FAQ
General
Grid-Tie Systems
Grid-tie home solar systems are much more prevalent for several reasons:
Cheaper up front to install – It is easier to tie-in to the grid than pay for and install a safe battery bank.
Net metering laws or, in some cases, feed-in tariffs are powerful incentives for homeowners to connect to the local grid. Net metering allows homeowners to trade with their utility. Excess solar energy produced during the day is used elsewhere and credited to the solar homeowner to offset the costs of using grid electricity at night. Feed-in tariff laws require the utility to buy that excess daily power at an inflated price, which can turn home solar power into a profit deal.
Grid-tie systems require less maintenance – Batteries need some occasional TLC and must be replaced every few years (at present technology levels). They can also be hazardous if not handled correctly.
Benefit the community electric grid – Feeding that clean, green solar energy into the grid during the day, when power demand is at its peak, eases the burden on an already overstressed electric infrastructure. It also helps cities and states reach their renewable energy goals. Furthermore, distributed generation (the collective term for home solar power systems) may play a key role in the Smart Grid of the future.
More flexibility – Being tied to the grid provides security in knowing that if you have a spike in energy usage (i.e. visit from family, in-home wedding, etc.), back-up is ready and waiting.
Off-Grid Systems
Getting off the grid has its definite advantages as well. Particularly for homeowners in remote areas, not to mention those in the developing world without any electric infrastructure, off-grid systems offer:
Total freedom – Off-grid home solar power means that when the grid goes down, you don’t. There is safety and security in knowing that your home is energy-independent as well. A downed power line 20 miles away and rolling blackouts don’t affect the off-grid homeowner.
Totally clean, totally green – Bye, bye transmission cables. When you’re off-grid, you are totally free of coal-fired and other fossil-fueled electricity. Your energy is clean and your home’s carbon footprint greatly reduced.
Off-grid systems also benefit the local community – They make life easier for the local energy grid by providing one less house in need of outside power sources.
Powering the outer limits – Off-grid systems are essential for folks who want to live “outside the box,” but don’t necessarily want to rough it for the rest of their lives. In comes off-grid home solar power to provide that comfortable, country home of your dreams.
The inverter system, sometimes called the "power center", is the most important part of your solar power system. This combo of inverter(s), charge controller(s) and safety components is responsible for running your off-grid power system.
Pre-wired Power Centers are pre-assembled on metal mounting plates. This is all the gear that converts DC electricity produced by your solar panels, wind turbines or gas generator into useable 120 or 240 volt AC power and directs it into your home (or business or workshop or cabin!).
Pre-wired, pre-tested power centers save you time and money. Of course, you may buy all the components separately and assemble them yourself or you can pay your installer or electrician to do so.
Paying a contractor to wire the essential electronics is costly, particularly if that professional has not done lots of them.
Storing water in a cistern or tank has many advantages. It's less expensive and more efficient than storing power in batteries. Since water is always a critical issue, we recommend the tank should be able to store a minimum 3 to 6 days worth of water or whatever you think your needs may be during cloudy weather or in case of a system failure.
Generally speaking, animals, plants and humans use less water on cloudy days. Conversely, the sunniest days are when we consume the most water and when the solar modules are providing the pump with the most power.
Almost always you should store water and not power when possible and you will have much better performance and reliability with your solar pumping system.
However there are cases where we recommend batteries in solar pumping systems, as in home pressure systems when you need a booster pump to maintain system pressures at night and in cases were it is more cost effective.
For example, if a home power system using batteries already exists and you need to pump water out of a well and into a pressure system, then connecting to your existing battery bank could be more cost effective.
The photovoltaic effect produces a flow of electrons. Electrons are excited by particles of light and find the attached electrical circuit the easiest path to travel from one side of the solar cell to the other.
This excitation of electrons causes an electron flow. The solar cell takes these electrons and directs them to flow in a path or an electrical circuit. Photovoltaics is the process of solar electric cells converting sunlight directly into DC power. This DC power is then used to run a pump.
