Solar Well Power

Convert you well to solar power now!

With the new Solar Pumping Inverter, when the sun is shining, you can be pumping. Converts Solar DC to AC for existing AC-powered well pumps. Now us can install solar modules to remove your well power consumption from your electric bill. This inverter can supply power in the place of existing utility power for pump motors up to 20HP.


  


                  Features

    - Solar power only, no batteries

    - Power existing AC pumps

    - Direct connect to solar panels

    - MPPT circuit for high efficiency

    - Low water sense and shutdown

    - 3/4HP & 1HP in stock

    - Up to 20HP by special order

    - Single or 3-phase options 

    - AC power input option

    - Rated for outdoor installation






                    

                    MySite Solar Pumping Inverter



Electric well water pumps are available in three forms:

1) AC powered, typically designed to operate at 240V for optimum efficiency

Most existing residential water pumps are AC powered, operating from either standard   utility power or from   electrical generators.  Users desiring to add solar power for these pumps will be required to install solar systems that include a battery bank and a DC-toAC power inverter. The cost benefit of avoiding battery-based systems may justify replacing the AC pump with a DC pump, thereby enabling pumping directly from solar panels.

2) DC Powered, operating from either batteries or solar modules

Modern solar powered pumps can operate directly from solar modules by using a pump controller.  DC pumps are available in standard size and capacities of historic AC powered pumps. Pumps can be of diaphragm or centrifugal design.  

Typical submersible pumps are of centrifugal design, designed to match the lift and capacity requirements of the target well. The physical diameter of submersible pumps must be selected to fit inside the existing well casing. Kits are available with all the standard installation components such as well cap, suspension rope, electrical feed wire and support I-hooks.

Surface pumps can also operate from DC power. Typical surface pumps operate at very high efficiency compared to older AC pumps. 

Care must be taken to locate pumps such that limited "suction" lift is required. This  ensures the pump will be self-priming. The theoretical pumping limit for a suction pump is approximately thirty-four feet at sea level, and less at higher altitudes (about 1 foot less per 1000 feet). The practical limit for a centrifugal pump is about twenty-feet because of pipe friction, non-perfect seals, etc. Other types of pumps often have much less suction capacity.


3) Combination AC/DC powered, capable of operating from either voltage format.

Grundfos is a common pump manufacturer that provides AC/DC submersible pumps. These pumps contain electronic circuits to automatically convert the incoming voltage format to match the pump needs. Not surprisingly, these pumps are more expensive, but many installations benefit from the ability to operate primarily from solar power, but use an electrical generator as emergency backup.


Low flow pumps can operate directly from solar or battery power. RV-style pumps from Shurflo often contain built-in pressure cut-off switches.  Diaphragm pumps are available for submersible applications down to 120ft  of depth for 1-2 gal/min flow rates.   Most are primarily intended for solar-direct use at 24 Volts rather than 12 Volts. Larger home power systems are often based on 24 Volts, but smaller systems are 12 Volts. These pumps will operate at half-flow on a 12 Volt system. 

These little pumps use less power than a 100 watt light bulb. To estimate, look at the data sheet for the pump you intend to use. Calculate your TOTAL lift as by adding your vertical lift + the pressure (1 PSI = 2.3 feet). 


Questions you must answer in order to select pump equipment

1) Max depth to water level when feeding typically water needs

2) Distance from pump head to water storage tank.

3) Elevation rise from top of well head to top of water tank

4) Pressure loss due to pipe friction due to distance and pipe size

5) Pressure tank cut-off pressure (if pumping directly into pressure tank)

6) What is the diameter of the well casing

7) What is the Gal/min water need

8) What is the gal/min capacity of the well


Energy Required

(Watt-Hours per Day) = Watts X Hours of pumping per day.  The following 

must be achieved:

1) If driving a DC pump directly from a solar panel+controller, the solar output must exceed the peak pump power by at least 20%, preferably by 50%.

2) If you are using battery power, the battery storage capacity must be 2 x your daily pump power consumption.  

