Sample WA State admin calc test with workings

[CaseyM]

I did the best I could approximating the test I have now take three times. Hopefully I will only have to take this one more time. I've given a copy to my current administrator for review and now I'm sharing this with the rest of you, also for review if you'll help me out.

1) What size inverse time circuit breaker is required for a
feeder supplying the following motors on a 480 volt three
phase delta system? One 15 hp 480v motor, two 10 hp 480v
motors, and one 75 hp 480v motor @ 15 minute intermittent
duty?

Per table 430.150
15hp 460 = 21A
10hp 460 = 14A
75hp = 96A (430.22 E) 96A * .85 = 81.6A

Per 430.52
81.6A * 2.5 =204A next size up 225A

Per 430.62
225A + 21A + 14A + 14A = 274A next size down 250A

250A inverse time breaker

2) In a 120/240v 1 phase commercial building with two
tenants, what is the service load in amperes for the
following? Both tenants require signage.
Tenant 1 has:
5100 square feet,
20kw of heat at 240 volts
1 2 hp 120 volt water pump
1 12 amp refer
1 10 hp 120 volt motor
1 4 kW hot water tank at 240 volts
12 feet of show window lighting
1 25 amp 240 volt AC unit
24 duplex receptacles
1 1500 VA Microwave oven
40? of multioutlet assembly

Tenant 2 has:
23,300 square feet
120 kW heat at 240 volts
2 5 hp 120 volt motors
1 1/2 hp 120 volt water pump
1 12 amp refridgerator
1 4 kW hot water tank
29 240 volt 32 amp rated transformer arc welders at 50%
duty cycle
50 feet of show window lighting,
1 5 hp 240 volt AC unit,
1 10 hp 240 volt motor,
45 duplex receptacles,
40? multioutlet assembly8
1 1500 VA microwave at 120 volts,!
20? of simultaneously used multioutlet assembly!

Gen ltg
220.3a
5100?2
+23300?2
28400?2 *2= 56800
215.2a
56800*1.25=(7100)

Show windows
220.12a
12?
+50?
62?*200va per? = 12400Va
215.2a
12400va * 1.25 = (15500Va)

Kitchen equipment
220.20
2 * 1500Va Microwave
+2 * 12amp Reefer
5800va * .8 = (4704Va)

Receptacles
220.3 b 9
24 receptacles
+45 receptacles
=69 receptacles * 180 va each = (2420Va)

Water Heat
4000
+4000
=(8000Va)

Heat Vs. Ac
220.21
Heat
20Kw
+120Kw
(140 Kw)
Ac
25A 240v = 6000Va
+28A 240v =6720
12,720Va-----Omit as smaller noncoincidental load

Multioutlet assemblys
220.3 b 8
40? = 1440va
40? = 1440va
+20? simultaneously used = 3600va
(6480Va)

Arc Welders
630.11 b
2 * 32A * 100% = 64A
32A * .85 = 27.2A
32A * .7 = 22.4A
+25 * 32A * .6 = 480A
593.6A * .71 = (421.45A)

Motors
2hp 120 1p = 24a
10hp 120 1p = 100A
5hp 120 1p = 56A
1/2hp 120 1p = 9.8A
10hp 240 1p = 50A
(239.8A)

total
7100va general lighting
15500va show windows
3000va signage
4704va kitchen equipment
12420va receptacles
8000va Water heaters
140000va heat
6480va Multioutlet assemblys
421A welders
+239.8A Motors
(Total service load 1482.48A)

3) A multi family dwelling served by a 120/240 volt service
has 4 units with 1,800 sq. ft of living space each. The
building has no common area loads and none of the units
contain laundry facilities. Use the optional method to
determine the feeder load in amperes.
Each unit contains:
1 13Kva Range
1 1.2Kva dishwasher
1 .6Kwa disposal
1 120V compactor 12A
2 120V A/C 18A
1 2.5 Kva 240V heater

General lighting and small appliance load
1800?2 * 4 units = 7200?2
220.3 a
7200?2 * 3va per ?2 = 21600va
+3000va small appliance load * 4 units = 1200va
(33600va)

Appliance load
13000va range * 4 units = 52000va
600va garbage disposal * 4 units = 2400va
1200va dishwasher * 4 units = 4800va
+12a 120 trash compacter * 4 units = 5760va
(64960va)

Ac Vs. Heat
220.21
Ac 2 * 18a * 4 units = (17280va)
Heat 2500va * 4 units = 10000va-----omit as smaller

Total
General Lighting & small appliance load 33600va
Appliances 64960va
+Ac (heat ommitted as smaller) 17280va
(115840va)

220.32
115840va * .45 = 52128va / 240v = Total service
load(217.2A)



4) A 120V/240V 3 wire service serves 13 units with 1,700
sq. ft. each. Each unit contains:
1 12Kva Range
1 1.5Kva dishwasher
1 .6Kva disposal
1 120V A/C at 23A
1 2.5Kva 240V heater

