Service Feeders and Branch Circuits - Section 8 Flashcards

1
Q

What is a “demand factor”?

What is a demand?

Why do we use them?

A

A percentage of the total demand of an electrical feeder circuit determined from statistical data.

A base wattage value of the expected average load put on a feeder or branch circuit.

Because not all loads (or components within a load) will operate at once.

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2
Q

When determining living area, what percentage of the basement is counted?

A

75%

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3
Q

What is a basic load based on?

How is it calculated?

A

Living area.

Living area divided by 90 m2 rounded up, plus 4 - all multiplied by 1000 W.

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4
Q

How would a service load be calculated for an electric range?

A

6000 W plus 40% of any demand exceeding 12000 W.

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5
Q

How would a branch circuit load be calculated for an electric range?

A

8000 W plus 40% of any demand exceeding 12000 W.

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6
Q

If a range is not provided for, how should the miscellaneous loads of the house be calculated?

A

100% of the total sum of demand (only counting loads exceeding 1500 W) up to 6000 W plus 25% of the demand exceeding 6000 W.

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7
Q

Which loads of a single dwelling are taken at 100% demand?

A
  • Air conditioning
  • Electric tankless water heaters
  • Electric water heaters for steaming
  • Swimming pools
  • Hot tubs
  • Spas.
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8
Q

If a single dwelling has an 85 m2 main floor and a calculated load of 89 Amperes, what will be the minimum ampacity of it’s service conductors?

A

100 Amperes, because of 8-200(1(b))

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9
Q

How are loads 1500 W and under accounted for in service calculations?

A

With the basic load.

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10
Q

Bus bar ampacity should always be “_____” the ampacity of the service conductors.

A

Equal or greater than.

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11
Q

What is the minimum number of branch circuit positions required in a single dwelling? And a dwelling unit?

A

16, where at least half could be double pole breakers and with at least two left open for future use.

8.

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12
Q

Generally, could a dryer always be fed with #10 conductors and protected by a 30A breaker.

A

Yes, unless specified as hardwired.

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13
Q

What is the first thing to ask yourself, when performing an apartment service calculation?

A

What wire am I sizing?

This is because there are multiple different subrules, which size:

Dwelling unit feeders, Main service feeders and house panel feeders, respectively.

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14
Q

When dealing with automobile heater recepticles, which rule must be referenced?

A

8-400.

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15
Q

When calculating a demand for an apartmain main service feeder, what is the demand factor for which to take additional resistive loads?

A

They are taken at 75%.

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16
Q

When calculating a demand for an apartmain main service feeder, why must one separate the heating/ AC loads out of the dwelling unit calculations?

A

This is beacuse not all residents will use all of their appliances at once, which allows us to put a significant demand factor on the smaller suite’s contribution to the total demand. However, since the building must be heated and cooled as a unit, we can only apply the specific demands associated to the total of all Heat/AC wattage.

17
Q

What is the minimum ampacity of an apartment panel feeder?

A

60A.

18
Q

When sizing an electric space heating branch circuit, what must be done to find the wire and overcurrent size?

A

Simply divide wattage, by nominal voltage and go buy your wire. Now take the ampacity of the wire you bought and divide that by 0.8; this will give you the ampacity to protect with your overcurrent device. For example, if the ampacity after upsizing was 27A, you go with a 30A breaker.

19
Q

What are the main uses for Table 39?

A

To size feeders and overcurrent devices for apartment dwelling units and single dwellings.

20
Q

Would you want to always use table 6 to size an apartment main feeder raceway?

A

No, often the neutral wire can be “de-rated” at 70% of the excess of 200A, so we will not always have three wires of the same size. In these cases we must use tables 8, 9 and 10.

21
Q

Which branch circuit loads are generally considered continuous?

A

Air conditioner.

Electric water heater.

Pool heater.

Electric vehicle charging.

Unknown loads.