Charge Controllers
Currently the most common charge controllers are Pulse width Modulation(PWM) charge controllers which simulates a variable current by switching a full current On and OFF at high speed for varying lengths of time. A Maximum Power Point tracking (MPPT) charge controller is a charge controller that operates the solar array at its maximum power point under a range of operating conditions as well as regulating battery charging.
The interesting features of the MPPT technology is that it usually allows you to have a solar panel array with a much higher voltage than your battery bank's voltage. The MPPT charge controller will automatically and efficiently convert the higher voltage down to the lower voltage. A big advantage to having a higher voltage solar panel array is that you can use smaller gauge wiring to the charge controller. And since a solar panel array can sometimes be over a 100 feet away from the charge controller, keeping the cost of the wiring down to a minimum is usually an important financial goal for the whole project. When you double the voltage (e.g. from 12 to 24 volts), you will decrease the current going through the wires by half which means you use a quarter as much copper (or cable with half of the diameter).
Example of Sizing an MPPT Charge Contoller
So, for instance, you could have a 1000 watt solar panel array that operates at 48 volts DC and your battery bank is 24 volts DC. MPPT charge controller are rated by the output amperage that they can handle, not the input current from the solar panel array. To determine the output current that the charge controller will have to handle we use the very basic formula for power (watts), which is: Power = Volts x Amps Here we know the power is 1000 watts, the battery bank is 24 volts, so: 1000 watts = 24 volts x Amps which gives us: Amps = 1000 watts/ 24 volts Amps = 41.7A We still want to boost this value by 25% to take into account special conditions that could occur causing the solar panel array to produce more power than it is normally rated for (e.g. due to sunlight's reflection off of snow, water, extraordinarily bright conditions, etc). So, 41.7A increased by 25% is 52.1A. In this case we'd probably choose a 60 Amp MPPT Charge Controller, like Outback Power's FM60 or Xantrex XW MPPT60 Be aware that MPPT charge controllers have an upper voltage limit that they can handle from the solar panel array. It's important that you make sure than there is no condition that the solar panel array voltage will go above this limit or you will like burn out the controller. You want to make sure that the open circuit voltage of the solar panel array does not go above this limit. You should also give yourself a little bit of a margin for an error to take in account the possibility that a solar panel array's voltage will actually increase the colder it gets. The voltage multiplier is based on the lowest expected ambient temperature where the system is to be installed. The NEC gives Table 690.7 for ambient temperatures below 25 degrees celcius. Most of the higher end charge controllers from Outback and Xantrex have an maximum Open Circuit Voltage (VOC) of 150VDC, the exception is the Apollo T80HV which has a VOC of 200 VDC. You want to make sure that the open circuit voltage of the solar panel array does not go above this limit. Here's an example: We'll use four 12 volt Evergreen 102 Watt solar panels all run in series for a nominal voltage of 48 volts and our battery bank is at 12 volts. We'd like to use BZ Product's MPPT500 charge controller because of its price. If we look at the panel's specification page we see that each panel has an open circuit voltage of 21.3V. That means the array has four times that (because there are 4 panels in series). So the array open circuit voltage is 21.3V x 4 = 85.2V. In central Oregon our lowest min recorder temperature is -26 dgreeF so we would multiply the 85.2V by our multiplier which is 1.25 and we get 106.5V. Now we'll look at the MPPT500's specifications and we see that it can only take a maximum of 100 volts. So we can't use that product in this instance and would need to use a product with a higher VOC such as the Outback FM60 or Xantrex XW MPPT60. However we could arrange the panels in two series string of two panels which would reduce our VOC to 53.25V
How do i view online status of Morningstar MPPT Charge Controller?
How do you reduce noise interference from PWM charge controllers?
What is the best charge controller with lowest RFI for wireless?
How do you calculate size of charge controller required?
What is the difference between MPPT and PWM charge controllers?