Do not consider house or laundry loads. Use the standard
method to determine the feeder load in Amperes

General lighting and small appliance load
1700?2 * 13 units * 3va per ?2 = 66300va
+ 2 1500va small appliance ckts * 13 = 39000va
105300va
220.11
105300va - 3000 = 102300va
3000va @ 100% = 3000va
+102300va @ 35% = 35805
(38805va)

Range
220.19
13 units * 12kw range (collumn C) = (28000va)

Appliances
220.17
1500va dishwasher
+600va disposal
2100va * 13 = 27300va * .75 = (20475va)

Heat vs. Ac
220.21
Heat 2500va * 13 units = 32500va (omit as smaller)
Ac 23a * 13 units * 120v = (35880)

Total
General lighting and small appliance load 38805va
Ranges 28000va
Appliances 20475va
+ Ac 35880
123160va / 240v = (513.16 Amperes)

5) A duplex served by a 120/240V 1 phase service has two
units each containing 1,900sq ft
1 9Kw Range
1 5A disposal
1 11A dishwasher
1 3Kw hot water
2 20Kw heater
3 3hp 240V A/C units
Using the standard method in amperes, what is the load on
the building feeder.

General lighting
220.3a
1900?2 * 2 units * 3va?2 = 11400va
Small appliance load
220.16a
2 * 1500va * 2 units = 6000va
Laundry
220.16b
1500va * 2 units = 3000va

Total general lighting/small appliance/laundry load 20400va
220.11
20400va - 3000va =17400va
3000va * 100% = 3000va
+17400va * 35% = 6090va
(9090va)

Ranges
220.19
9000va ranges * 2 units per collumn c = (11000va)

Appliances
220.17
600va disposal
1320va dish washer
+3000va Water heater
4920Va * 2 units * .75 = 7380va

Heat vs. Ac
220.21
Heat (Siberia) 2 * 20000 * 2 units = (80000va)
Ac 17a (430.148) * 2 units * 240 = 8160va (omit)

Total
General lighting/small appliance/laundry load 9090va
Ranges 11000va
Appliances 7380va
+Heat 80000va
107470va / 240v = (447.79 Amperes)

6) A duplex served by a 120/240V 1 phase service has two
units each containing 1,900sq ft
1 9Kw Range
1 5A disposal
1 11A dishwasher
1 3Kw hot water
2 20Kw heater
3 3hp 240V A/C units

Using the optional method for two units, what is the load on
the building feeder in amperes.

220.33 (3 units)

General lighting
220.3a
3 units * 1900?2 * 3va per?2 = (5700va)

Small appliance/laundry load
3000va
+1500va
4500va * 3 units = (13500va)

Appliance load
9000va range * 3 units = 27000va
600va disposal * 3 units = 1800va
1320va dishwasher *3 units = 3960va
+3000va water heater * 3 units = 9000va
(41760va)

Heat vs. Ac
220.21
Ac omitted as smaller load
2 * 20000va * 3 units = 120000va

Total
220.32
General Lighting 5700va
Small appliance/laundry load 13500va
Appliance load 41760va
+Heat 120000va
180960va * 45% = 81432va / 240v = (339.3 Amperes)

7) What is the motor feeder demand load in VA for a 480V 3p
service transformed at the service to 120/240 volts,
containing:
1 115v 1ph 5hp nameplate 46.8 amps continuous rated
1 230v 1ph 7.5hp nameplate 33.2 amps 5min intermittent
1 230v 1ph 10hp nameplate 41.5 amps continuous rated
1 460v 3hp 7.5 hp nameplate 9.13 amps continuous rated
1 460v 3ph 20 hp nameplate 22.41 amps 5 min intermittent
1 460v 3ph 40hp nameplate 43.16 amps continuous rated

Single phase motors
115v 5hp = 56a
430.22e 230v 7.5hp = 40a * 85% = 34a
230v 10hp = 50a
Three phase motors
460v 7.5hp = 11a
430.22e 460v 20hp = 27a * 85% = 22.95a
460v 40hp = 52a

Total
430.24
56a * 125% = 70a
34a
50a
11a
22.95a
+52a
(239.95a) #250 cu thwn

 

[resistance]

Re: Sample WA State admin calc test with workings

Cassey-

I'm going to focus on your Multi-family calculation. #3

Take a good look at your calculations again, and post your answer. You where doing good until the end (Totals). Also, there is a trick in this question, and this is where I was talking about reading the question.

I would also like you to post the answers if you have them, so others will have something to work with. (This will also let me show you where the trick is)

Thanks. I will post my answer after your response to Number 3.

They actually got it where you could have a 60a non-service rated panel in each unit (Wow)!

