Information Bulletin: Load calculations for row-housing

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Technologies

Technologies
Reference number
IB-EL 2014-01
Revision Number
Rev 1

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 dwellings with secondary suites. (Note: Installers intending to incorporate a secondary suite in a single family 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 (SFD) – a dwelling unit consisting of a detached house, one unit of a row house, or one unit a semi-detached, duplex, triplex or quadruplex house.

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 family dwellings with a suite.

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 valve 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 80m2 or more:

  • 24000 W is the minimum allowed load used in the calculation.
  • If the calculated load exceeds 24000 W, the calculated load value must be used.

For buildings where units are less than 80m2:

  • 14400 W is the minimum allowed ampacity of the feeder or service.
  • If the calculated load exceeds 14400W, 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 80m2 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 SFD with a suite, a triplex, a quadruplex, or townhouses where the unit is fed from a common service or feeder.

Each unit of a duplex is 75m2, 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 valve is greater than the minimum 60A for units that are less than 80m2 from 8-200 1) b) ii). Therefore this calculated valve 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 80m2 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 SFD with a suite, a triplex, a quadruplex, or townhouses where the unit is fed from a common service or feeder.

Each unit of a duplex is 75m2, 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 valve is greater than the minimum 60A for units that are less than 80m2 from 8-200 1) b) ii). Therefore this calculated valve 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 80m2 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 SFD with a suite, a triplex, a

quadruplex or townhouses where the units are fed from a common service or feeder.

Each unit of a duplex is 85m2, 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 80m2 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) *

Example3:

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 m2 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) 1st 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) 1st unit @ 100% = 15,875 W
8-202 3) a) ii) 2nd 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) 1st 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 85m2, 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 80m2) 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