Inverters
An inverter takes the DC input and runs it into a pair (or more) of power switching transistors. By rapidly turning these transistors on and off, and feeding opposite sides of a transformer, it makes the transformer think it is getting AC. The transformer changes this "alternating DC" into AC at the output. Depending on the quality and complexity of the inverter, it may put out a square wave, a "quasi-sine" (sometimes called modified sine) wave, or a true sine wave.
Although the Outback Power & Xantrex are considered by many to be the top of the line, it does not make sense to spend $500 to $3000 when all you need is a little Statpower Prowatt or Exeltech 125 watt sine wave to power up a laptop. The best way to decide on what inverter is best is to work backwards - figure out what you are going to use it for and the continuous power wattage required. i.e what appliances will you be running all at once), and then find one that fits those requirements. Also, some inverters have built in chargers, which may be needed in some systems. The Outback, Apollo Magnum & Xantrex sine wave units include software and hardware for remote generator start, alarms, remote control and monitoring, computer data, and other functions - in many applications this is very important. If you are running pumps or other large motors, Xantrex, Magnum, Apollo or Outback are the only ones we will recommend, even though some others might work.
The difference between a off grid inverter and a grid tie inverter is an off grid inverter converts stored energy from a solar battery bank and converts or inverts the stored electrical energy in to AC household current. A grid tie inverter on the other hand takes solar or wind energy as it is produced and stores it in an electrical grid. Inverters from Outback (GVFX and GFX) and Xantrex (XW) can be used as grid tied inverters with battery backup. We do not recommend using the Outback inverters in off grid applications as it will have trouble excepting the rough AC power from a back up gas or propane gen set.
Electrical Accessories
Use the wire loss charts to calculate maximum distances and/or maximum amps for certain % loss.
Maximum Ampacities for Wire and Cables based on wire size and temperature.
FAQS Summary:
Why Ground? The following is a list of the reasons to ground: To limit voltages due to lightning, line surges or unintentional contact with higher voltage lines. To stabilize voltages and provide a common reference point being the earth. To provide a path in order to facilitate the operation of overcurrent devices. There are two specific ways to group a system: equipment grounding and system grounding. It is important to know the difference between the two.
FAQS Content:
Grounding Explained
The following list contains the NEC® definitions (NEC® 2011, Article 100) for the grounding terms you should be familiar with.
• Grounded:
Connected to the earth or to some conducting body that serves as earth.
• Grounded conductor:
Current carrying conductor that is grounded at one point. Conventionally the white wire.
• Grounding conductor:
A conductor not normally carrying current used to connect the exposed metal portions of equipment or the grounded circuit to the grounding electrode system. Normally bare copper or green wire.
• Grounding electrode conductor:
Bare copper wire connecting grounded conductor and/ or equipment grounding conductor to the grounding electrode.
• Grounding electrode:
Usually a ground rod or bare metal well casing.
• Ungrounded conductor:
Current carrying conductor not bonded with ground. Conventionally the red, positive wire on DC; conventionally black, any color besides white, gray, green or bare copper on the ac side.
1. Equipment Grounding
Equipment grounding provides protection from shock caused by a ground fault and is required in all PV systems by the NEC®. A ground fault occurs when a current-carrying conductor comes into contact with the frame or chassis of an appliance or an electrical box. A person who touches the frame or chassis of the faulty appliance will complete the circuit and receive a shock. The frame or chassis of an appliance is deliberately wired to a grounding electrode by an equipment grounding wire through the grounding electrode conductor. The wire does not normally carry a current except in the event of a ground fault. The grounding wire must be continuous, connecting every non-current carrying metal part of the installation to ground. It must bond or connect to every metal electrical box, receptacle, equipment chassis, appliance frame, and photovoltaic panel mounting. The grounding wire is never fused, switched, or interrupted in any way. When metal conduit or armored cable is used, a separate equipment ground is not usually necessary since the conduit itself acts as the continuous conductor in lieu of the grounding wire. Grounding wires are still needed to connect appliance frames to the conduit.
