (6) for circuit loading are not compromised.
3. Use of the EVSE without relaxation, allowed by Rule 8-106(10) or (11)
In this case, each individual EVSE load must be considered with 100% demand factor, as required by the applicable Rules 8-200 – 8-210 of the CE Code.
It should be also noted that the system standard for such sophisticated integrated EVEMS system (consisting of various pieces of equipment interconnected in the field) is currently under development by the CSA technical subcommittee, and until the system standard is developed and published by the CSA for use under provisions of the CE Code, application of such EVEMS must be only done for a specific installation site under the discretion of the local AHJs, as each local AHJ applies different acceptance criteria for use of this (not well known) entity.
Until the standard for such sophisticated integrated EVEMS is developed and published, questions surrounding this mysterious (yet unknown) system, have been formulated by the Code users as follows:\
1. If pieces of equipment comprising this integrated system must be interconnected in the field during the installation, is it intended by the system standard that such interconnection of various pieces of equipment comprising this complete system, meeting conditions outlined in Subrule 8-106(11) of the CE Code, will be done in accordance with the standard, as installation in accordance with the CE Code applies only to approved electrical equipment, and Code rules do not address such interconnection?
2. If the answer to question 1 above is “Yes”, what kind of interconnection requirements are planned to be provided in this standard?
3. Is it intended that the electrical contractor involved in field interconnection of various pieces of equipment comprising this complete system, will not have to obtain installation permit from the AHJ, (as AHJs only provide inspection services for installation of approved electrical equipment under provisions of the CE Code, and not in accordance with unknown system standard)?
4. Is it intended that any electrical work related to field assembly of such integrated system, will be subjected to verification or commissioning in accordance with a specific verification document, similarly to a verification of a fire alarm system, and whether the system standard under development will include such verification/commissioning protocol?
So, until these questions are resolved by the S/C for development of the standard for the integrated system, use of relaxation under conditions listed in Subrule 8-106(11) of the CE Code, should be done only with the consent of the local AHJ, enforcing the legally adopted CE Code.
AHJ, enforcing the legally adopted CE Code. Thirdly and finally, it should be also noted that the Technical Committee for the development of the CE Code has approved a few important changes related to the recognition of the fact, that occasionally, electric vehicle supply equipment located in a public parking garage of an apartment building, could be connected to the panelboards supplying loads of individual dwelling units in the apartment building (see changes to Rule 8-202 below in bold italics):
Rule 8-202 Apartment and Similar Buildings(see Appendix B)
(1) The calculated load for the service or feeder from a main service supplying loads in dwelling units shall be the greater of Item (a) or (b):
(a) (i) a basic load of 3500 W for the first 45 m2 of living area (see Rule 8-110); plus
(ii) an additional 1500 W for the second 45 m2 or portion thereof; plus
(iii) an additional 1000 W for each additional 90 m2 or portion thereof in excess of the initial 90 m2; plus
(iv) any electric space-heating loads provided for with demand factors as permitted in Section 62 plus any air-conditioning loads with a demand factor of 100%, subject to Rule 8-106(3); plus
(v) any electric range load provided for as follows: 6000 W for a single range plus 40% of any amount by which the rating of the range exceeds 12 kW; plus
(vi) any electric tankless water heaters or electric water heaters for steamers, swimming pools, hot tubs, or spas with a demand factor of 100%; plus
(vii) any electrical vehicle supply equipment loads, if they are supplied from a panelboard installed in a dwelling unit, with a demand factor of 100%; plus
(viii) (vii) any loads provided for, in addition to those outlined in Items (i) to (vi), at
(A) 25% of the rating of each load with a rating in excess of 1500 W, if an electric range has been provided for; or
(B) 25% of the rating of each load with a rating in excess of 1500 W plus 6000 W, if an electric range has not been provided for; or (b) 60 A.
(2) The total load calculated in accordance with Subrule (1) and Subrule (3)(a), (b), and (c) shall not be considered to be a continuous load for the application of Rule 8-104.
(3) The calculated load for the consumer’s service or feeder supplying two or more dwelling units shall be based on the calculated load obtained from Subrule (1)(a) and the following:
(a) excluding any electric space-heating loads and any air-conditioning loads, the load shall be considered to be
(i) 100% of the calculated load in the unit having the heaviest load; plus
(ii) 65% of the sum of the calculated loads in the next 2 units having the same or next smaller loads to those specified in Item (i); plus
(iii) 40% of the sum of the calculated loads in the next 2 units having the same or next smaller loads to those specified in Item (ii); plus
(iv) 25% of the sum of the calculated loads in the next 15 units having the same or next smaller loads to those specified in Item (iii); plus
(v) 10% of the sum of the calculated loads in the remaining units;
(b) if electric space heating is used, the sum of all the space-heating loads as determined in accordance with the requirements of Section 62 shall be added to the load determined in accordance with Item (a), subject to Rule 8-106(3);
(c) if air conditioning is used, the sum of all the air-conditioning loads shall be added, with a demand factor of 100%, to the load determined in accordance with Items a) and b), subject to Rule 8-106(3);
(d) except as permitted by Rule 8-106(11), any electric vehicle supply equipment loads not located in dwelling units not supplied from a panelboard installed in a dwelling unit in accordance with Rule 8-202(1)(a)(vii), shall be added with a demand factor as specified in Table 38; and
(e) in addition, any lighting, heating, and power loads not located in dwelling units shall be added with a demand factor of 75%.
(4) The ampacity of feeder conductors from a service supplying loads not located in dwelling units shall be not less than the rating of the equipment installed with demand factors as permitted by this Code.
Hopefully, this article provides some clarification on the subject at hand.
This article was originally featured in Electrical Line Magazine.