NABCEP STUDY GUIDE
Acronym for OSHA's Safety and Health Regulations for Construction
29 CFR Part 1926
Central Inverters
30- 50 kW systems interconnected to 3-phase grids. Great for homogeneous PV arrays
Maximum Power Current (Imp)
Current corresponding to Pmp
Response to Irradiance
Current is directly proportionate to irradiance
UL1703
Safety Standard for Flate Plate Photovoltaic Modules and Panels
Equipment Grounding
EGC Connects non-current carrying metal parts to ground. Achieved with a GROUNDING CONDUCTOR
What are coloring requirements for PV Source Circuit
It can be black as long as the termination is appropriately marked off with the correct color.
Average daily amp hours required
The amount of battery energy (amp-hours) needed to run the loads for one day.
Surge
The increased current draw for a very short time span when certain loads such as a motor are starting.
Voltage Drop % Equation For AC
Voltage Drop %= (0.2)(D)(System Imp)(Resistance) ________________________ (Inverter Output Vnom)
Voltage Drop % Equation For DC
Voltage Drop %= (0.2)(D)(System Imp)(Resistance) ________________________ (System Vmp)
Maximum Power Voltage (Vmp)
Voltage corresponding to Pmp
Determine Number of roof attachments required per row of modules
# of attachments = Lp/Plag Wherein: Lp = (ft^2 of row)*(wind uplift rating) Plag = (Pull out strength per inch)*(# threaded inches)
Stand-alone systems
(Also known as "off grid" systems) Not connected to the utility and are the primary energy source for the connected electrical loads, which may be ac and/or dc
Valve-regulated lead-acid (VRLA)
(Also known as sealed lead-acid) Batteries that do not allow access to the battery's electrolyte, but have non-openable valves that allow any excess pressure to escape.
One Amp is....
1 columb per second
Color Options for Grounded Conductors
1) Continuous White 2) Continuous Grey 3) Three Continuous White Stripes
Determining Max Voltage of PV System Method #1: Manufacturer's Temperature Correction Factor (The Percentage Method)
1) Convert Temperature Coefficient % to number Ex: Temp Coefficient is symbolized as @Voc @Voc = - 0.37%/C = -0.0037/C 2) Find Temperature Correction Factor TCF = 1 + [@Voc x (Temp Low - Temp Rated)] = 1 + [ (-0.0037/C) x (-12C - 25C) ] = 1 + (-0.0037 x -37) = 1 + 0.137 TCF= 1.137 3) Then use correction factor to find Max System Voltage (Voc) x (# of Modules wired in series) x (Voltage Correction Factor)
7 Requirements for Load Side Connections
1) Each inverter must have a dedicated disconnect and overcurrent protection device. 2) Sum of Ampere Ratings Of OCPD connected to a busbar does not exceed 120% of Busbar rating. 3)** Interactive Inverters must be interconnected on the line side of all ground-fault protection devices. ** 4) All distribution equipment must have labels 5) Circuit breakers used for inverter connections must be suitable for backfeeding. 6) Fastening is not required for breakers fed by inverters 7) If the sum of the OCPD ratings is greater than 100% of the busbar rating than the PV breaker must be on the opposite side of the utility power supply in the MDP.
Formal Equation for Row to Row Spacing
1) Find Spacing between rows (without Azimuth Adjustment) Tan(Sun Alt Angle) = (Height of Row)/(Spacing between Rows) 2) Multiply Spacing by COS of Azimuth Difference from Array COS(Azimuth Diff) x (Spacing Between Rows) = ANSWER
Acceptable colors for EGC
1) Green 2) Green with yellow stripes
Insulation Resistance Testing
1) Isolate circuits (leave bonding and grounding in tact) 2) Remove surge suppression equipment from circuit. 3) Connect the positive and negative homeruns. Connect this to the Positive Terminal of Insulation Tester 4) Connect Negative Terminal of Insulation Tester to Array Grounding Point. 5) Apply a test voltage of 500 V 6) Measure resistance in MEGA OHMS If a fault exists, resistance measurements will decrease significantly.