2. System Grounding
System grounding is taking one conductor from a two wire system and connecting it to ground. The NEC® requires this for all systems over 50 volts (NEC® 2011, Article 690.41). In a DC system, this means bonding the negative conductor to ground at one single point in the system (NEC® 2011, Article 690.42). Locating this grounding connection point as close as practical to the photovoltaic source better protects the system from voltage surges due to lightning (NEC® 2011, Article 690.42, FPN). In grounded systems, the negative becomes our grounded conductor and our positive becomes the ungrounded conductor. If you choose not to system ground a PV system under 50 volts, both conductors need to have overcurrent protection (NEC® 2011, Article 240.21), which is often more cumbersome and costly. Most PV installers simply choose to system ground even if the system operates under 50 volts.
3. Ground-fault Protection
Roof-mounted, DC PV arrays located on dwellings must be provided with DC ground-fault protection (NEC® 2011, Article 690.5). Many grid-tied inverters offer built-in ground fault protection. If a system is to be roof-mounted on a dwelling and the system is not using an inverter package with built-in ground-fault protection, ground fault protection must be wired in separately. Ground-fault protection isolates the grounded conductor (in DC, this is the negative wire) from ground under ground-fault conditions, as well as disconnecting the ungrounded conductor (the positive wire).
Size of Equipment Grounding Conductor
The size of the equipment grounding wire for the PV source circuits, such as the PV to battery wire run; or for grid-tied systems with no battery back up, the PV to inverter wire run, depends on whether or not the system has ground-fault protection.
If the system has ground-fault protection, the equipment grounding conductors can be as large as the current carrying conductors, the positive and negative wires, but not smaller than specified in NEC® 2011, Table 250.122. This table is based on the amperage rating of the overcurrent device protecting that circuit. For example, if the circuit breaker protecting the circuit is rated at or between 30 amps and 60 amps, you can use a #10 AWG copper equipment grounding wire. If the positive and negative conductors have been oversized for voltage drop, the equipment grounding wire also must be oversized proportionally (NEC® 2011, Article Proper ground-fault protection 250.122(b)). From the example in the Wire Sizing Exercise, you increase the necessary wire size from #6 AWG to #1/0 AWG to satisfy a 2% voltage drop requirement. Here you would have to increase your equipment grounding wire from #10 AWG to #4 AWG.
If the system does not have ground-fault protection, the equipment grounding wire must be sized to carry no less than 125% of the PV array short circuit current. For example, if your PV array has a short circuit current of 30 amps, the equipment grounding wire would have to be sized to handle at least 37.5 amps (30 amps X 1.25). Similar to the PV systems with ground-fault protection, if the positive and negative conductors have been oversized for voltage drop, the equipment grounding wire also must be oversized proportionally (NEC® 2005. Article 250.122(b)). From the example in the Wire Sizing Exercise, you increase the necessary wire size from #6 AWG to #1/0 AWG to satisfy a 2% voltage drop requirement. Here you would have to also increase the equipment grounding wire from #10 AWG to #4 AWG.
Size of Grounding Electrode Conductor
The DC system grounding electrode conductor, which is the bare copper wire connecting grounded conductor (the negative wire) and/or equipment grounding conductor to the grounding electrode (the ground rod), cannot be smaller than #6 AWG aluminum or #8 AWG copper or the largest conductor supplied by the system (NEC® 2011, Article 250.166). Even though many PV systems have larger conductors in the system (for example, #4/0 inverter cables), they can use #6 AWG copper wire for the grounding electrode conductor if that is the only connection to the grounding electrode (NEC® 2011, Article 250.166(C)).
Grounding Electrodes
Because all PV systems must have equipment grounding, regardless of operating voltage, PV systems must be connected to a grounding electrode.
