This article was posted 08/30/2006 and is most likely outdated.

Protecting Submergible Pump from Lightning
 

 
Topic - Lightning and Surge Protection
Subject - Protecting Submergible Pump from Lightning

August 31, 2006  

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Protecting Submergible Pump from Lightning

 

Question from newsletter member:

 

imageMike,

 

I have a 150’ ground water well with a steel encasement, the well has a submergible pump located at the bottom of the well with a ground wire going to the pump.

 

The steel pipe/encasement for the submergible pump is not grounded to the electrical system. The pump seems to burn out and trip the breaker for no apparent reason.

 

I am thinking of grounding the steel pipe/encasement to the submergible pump ground wire, due to lightning traveling down the ground wire 150’ to the pump housing. However, I am not sure if that will only make the problem worse, due to more surface contact with the earth. This site is located in the Florida Everglades with lots of lightning, any recommendations?

 

Chuck Maxfield

Apex Electric

 

Mike asked his friend John West with Power & Systems Innovations, Inc. to respond:

 

Most wells are installed without consideration of the impact the earthing effect of the casing and what can happen with nearby lightning events. The energy of lightning is not predictable, but most often it follows any and all paths that present a lower potential. Lightning traveling in the ground will see the well casing the same as lightning in the air would see a 150’ tower. It will couple with the casing and follow the conductors of the pump back to the “lower” potential. That most often will burn the pump out. There are two things you can do; bond the casing to the service ground and install a good performance TVSS (surge protector).

 

If I understand the installation (if I don’t please correct me) the well casing is not bonded or connected in any manner to your electrical service ground bond. There is no doubt the well casing is the best ground you have available. As you have stated it is probable the pump damage has resulted from lightning.

 

Part 1: I recommend you bond the well casing to your service entrance grounding. The distance between the well and your electrical service would determine the size of the conductor. Our firm uses 4/0 bare stranded conductor in most cases. In corrosive or salt soil areas we use tinned wire. The larger the size of the bonding conductor the better. The well casing may be “pickled” steel and if so you will need to use a bi-metal clamp to transition from the steel to copper. The key is surface area…. if necessary use some Penitrox, but make 100% sure you have a very solid connection as it can be under severe stress during a lightning event. Most of the energy during a lightning event will follow the “bond” you have created and not end up burning up your pump motor. I recommend you verify the service ground is 25 Ohms or less and the X/O bond is well made. The well casing will act as a shield (such as conduit can for the wire inside) and keep the energy away from the pump motor.

 

Part 2: Install a substantial (50-100kA per mode) TVSS at the well (my preference) or on the panel feeding the well. If the circuit is less than 40-amps (any single phase voltage) there are series installed TVSS rated at 72kA available.  You cannot have too much surge protection when lightning is involved. My own home has a well for irrigation I have a robust panel surge protector installed on the main panel and series connected on both my well and AC unit.

 

Our firm has worked with US Sugar, numerous growers and Bonita Springs Utilities to solve similar issues. If I can assist further please contact me.

 

One major grower we have worked with has over 200 wells. Most are three phase and over 100hp. Bonding the service entrance to the well casing along with surge protection stopped all but a very few of their pump motor damage issues.  US Sugar told me the combination all but stopped their damage and also significantly lowered their unexplained failures.

 

Nothing is “lightning proof” but I am sure you will see a significant lowering of the damage…….

 

John N. West, Sr.

Power & Systems Innovations, Inc.

P.O. Box 590223

Orlando, FL 32859-0223

Phone: (407) 380-9200

Fax: (407) 380-3911

 

 
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Comments

  • Jim, you are welcome to the title of lightning capital. It is not as much fun as you may think. Cuts down on my afternoon fishing.

    The main reason the steel wells seem so popular down here is the depth they go to, often 400 feet or more. I know of two large wells that are just under 600 feet. Shallow wells are often nothing more than a 2 inch well point with 30-60 feet of PVC. They are most often for irrigation use only.

    In NC you have far better soil conditions for grounding. Florida in most areas is sand and every now an then a layer of limestone... in south Florida they have coral rock in some ares. That is a real stinker when you trying to ground a facility. I have done gounding work all over the USA and many projects out of the USA. Most of our work is high performance grounding and associated with the dissipation of lightning energy. Experience has shown me the lower the resistance and larger the wire at the service entrance the less energy you will see getting past the meter base and service disconnect. Given a low impedance and low resistance path much of the "lightning" energy will arc to ground. When you think about electrical panels, disconnects and switchgear every distance is a calibrated spark gap... give the energy you don't want in the facility a better path to earth and most of it will go there and the little left you can deal with very well by installing a proper system of TVSS devices. Our almost 15 years in business has seen this over and over with our customers. We have had meters come out of the meter base like birdshot... the disconnect melted and NO interior surge damage.

    My first well experience was with the well at my home in Longwood, FL many years ago (1976). It is a 170 foot deep well and steel cased. It was not bonded to the house and typical of many wells in Florida only the to phase wires were run to the well. I asked a fellow I knew then I fished with (retired master electrician from Chicago) what I needed to do after lightning took out the well. He told me to bond it with a "big wire" and he would install some MOV's. He had some large GE MOV's he purchased at a local electronics salvage store in Winter Park, FL. I lived in that house until 1986 and while my neighbors lost their wells due to lightning all I ever had to do is replace the MOV's a couple of times. The "fix" was crude, I used 1/0 I got at the same place he got the MOV's and buried it about a food deep in the yard and ran it the 40 feet from the well to the service entrance and he made the bond in my breaker panel. I worked for a company then that had very 4" bimetal clamps. We used 6 of them and spread the wire out to get a good bond, the pipe was black pipe and so we cleaned it and used Penatrox to insure a good bond. While it was not perfect it worked and lasted me for years.

    My goal in all this is to try to get people to understand the critical nature of proper grounding and bonding as it relates to lightning energy. Mike is the expert on the code.

    John West, Sr.
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