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Solar panel safety

Solar panel bundle
250W Renogy mono-crystalline panel
Buy Bundles;
4 panels 250 watt at Amazon $1275
6 panels 250 watt at Amazon
10 panels 250 watt at Amazon
20 panels 250 watt at Amazon

Solar panel connectors
Buy solar panels at Amazon

How to set up solar array
Solar resources

string of solar panels String is several panels wired in series, with + connect to - on each panel.
Each panel has + wire and - wire
Connect the + on first panel to - on next panel in series - string.
Array is several strings wired together into parallel strings

Caution: Do not connect solar panels with panel facing sun, or there will be electric power on the wires.

How to set up solar array
Solar resources

Safety first....
120 volts AC is the most common voltage, and most common killer, 12 volts DC car batteries are generally not harmful... but can deliver a jolt of amps ... and high amperage on the line is dangerous, just like high voltage. Solar panels produce DC electricity that can be both high voltage and high amperage. Do NOT underestimate electrical danger from solar panels.
Two Renogy 250 watt panels wired in parallel will produce 30.1 volts x 16.4 amp and 493 watt.
Three Renogy 250 watt panels wired in parallel will produce 30.1 volts x 25 amp and 751 watt.
Two Renogy 250 watt panels wired in series will produce 60.2 volts x 8.2 amp and 493 watt.
Three Renogy 250 watt panels wired in series will produce 90.3 volts x 8.2 amp and 740 watt.

Electrical burns can disfigure and permanently disable.
They affect outside of body just like ordinary fire, plus damage interior parts of body including blowing out heart, nerve circuits, tearing away muscle structure etc.
This description of damage is not meant to be graphic more than to illustrate risk of working with electrical power, both AC and DC, especially outside while standing on ground.
Rule #1: All electricity is attracted to ground, and if you're standing on ground or touching anything that is grounded, you are giving electricity a direct route to ground.
Search Internet for 'first aid for electrical burns.'
For example a regular burn you apply water to relieve symptoms. But with electrical burns you do not apply water to the burn.
Electric safety book
First aid books
First aid kits
Troubleshoot household electricity
Compare AC and DC
What is electricity
Do wiring at night:
Ground, dirt or soil is the attractor of all electric current. Dry rocks are less conductive, and salty damp soil is more conductive, but anything sitting on earth's surface can conduct electricity is the voltage exceeds the resistance of the material. For example, rubber is considered non-conductive... but apply enough voltage and it will conduct electrons to ground.
When you stand on ground you are basically standing on one end of a battery.
So when you work with solar panels, or any AC or DC electricity while outdoors, then you are standing on one end of a battery while working on the other end of the battery.

Solar panels have live power when the sun shines  on them.
In a sense you can say solar panels are like a live overhead power line that is constantly energized.
So hopefully you are wiring at night time and after panels are installed you want to install a safety cut off switch, breaker or combiner box on the solar panel installation.
Combiner boxes at Amazon 

Different image
Use safety switch:
After connecting the solar panels together in the nighttime, you want to run the wires into a safety switch or disconnect or combiner box which can turn off the power from solar panels. This is usually code for any solar installation for public safety purposes. And it lets you finish wiring rest of installation during daytime hours.
Caution: Safety switch must be rated for DC power.
Most safety switches have an AC rating but are only rated for 48 V DC. Check the specifications.
AC and DC are different. Solar panels produce DC power, and the problem of arc extinction becomes a concern with any kind of switching when voltages exceed 48 VDC.
Read about arc extinction
Some more expensive shut offs have both an AC and the DC rating and usually the DC is rated for half the value of the AC so if the AC wiring is 240 V then DC rating would be for 120 V.
In my research I found it difficult to find off-the-shelf products that were rated for DC.
DC rating is vitally important for any switching: including contactors, relays, thermostat, breaker, fuse, shut-off, etc.
Always check manufacturer's specification.

