Apartment calculations

I'm currently doing my second year and we are doing an apartment project and I'm really stuck.

I really need some help interpreting 8-202(3)(a). I don't understand the breakdown of it. Starting at (ii) it says you take 65% of the sum of the calculated loads in the next 2 units having the same or next smaller loads to those specified in subparagraph (i).

Now my question is if you only have 1 unit there instead of 2 do you the multiply by 1? Plus what do I do for my next different calculated load? Do I have to take the remaining of the one unit from the 60% or do I immediatly move to 40%.

I've tried working this out every which way but my numbers don't add up to the other guys in the course.

Waterski-Guy:

I will give you an example

An apartment with 6 units
unit 1 20000W
unit 2 19000W
unit 3 18000W
unit 4 17000W
unit 5 16000W
unit 6 15000W


100% * 20000W
65% * 19000W
65% * 18000W
40% * 17000W
40% * 16000W
25% * 15000W
+____________________
61000W

][/QUOTE]

<font color="#a62a2a" size="1">[ December 11, 2003 12:57 AM: Message edited by: ccrash ]</font>

EXAMPLE CALCUALTION:

41 Unit Apartment Calcualtion

1)Dimensions are 36’ x 25’ (approximately 900 sq. ft)

2)Each apartment contains a 12-kw Range

3)Houseloads are: 5 Dryers @ 6-kw each, 1 Boiler @ 20-kw, 5 Washers @ 1.5-kw each, 1 Elevator @ 7.2 kw, and 6.4-kw lighting (40-Flourescent Fixtures 4 x 40w)

4)Service is 120/208v 1ph for each unit

5)NO AIR CONDITIONING LOADS INCLUDED IN CALCULATION

900 sq.ft. Units

Conversions for Apartment Dimensions

36’ divided by 3.281= 10.97-metres
25’ divided by 3.281= 7.62-metres

A= L x W= 10.97 x 7.62 = 83.61-sq.metres

Demand Load for Each 83.61m2 Units

1st. 45m2 = 3500-w
2nd. 45m2 = 1500-w
12kw Range = 6000-w
11,000-watts

Feeder Size for Each 83.61 m2 Unit

11,000-watts divided by 208-volts single phase = 52.88-amps

1st. 5 Units

1st. Heaviest Load x 100% = 11,000-watts
Next 2 loads x 65% = 14,300-watts
Next 2 loads x 40% = 8,800-watts
TOTAL = 34,100-watts

Remaining 36 Units

41 Units – 5 = 36 Units x 25% = 99,000-watts

Total Demand for all Suites

99,000w + 34,100w = 133,100-watts

Houseload Demand

Lighting = 6,400-watts
Dryers = 30,000-watts
Washers = 6,500-watts
Boiler = 20,000-watts
Elevator = 7,200-watts

TOTAL = 70,100w x .75% = 52,575-watts

Building Demand

133,100-watts + 52,575-watts = 185,675-watts divided by 208 x 1.73 = 515-AMPS

Tony Moscioni
Electrical Inspector
Electrical Safety Authority

Thanks, that is exactly what I was looking for. Now my answers are lining up. Thanks again.

waterski_guy,

Using the CEC, I get a slightly different answer than Tony did. He may be using an Ontario Ammendment?

Below is a copy of his example with my changes in bold.

EXAMPLE CALCUALTION:
41 Unit Apartment Calcualtion

1)Dimensions are 36? x 25? (approximately 900 sq. ft)

2)Each apartment contains a 12-kw Range

3)Houseloads are: 5 Dryers @ 6-kw each, 1 Boiler @ 20-kw, 5 Washers @ 1.5-kw each, 1 Elevator @ 7.2 kw, and 6.4-kw lighting (40-Flourescent Fixtures 4 x 40w)

4)Service is 120/208v 1ph for each unit

5)NO AIR CONDITIONING LOADS INCLUDED IN CALCULATION

900 sq.ft. Units

Conversions for Apartment Dimensions

36? divided by 3.281= 10.97-metres
25? divided by 3.281= 7.62-metres

A= L x W= 10.97 x 7.62 = 83.61-sq.metres

Demand Load for Each 83.61m2 Units

1st. 45m2 = 3500-w
2nd. 45m2 = 1500-w
12kw Range = 6000-w
11,000-watts

Feeder Size for Each 83.61 m2 Unit

11,000-watts divided by 208-volts single phase = 52.88-amps

1st. 5 Units

1st. Heaviest Load x 100% = 11,000-watts
Next 2 loads x 65% = 14,300-watts
Next 2 loads x 40% = 8,800-watts
TOTAL = 34,100-watts

Next 15 units - 11,000 x 15 units x 25% = 41,250 watts
Remaining 21 Units - 11,000 x 21 units x 10% = 23,100 watts

Total Demand for all Suites

34,100 w + 41,250 w + 23,100 w = 98,450 watts

Houseload Demand

Lighting = 6,400-watts
Dryers = 30,000-watts
Washers = 6,500-watts
Boiler = 20,000-watts
Elevator = 7,200-watts

TOTAL = 70,100w x .75% = 52,575-watts

Building Demand

98,450 watts + 52,575 watts = 151,025 watts divided by 208 x 1.73 = 419.7 amps

Note - Some designers consider the house load in an apartment building to be a continuous load (8-202 Subrule 2), which would have the effect of increasing the total load.

Ed

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