Which pump is better, single-phase or three-phase?

When looking to get a new well pump, you may come across pumps with the option of getting a single-phase or three-phase motor. Which one is the better choice depends on your specific situation and what you plan on doing with the pump. Hopefully this post can help you decide whether a single-phase or three-phase pump is the best option for you. 

So the main difference between these pumps is that they use different types of power. Single-phase power is the kind of power most people come in contact with in their everyday lives as it is the type of power you have in your home. With single-phase power, the power is supplied through two wires, one hot and one neutral wire . Three-phase power is mostly used for industrial purposes as it is better at supplying high power demands that you would need in order to run large machinery. Three-phase power is supplied through either three or four wires, each of the hot wires carrying part of the electrical load. Three-phase motors cannot work unless supplied with three-phase power. This means you will not often see pumps with three-phase motors installed for residential use. 

So for most people, a single-phase pump will be the way to go as they will have single-phase power available to them at their home. But there are some cases where you may want a three-phase pump even if you do not have three-phase power at your residence. One of those reasons will be if you have a very deep well, as in 800 feet or deeper. The reason for this is because with that deep of a well, you will need a larger HP pump, often a 3-5HP. And with a pump motor that large being down 800 or more feet, you will need to get a very large wire to supply the power to your well pump. As the length of a wire gets longer, you need to get a larger wire to make sure you don’t experience voltage drop along the length of wire. And a 5HP pump requires quite a lot of power to run, so it will require a larger wire to combat voltage drop and ensure the pump has enough power to run. For a 5HP single phase motor at 800’+, that would require a 3 gauge wire. 3 gauge wire is a very large size of wire, and also very expensive, for an install of 1000’ it can be 3-4x the price of the pump alone. Three-phase power does not require as large of a gauge of wire due to the power being split among three or four hot wires instead of being focused into one. A pump with a three-phase motor will save thousands of dollars on wire cost alone for an extremely deep well install. 

Another reason to go with a three-phase pump for your well is if you wanted to use a variable frequency drive. A variable frequency drive (VFD) is a system that allows you to control the speed at which the pump pumps. This can be done because a three-phase motor will take power at different frequencies which will cause it to spin at different speeds, and a single-phase motor isn’t designed to take different power inputs other than 60Hz. A VFD also allows you to soft start your pump, where it turns on slowly and ramps up to full speed, compared to a single-phase pump which draws a lot of power on start up to kick the motor on. A soft start can help increase the lifespan of your pump, as well as not strain your power source with high current draw on startup. A VFD will usually accept single-phase power and convert it to power the three-phase motor can utilize. 

If you had any questions about what kind of pump would work best for you, you can always call and talk to one of our pump specialists at 855-560-5670.