Taking Washington admin test

utahspud

Member
Location
washington
Occupation
electrician
I am preparing to re take my Washington administrator test and I had a question. Say you are given a church that is 50x120 sq feet and asked to figure the general lighting load of 120v 20 amp lighting circuits.

Do I need to de rate my circuits to only load them to 80% when calculating my circuit number or figure them at the 2400va?
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
If you are calculating the total lighting load, then legomywago is right. If you are calculating the number of circuits you need in order to supply that load, then I believe that each circuit should be loaded no higher than 80% (1920 VA).
 

utahspud

Member
Location
washington
Occupation
electrician
I guess that’s where it’s confusing. It gives the sq footage and asked for the number of circuits. It of course has both answers on the test. Thanks for the help.
 

thomasbl7

Member
Location
US
I guess that’s where it’s confusing. It gives the sq footage and asked for the number of circuits. It of course has both answers on the test. Thanks for the help.
You asked 2 different questions. The general light load=( sqft x 2.2 v) is a different answer than what the number of circuits .. number of circuits= (50x 120x 2.2va) divided by (120v x 20a)
I wouldn't us the 80% because the 125% was already multiplied in the general light load based on the note under table 220.42a

the 125% continuous load is the same as dividing the 80% to offset the not loading the circuit Charlie spoke of..
What's your take on this Charlie?
up until 2017 it wasn't notated in 220.42 that 125% was added to the va in the table. not until 2020 code cycle.
 

utahspud

Member
Location
washington
Occupation
electrician
You asked 2 different questions. The general light load=( sqft x 2.2 v) is a different answer than what the number of circuits .. number of circuits= (50x 120x 2.2va) divided by (120v x 20a)
I wouldn't us the 80% because the 125% was already multiplied in the general light load based on the note under table 220.42a

the 125% continuous load is the same as dividing the 80% to offset the not loading the circuit Charlie spoke of..
What's your take on this Charlie?
up until 2017 it wasn't notated in 220.42 that 125% was added to the va in the table. not until 2020 code cycle.
I guess my question is when figuring the circuits I would use 50x120 for my sq feet. multiply that times my 2.2va a sq foot to get my va required for the space. When figuring up a 120v 20 amp circuit fully loaded would be 2400va but you cant run circuits to their max so would you only be able to load the circuits up 80%,1920 va. On the test its a difference of three or four circuits.
 
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