This is usually done by attaching the equipment grounding wire to a ground rod, via a grounding electrode conductor. PV systems often have AC and DC circuits where both sides of the system can use the same grounding electrode. Some PV systems may have 2 grounding electrodes, which is often the case for pole mounted PV arrays. One electrode is for the AC system and one electrode is for the DC system at the array. If this is the case, these 2 grounding electrodes must be bonded together (NEC® 2011, Article 690.47) with a barrier separating the AC conductors from the DC conductors.
Miscellaneous Code Issues
Stand-alone systems must have a plaque or directory permanently installed in a visible area on the exterior of the building or structure used. This sign must indicate that the structure contains a stand-alone electrical power system, and the location of the system’s means of disconnection (NEC® 2011, Article 690.56). Alternating current and direct current wiring may be used within the same system, although they may never be installed within the same conduit, or electrical enclosures without some type of physical barrier separating the AC conductors from the DC conductors.
FAQS Summary:
Solar panels originally came with a junction box (JBox) that needed individual wires to be attached to connect them together. This made installation very time-consuming, so pre-installed quick connect cables and plugs were developed, and these have replaced the junction box only modules.
FAQS Content:
Connectors and Cables
Solar panels originally came with a junction box (JBox) that needed individual wires to be attached to connect them together. This made installation very time-consuming, so pre-installed quick connect cables and plugs were developed, and these have replaced the junction box only modules. Changes in the NEC code now require the use of locking connectors in publicly accessible locations.
The most common locking connector is the Multi-Contact MC4. Others are the Amphenol H4, SMK, and the TE Connectivity connectors. The NEC code also introduced new wire insulation requirements for use with ungrounded PV arrays (Source Circuits) when wires are not run in conduit or wire raceways. The new PV-Wire specification requires that the conductor must be listed to UL Standard 4703. Ungrounded arrays are arrays that do not have a ground fault fuse tying one of the source conductors to ground. This is typically found in the new “Transformerless” range of inverters. Most module manufacturers are now supplying their products with locking connectors and PV-Wire to comply with the new standards.
Batteries & Accessories
AGM batteries have several advantages over both gelled and flooded, at about the same cost as gelled: Since all the electrolyte (acid) is contained in the glass mats, they cannot spill, even if broken. This also means that since they are non-hazardous, the shipping costs are lower. In addition, since there is no liquid to freeze and expand, they are practically immune from freezing damage. Nearly all AGM batteries are ""recombinant"" - what that means is that the Oxygen and Hydrogen recombine INSIDE the battery. These use gas phase transfer of oxygen to the negative plates to recombine them back into water while charging and prevent the loss of water through electrolysis. The recombining is typically 99+% efficient, so almost no water is lost. The charging voltages are the same as for any standard battery - no need for any special adjustments or problems with incompatible chargers or charge controls. And, since the internal resistance is extremely low, there is almost no heating of the battery even under heavy charge and discharge currents. The Concorde (and most AGM) batteries have no charge or discharge current limits. AGM's have a very low self-discharge - from 1% to 3% per month is usual. This means that they can sit in storage for much longer periods without charging than standard batteries. The Concorde batteries can be almost fully recharged (95% or better) even after 30 days of being totally discharged. AGM's do not have any liquid to spill, and even under severe overcharge conditions hydrogen emission is far below the 4% max specified for aircraft and enclosed spaces. The plates in AGM's are tightly packed and rigidly mounted, and will withstand shock and vibration better than any standard battery. Even with all the advantages listed above, there is still a place for the standard flooded deep cycle battery. AGM's will cost 2 to 3 times as much as flooded batteries of the same capacity. In many installations, where the batteries are set in an area where you don't have to worry about fumes or leakage, a standard or industrial deep cycle is a better economic choice.
While batteries may seem like a good idea, they have a number of disadvantages in pumping systems. First, they reduce the efficiency of the overall system. Second, they are another source of problems and maintenance. Third, they add cost to the system.
Water Pumps
Solar water pumping is the process of pumping water with the use of power generated by sunlight. The advantages of solar water pumping are many.