Daily Pump power consumption = Pump Volts x Amps x pumping hours per day

Battery storage capacity = Battery volts x Amps Hr rating

3) In order to adequately recharge the battery, the solar power must  exceed the daily pump power consumption.

Solar power production = hours of peak solar power (typically 5 hrs) x total DC rating of solar modules  x .80


Pump Controllers

Many of these solar pumps require a special controller if they are to be powered directly by PV modules (without batteries). The controller, or linear current booster (maximum power point tracker) acts like an automatic transmission, allowing the pump to start and run in low light conditions, such as overcast or early morning & evening. With a battery power source, the controller may not be required at all or a special controller may convert 12 Volt battery power to 30 Volts to run the pump at top speed. 

A wide variety of pump controllers are available. Although commonly called "controllers", these are actually specialized DC to DC converters, often called "LCB"’s, or linear current boosters.  These work to boost the current, especially under low light conditions, cloudy days, and early morning or late evening. The voltage current of the PV panels is often too low to run a pump under these conditions, so the controller boosts the voltage enough to run the pump. In effect, these act like a perfect "gearbox", and match the output of the panels to the pump. These typically increase water flow by 25% to 50% over the day. Some controllers have extra inputs for remote control and/or low or high water shutoff, using water level sensors. 


Pressure Drop Caused by Pipe

The pipe that drops from the well top down to the pump is called "drop pipe". We use flexible black POLYETHYLENE PIPE. Get drinking water grade pipe, NOT utility grade pipe or irrigation tubing. It should have at least a 100 PSI rating. This flexible pipe allows easy installation and removal by hand, without the need to disassemble joints every 20 feet. In most cases, use 1/2 inch diameter pipe. If your pump is designed for 24 Volt use and has a 3/4 inch outlet, and you are using it at 12 Volts, adapt it down to 1/2 inch pipe size.

We use minimal diameter drop pipe for two reasons:
(1) Water is heavy. Small pipe holds a low enough weight of water that the pump may be pulled by hand.
(2) Small pipe allows the water to flow upward at a higher velocity, so that sand or sediment can be exhausted from the pipe.
If you use larger pipe, the water will rise so slowly that the sand may settle within the pipe. When sand accumulates, it causes abrasion and pump problems. Water well professionals are accustomed to larger AC pumps and use 1 inch pipe or larger, of a thick, rigid variety. This type of pipe is NOT appropriate for these pumps. The low power pump will not "kick" when it starts, so it does not require heavy-wall pipe (or a torque arrestor) for support.


Supply Pipe

The horizontal pipe from the wellhead to your tank should be PVC, or whatever you prefer. Do NOT use polyethylene pipe underground, as it may develop joint leakage after many years. Use at least 1 inch pipe since who knows, maybe you'll put a bigger pump in someday. Also, you may be using the same pipe to let water OUT of your tank. If it flows down by gravity, you'll want big pipe for a good flow. It cannot be too big, only too small. Check a pipe sizing chart to be sure.

On-line pressure loss calculator for pipe sizing

Check Valve

These diaphragm pumps have internal check valves, without which they would not function. So when the pump stops, water does not readily flow back down the drop pipe. However, the valves aren't perfect, and may allow a slow downward trickle when the pump stops. If you want this to occur, in order to drain above-ground pipe for freeze protection, then do not install a check valve. Otherwise, place one or more check valves at the pump and/or in the line to the tank. For longest life of system components, install a check valve for every 250 ft of vertical lift.


Wire Size

Wire for low voltage power transmission must be relatively large (expensive) to minimize power loss. If the distance from your home's power center to the well and down to the pump is more than 200 feet, the size of the feed wire should be increased one size for every 200ft.  If the pump voltage can be increased, the size of the wire may decrease proportionately.   Pumps are available for voltages up to 180 volts. Higher voltages are an advantage with larger pumps because they reduce voltage drop and allow the use of smaller wire.

Chart shows wire size required versus length of distance


Online Voltage Drop Calculator


Storage tank with pressure booster pump

In case of a low flow capacity  pump, water may be accumulated in a storage tank so that it can be released on demand. Use of a storage tank with a booster pump provides ability to charge a  pressure tank. Alternatively, an elevated storage tank can use gravity flow in place of the booster pump and pressure tank. 


Pumping and lift

The water pump must supply the effort to drive water vertically out of the well,  horizontally across the distance to the water tank, and with sufficient force to pressurize the pressure tank.  

Pressurizing 1 PSI = lifting 2.31 feet. Pressurizing to 43 PSI (a typical pressure) is equivalent to lifting 100 feet. So, a pump that can lift 230 feet maximum can lift only 130 feet if it is also pressurizing to 43 PSI.


Pressure Tank

A "CAPTIVE AIR" pressure tank is now very common.  A PRESSURE TANK is used to accumulate water so that it can be released quickly when you open a faucet. Get a large one, like the 80 gallon size or above. This can store over 30 gallons of water, enough water to fill a small bathtub before the pressure gives out.  Multiple pressure tanks of various sizes can be used simultaneously to add water storage capacity.


Pressure Adjustment

Install a pressure switch and a pressure gauge on your system. Purchase a pressure switch of the type used with conventional AC pumps. You might buy a switch that says "cut-in 30 PSI / cut-out 50 PSI" This indicates the factory settings, but they are adjustable. The setting determines the pressures at which the pump turns on and off. The cut-out adjustment is also called "differential", since it sets the difference between cut-in and cut-out. It is desirable to use the LOWEST pressure that will satisfy your flow requirements. The lower you can set the cut-out, the less power your pump will require AND the more water your pressure tank will store. Read the instruction card that comes with the switch.      


Pressure Tank Pre-charge

Inside your pressure tank is a big rubber balloon. It is filled, at the factory, with pressurized air from a valve on the tank that looks like a valve on your car's tire. It is pressurized at a HIGHER pressure than you need. Check it with a tire pressure gauge. With this high setting, the water cannot compress the air balloon, so the tank is not yet effective. Once you have set your pressure switch as described above, you need to let some air out of the tank. To do this, turn off the power to your pump. Open a water outlet to relieve the pressure in the tank, then close it again. Now let air out of the tank until the tire gauge indicates 2 or 3 PSI LOWER than your cut in pressure. This is also described on instructions that come with your pressure tank. If you have more than one pressure tank, adjust them equally. Turn your pump on, and measure how long it takes to charge the tank to cut-off. As soon as the pump starts, the pressure should quickly rise to the pre-charge pressure. Then it will rise very slowly as it compresses the air in the tank. Fix yourself a sandwich or something. When it finally reaches cut-out pressure and shuts off, note how long it took, and write down "cycle time." on the wall near the tank. Also record your cut-in and cut-out pressure settings. If you have an ammeter measure the current (Amperes) that your pump draws at the beginning and at the end of the pumping cycle. If you have trouble in the future, changes in these readings will indicate where the problem lies.


Determining the Optimum Depth to Set a Submersible Diaphragm Pump

Drillers and pump installers are in the habit of placing pumps down near the bottom of the well. Conventional pumps (centrifugal impeller mechanism) are not adversely effected by great submergence, so it doesn't hurt. Also, they cannot tolerate dry running if the water level should drop, so it is safer to place them low.

Diaphragm submersibles are fundamentally different. Diaphragm stress increases with pressure, so life expectancy decreases. They have good tolerance for running dry. Low voltage pumps require larger, more expensive wire, so length should be minimized to reduce cost. So, it is most advantageous to set the solar-powered pump HIGH in the well, under just 5 or 10 feet of water, unless the water level is expected to vary. See manufacturer's ratings for maximum submergence. Do NOT approach the maximum unless you must.  If the well yield is MORE than double the pumping rate, set the pump only 5-10 feet under the static water level. If well yield is LESS than double the pumping rate, anticipate the draw down level of the well (take a guess or talk to the driller) and set the pump below that level.  Measure the water level using a string with a weight. Run the pump a full day, and measure the level again. Also, listen. If the pump begins sucking air, you will hear it. If your well yield is very low or uncertain, use a pump controller with under-load sensing and auto-shut-ff.  Long-term dry running may damage the pump, especially if there is sand in it.



Detailed Guide to Water System Design 

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