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Discussion Starter · #1 ·
I am not sure that I completely understand the proper way to totally protect an irrigation controller in the event of a lightning strike, and after using the search feature I believe that there are probably others in the same boat as I am.

First I understand that with a direct lightning strike all will be lost and that there is probably little anyone can do to prevent that, I am concerned with the surge voltage that could come from a nearby strike and travel into the wiring coming back to the controller. I currently use metal oxide varistors on the valve side of the controller and this arrangement is grounded to 100 feet of 1 inch copper water main buried in my front lawn, I feel fairly confident that this will protect the controller from voltage surge originating on the valve side of the controller. I have concerns about voltage surge traveling on the power line to the controller. Will the transformer protect the controller from a power line voltage surge? Should I use a computer type power strip that protects from voltage spike in this application? Every irrigation controller I have ever seen is simply plugged into the nearest wall outlet so maybe this isn't't an issue, but I know that you folks will know. Thanks in advance for your comments.
 

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Discussion Starter · #6 ·
You could always MOV the 24-volt controller supply. Most controllers already have this stuff built in.
Okay, I didn't realize that controllers have MOV protection, mine does not. On controllers that do have power side MOV protection do these devices reset after a voltage surge (lightning strike)? It is my understanding that most of these MOV devices offer one time protection and after a voltage surge they must be replaced, but this may not be the case. Do Professional Irrigation contractors often change out the MOV in these controllers after a lightning incident? In my mind if the MOV does not reset and the MOV is not replaced then the controller would be changed out and nothing was really gained. I am simply looking for the right level of protection for my own control system. Thanks again.
 

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Metal Oxide Varistor - kind of like a bag of diodes mashed into a tiny component. One on all controller outputs. They just sit there, until the voltage exceeds a certain amount, and then they turn from a very high resistance to a very low resistance, and thus dissipate a voltage surge.
 

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Okay, I didn't realize that controllers have MOV protection, mine does not. On controllers that do have power side MOV protection do these devices reset after a voltage surge (lightning strike)? It is my understanding that most of these MOV devices offer one time protection and after a voltage surge they must be replaced, but this may not be the case. Do Professional Irrigation contractors often change out the MOV in these controllers after a lightning incident? In my mind if the MOV does not reset and the MOV is not replaced then the controller would be changed out and nothing was really gained. I am simply looking for the right level of protection for my own control system. Thanks again.
MOVs don't reset - they divert the high voltage away from the controller. A very high strike can and will burn the MOVs right out, but usually they just do their job, and protect the controller from frying. In the event the MOVs do fry, they have also done their job of keeping the strike from entering the primary and cooking your electrical system.

No one I know replaces a MOV - they replace the controller.

Get some surge protection on the primary side, put in a grounding grid, get a controller with MOVs (or add your own MOV strip between the controller and your field wiring), and hope it hits your neighbor's.:laugh:
 

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Discussion Starter · #12 ·
Thank you everyone for your comments.

I use Rain8 home automation controllers in my system and they are driven by a PC with MCSprinklers software. Once again I have added the MOV protection to the valve side of the controller but was still concerned about the power line side, I believe with all of your comments that I have convinced myself that a good high quality computer grade surge protector will provide me with all the protection that I would need. Thanks again.
 

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Thank you everyone for your comments.

I use Rain8 home automation controllers in my system and they are driven by a PC with MCSprinklers software. Once again I have added the MOV protection to the valve side of the controller but was still concerned about the power line side, I believe with all of your comments that I have convinced myself that a good high quality computer grade surge protector will provide me with all the protection that I would need. Thanks again.
Nothing totally protects against lightning but any precaution is better than none.
 

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Discussion Starter · #14 ·
So I know that when professional installers complete an irrigation system they ground the controller, but to what? I have installed my controller ground to my 100 foot long copper pipe water main, but my home electrical system is grounded with an 8 foot long copper clad ground rod driven into the soil near the service entrance. It didn't occur to me previously but I believe that I have created a looped ground. Do you folks always ground to the homes main ground system? Is there ever a situation were you drive a separate ground rod and does this create the looped ground situation? Thanks everyone for your suggestions and help.
 

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Discussion Starter · #16 ·
There are also controllers that are not grounded, and they still have the MOV protection.
Okay, I guess that I can understand the MOV sending the overcurrent back on the neutral wire, but I am still interested in grounding to earth and if separate ground rods are driven or if the connection is made to the homes electrical ground. I believe that there could situations that result in looped grounds and that is a bad thing.
 
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