## Open Book Exam

10 calculations from actual Houston Exams. Only your calculator (non scientific) and code book allowed

You only have 4 hours to complete. Some of these I have answers too, some I have not worked. If you send me your answers I will look over them if I have time.

You only have 4 hours to complete. Some of these I have answers too, some I have not worked. If you send me your answers I will look over them if I have time.

1. single phase 200v 200kvar capacitor draws _______ amperes

a. In question 1 what is the ohmic value

b. at 60 HZ what is the Farads

2. An Office Building is being planned in the City of Houston with the following parameters

20 floors 20k Sqft per floor

Each floor consist of store occupancies

Each Floor has 3- 10hp 480v 3ph fans

Each Floor has 3- 480v 3ph 6kw heaters

3- 10hp 480v pumps 3 ph total

10-14a 480v A/C motors

Find Service line amperes 480/277 and OCP

3.A commercial building in the City of Houston is supplied by a 480/277 3ph service. Due to a new power factor factor correction installation the demand KVA was reduced to 621 KVA. THe power factor of the system was improved from 86% to 97%. Calculate the demand KVA before the new capacitor install. Was size capacitors in KVAR was necessary to complete the install. What size capacitors in KVAR would be required to improve the power factor to unity.

KVA_______

KVAR______

KVAR______

4. find the ampacity of these conductors cu

a. 6- #8 thw @ 45deg F in a 1" al nipple

b. 4- #12 thwn in a 2" conduit@ 100 deg F feeding a 1kw load @ .7 PF 240v

c. 6- #1 thw in conduit feeding cranes rated with 15 minute ratings

d. what size conductors for 4- 50 hp 480v 3ph motors in same conduit in a 25 deg c environment (75deg insulation)

5. the inductance of a winding is 0.326H. Find

a. the inductive reactance with a frequency of 60hz

b. the inductive reactance with a frequency of 50hz

6. 100 unit motel 120/240v 3p 4w

each unit 500sq ft

10a 240v 1p A/C heat pump

find amperes for each phase

7. Find the main feeder for these welders and cranes combined

Resistance welders 480v 3ph

30 kva 40% duty

20 kva 50%

15 kva 30%

15 kva 30%

10 kva 20%

AC Transformer and dc arc welders

35 kw 80% duty

30 kw 70%

25 kw 60%

20 kw 50%

4- 480v 3ph cranes each has these motors

motion a 2- 20hp

motion b 1- 15 hp

motion c 2- 10 hp

8. School (just about every Houston test will have a school)

9. Given 3- 7200v, 3-120/240 xfmrs connect primary and secondary for 120/240/208 wild leg delta (show all work)

10. What is the feeder demand for 29 8kw household ranges on a 120/208 4w feeder

11. Hospital (better throw one in because Houston has the largest medical center in the world (about 100,000 employees)

277/480 3ph 4w 350,000 SQ FT

1000- 200va lighting fixtures 277v

200- Patient care room ( two general care locations each room)

6- 24 kw diagnostic x-ray units 480v 3ph

5- 15 kw therapeutic x-ray 480v 3ph

1- 50 kw sterilizer 480v 3 ph

2- 10 kw 277/480v 3ph 4w sign

9- 10 hp air handler 480v 3ph

1- 100hp 480v 3ph a/c compressor synchronous motor . 8 pf

Find line amperes

a. In question 1 what is the ohmic value

b. at 60 HZ what is the Farads

2. An Office Building is being planned in the City of Houston with the following parameters

20 floors 20k Sqft per floor

Each floor consist of store occupancies

Each Floor has 3- 10hp 480v 3ph fans

Each Floor has 3- 480v 3ph 6kw heaters

3- 10hp 480v pumps 3 ph total

10-14a 480v A/C motors

Find Service line amperes 480/277 and OCP

3.A commercial building in the City of Houston is supplied by a 480/277 3ph service. Due to a new power factor factor correction installation the demand KVA was reduced to 621 KVA. THe power factor of the system was improved from 86% to 97%. Calculate the demand KVA before the new capacitor install. Was size capacitors in KVAR was necessary to complete the install. What size capacitors in KVAR would be required to improve the power factor to unity.

KVA_______

KVAR______

KVAR______

4. find the ampacity of these conductors cu

a. 6- #8 thw @ 45deg F in a 1" al nipple

b. 4- #12 thwn in a 2" conduit@ 100 deg F feeding a 1kw load @ .7 PF 240v

c. 6- #1 thw in conduit feeding cranes rated with 15 minute ratings

d. what size conductors for 4- 50 hp 480v 3ph motors in same conduit in a 25 deg c environment (75deg insulation)

5. the inductance of a winding is 0.326H. Find

a. the inductive reactance with a frequency of 60hz

b. the inductive reactance with a frequency of 50hz

6. 100 unit motel 120/240v 3p 4w

each unit 500sq ft

10a 240v 1p A/C heat pump

find amperes for each phase

7. Find the main feeder for these welders and cranes combined

Resistance welders 480v 3ph

30 kva 40% duty

20 kva 50%

15 kva 30%

15 kva 30%

10 kva 20%

AC Transformer and dc arc welders

35 kw 80% duty

30 kw 70%

25 kw 60%

20 kw 50%

4- 480v 3ph cranes each has these motors

motion a 2- 20hp

motion b 1- 15 hp

motion c 2- 10 hp

8. School (just about every Houston test will have a school)

9. Given 3- 7200v, 3-120/240 xfmrs connect primary and secondary for 120/240/208 wild leg delta (show all work)

10. What is the feeder demand for 29 8kw household ranges on a 120/208 4w feeder

11. Hospital (better throw one in because Houston has the largest medical center in the world (about 100,000 employees)

277/480 3ph 4w 350,000 SQ FT

1000- 200va lighting fixtures 277v

200- Patient care room ( two general care locations each room)

6- 24 kw diagnostic x-ray units 480v 3ph

5- 15 kw therapeutic x-ray 480v 3ph

1- 50 kw sterilizer 480v 3 ph

2- 10 kw 277/480v 3ph 4w sign

9- 10 hp air handler 480v 3ph

1- 100hp 480v 3ph a/c compressor synchronous motor . 8 pf

Find line amperes