[ June 12, 2005, 01:03 PM: Message edited by: resistance ]

 

[dillon3c]

Re: Sample WA State admin calc test with workings

Casey,
In going over your post,I did my calculations for your questions.What I came up with:

Question 1:Correct

Question 2: 406,636va/240=1694=amperes:*Edited
* GL calculation.
*also convert motors/welders to VA.

Question 3:Correct

Question 4:Correct

Question 5:Correct

Question 6: 86,562va/240=361amperes *useing 220.33 and table 220.32
*1900x3=5700x3va=17100va-GL

Question 7:*in VA-
5hp115v=56Ax1.25=70Ax115=8050va
7.5hp230v=40Ax0.85=34Ax230=7820va
10hp230v=50Ax230v=11500va
7.5hp460v=11Ax796=8756va
20hp460v=27Ax0.85=22.95x796=18268.2va
40hp460v=52Ax796=41392va

Total of:95,786va

* my answers/ calculations,recorded for the checking.

[ June 15, 2005, 02:23 PM: Message edited by: dillon3c ]

 

[resistance]

Re: Sample WA State admin calc test with workings

Dillion is correct on number three, yet, if you post the answers, I'll be able to tell you where the trick is in the question--if the answer you posted is not listed in the test ansers.

[ June 13, 2005, 10:10 PM: Message edited by: resistance ]

 

[CaseyM]

Re: Sample WA State admin calc test with workings

Thank you Dillon, Resistance.
So for question 6 I forgot to multiply my footage the third time. Opps. 7 I just generally smeared all over the place, didn't even pay attention to my own question. For number two... I don't see what I did wrong, except that I glossed over my notes and used amperage as wattage once. But I'm lost on the general lighting. What did I do wrong there?
I wasn't allowed to take my notes out of the test center Resistance so I made this all up. I figured that if people agree with how I answer the basic form of the question than I can handle the test. I did the best I could at remembering the form and simply added my own numbers to the equations. So what's the trick for number three, I don't see it yet?

 

[dillon3c]

Re: Sample WA State admin calc test with workings

Casey,
In question 2:
Gen.ltg
220.3a
5100'2
+23300'2
28400'2=56800
215.2a
56800*1.25=*7100<---71,000va*
*motors & welders [E x I= P]


Question 2:-I returned to adjusted my total.Made mistake on my welder totals, in early morning hours..

*arc welders,29 total count:32A,240V,50%duty

32Ax240v=7680VAx0.71=*5452.8VAx2welders =*10906va--@100% *as determined in table 630.11(A)
*5452.8VAx0.85=*4634.88va- welder three
*5452.8VAx0.70=*3,816.96va- welder four
*5452.8x 25 welders =136,320x0.60=*81792va

welders total:*101,149.84va
Question 2:
71,000va GL
140,000 heat
44,416va motors
2,880va fridges
8,000va waterheaters
101,150va welders
6,480va multioutlets
3,000va microwaves
11,210va receptacles-*see table 220.13
15,500va S.Windows
3,000 signage
+--------------------
406,636va/240=1694amperes

[ June 15, 2005, 03:26 PM: Message edited by: dillon3c ]

 

[resistance]

Re: Sample WA State admin calc test with workings

I hear ya! I can't really tell you where the tricks are unless I can see the answers. Example: Lets say we have a calcualtions question that says 2 A/C units (Note: even though this says two a/c units it doesn't mean that there is only 2 a/c units), yet you have 32 units. I wouldn't be able to tell you if the 2 A/C units serve the entire building, or if there is 2 A/C's for each unit, because I do not have any answers to go on. Now, I can work the problem correctly--yet this would be under the assumption that one (A/C in all units or two A/C units serving the entire building) out of two possibles of the above is correct. This is just an example, yet it holds true. "Trust me!" The writer has set the test up to be failed. Yet, the test is not in error. I would practice the examples www.mikeholt.com/codeforum/ultimatebb.php?ubb=get_topic;f=6;t=000311 given by some of the members who've posted with answers. This will give you a good idea on rather you Know it or not. You can then follow up with questions.

Dillion and Charlie B are very good sources on the topic.

[ June 15, 2005, 10:17 PM: Message edited by: resistance ]

 

[CaseyM]

Re: Sample WA State admin calc test with workings

Thanks for the responses! I'll keep working on it.

Any other tips/suggestions anyone can think of will be welcome!

 

[CaseyM]

Re: Sample WA State admin calc test with workings

I'm getting ready to take the test again this weekend so I thought I'd ask for help again, to see if anyone has anything else to throw into the mix. And I also have a new question: Does a water heater count as kitchen equipment for the purpose of 220.20 if it isn't specifically identified in the question as kitchen equipment.

 

[charlie b]

Re: Sample WA State admin calc test with workings

If they do not say a water heater is in the kitchen, or that it is a booster heater for the dishwasher, then they don't want you to count it amongst the kitchen loads.

 

[CaseyM]

Re: Sample WA State admin calc test with workings

Thank you charlie b. This is what my local inspector told me today as well so that's what I'll stick with