Supply Side Connection Requirements
1) Must have a service rated disconnect and a OCPD rated for at least 60 Amps 2) Fcuk it
Tests to be done during commissioning
1) Test AC Circuits for Continuity, phasing, voltage 2) Test DC circuits for continuity of grounding conductors 3) Verify correct DC polarity 4) Test String open circuit voltage 5) Test String Short Circuit Current 6) Verify System Functionality 7) Test insulation resistance for PV arrays source and output circuits.
Two factors that increase voltage drop
1) increasing current 2) long homerun lengths
Minimum Size Wire to be used with 30, 40 & 60 Amp OCPD
10 AWG
How many Amps will freeze your muscles
10 mA
Minimum Size Wire to be used with 20 Amp OCPD
12 AWG
What percentage of young worker workplace deaths are caused by electrocution?
12%
Minimum Size Wire to be used with 15 Amp OCPD
14 AWG
Sizing Wire (page in NEC)
149
Acceptable range for voltage drop
2% to 5% of operating voltage
Where in NEC is Ground Wire Size Specified based on OCPD
250.122 .....but you need #6 for module frames and rails
Working Clearance for Electrical Equipment
3 foot clearance from front Width = 30 inches or width of equipment See NEC 110.26
NEC recommended voltage drop
3% to 5% Found in the "Branch Circuits Section"
At what operating voltage is voltage drop not such a big deal
300 V
If grounding electrode is encased in concrete the minimum size AWG is...
4 AWG
At what operating voltage is voltage drop a huge concern
48 V
How many workers are electrocuted each week
5
What is the minimum size EGC that can be ran outside of conduit
6 AWG
One columb is
6.24 billion billion electrons 6.24 x 10^18
Frequency of american electrical system
60 Hertz/second
Where is Maximum Photovoltaic System Voltage found in the NEC
690.7
How many amps will cause an inefficient heartbeat?
75 mA
Requirements for Feeder Taps (page in NEC)
92
1000 Watts per Meter^2 Equals ....(feet^2)
92.9 watts per foot^2
Solar Radiation
???Electromagnetic radiation from the sun???
Ballasted Mounting Systems
Used for large scale flat commercial roofs.
Grounding Electrode (GE)
A conducting object, often a rod, ring, or plate, establishing a direct connection to earth
Ungrounded conductor
A current-carrying conductor that has no connection to ground, and therefore is normally energized with reference to ground and the grounded conductor. Whether ac or dc, and regardless of polarity, ungrounded conductors must be any unique color other than white, gray, green, or bare.
Grounded conductor
A current-carrying conductor that is intentionally connected to earth ground at one point to create a zero-voltage reference. Whether ac or dc, and regardless of polarity, grounded conductors must be white or gray.
Ground fault protection device (GFPD)
A device that detects whether fault current is being carried by the equipment grounding conductors and can disable the system
Battery bank
A group of batteries wired in series and/or parallel wiring configurations to a specific voltage and capacity
UL1741
Used in conjunction with IEEE1547
Equipment grounding conductor (EGC)
A non-current-carrying conductor used to connect the exposed metal parts of equipment, modules, and other metallic items to the grounding electrode conductor or system ground
Backed-up load panel
A subpanel in a grid-tied with battery back-up system that can be isolated from the utility grid and receive power from the battery bank during power outages.
