Equations

Question 1

Power Equation - Watts =

Answer 1

Voltage X Amps X PF

Question 2

Ohms Law

Answer 2

V = I*R, I = V/R

Question 3

Room Cavity Ratio

Which is worse, tall and narrow or short and wide?

Answer 3

RCR = (5xHx(L+W))/(LxW)
RCR = (2.5x H x room perimeter length)/room area
Tall and narrow is worse and higher value

Question 4

Illuminance at Point

Answer 4

Inverse Square Law
Ehor (illuminance) = I (lumious intensity) (at the angle) x cos (of the angle) / Dsquare
Evert * Dsquare = I (at the angle) x sin (of the angle) / Dsquare
Use the angle to get the light to be perpendicular to the measured surface

Question 5

Lumen Method

Answer 5

Required Illuminance
E = (Total Lamp Lumens/luminaire x # luminaires x CU x LLF) / Area
# of luminaires required = (Required illuminance x Area) / (Total Lamp Lumens/luminaire x CU x LLF)

Question 6

Simple Payback

Answer 6

of years to pay back = Incremental cost of new lighting system (hardware + labor) / annual energy savings

Question 7

Simple rate of return/ROI

Answer 7

ROR = A/I = annual energy savings/initial cost. Inverse of simple payback

Question 8

Steps to calc average maintained illuminance

Answer 8

1. Choose luminaire
2. Find room dims and reflectances
3. Calc total lumens from luminaire
4. Calc RCR, CCR, FCR
5. Obtain effective Ceiling cavity reflectance from table
6. Obtain effective floor cavity reflectance from table
7. Obtain CU from spec sheet
8. Calc LLF
9. Cal Average Maintained Illuminance

Question 9

Wiring installation cost

Answer 9

luminaires X ((kw/luminaire)/pf) x KVA

Question 10

How to use spacing criteria

Answer 10

Luminaire spacing = Height * SC

SC = Luminaire spacing/Height

Question 11

Energy equation

Answer 11

Energy = Power * Time

Question 12

Flicker index

Answer 12

Area 1 / (Area 1 + Area 2)

Question 13

Percent flicker

Answer 13

100* ((A-B)/(A+B))