At some point in your water systems career, you have no doubt stood in front of a homeowner or other end-user who was indignant at his submersible pump cost. This conversation often stems from having replaced another motor around the house at some time. Maybe it was an HVAC motor, a sump pump, whatever; “That motor cost me this much, and this submersible motor you want to sell me is way more than that! What gives?”
Here’s what gives. They’re not even close to being the same. The conditions and environment in which a submersible motor is expected to operate are totally different from any of their above-ground counterparts. Different environments, different motors. Here are six things that make a submersible motor unique and different (and more expensive):
- Really stating the obvious here, but number one, a submersible motor lives underwater. One of the first things we all learned about electricity is to never mix it with water. So, what do we do? We take an electric motor and install it not just a little ways underwater, as in the case of a sump pump, but potentially hundreds of feet underwater. That means a tremendous amount of water pressure trying to reach the electrical part of the motor. There are numerous design and manufacturing considerations that go into keeping the water in the well away from the electricity in the motor.
- All motors generate heat, and heat is the arch enemy of motor reliability. Engineers who design above-ground motors just give them enough surface area to dissipate all the heat. However, a 6-inch motor, by definition, has to fit in a 6-inch casing. So, a lot of heat is concentrated into a small cross-sectional area. Special and proprietary materials are required to make sure that the heat generated in a submersible motor gets carried away.
- When we push water up the drop pipe, it pushes back with a lot of force. No above-ground motor ever sees this challenge. But, a submersible motor needs specialized and highly-machined thrust bearings to handle all the down thrust it generates when it delivers water out of the ground.
- Electrical surges and lightning are looking for the easiest path to ground, and the water strata is ground. So, a submersible motor resides in the very place a surge is looking to go. As a result, submersible motors and systems need specialized surge protection.
- Not all water that we place a submersible unit in is the same. Sometimes it’s corrosive and special materials are required. Once again, an above-ground motor will never see this challenge.
- Finally, a submersible pumping system has to be extremely dependable for two reasons: it’s delivering a critical resource to the home or business or farm, and, it’s not easy to replace. Special equipment is required in the form of a rig, along with specialized troubleshooting and application expertise.
A submersible installation remains one of the most reliable things out there, performing flawlessly for years and years. However, that’s because of the engineering and manufacturing that goes into it, along with the expertise of the installing contractor. Beyond a couple of general principles, submersible motors aren’t even related to above-ground motors. And, the value and cost just can’t be compared. So next time, when someone doesn’t understand why a submersible motor or pump costs more than an above-ground one, don’t hesitate pull these points out of your back pocket to explain the difference.