Solar pumping systems are reliable stand-alone systems that require no fuel and very little attention. Generally, when water is needed most, is when the sun shines the brightest. Solar panels generate maximum power in full sun conditions when larger quantities of water are typically needed. Because of this natural matching effect, solar water pumping is an obvious and economical choice over windmills and engine-driven generators for most locations away from utility power.
Grundfos SQ-Flex solar pumps will pump water up to 820 foot total head, and can pump up to 85 gallons per minute for shallow wells, depending on model of pump. The helical rotor pumps are recommended if you have any dirt, sand, sediment, or high mineral water from your well. The pump can tolerate up to 50 PPM of sand contant. The 3 SQF, 6 SQF, and the 11SQF are helical rotor type pumps. All others are centrifugal. All SQF pumps are 17 to 23 pounds in actual weight.
Model NumberTypeMax HeadMax FlowPV Watts (Min-Max) **Pump Diameter (Pipe Size)3 SQF-2Helical Rotor360 Feet3 GPM100-9003" (1" NPT)3 SQF-3Helical Rotor600 Feet2 GPM130-9003" (1" NPT)6 SQF-2Helical Rotor360 Feet6 GPM100-9003" (1" NPT)6 SQF-3Helical Rotor820 feet6 GPM100-14003" (1" NPT)11 SQF-2Helical Rotor300 Feet11 GPM50-14003" (1-1/4" NPT)16 SQF-10Centrifugal210 Feet20 GPM400-14004" (1-1/4" NPT)25 SQF-3Centrifugal45 Feet40 GPM120-14004" (1-1/2" NPT)25 SQF-7Centrifugal185 Feet39 GPM130-14004" (1-1/2" NPT)40 SQF-3Centrifugal45 Feet38 GPM200-14004" (2" NPT)40 SQF-5Centrifugal90 Feet70 GPM300-14004" (2" NPT)60 SQF-3Centrifugal45 Feet85 GPM20-14004" (2" NPT)
** The watts shown for the PV panels or array are absolute minimum that the pumps needs at the shallowest depth. See the pump curves for more information. To account for wire and other system losses we recommend 15% to 25% more.
There are two main categories of water pumps, submersible and surface mounted. Submersible pumps are installed under the water while surface pumps are mounted out of the water. Submersibles are usually installed below the water level in a well but can be installed in a lake, cistern or river.
Surface pumps are usually mounted above the water level which requires a suction lift,the distance between the water level and the inlet of the pump. However if a water storage tank is used the water level could be above the pump creating a positive suction head.
Grundfos SQFlex Solar Water Pumping Kit INSTALLATION MANUAL
Solar Water Pumping Systems for Ranchers
What is the max number of 60 Cell solar panels i can run in seri
Shurflo 9300 Solar Pump Maintenance Schedule
Design of Small Photovoltaic (PV) Solar-Powered Water Pump Syste
Solar Powered Water Pumping Overview
What size inverter is recommended for AC well pumps?
What is the difference between a submersible pump and a surface
What is solar water pumping, and why would I need it?
Should I use batteries in my solar pumping system?
How does a solar panel power a solar pump?
Do I need a water storage tank or cistern?
Installing Solar Well Pump Tips
Dankoff Solar Booster Pumps Installation Manual
Grundfos SQFlex Service and troubleshooting guide ( Text Only)
Grundfos SQFlex Pumps Product Guide ( Text Only)
Shurflo 9300 Solar Pump 902-200 Controller Manual
Using Poly Pipe for drop pipe on wells
Using SCH80 PVC drop pipe on wells
How do i wire the Grundfos CU200 controller
What is the difference between a helical pump and centrifugal pu
Can i use a larger pipe size than outlet on water pump?
What are the main differences between the different SQflex pumps
Combiner Boxes and Breakers
Home and Garden
Monitors & Metering
Pre-Designed Systems
Pre-Wired Power Centers
PV Solar Panels
Any question?
If we still haven't answered your question, you can contact us below and we will get back to you as soon as possible.