Wires should be rated 600 volt, which is standard, off-the-shelf electrical wirging from the hardware store. Check printing on side of wire. This means you can buy wire locally at any hardware. Be cautioned that 600 volts will be printed on side of wire, so if you buy 14 gauge lamp cord or 12 gauge extension cord, then these items are NOT rated 600 volt and should never be used for permanent wiring installations.

Resistive loads like elements are not switchgear and need only the volt rating. 
Resistive loads like elements are not affected by arc extinction, or by difference between AC and DC electricity. For example you can connect 200 volt DC directly to element rated for same voltage.... but you cannot use ordinary water heater thermostat because it will melt, stick closed, or catch fire, and generally not function with DC voltages over 24-48 volt.

3-pole / outdoor/ 30 amp DC/ fuseable
Combiner boxes at Amazon 
How to wire safety switches
DC safety switch
How to wire DC water heater/ high voltage
How to wire DC water heater/ low voltgae
Color code for wire
Figure volts amps watts
DC circuit breaker Use DC circuit breaker
AC and DC are different because of arc extinction.
Solar panels produce DC electricity, and require switchgear rated for DC.
You can use circuit breaker instead of safety switch shown above.
Buy from my affiliate links:
DC circuit breakers
High voltage DC circuit breakers at Amazon
Combiner boxes at Amazon

Read about arc extinction
How to set up solar array
insulated electrical gloves

Above is example of lineman gloves, and example of bad photoshopping by me.

linesman pliers
Insulate yourself from power
It is important to always put a dry surface such as 2x4, plywood or rubber on the surface where you are working.
Do not ever stand on soil or damp surface or lean against anything made of metal. Remove all metal from pockets. Do not hold metal tools in mouth.
Wear rubber sneakers. Do not work in the rain, on a damp surface, or when dew is on the ground.
Some resources say to avoid grounding mats as unreliable, but more research is recommended. Power company linemen use shielding materials and grounding mats for some applications.
With higher voltage, it is debatable, but generally thought best NOT to ground yourself lest you attract the current you want to avoid. I would not use a static line or ground connected directly to myself. Keep in mind that power company linemen are not directly grounded, but use insulated equipment and wear insulated gloves, suits, etc.
Insulated gloves are rated by voltage and do not protect other surfaces of body. Defects and damage to gloves will certainly increase risk.
Use insulated tools and inspect surface for breaks and damage.
I recommend searching internet for electrical safety tips for working outdoors such as using insulated gloves, rubber boots, and perhaps devising your own instruments using fiberglass hot sticks      similar to power company tools.
Always make sure the solar array is grounded on the negative side.

Additionally I recommend attaching testing instruments to wooden sticks and using the wooden stick to hold the probe against anything you are testing.
That puts an insulator between your hands and the terminal point being tested.

Insulated electrical gloves
Insulated tools
Wire strippers at Amazon
Linesman pliers

lightning Lightning
Working with metal that is installed on roof carries risk.
Move indoors when storms are within 5 miles.
Move indoors and do not stay on roof, or move metal ladders, or touch anything made of metal when lightning is within 5 miles or can be heard or seen.
Copper pipes and metal on roof attract lightning
Use lightning rod system in areas where lightning is common.
Risk of lightning is higher when home is near pond, high elevation, or sitting alone.
Higher structures or multiple structures nearby, will reduce lightning risk.
Lightning within 100 feet can damage any home not protected by lightning rods.
Bond solar panel to ground rod All solar system must be grounded. Check local electric codes.
What does this mean? Drive ground rod 8-10 feet into soil. Bond #6-8 bare copper wire to ground rod and to solar panels and pipes on roof.
Do NOT ground electric system to water pipes. Ground must be connected to ground rod. Stray current corrosion can cause pipes to deteriorate. Uncertain bond to ground because of plastic pipes.
Ground rod and clamps at Amazon
Bonding lugs
Solar panels on roof

Do you have to buy ladders?