Surge protection device (SPD)
A voltage actuated device designed to safeguard equipment from electrical surges and spikes, including those caused by lighting
You are designing an off-grid PV system for a home with a dirt floor crawl space. The battery bank has 2/0 conductors feeding the DC panel. The charge controller has #4 conductors feeding the battery bank. Size the grounding electrode and grounding electrode conductors for a 150 amp rated AC panel being fed by four 3600 watt inverters configured for 240 volt output. a. 2 ground rods 6' apart with a #6 GEC c. Concrete encased electrode with #4 GEC b. 2 ground rods 6' apart with a #8 GEC d. 1 ground rod with 2/0 GEC
ANSWER: A 3600 x 4 = 14400 ÷ 240 = 60 amps x 125% = 75 amps The OCD will be 75 amps Table 310.15(B)(16) shows #4 to be rated for this ampacity. Art 690.47(C)(2) allow for a common grounding electrode with the grounding electrode conductor sized according to 250.166. If we size the grounding electrode conductor for the AC side Table 250.66 shows a #8 grounding electrode conductor to be adequate. The smallest grounding electrode that can be installed is a pipe or ground rod. A second grounding electrode installed at least 6' away form the other is required if the ohms to ground is more than 25 ohms; (it always is). 250.166 states that the DC grounding electrode conductor be no smaller than the largest conductor serving the system (2/0). Although an allowance is made if the AC grounding electrode is a rod or pipe. In this case the grounding electrode conductor is not required to large than a #6 cu.
The residence has a 200 amp service and is grounded with a concrete encased electrode. What size grounding electrode conductor is required to be installed from the inverter to the grounding electrode system for a 5kW residential inverter fed by a 6kW PV array with #10 output conductors? a. #8 copper c. #4 copper b. #6 copper d. #4 tin coated aluminum
ANSWER: A Art. 250.166 requires the grounding electrode conductor to be no smaller than the largest conductor feeding the system and no smaller than #8.
The PV array of a grid-interactive PV system is ground mounted and located more than 6' away from the existing premises grounding electrode system. The existing grounding electrode system is a concrete encased electrode. The PV array combiner is fed with #12 PV wire and the output conductors are #1 copper conductors running underground in PVC conduit over to the inverter location by the premises wiring. You have galvanized metal posts for array supports and decide to add a grounding electrode 6' away from the poles. What size bonding conductor must be run from the ground rod to the main premises grounding electrode? a. #1 c. #6 b. #10 d. #4
ANSWER: D Art 690.47(C)(1) refers to the need for DC grounding. This could either mean a total DC system or a DC to AC system that is more than 6' from the existing premises grounding electrode. Art. 250.166(C) allows for the grounding electrode conductor to be no larger than the electrode selected (pipe and rod). Art. 690.47(C)(1) also states that the grounding electrode can be no smaller than the largest grounding electrode conductor of either system.
52. Which of the following AC systems can a single phase 208/240/277 volt inverter not be connected to. a. Residential 120/240 volt 1 phase transformer c. Commercial 480 volt Wye transformer b. Commercial 120/208 volt Wye transformer d. Commercial 480 volt Delta transformer
ANSWER: D The 480v delta does not have a neutral conductor.
What is the smallest wire allowed by NEC
AWG 14
Load Side (in reference to MDP)
After the MDP
Inverter Bypass Switch
Allows for grid/generator to power loads when inverter needs maintenance
Grounding conductor
An equipment grounding or grounding electrode conductor. It must be green, green with yellow stripes, or bare.
Ground fault
An unintentional, electrically conducting connection between a current-carrying conductor of an electrical circuit and the normally non-current-carrying conductors, metallic enclosures, metallic raceways, metallic equipment, or earth.
Rough guide for array-inverter sizing
Array = Inverter *1.2
Where is interconnection discussed in the NEC
Article 705
Equation for sizing battery system
Avg. Amp Hours/day = (Avg daily load)/(Inv eff)/(DC System Voltage)
Considerations for AC wire sizing
Based on continuous current calculation (Output/240*1.25) However, must make sure breaker regulations are also met. See NEC 240.4(D)
Flooded lead-acid (FLA)
Batteries that have cell caps that can be opened, allowing access to refill the cells with distilled water periodically.
Multi-Mode Inverter
Battery based inverters that interact with the grid. When Battery is charged, excess Power goes to the grid.
Supply Side (in reference to MDP)
Before the MDP
Passive Cooling based on Mounting System
Best: Rack Mount So-S0: Common Standoff (best at 3-6 inch roof clearance) Worst: Direct Mount
What colors are utilized by a 277 volt system?
