California State Exam

[Cali Mike]

How's it going, I have been studying for my California State exam and recently took a practice test supplied by the testing agency.

There were a couple questions that I was hoping you could help me out with. I reviewed the material I have from Mike Holt and did some digging around online for similar questions and couldn't find anything. Any help would be appreciated.
Question 1:

-A 3-hp pump is installed 220 feet from the 220-volt main service. What is the voltage drop when using 12 AWG solid wire?

I have been reviewing the voltage drop calculation material and can't seem to find anything similar to this question. They don't give you the current which makes it confusing to me. I'm not sure which type of equation I should be using.

Question 2:

-A feeder supplies a continuous lighting load of 45 amperes and a single motor load of 30 amperes. What is the ampere rating of the feeder?

My answer: 86 amps

Correct Answer: 94 amps

I used code section 215.2(A)(1)(A) and am not quite sure what I missed.

215.2 Minimum Rating and Size.
(A) Feeders Not More Than 600 Volts.
(1) General. Feeder conductors shall have an ampacity not
less than required to supply the load as calculated in Parts
III, IV, and V of Article 220. Conductors shall be sized to
carry not less than the larger of 215.2(A)(l)(a) or (b).
(a) Where a feeder supplies continuous loads or any
combination of continuous and noncontinuous loads, the
minimum feeder conductor size shall have an allowable
ampacity not less than the noncontinuous load plus
125 percent of the continuous load.

Question 3:

-Approximately how many kilowatts are used by a three-phase, 480-volt ac motor that draws a current of 52 amperes and has a power factor rating of 88%?

I'm not sure what equation to use for this one either.

Thanks again,
Mike

 

[Fulthrotl]

How's it going, I have been studying for my California State exam and recently took a practice test supplied by the testing agency.

There were a couple questions that I was hoping you could help me out with. I reviewed the material I have from Mike Holt and did some digging around online for similar questions and couldn't find anything. Any help would be appreciated.
Question 1:

-A 3-hp pump is installed 220 feet from the 220-volt main service. What is the voltage drop when using 12 AWG solid wire?

I have been reviewing the voltage drop calculation material and can't seem to find anything similar to this question. They don't give you the current which makes it confusing to me. I'm not sure which type of equation I should be using.

Question 2:

-A feeder supplies a continuous lighting load of 45 amperes and a single motor load of 30 amperes. What is the ampere rating of the feeder?

My answer: 86 amps

Correct Answer: 94 amps

I used code section 215.2(A)(1)(A) and am not quite sure what I missed.

215.2 Minimum Rating and Size.
(A) Feeders Not More Than 600 Volts.
(1) General. Feeder conductors shall have an ampacity not
less than required to supply the load as calculated in Parts
III, IV, and V of Article 220. Conductors shall be sized to
carry not less than the larger of 215.2(A)(l)(a) or (b).
(a) Where a feeder supplies continuous loads or any
combination of continuous and noncontinuous loads, the
minimum feeder conductor size shall have an allowable
ampacity not less than the noncontinuous load plus
125 percent of the continuous load.

Question 3:

-Approximately how many kilowatts are used by a three-phase, 480-volt ac motor that draws a current of 52 amperes and has a power factor rating of 88%?

I'm not sure what equation to use for this one either.

Thanks again,
Mike

this is a dumb question, but is this sample questions for
the calif state journeyman's license?

 

[Cali Mike]

Yes, these were questions i got wrong on a practice exam.

Mike

 

[Ingenieur]

-Approximately how many kilowatts are used by a three-phase, 480-volt ac motor that draws a current of 52 amperes and has a power factor rating of 88%?

P = sqrt3 x I x V x pf
= 1.732 x 52 x 480 x 0.88
= 38044 W ~ 38 kW


-A 3-hp pump is installed 220 feet from the 220-volt main service. What is the voltage drop when using 12 AWG solid wire?

since they do not give pf
3 hp x 746 w/hp = 2238 w
2238/220 = 10.17 A

in reality the pf x eff is 0.6 range and va = 2238/0.6 = 3730 va
i = 3730 / 220 = 17 A
nec lists 17 A at 230 vac

but since they do not give you pf or eff use 1

 

[Ponchik]

I used table 430.248 to get my motor amp draw, I used table 8 in chapter 9 to get the conductor specs.

