Information Bulletin: Load calculations for row-housing
Persona
Technologies
This bulletin provides guidance on the application of 2018 BC Electrical Code Regulation. The requirements of local municipal authorities having jurisdiction may vary. Installers should consult with local authorities having jurisdiction before starting work to understand their requirements.
Scope:
This bulletin provides clarification on rule 8-200 2) for the calculation of the minimum ampacity of service or feeder conductors from a main service supplying two or more dwelling units of row-housing, and includes single detached buildings with 2 or more separately metered dwelling(s). (Note: Installers intending to incorporate a second dwelling in a single detached building (dwelling) are advised to consult with the authority having jurisdiction for the BC Building Code.)
Code definitions related to Rule 8-200 2)
Single dwelling – a dwelling unit located within a detached building, and may contain multiple eating, sleeping and cooking facilities and can also be; one dwelling unit of row housing, a semi-detached unit, one unit of a duplex, triplex or quadruplex building.
Dwelling unit – one or more rooms for the use of one or more persons as a housekeeping unit with cooking, eating, living and sleeping facilities.
Row-housing – This is not defined in the BC Electrical Code or the BC Building Code. The local authority having jurisdiction for the BC Building Code may have by-laws that provide a definition. Typical examples of row-housing include: duplexes, triplexes, quadruplexes, townhouses, and single dwelling with separately metered secondary dwelling(s).
When calculating the minimum ampacity of a service or feeder conductors supplying two or more dwelling units of row housing, the code requires the use of a greater value from 8-200 1) a) or b), and application of the demands from 8-202 3) a) i) to v) plus the requirements of rule 8-202 3) b) to e).
For buildings where units are 80m^{2 }or more:
- 24000 W is the minimum allowed load used in the calculation.
- If the calculated load exceeds 100A, the calculated load value must be used.
For buildings where units are less than 80m^{2}:
- 60 A is the minimum allowed ampacity of the feeder or service.
- If the calculated load exceeds 60 A, the calculated load value must be used.
In addition to the minimum conductor ampacity, the calculation determines the required rating of the busbar in a multi-gang meter based where one is used.
Examples Rule 8-200 2)
The point of the rule is to understand examples of how to combine more than one unit of row housing to arrive at the minimum allowable ampacity of the main service or feeder. To simplify examples, the load calculation in accordance with 8-200 1) for the individual units is not shown.
Example 1 a:
A duplex under 80m^{2} per unit. Service voltage is at120/240 volts. Each unit is calculated in accordance with rule 8-200 1). The following method is also used for a Single Detached Dwelling with a separately metered secondary dwelling, a triplex, a quadruplex, or townhouses where the unit is fed from a common service or feeder.
Each unit of a duplex is 75m^{2}, with typical loads equalling 13,125 W and a baseboard heat load of 4000W. The result is a calculated total of 17,125 W. Rule 8-200 2) directs us to 8-200 1) where the calculated load is this example has been determined to be 17,125W/240V – 72A. This calculated value is greater than the minimum 60A for units that are less than 80m^{2 }from 8-200 1) b) ii). Therefore this calculated value is used in the calculation.
Then apply demand factors from 8-202 3) a) i) to v) plus 8-202 3) b) d) & e).
Calculated load= 17,125 W
Rule | Demand Application | Result |
---|---|---|
8-202 3) a) | 17,125 W – 4,000 W (heat) | = 13,125 W |
8-202 3) a) i) | 1@100% | = 13,125 W |
8-202 3) a) ii) | 1 @ 65% (.65 X 13,125 W) | = 8,531 W |
8-202 3) a) & b) | Heat 2 X 4,000 W | = 8,000 W |
Total | = 29,656 W |
Service conductors shall have a minimum ampacity of 124 A (29,656 W / 240V). *
Example 1 b:
(note the use of 208v)
A duplex under 80m^{2} per unit. Service voltage is at 120/208 volts. Each unit is calculated in accordance with rule 8-200 1). The following method is also used for a Single Detached Dwelling with a separately metered secondary dwelling, a triplex, a quadruplex, or townhouses where the unit is fed from a common service or feeder.
Each unit of a duplex is 75m^{2}, with typical loads equalling 13,125 W and a baseboard heat load of 4000W. The result is a calculated total of 17,125 W. Rule 8-200 2) directs us to 8-200 1) where the calculated load is this example has been determined to be 17,125W/208V – 82A. This calculated value is greater than the minimum 60A for units that are less than 80m^{2 }from 8-200 1) b) ii). Therefore this calculated value is used in the calculation.
Then apply demand factors from 8-202 3) a) i) to v) plus 8-202 3) b) d) & e).
Calculated load= 17,125 W
Rule | Demand Application | Result |
---|---|---|
8-202 3) a) | 17,125 W – 4,000 W (heat) | = 13,125 W |
8-202 3) a) i) | 1@100% | = 13,125 W |
8-202 3) a) ii) | 1 @ 65% (.65 X 13,125 W) | = 8,531 W |
8-202 3) a) & b) | Heat 2 X 4,000 W | = 8,000 W |
Total | = 29,656 W |
Service conductors shall have a minimum ampacity of 143 A (29,656 W / 208V).