Brown-Orange-Yellow
Load shedding
Can be programmed into some systems so that when the battery voltage reaches a certain level, less critical loads are turned off, allowing the more important loads to continue to operate.
Inverter/chargers
Can function both an inverter--changing dc electricity to ac electricity-- and as a battery charger--taking ac electricity and converting it to dc electricity to charge a battery bank.
Where are Conduit Requirements found in the NEC
Chapter 3 your mother ****er
Pulse width modulated (PWM)
Charge controllers regulate battery charging by switching the PV array on and off hundreds or thousands of times a second to taper the array output current.
Module Maintenance
Check For 1) De-lamination 2) Moisture or corrosion within the modules 3) Discoloration within the modules 4) Degradation of Solar Bonds at internal cell connections - This can lead to hot spots, burning through back of module, fire, death and lawsuits.
System grounding
Connecting one current-carrying conductor of a system to ground at one point to create a reference to zero
System Grounding
Connects a current carrying conductor in an electrical system to ground Achieved with a GROUNDED CONDUCTOR
Inter Row Spacing
D = 3H D is distance between rows H is height of module
Solar Altitude Angle
Defines the Suns elevation above the horizon.
Solar Azimuth Angle
Defines the direction of the sun's horizontal projection relative to a point on Earth.
Low voltage disconnect (LVD)
Disconnects loads from the battery bank at a certain voltage in order to prevent over-discharging and damage to the batteries.
Bonding
Electrically connecting metal parts together so that they stay the same voltage.
In regards to explosion concerns, what must be installed to vented battery cells
Flame arrestor
Four Types of Electrical Injuries
From Direct Contact 1) Electrocution (death) 2) Electrical Shock 3) Burns From Indirect Contact 4)Shock
Grounding Electrode Conductor
GEC Connects the Grounding System Electrode to the Equipment Grounding Conductor or the System Grounding Conductor A GEC that is #6 AWG can be used outside of conduit Anything Smaller than #6 must be put inside of conduit.
Inverter GFDI
GFDI = Ground Fault Detection Interrupter Grounded PV Inverters (residential ) have fuses that are 0.5 - 1 amp Grounded PV inverteres (commercial) have fuses that are 2-4 amps Ungrounded systems have none fused GFDI that shut the inverter off.
Bifacial Module
Generate energy from both sides of module
Sine Wave Explanation
Go **** yourself
Where do you find specific properties about various conduits?
Go to Appendix in NEC (all are clearly labelled).
Deep-cycle batteries
Have the ability to be discharged up to 80 percent and are commonly used in RE systems
Proper ladder set up
Horizontal distance from the top support to foot of ladder is 1/4 length of working length (hypotenuse).
Ohm's Law
I = V/R Ohm was from Transylvania.... I Vill Remember!!! Most common application is solving for Resistance: R = V/I .....Remember Vill I?
When is a charge controller needed?
If .... (Maximum charge rates for the PV array) x 1 Hour = 3% of the battery nominal amp-hour capacity.
Where can you find Resistance / kFt
In the NEC Chapter 9 Table 8
Stand-alone dc load-only systems
Include a PV array, charge controller, battery bank, and dc load(s)
What do you do if battery fault current is higher than over current devices?
Install current limiting fuses
Output of inverter for a 3 phase wye 208 V transformer
Inverter Rating / 208 / [Sqroot(3)] **1.73 is the square root of three**
Safety Precaution: Tagging
Labeling deactivated controls, de-energized equipment, and circuits at all points where they can be energized. Must identify the circuits being worked on.
Array Cooling based on Module Orientation
Landscape orientation provides better cooling than Portrait orientation
Voltage limitations for battery installations in dwellings
Less than 50 Volts
Determine Solar Altitude Angles for Region
Maximum and Minimum Solar Altitude Angles are determined by the Winter and Summer Solstice. The equation is as follows: 90 - (Latitude) + Solar Declination Example: At Latitude 40 the range would be determined as follows SUMMER SOLSTICE 90 - 40 + 23.45 = 73.45 WINTER SOLSTICE 90 - 40 + (-23.45) = 26.55 ALTITUDE ANGLE RANGE FOR 40 Deg LAT 73.45 to 26.55
DC input voltage
Must match nominal battery voltage, which is typically 12, 24, or 48 Vdc.
Required precautions when dealing with electrical shit can be found in what tantalizing document
NFPA 70E - Electrical Safety in the Workplace
Do bypass diodes function while getting Voc Readings?
No
How far can safety nets be deployed?
No more than 30 ft below where work is being performed
Power clipping
Occurs when the array power is greater than an inverter or charge controller can output, and the device will decrease the power output.
Shallow-cycle batteries
Only meant to be discharged 10 to 20 percent, and are not suitable for most RE systems
Who unlocks a Lock-Out breaker?
Only the person who applied it
Interactive PV Systems
Operate in parallel and are interconnected and synchronized with the electrical grid.
What Size Battery System Does Not Require Grounding?
Over 48 V - You are not required to have a grounded current carrying conductor if.......... 1) The PV Source and Output Circuits Must have a grounded current carrying conductor (or meet requirements for ungrounded PV systems) 2)DC and AC load circuits for the system must also be solidly grounded. 3) Both Positive and Negative Ungrounded Battery Circuit Conductors must have a switched disconnect means and overcurrent protection. 4) GFDI is required
What gases are produced during battery charging?
Oxygen and hydrogen
Where do you find information about Battery System requirements in the NEC?
P. 360 Article 480.5
Where do you find working clearances in the NEC
Page 38 Table 110.26(A)(1)
Safety Precaution: Lockout
Physically locking the power source disconnect in the OFF position with a padlock
Point of Connection
Point where distributed generator (PV System) interfaces with the utility system
In regards to explosion concerns, what must be installed to sealed battery cells
Pressure relief valves
Average daily load
Refers to the average amount of energy used in a day; this value is critical for off-grid sizing.
Agonic Line
Region where magnetic declination is zero
Charge controllers
Regulate how much energy is sent into the batteries to ensure that the batteries do not get overcharged. In a PV system, the charge controller is located between the array and the batteries
Ungrounded systems
Require equipment grounding but do not have system grounding; there is no dc current
Three types of eye protection
Safety Glasses Goggles Face Shield
29 CFR Part 1926 Subpart X
Stairways and Ladders
IEEE 1547
Standard for Interconnection of Distributed Resources with Electrical Power Systems Focus is distributive resources with capacity less than 10 MVA.
SLI Battery
Stands For: Starting, Lighting & Ignition Battery. This can deliver high discharge currents but is damaged during frequent and deep discharges (seldom used in PV)
VRLA Batteries
Stands For: Valve Regulated Lead Acid Batteries Have immobilized electrolyte in gel form. They are spill proof and do not require electrolyte maintenance. (Most expensive though and less tolerant of overcharging.)
Adjustment Factors (Going from System Size to Expected Performance)
Start with System Size W (DC) @ STC 1) Temperature Derating = 1 - [(Temp - 25) x (Temp Coefficient)] 2)Irradiance Rerating = (Irr / 1000 W per M2) 3) Inverter Efficiency 4) Mismatch/Wiring 5) Soiling
What are the requirements for EMT support
Support every 10' with an additional support 3' from Box
Voltage drop / wire size
Systems operating under 100 votes will determine wire size based on voltage drop
Grid-tied with battery back-up systems
Systems that can sell excess energy to the utility grid and that have batteries to power backed-up loads during a utility outage.
Integral Mounting Systems
Systems where modules are integrated into the roofing or building exterior
Energy (definition)
The TOTAL amount of power used over time **Think Total Income**
Magnetic Declination
The angle between magnetic north and the true geographic North Pole.
Equipment grounding
The bonding to ground of all non-current-carrying exposed metal parts that may become energized in a fault situation
Grounding electrode conductor (GEC)
The conductor used to connect the grounding electrode or grounding electrode system to the system grounded conductor, to the equipment grounding conductor, or both
Ground
The earth
Inverter rated maximum continuous ac output power
The highest power (watts) that the inverter can provide, which in an off-grid system must be large enough to operate all loads that could run simultaneously.
Solar Noon
The local time when the Sun is at it's highest point in the sky and crossing the local meridian (line of Longitude). It's rarely noon. Best way to find it is to find the projected sunset and sunrise time and then determine the midway point.
What is a cathode
The negative side of a diode
Days of autonomy
The number of consecutive days a battery can provide energy to loads without being recharged
Maximum Power Point (Pmp)
The operating point on an IV curve where the product of current and voltage is at a maximum
Depth of discharge (DOD)
The percent of battery capacity that been used. 100% DOD indicates an empty battery
State of Charge (SOC)
The percentage representing the amp-hours remaining in the battery bank. 100% SOC indicates a full battery
What is an anode
The positive side of a diode
Solar Irradiation
The suns radiant energy incident on the surface of a unit area. Often expressed in kWh/m2 aka Solar Insolation
Solar Insolation
The suns radiant energy incident on the surface of a unit area. Often expressed in kWh/m2 aka Solar Irradiation
Solar Irradiance
The suns radiant power incident on the surface of a unit area. Often expressed in W/m2
If the voltage drops on one module what happens to the string?
The voltage of all modules are averaged
Albedo Radiation
This is reflected radiation
Grounded
To be intentionally connected to earth through a ground connection, at a reference point of zero volts or zero potential
Hard Hats
Type 1: Protects from fallings objects Type 2: Protects from falling objects and side swipes Class G: Reduce danger of contact with low voltage conductors (proof tested for 2,200 Volts) Class E: Reduce danger of exposure to high voltage conductors (proof tested for 20,000 V) Class C: Provide no protection from electrical conductors.
What is the exception to the system grounding rules in the NEC
Ungrounded PV arrays that meet all requirements in 690.35
Safety Precaution: Working with Energized Equipment
Use proper PPE 1) Class G Hardhat 2) Electrical Hazard Rated Footwear (EH) 3) Face Shields 4) Gloves 5) Flame resistant clothing
When is hearing protection required
When noise exposure exceeds 8 hr weighted average at 90 dBa or above. Must monitor noise levels when 85 dBa is reached.
When is a battery system considered grounded
When the PV Power Source is Grounded
Stacking inverters
When the output of two or more inverters is coupled in series to produce a higher output voltage.
When are PV source circuits required to be fused?
When the series fuse rating of the module is less than the Isc of the modules * number of modules wired in series.
Equation for Finding Wire Size based on Voltage Drop
Wire Resistance (Ohm/kFt) = (Voltage Drop)(System Vmp) _____________________ (0.2)(D)(Max Power Current) **NOTES** Select wire with a resistance lower than the calculated value to achieve the desired voltage drop
Equation for Incident Angle
Zenith Angle - roof pith
Question about altitude derating... Your company has installed two identical commercial 100kW systems in two very different locations. One is located in Georgia at 1000' altitude the other is located in Montana with an altitude of 8000'. What size adjustment should be made to the installation in Montana compared to the one in Georgia?
a. The inverter should be 20% larger c. No change is necessary. b. The inverter should be 20% smaller d. The inverter should be 50% larger ANSWER: A 7000' ÷ 33,000' = .212 21.2%
What is peak sun hours expressed in?
kWh/m^2/day
GEC Size when connected to rod, pipe or plate electrodes
page 128 Does not need to exceed 6 AWG
Where do you find information about Junction and Pull boxes in terms of minimum sizes....
page 183 in NEC
When factoring in module mismatch what should you derate?
roughly 1.5% or half the negative side
Inverter Efficiency
(AC Power Output) / (DC Power Output) Example: 95000W AC Output 10000 W DC Input Creates a 95% efficient inverter0
Determining Max Voltage of PV System Method #3: Use NEC Temperature Correction Factor
(Voc) x (# of Modules wired in series) x (Voltage Correction Factor based on NEC) [NEC Table 690.7]
Acceptable Sizes for Overcurrent Protection Devices
1) Increments of 1 Ampere in between 0-15 Ex: 1,2,3.....15 2)When Amp > 15, they shall always be rounded up. Allowable sizes can be found in 240.6 (A). Ex: 20, 25, 30, 35, 40, 45, 50,60,70,80,90,110,125,150 etc
Order of Circuits
1) PV Source Circuit 2) PV Output Circuit 3) Inverter Input Circuit 4) Inverter Output Circuit
1 Megawatt = ?
1,000,000 Watts (Myyyyyyyyyyyy..........KingHenrysDrunkenUncleDrinksChocolateMilk
Peak Sun
1000 W/m2 (Typical for sea level, facing the sun on a clear day at solar noon)
STC - Standard Testing Conditions
1000 W/m2 1.5 Atmosphere 25 Degree Celsius cell temperature
How many employees can a company have before OSHA requires company to maintain a record of occupational injuries and illness.
11 or more employees
Utility Scale Inverters
500 kW to 1 MW and Higher. For Solar Farms.
Sun Path Diagram
A graphical representation of the Sun's altitude and Azimuth angles over a given day of the year (for a specific latitude)
Motive Power
A lead-acid battery designed for use in deep discharge applications (commonly used with PV) A.K.A: A Traction Batter
Traction Battery
A lead-acid battery designed for use in deep discharge applications (commonly used with PV) A.K.A: A motive Power
Battery Capacity
A measure of the stored energy that a battery can deliver under specific conditions. Measured in Amp Hours A nominal 6 volt battery rated for 220 Ah stores 1.32 kWhs Usage capacity is always less than the rated battery capacity due to discharge rate, cut-off voltage, temperature and age of the battery.
Inverter Output Circuit
AC conductors from inverter output to utilization load. To find maximum current: 1) check inverter spec sheet. If not listed..... 2) (continuos power rating) / (nominal AC voltage)
Standoff Mounting Systems
AKA Flush Mount. The mounting system that Dan Whitson uses
Zenith Angle
Angle of the sun in comparison to the zenith (90 degrees) Opposite of Altitude Angle (added together the two should be 90)
Peak Sun Hours
Average daily amount of solar energy received on a given surface. Equated to number of hours that the solar irradiance would need to be at peak level of 1 kW/m2 to accumulate the total amount of daily energy received.
Conductor Size
Circuit conductor size will be the larger of the two: 1) Max Current, as defined in 690.8 (A), multiplied by 1.25 2) Max Current, as defined in 690.8 (A), after conditions of use have been applied.
Contour Chart
Compares the effects of array orientation on the amount of Solar energy received.
Inverter Input Circuit
Conductors from DC disconnect to inverter Max current should be same as PV OUTPUT CIRCUIT
PV Source Circuits
Conductors from modules to source circuit combiner box To find maximum current: Isc x 1.25
PV Output Circuit
Conductors from source circuit combiner box to DC disconnect. To find maximum current: Sum of all Max currents wired in Parrallel.
Discharged Battery
Converts chemical energy to electrical energy
Charged Battery
Converts electrical energy to chemical energy
29 CFR Part 1926 Subpart K
Electrical
Bypass Diode
Electrical check valves that permit flow of current in one direction only. Prevent cells from overheating when a part of module is shaded.
Energy (Equation)
Energy (Wh) = Avg. Power (W) x Time (hr)
29 CFR Part 1926 Subpart M
Fall Protection
What is leading cause of death in construction industry
Falls
Fall Equinox
First Day of Fall (September 21st)
Spring Equinox
First Day of Spring (March 21st)
Summer Solstice
First Day of Summer (June 21st)
Winter Solstice
First Day of Winter (December 21st)
Specific Gravity of a Charged Lead Acid Battery
Fully charged the specific gravity is 1.26 to 1.28 at room temperature. This may be increased for lead acid batteries in cold weather applications and decreased for warm climates (to conserve battery life).