I get about 14.5V voltage drop

.4246 ohms multiply by 17A multiply by 2

 

[Cali Mike]

Thanks guys, I appreciate the help. The 38kw was the correct answer, now that I see the equation that makes sense.

For the voltage drop question, the answer they gave was 8.8 volts. I can't figure out how they came up with it.

 

[thomasbl7]

Question 1 , i got a similar answer as Edward using...2kil/cma. 2=distance of wire,k =ohms if you dont have the ohms use 12.9 for cu and 21.2 for aluminum (l) = actual length of wire divided by cma= circular mils as stated by Edward in chapter 9 table 8
Question 2 if the correct answer was 94 amps . i would think they used the motor as continuous load as well. Note at table 430.22E. All motor loads shall be considered as continuous duty. So 45+30 =75×1.25=93.75 rounded up to 94amps. Please forgive me if this is incorrect and hopefully someone with a better understanding can enlighten us both.
Question 3 i received the same as Mike.

 

[docj67]

reply to feeder size q:

reply to feeder size q:

( I see this a duplicate-sorry- tough to get flow of posts on iphone so now I'm on a laptop)
Hey Bro! i'm doing the same thing,studying for calif c-10

The reason why the answer is 94 is bc u size a feeder or a breaker to 125% of load.

I believe q3 answer to be :

480x52x.88x1.72 (1.72 is sq root of 3 )
=37779w or 37.79kw

js

How's it going, I have been studying for my California State exam and recently took a practice test supplied by the testing agency.

There were a couple questions that I was hoping you could help me out with. I reviewed the material I have from Mike Holt and did some digging around online for similar questions and couldn't find anything. Any help would be appreciated.
Question 1:

-A 3-hp pump is installed 220 feet from the 220-volt main service. What is the voltage drop when using 12 AWG solid wire?

I have been reviewing the voltage drop calculation material and can't seem to find anything similar to this question. They don't give you the current which makes it confusing to me. I'm not sure which type of equation I should be using.

Question 2:

-A feeder supplies a continuous lighting load of 45 amperes and a single motor load of 30 amperes. What is the ampere rating of the feeder?

My answer: 86 amps

Correct Answer: 94 amps

I used code section 215.2(A)(1)(A) and am not quite sure what I missed.

215.2 Minimum Rating and Size.
(A) Feeders Not More Than 600 Volts.
(1) General. Feeder conductors shall have an ampacity not
less than required to supply the load as calculated in Parts
III, IV, and V of Article 220. Conductors shall be sized to
carry not less than the larger of 215.2(A)(l)(a) or (b).
(a) Where a feeder supplies continuous loads or any
combination of continuous and noncontinuous loads, the
minimum feeder conductor size shall have an allowable
ampacity not less than the noncontinuous load plus
125 percent of the continuous load.

Question 3:

-Approximately how many kilowatts are used by a three-phase, 480-volt ac motor that draws a current of 52 amperes and has a power factor rating of 88%?

I'm not sure what equation to use for this one either.

Thanks again,
Mike

 

[Sierrasparky]

Are you referring to this?
[FONT=TimesNewRoman,Bold][FONT=TimesNewRoman,Bold]
430.26 Feeder Demand Factor. [/FONT][/FONT][FONT=TimesNewRoman,Bold][FONT=TimesNewRoman,Bold]
[/FONT][/FONT]Where reduced heating of
the conductors results from motors operating on duty-cycle,
intermittently, or from all motors not operating at one time,
the authority having jurisdiction may grant permission for
feeder conductors to have an ampacity less than specified
in

430.24, provided the conductors have sufficient


ampacity for the maximum load determined in accordance
with the sizes and number of motors supplied and the
character of their loads and duties


[FONT=TimesNewRoman,Bold][FONT=TimesNewRoman,Bold]430.24 Several Motors or a Motor(s) and Other
Load(s)
[/FONT][/FONT][FONT=TimesNewRoman,Bold][FONT=TimesNewRoman,Bold]
[/FONT]
[/FONT]Conductors supplying several motors, or a
motor(s) and other load(s), shall have an ampacity not less
than the sum of each of the following:
(1) 125 percent of the full-load current rating of the
highest rated motor, as determined by
430.6(A)
(2) Sum of the full-load current ratings of all the other
motors in the group, as determined by
430.6(A)
(3) 100 percent of the noncontinuous non-motor load
(4) 125 percent of the continuous non-motor load.