Electrical Systems 1 Exam 2 Study
Guide Test.
Standard Ratings for Transformers (written on back page of NEC) - CORRECT ANSWER 15, 30, 45 ,75,
122.5, 150, 225, 300, 500, 750, 1000
ALL IN KVA (apparent power)
What are the 2 types of transformers? - CORRECT ANSWER Dry type and liquid filled type
Dry type transformer - CORRECT ANSWER Commonly indoors and outdoors
For 480 - 208/120V transformers
Cooling medium is air
Liquid type tranformer - CORRECT ANSWER Used for higher voltages
Cooling medium is typically oil
Must have containment if indoors
What is the most common transformer in buildings? (we drew this in our notes pretty recently) -
CORRECT ANSWER 480V, 3 phase delta primary with a 208/120v 3 phase 4 wire wye secondary
Where can transformers be mounted? - CORRECT ANSWER Floor (needs 3.5" pad)
Wall
Suspended
Stacked
*75 KVA and smaller can be suspended or wall mounted*
If you have higher voltage, you have _____ amperage. - CORRECT ANSWER Lower
If you have lower voltage, you have _____ amperage. - CORRECT ANSWER Higher
, Rated primary/secondary current (Ip and Is) - CORRECT ANSWER Ip = (VA of xfrmr / primary voltage)
Is = (VA of xfrmr / secondary voltage)
What is the square footage range for having an electrical room on a floor? - CORRECT ANSWER 1
electrical room per every 25,000 - 30,000 SF
How many electrical rooms per floor would a 3 story, 300'x150' base plate need? - CORRECT ANSWER 2
electrical rooms per floor
Standard panelboard bus ratings (written on back page of NEC) - CORRECT ANSWER 100, 225, 250, 400,
600
All in amps
Standard distribution panel ratings (written on back page of NEC) - CORRECT ANSWER 400, 600, 800,
1000, 1200
All in amps
What tab do I look under in my NEC to figure out the different clearances and spacing for equipment
and room layout? - CORRECT ANSWER Working Clearances (110.26(A)(1) and the next couple pages
have helpful pictures)
What distance is always safe for clearance distance? - CORRECT ANSWER 4 feet (depends on voltage for
this distance but 4 feet is the max value and therefore always safe)
What tab do I look under in my NEC to figure out the difference dedicated space requirements? -
CORRECT ANSWER Working Clearances then flip a few pages forward to pg 43 (NEC 110.26 E)
What is the minimum distance to use for dedicated space? - CORRECT ANSWER 6 feet or to the
structural ceiling
Are transformers included in the requirements for dedicated spaces? - CORRECT ANSWER No
Guide Test.
Standard Ratings for Transformers (written on back page of NEC) - CORRECT ANSWER 15, 30, 45 ,75,
122.5, 150, 225, 300, 500, 750, 1000
ALL IN KVA (apparent power)
What are the 2 types of transformers? - CORRECT ANSWER Dry type and liquid filled type
Dry type transformer - CORRECT ANSWER Commonly indoors and outdoors
For 480 - 208/120V transformers
Cooling medium is air
Liquid type tranformer - CORRECT ANSWER Used for higher voltages
Cooling medium is typically oil
Must have containment if indoors
What is the most common transformer in buildings? (we drew this in our notes pretty recently) -
CORRECT ANSWER 480V, 3 phase delta primary with a 208/120v 3 phase 4 wire wye secondary
Where can transformers be mounted? - CORRECT ANSWER Floor (needs 3.5" pad)
Wall
Suspended
Stacked
*75 KVA and smaller can be suspended or wall mounted*
If you have higher voltage, you have _____ amperage. - CORRECT ANSWER Lower
If you have lower voltage, you have _____ amperage. - CORRECT ANSWER Higher
, Rated primary/secondary current (Ip and Is) - CORRECT ANSWER Ip = (VA of xfrmr / primary voltage)
Is = (VA of xfrmr / secondary voltage)
What is the square footage range for having an electrical room on a floor? - CORRECT ANSWER 1
electrical room per every 25,000 - 30,000 SF
How many electrical rooms per floor would a 3 story, 300'x150' base plate need? - CORRECT ANSWER 2
electrical rooms per floor
Standard panelboard bus ratings (written on back page of NEC) - CORRECT ANSWER 100, 225, 250, 400,
600
All in amps
Standard distribution panel ratings (written on back page of NEC) - CORRECT ANSWER 400, 600, 800,
1000, 1200
All in amps
What tab do I look under in my NEC to figure out the different clearances and spacing for equipment
and room layout? - CORRECT ANSWER Working Clearances (110.26(A)(1) and the next couple pages
have helpful pictures)
What distance is always safe for clearance distance? - CORRECT ANSWER 4 feet (depends on voltage for
this distance but 4 feet is the max value and therefore always safe)
What tab do I look under in my NEC to figure out the difference dedicated space requirements? -
CORRECT ANSWER Working Clearances then flip a few pages forward to pg 43 (NEC 110.26 E)
What is the minimum distance to use for dedicated space? - CORRECT ANSWER 6 feet or to the
structural ceiling
Are transformers included in the requirements for dedicated spaces? - CORRECT ANSWER No