29 CFR Part 1926 Subpart C
General Safety and Health Provisions
Power Conditioning Components
Inverters, Charge Controllers, Maximum Power Point Trackers
Pole Mounted Systems
Manufactured racks are attached to a pole (ground mount)
Open Circuit Voltage (Voc)
Max DC voltage on an IV curve. Operating Point for a module with no connected load. Independent of PV cell area. Has direct correlation to operating cell temperature.
Short Circuit Current (Isc)
Max current on an IV curve Operating Point for a module with no connected load. Directly proportionate to solar irradiance
Allowable Depth of Discharge
Maximum limit of battery discharge in operation. Usually limited to no more than 75% to 80% for deep cycle batteries. Must be limited to protect Lead Acid Batteries from freezing in extremely cold conditions.
When is OSHA poster required?
Must be displayed Within 8 hours of an accident that results in hospitalization or death of 3 or more employees.
29 CFR Part 1926 Subpart D
Occupational Health and Environment Controls
Stand Alone PV Systems
Operate independently of other electrical systems (ie the Grid)
29 CFR Part 1926 Subpart E
PPE
State of Charge
Percentage of available battery capacity compared to a fully charged state
Depth of Discharge
Percentage of capacity that has been removed compared to a fully charged state
Power Density (Equation)
Power Density of Module = Watts of Module / Square Footage of Module Ex: 175 W module that is 14.4 Square Feet has power density of 12.2 W/sf
Power
Power is the RATE of transferring energy. Expressed in Watts. *Think of an hourly wage**
Power Density (Define)
Power per area of measurement (Watts/Square Foot)
Rate of Charge (or Rate of Discharge)
Ratio of the nominal battery capacity to charge (discharge) time period in hours. EX: A nominal 100 Ampere-Hour batter discharged at 5 amps for 20 hours is considered a C/20 or 20-hour discharge rate. The higher the discharge rate > the less capacity can be withdrawn The lower the temperature > the less capacity can be withdrawn
IV Curve
Represents infinite number of current and voltage operating point pairs for a PV device at a given solar irradiance and temperature operating condition.
Declination
The angular distance of a point north or south of the celestial equator. *The sun varies + or - 23.45 degrees throughout the year
Array Tilt Angle
The array tilt angle is the angle between the array surface and the horizontal plane
Array Azimuth Angle
The direction an array surface faces based on a compass heading or relative to due south
Solar Window
The range of Sun paths for a specific latitude between Winter and Summer solstices. What you see on the Suneye
Specific Gravity
The ratio of the density of a solution to the density of water.
Requirements for PV Module Labels
There are 8 Requirements: 1)Polarity of Terminals 2) Maximum Overcurrent Device Rating for Module Protection 3) Isc 4)Voc 5)Vmp 6)Imp 7) Maximum Permissible Systems Voltage 8) (Pmp) Maximum Power
29 CFR Part 1926 Subpart I
Tools, hand and Power
Balance of System Compontents
Used to conduct, distribute and control flow of power in the system. (Everything besides modules and inverters).
Response to Temperature
Voltage is directly related to temperature. Temperature Coefficients are used to predict drops and hikes in voltage based on temperature variance during testing conditions. Usually, the temperature coefficient is as follows: -0.4% per Degree Celcius (however, you should use what's on the module spec sheet)
Where are OSHA Standards found?
Volume 29 of the U.S. Code of Federal Regulations (29 CFR)
Equation for Peak Voltage of Pure Sine Wave
Vpeak = Vrms x Squareroot(2)
Positive Magnetic Declination
When Magnetic North is East of true north.
Negative Magnetic Declination
When Magnetic North is West of true north.
When do you need an equalizing charge?
When there are inconsistent specific gravity readings between cells in flooded lead-acid batteries.
When is fall protection required?
When you can fall 6 feet or more