Take apart extension ladder, and you have 2 ladders

We use two aluminum ladders chained together to climb down sides of roof.
Best way to get on roof is along the pitched side. Set ladder at angle, as illustrated with wooden ladder, so both ladder feet are flat on ground, then set ladder at angle until both rails are flat against roofline.
This is counter-intuitive to set ladders this way, but very effective and safe.
We also used ropes to secure ladder from falling over, we also made one ladder leg longer on aluminum and wood ladders by adding stout 2x4 or 1x4 yellow pine.
When setting ladder against gutter... use wire to tie ladder to gutter nail. Set bag of dirt behind ladder feet.
When setting ladder on grass or dirt, turn the feet so they stab into soil. Dig small holes for feet.
Choose grass-dirt over concrete surface when setting ladder.
Never set extension ladder on wet concrete, or concrete that slopes away from ladder. Sweep surface clean.
Never set extension ladder on tile surface without full bracing behind feet. Higher person climbs, less stable ladder.
Always make sure 4 points of ladder touch... 2 feet firmly at bottom and 2 rails firmly at top
Ladder safety How to check extension Ladders
Extension ladder has several parts: 1) Rung locks, 2) anti-slip safety feet, 3) Slide rails, 4)
Base rails, 5) Rungs etc
Do not use ladder that is bent.
Check the bolt that connects rung lock to ladder. Look for cracks in aluminum rail... add fender washer to strengthen
Check if bolt is bent excessively. Must use hardened bolt.
Always check that rung lock is over both rungs.
ALWAYS make sure both rung locks are in place.
Treat your ladder like it was airplane... you are the pilot... inspect plane BEFORE flying
Ladder replacement feet with hardened bolts
Aluminum ladder leveler for uneven ground
Safety step ladder
Ladder parts and stabilizers at Amazon
 Call insurance company and ask if homeowner insurance covers external solar panels.
Do you need special insurance?
Are the installers insured?
Who will repair and maintain system, how much will it cost, and are you covered from liability?
If you are climbing on roof once each year to clean solar panels, what is cost of one broken leg?
Weatherproof wire connector
You can apply ample amount of silicone to the connection and then apply the wire nut for a more waterproof connection.
Buy from my affiliate links
Weatherproof size 14 to 6 Amazon
Weatherproof size 22 to 8 Amazon

How to select and install twist-on wire connectors

Notes on DC elements
Single U and double U DC elements, 24 volt 500-900 watts.

The single U is ordinary residential water heater style with 2 screws to connect the wires. So your solar panels are connected directly to the element.
DC elements
Single U element at Amazon
Double U element at Amazon
single U element
double U element

The double U has 4 screws for 4 wires and can accommodate two separate connections.... meaning you can have two separate sets of solar panels, and each set of solar panels can supply power to one of the U

3U elements are usually larger thread and will not fit a residential tank.

Typically in residential water heating, small water heaters (20 gallon) use 1000-1500 watt elements. Ordinary shower uses 10 gallons hot, ordinary bath uses 20 gallons hot.
You can dial up thermostat to get more miles out of a tank of hot.

Larger water heaters use elements with more wattage in order to heat the water.... if the tank is full of unheated water, it will cool the water that is heated.
A 500 watt element would struggle to heat a 40 gallon tank

5.866689  Kwh to raise 40 gallons of water 60F (starting at 60- and ending at120F)
Typical shower might be 104F
1000 watts for 1 hour is 1 Kwh
Your 500 watt element produces 1 Kwh for each 2 hours operation
So you would need 5.867 x 2 hours or 11.73 hours to heat a tank ... and that is with ideal conditions, no consumption of hot during those hours, full sunshine, no cooling of tank etc etc ... except the tank would cool, and sun is not dependable each day.
.. or if you satisfied with less-than-thermostat-setting hot water, say 80?

Now if you have a double U element, the time would be less.

Conclusion: your plan would work well with a smaller (20 gallon), well insulated tank.... and that was the project I was planning at my house, except old age and other projects have their foot in the door right now.
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