Why can't Earth Ground be used in place of neutral?


  #1  
Old 03-07-21, 07:12 PM
C
Member
Thread Starter
Join Date: Dec 2020
Posts: 32
Received 1 Vote on 1 Post
Why can't Earth Ground be used in place of neutral?

A bit of a story on how I got to this question. I have irrigation valves running off a 26v AC timer. The neutral to one of the valves is no longer functioning. It only reads 20v, and is showing no continuity. When I measured amps on the wire (using a 220 ohms resistor), I didn't get any reading, but when tested with a good wire it measured 120 milliamps. So the wire seems non functional. Running a new wire will be a major PITA, so I thought what if I just drove a grounding stake into the ground next to the valve, and connected the solenoid neutral wire to it instead. But then I thought that would just cause the GFCI to trigger. Being ever curious, I set about doing a little experiment to prove as much. For a working valve, I disconnected the neutral wire that runs from the timer to the valve. I did so at the terminal in timer. I then instead secured the neutral wire an earth ground. I used plumbing at the well pump head for that, which is just a few feet a way. I then turned the timer on for that valve and...nothing. The valve did not engage and the GFCI did not trip. I'm not sure why. Are my expectations wrong, or should I recheck everything to make sure I did the experiment correctly?
 
  #2  
Old 03-07-21, 07:34 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: United States
Posts: 14,083
Received 331 Votes on 285 Posts
The GFCI didn't trip likely because the control transformer is isolating the 24-volt output from the 120-volt input.
You will also likely find that using the earth is not going to work. The 24-volt transformer is isolated from the earth. The earth is also a poor conductor and even if you did drive a rod at both the valve and the control you will likely find the earth has too much resistance for 24 volts to work.

Typically with sprinkler controls you only have one "common" wire (what could be called the neutral) for all the valves and one separate control wire to open each valve.
 
  #3  
Old 03-07-21, 08:50 PM
C
Member
Thread Starter
Join Date: Dec 2020
Posts: 32
Received 1 Vote on 1 Post
I was also starting to think it might be the transformer. Thanks for confirming. Guess it's time to start trenching.
 
  #4  
Old 03-07-21, 09:20 PM
C
Member
Thread Starter
Join Date: Dec 2020
Posts: 32
Received 1 Vote on 1 Post
Typically with sprinkler controls you only have one "common" wire (what could be called the neutral) for all the valves and one separate control wire to open each valve.
I forgot to reply to this. There is just one common/ground terminal. There are two wires coming off it. One goes to about 8 valves, the other just to a single valve box with 2 valves, and that is the one with issues. I'm fortunate I guess in that if it was the other wire, the needed trenching would have been 5x worse.

BTW, for the 8 valves handled by the one working wire, I was surprised not to see the wire running into and out of every valve box, treating the valve boxes as one linear circuit. Instead it looks like the wire must be pigtailed 2 or 3 times underground (not in the valve boxes). I'm surprised this doesn't cause issues with all the moisture they are exposed to, but it's been this way for nearly 30 years now, and the wire that has issues is the only one that is a straight run from the timer to the valve box.
 
  #5  
Old 03-08-21, 05:07 AM
P
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 25,081
Received 867 Votes on 798 Posts
Usually irrigation cable has many conductors and often all are not used. Look at your wiring at both ends and see if there is a wire not being used and you can use that for your ground wire without having to dig and run a new cable.
 
  #6  
Old 03-08-21, 08:12 AM
C
Member
Thread Starter
Join Date: Dec 2020
Posts: 32
Received 1 Vote on 1 Post
Usually irrigation cable has many conductors and often all are not used. Look at your wiring at both ends and see if there is a wire not being used and you can use that for your ground wire without having to dig and run a new cable.
There are just the 3 conductors. 2 control for the 2 valves and one common. I converted one of the control to a common so I can at least run one valve off the the timer, and the other I now control manually.
 

Last edited by cplum; 03-08-21 at 09:49 AM.
  #7  
Old 03-08-21, 08:40 AM
2
Member
Join Date: Jan 2014
Location: USA near Boston, MA
Posts: 1,185
Received 94 Votes on 80 Posts
Depending upon the sizeof the areas and the number of heads in each, you might be able to run both zones simultaneously by connecting both solenoids to the working wires. If too many heads there might not be enough pressure. You can test first by activating the good zone and opening the other one manually at the same time.
 
  #8  
Old 03-08-21, 09:48 AM
C
Member
Thread Starter
Join Date: Dec 2020
Posts: 32
Received 1 Vote on 1 Post
Depending upon the sizeof the areas and the number of heads in each, you might be able to run both zones simultaneously by connecting both solenoids to the working wires. If too many heads there might not be enough pressure. You can test first by activating the good zone and opening the other one manually at the same time.
That won't work since one is for grass sprinklers and runs about 15 minutes at a time and the other is for drip irrigation and runs for about 3hrs at a time.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: