2-Wire Vs. 3-Wire Submersible Pump: What Are The Major Differences?
The time has come to replace the submersible pump in your residential water well. There are a variety of options to consider. Of the options, there is one that confuses homeowners more than any other? Which is the better option? A 2-wire or 3-wire submersible pump.
The starting capacitor and other electronic control locations are the only differences in a 2-wire and 3-wire residential submersible pump. There are certain advantages to both a 2-wire configuration and a 3-wire configuration for a residential submersible pump. Understanding the advantages and disadvantages of both systems makes the decision easier.
Many decisions go into the choice of a submersible pump for your residential water system. The demands of your home and family for domestic water, irrigation needs for landscape, water features such as a pool or hot tub, and the depth of the well are all contributing factors to pump selection. Choosing a 2-wire or 3-wire pump depends in part on these factors and decisions.
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How Do I Tell What Kind of Pump I Have Now?
Before you start shopping for a new pump, it is wise to know what kind of pump is in your well now. You can do this by examining the wiring going down the well to your pump. Before you start examining the wiring on your pump, be sure the electricity to the pump is disconnected. Handling live electrical wiring to a submersible pump can be hazardous.
2-Wire Pump Installations
When you examine the wiring going down to your submersible pump and find two black wires and a single green wire, your submersible pump is a 2-wire pump. This type of pump has the starting capacitor and the electronic controls installed with the pump at the bottom of your well.
2-Wire pump Advantages
- Submersible pump installations with a 2-wire configuration are usually easier to install under most circumstances. All the electronic pump controls and the starting capacitor are part of the pump. There is less equipment needed at the top of the well.
- The size of the wire needed to serve a submersible pump that uses a 2-wire configuration is usually smaller than the wire needed for a 3-wire system. Smaller gauge wire is much cheaper and easier to install.
- The electrical components, including the starting capacitor, are sealed with the pump motor. Having the components sealed reduces oxidation from air exposure and means less maintenance and repairs.
2-Wire Pump Disadvantages
The major disadvantage to a 2-wire submersible pump system is the time and cost of repairs if the starter capacitor or electronic controls fail. Such a failure then requires the pump to be pulled from the well to be repaired or replaced, which can become expensive. There are other disadvantages to a 2-wire pump to consider.
- Unlike a 3-wire submersible pump, the starting capacitor and controls can’t be repaired or replaced easily. If the starting capacitor or controls fail in a 2-wire submersible pump, the entire pump assembly must be pulled from the well and replaced. A failed capacitor in a 3-wire system can be replaced quickly at a minimal cost.
- Puling the entire 2-wire submersible pump may require special heavy-duty equipment that can damage landscaping, lawns, or other structures. Such damage can be expensive to repair or replace, adding to the cost of the project.
When Does a 2-Wire System Make Sense?
For the most part, for most residential submersible pumps, a 2-wire system makes a lot of sense. Easier and cheaper installation is one of the big advantages. Typically, the controls on a 2-wire system have a longer life which translates into lower maintenance and upkeep costs. Opting for a 2-wire system makes a great deal of sense for the average homeowner with a domestic water well.
However, on deeper wells or higher horsepower pumps, a 2-wire pump installation may not be feasible. Your pump installer is a source of excellent information about when your well and pump installation may require a 3-wire connection.
3-Wire Pump Installations
Typical 3-wire pump installations are identifiable by the colors and numbers of wires in the circuit. The standard 3-wire pump wiring has:
- One black wire
- One red wire
- One yellow wire
- One green wire
In addition to the four colored wires going down to the pump, you should find an electrical service box near the well. This electrical service box houses the electronic controls and the starting capacitor that serves the submersible pump’s motor.
3-Wire Pump Installation Advantages
- The components of the pump that are most likely to fail are easier to access and to service. The electronic controls and starting capacitor can usually be repaired or replaced in forty-five minutes on a 3-wire pump installation.
- 3-Wire installations usually provide higher starting torque. This higher starting torque allows deeper submersible pump installations and larger horsepower pumps.
- Repair costs are usually cheaper because you don’t need to pull the submersible pump from the well to make repairs to the components most likely to fail.
Disadvantages of a 3-Wire Pump Installations
3-Wire submersible pump installations suffer from several disadvantages for the typical residential submersible pump installations.
- A 3-wire submersible pump installation is usually more complicated and more expensive than a 2-wire pump installation. The installation of the controls and starting capacitor requires more equipment, usually not included in the cost of the submersible pump.
- The wiring of a 3-wire system requires a larger gauge wire than a 2-wire system. Larger gauge wire is more expensive upfront.
- You must provide a protective environment for the electrical box that houses the pump controls and starting capacitor.
- Even with a protective environment, the electronic controls and the starting capacitor are more susceptible to corrosion that can cause the components to fail.
When does a 3-Wire System Make Sense?
If you have an exceptionally deep well, a well larger than four inches, a 3-Wire submersible pump installation may be a better option. Anytime you require a higher torque pump, a 3-wire installation is generally a better choice.
Typically, any submersible pump installation greater than 1.5 horsepower means a 3-wire installation for your well.
My Pump Only has Two Black Wires
It is not uncommon for older pump installations to only have two black wires. The green wire, a ground wire, was not typically installed until a few years ago. When you repair your existing 2-wire submersible pump, your pump installer will likely run a new wire back down the well.
If you perform your own pump maintenance, we highly recommend running a new well wire with the two black wires and the green ground wire. If you aren’t sure how to wire the green wire into your electrical service, you should consult a licensed electrician for help.
Can I Replace a 2-Wire Pump with a 3-Wire Pump?
Certainly, you can place a 3-wire submersible pump in a well previously fitted with a 2-wire pump. However, to make the conversion requires that you provide a shelter to house the electrical control box and run a 3-wire pump cable to serve the new pump.
You must also make sure that the electrical service to your well can handle the additional loads that many 3-wire submersible pumps demand. In some cases, your entire electrical system serving your well may need upgrading.
Can I Replace a 3-Wire Pump with a 2-Wire Pump?
It is possible to replace an existing 3-wire pump with a 2-wire submersible pump. It is not as simple as dropping a new pump into the well and hooking up the wires. You will have one extra wire in the system that must be disconnected and capped off.
The electrical control boxes at the top of the well in a 3-wire pump system must also be disconnected and removed. The starting capacitor and controls of a 2-wire system are housed with the pump. A 2-wire pump makes the control box at the top of the well used by the 3-wire system unnecessary.
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The General Overview
Comparing the two types of submersible pumps and their advantages and disadvantages, we can make some general observations.
- In most instances, installing a 2-wire submersible pump in a residential, domestic water system is cheaper than installing a 3-wire submersible pump.
- Typically, a 2-wire submersible pump has a longer life expectancy than the control parts and starting capacitor of a 3-wire submersible pump.
- The most likely components to fail in any submersible pump installation are the controls and the starting capacitor.
- Repairs to the starting capacitor and controls in a 3-wire submersible pump installation are usually quicker, easier, and less costly.
- You must pull a 2-wire pump and replace the pump if the starting capacitor or controls fail. The starting capacitor and controls can be easily and quickly replaced on a 3-wire system.
In our view, most residential homeowners do well by choosing a 2-wire submersible pump for their domestic residential water system. There are instances and circumstances when a 3-wire system makes more sense. However, the needs and requirements of most residential water supply systems make a 3-wire system a bit of overkill and don’t justify the extra expense of the installation.
Dennis is a retired firefighter with an extensive background in construction, home improvement, and remodeling. He worked in the trades part-time while serving as an active firefighter. On his retirement, he started a remodeling and home repair business, which he ran for several years.
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