2 Timers Wired Together

Hayduke

LawnSite Senior Member
Location
Oregon
Now I know this thread might open a can of worms; I've searched through the thread history and found a few things but looking for more info.
Got a call from a new client asking me to replace an old 8 station Rain Dial that had stopped working after a power outage. I was in the middle of a big install, but figured it was an easy service call (first big mistake) to just run over and install a new timer and call it good.
Wired up everything as it was before, tested, and all was good. I noticed another timer that was installed nearby, but payed no attention to it (second mistake) as I was in a hurry (never good to be in a hurry on a service call). Got a call a few days later that there was some irregularities in the stations and they wanted me to come back and check it out.
Thats when I paid more attention to the other timer and realized it had a nasty mess of wiring from the previous installer and there was a common wire connected to the common terminal of both timers along with the rest of the nasty wiring mess which looked like someone barfed up a pinata after too many tequila shots.
I have never seen two timers share a common wire, and after searching it up, I'm in over my head with electrical jargon out of phase etc etc.
My question is: what kind of issues can come up when two timers are connected via one common, and whether I should be too concerned about it. I need to let the client know what we are dealing with and whether I need to do a complete wiring re-do and clean-up of the previous installers mess....
 

Wet_Boots

LawnSite Fanatic
Location
metro NYC
Timer commons connected together equals a possible phase mismatch and endless electrical errors. Avoid if at all possible.
 

ArTurf

LawnSite Fanatic
Location
Ark
You can tell a lot about a man by his wiring job.

Along a similar line, Someone once said to me "If a man keeps a dirty truck his underwear are probably dirty". True story, I didn't make this up
 

HunterTekGeek

LawnSite Senior Member
Location
San Marcos, CA
To prove to your customer there are shared commons, set your voltmeter to the lowest scale for reading resistance. Ohms. Touch the black probe to the common wire on Clock "A". Touch the red probe to the common wire on Clock "B". Take a reading.
If 0 to 5 Ohms, the commons are shared.
If infinity (open), the commons are not shared.
(Black/Red -- doesn't matter. Just easier to explain.)

If the probes (likely) won't reach from clock to clock, just run a length of wire from one clock to the other. Lather, rinse, and repeat the above.

Now, best option? Install ONE controller that has enough stations to handle everything. Then you can safely pull all the commons into one terminal. Problem solved.

There is another option but I am not a huge fan. Install an isolation relay between the two controllers. I attached a relay design using a Hunter REL2 relay. This would be a last resort option, in my opinion.

Shared commons can cause controllers to do some strange things. It is also a violation of the National Electric Code (NEC). The NEC office in Washington, DC happens to be next door to the "Do not remove this tag from your mattress under penalty of law" Department. :laugh: Meaning that people don't always take these NEC regulations seriously.

Protect yourself from any liability and just install a higher capacity controller. The disadvantage of installing a relay is this...When Clock "A" is irrigating, Clock "B" will have no connection to the field (and vice-versa). It will NOT irrigate until Clock "A" finishes his cycle. For that reason you cannot overlap start times. Not that you want to, but once you leave the property anything can happen and you might get the blame for dead plant material.

I hope this helps. And sorry, I will be offline through the weekend but I will check back next week. Good luck! Make a sale!
 

Attachments

1idejim

LawnSite Fanatic
To prove to your customer there are shared commons, set your voltmeter to the lowest scale for reading resistance. Ohms. Touch the black probe to the common wire on Clock "A". Touch the red probe to the common wire on Clock "B". Take a reading.
If 0 to 5 Ohms, the commons are shared.
If infinity (open), the commons are not shared.
(Black/Red -- doesn't matter. Just easier to explain.)

If the probes (likely) won't reach from clock to clock, just run a length of wire from one clock to the other. Lather, rinse, and repeat the above.

Now, best option? Install ONE controller that has enough stations to handle everything. Then you can safely pull all the commons into one terminal. Problem solved.

There is another option but I am not a huge fan. Install an isolation relay between the two controllers. I attached a relay design using a Hunter REL2 relay. This would be a last resort option, in my opinion.

Shared commons can cause controllers to do some strange things. It is also a violation of the National Electric Code (NEC). The NEC office in Washington, DC happens to be next door to the "Do not remove this tag from your mattress under penalty of law" Department. :laugh: Meaning that people don't always take these NEC regulations seriously.

Protect yourself from any liability and just install a higher capacity controller. The disadvantage of installing a relay is this...When Clock "A" is irrigating, Clock "B" will have no connection to the field (and vice-versa). It will NOT irrigate until Clock "A" finishes his cycle. For that reason you cannot overlap start times. Not that you want to, but once you leave the property anything can happen and you might get the blame for dead plant material.

I hope this helps. And sorry, I will be offline through the weekend but I will check back next week. Good luck! Make a sale!
Where are you going?
 

HunterTekGeek

LawnSite Senior Member
Location
San Marcos, CA
Sorry. I wrote my post before I saw Jim or Ron's. We're all on the same page. I know that RB has relay designs too. And because we each sell slightly different relays the schematics will not look the same because of the contact positions/numbers. Any double-pole/double-throw relay will work if you follow the electrical logic.
 

Top