Example 2:
A duplex over 80m^{2} per unit. Service voltage is at120/240 volts Each unit is calculated in accordance with rule 8-200 1). The following method is also used for a Single Detached Dwelling with a separately metered secondary dwelling, a triplex, a
quadruplex or townhouses where the units are fed from a common service or feeder.
Each unit of a duplex is 85m^{2}, with typical loads and 4,000 W of baseboard heat. Rule 8-200 2) directs us to 8-200 1) where the calculated load for this example has been determined to be 17, 125W/240V+ 72 A. This calculated value is less than the minimum 100A for units that are 80m^{2} or greater from 8-200 1) b) ii). The minimum of 100A from 8-200 1) b) i) is used in the calculation.
Then apply demand factors from 8-202 3) a) i) to v) plus 8-202 3) b), c), & d).
100A – 24,000 W
Rule | Demand Application | Result |
---|---|---|
8-202 3) b) | 24.000W – 4,000W (heat) | = 20,000 W |
8-202 3) a) i) | 1 @ 100% | = 20,000 W |
8-202 3) a) ii) | 1 @ 65% (.65 X 20,000 W) | = 13,000 W |
8-202 3) a) & b) | Heat 2 X 4,000 W | = 8,000 W |
Total | = 41, 000 W |
Service conductors shall have a minimum ampacity of 171 A (41,000 W / 240 V) *
Example 3:
A duplex with a calculated load over 100A per unit. Each unit is calculated in accordance with rule 8-200 1). The following method is also used when units are fed from a common service or feeder.
Each unit of a duplex is 191 m^{2} with typical loads and 12,000 W of baseboard heat. Rule 8-200 2) directs us to 8-200 1) where a calculated load is determined to be 27,375 W at 240 V= 114 A.
Rule | Demand Application | Result |
---|---|---|
Heat (individual unit) | = 12,000 W | |
62-116 2) a) | 1^{st} 10,000 W @ 100% | = 10,000 W |
62-116 2) b) | Balance @ 75% | = 1,500 W |
Total Heat per unit | = 11,500 W | |
Basic calculated load for each unit, excluding heat demand of 11,500 W |
||
8-200 2) a) & b) | (27,375 W – 11,500 W) | = 15,875 W |
Note: see above for rule 62-116 calculation | ||
8-202 3) a) i) | 1^{st} unit @ 100% | = 15,875 W |
8-202 3) a) ii) | 2^{nd} unit @ 65% (.65 X 15, 875 W) | = 10,318 W |
Subtotal (15,875 W + 10,318 W) | = 26, 193 W | |
8-202 3) b) | Total heating loads | = 24,000 W |
62-116 2) a) | 1^{st} 10,000 W @ 100% | = 10,000 W |
62-116 2) b) | Balance 14,000 W @ 75% | = 10,500 W |
Total calculated heating demand | = 20,500 W | |
Total calculated demand | (26,193 W + 20,500 W) | = 46, 693 W |
Example 4:
A 10 unit townhouse complex fed from a main electrical room, with one service to a meter stack, each unit is 85m^{2}, and with typical loads including 4000 W of baseboard heat. A house load of 11 X 175 W Street Light,. 6 X 120 V, 20 A Vehicle Charging Receptacles and 1000 W of heat. Calculated load for each unit, including heat, is 17,125 W/240 V = 72 A.
The calculated load, 72 A, is less than 100 A. The rule requires 100 amps minimum because of 8-200 1) b) (over 80m^{2}) then apply demand factors from 8-202 3) a) i) to v) plus 8-202 3) b), c) & d)
Rule | Demand Application | Result |
---|---|---|
8-200 2) a) & 1) b) | 100 A X 240 V | = 24,000 W |
8-200 2) & b) | 24,000 W – 4,000 W heat | = 20,000 W |
8-202 3) a) i) | 1 unit @ 100% | = 20,000 W |
8-202 3) a) ii) | 2 units @ 65% | = 26,000 W |
2 units @ 40% | = 16,000 W | |
5 units @ 25% | = 25,000 W | |
Subtotal | = 87,000 W | |
Rule 62-116 2) | Heat load = 10 X 4,000 W | = 40,000 W |
1st 10,000 W @ 100% | = 10,000 W | |
Remainder 30,000 W @ 75% | = 22,500 W | |
Heat (subtotal) | = 32,500 W |
Rule | Demand Application | Result |
---|---|---|
House Loads | ||
8-202 3) e) | Lights = 11 X 175 W @ 75% | = 1,444 W |
8-202 3) e) | Heat 1,000 W @ 75% | = 750 W |
8-202 3) d) | Chargers 6 X 120 V X 20 A @ 100% | = 14,400W |
Subtotal | = 16,594 W | |
8-104 5) a) | House Load deemed Continuous | = 20,743 W |
(16,594 W X 1.25) | ||
Total demand | ||
Units (from previous page) | = 87,000 W | |
Heat (from previous page) | = 32,500 W | |
House load | = 20,743 W | |
Total | = 140,243 W |
The minimum ampacity of the service conductors is 584 A (140,243 W / 240V). *
* 2018 Code rule 8-200 1) b) instructs you to use wattage instead of amperage. This will result in a conductor and service size increase based on 208v.
Provincial Safety Manager