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. Continue reading