3-way relay for sprinklers

I want to be able to control my lawn sprinklers from two different switches. 24v turns the sprinklers on. The first one being the regular sprinkler timer control box that is already installed on the side of the house (let's just call this the "control box"). The second being a pool automation base (it's a Hayward Omnilogic pool automation base, let's call this "Omnilogic") which has 24v relays I can turn on/off with my cell phone as it's networked with my home network.

The reason I want to be able to turn them on from either the control box or the Omnilogic is so the lawn maintenance guys can still set the timers from the control box they are use to using but then I also have the ability to turn the sprinklers on with my cell phone through the Omnilogic. I do not need to be able to turn them off with my cell phone if the timer has turned them on or be able to turn them off with the timer if the Omnilogic turned them on. In other words, what I think I need is a 3-way switch that allows 24v to pass through to switch the sprinklers on when either the control box or the Omnilogic is on but not double up the voltage if both are on. I think a 3-way relay would accomplish this purpose. Am I thinking of this correctly?

What switch would I need? I would like it to be as small as possible as I will leave them inside the control box. I have some soldering skills, so I can solder the connections if I need to.

Is there anything else I would need to consider?

A relay would be simplest. Not sure what you mean by 3-way. Relays are defined in terms of "poles" and "throw".

If I read you correctly, what you want would be accomplished by getting a relay with multiple poles (or get multiple discrete relays, same thing really just split up instead of being all-in-one) but wiring the primary contacts in parallel and then wiring the individual coils to separate control sources. That way, multiple sources can drive the coils, but the coils basically all control the same thing.

I don't know what you mean by voltage doubling up either. That won't happen if there's only one 24V source. You just want multiple control sources to be able to connect the sprinklers to the 24V source right?

It's very possible I am using the wrong term. I thought a 3-way switch, like when you are talking about light switches in your house, are where you can turn a light on from either one switch or another.

dknguyen said:

I don't know what you mean by doubling up either. That won't happen if there's only one 24V source.

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There are two discrete 24V power sources, one from the control box and one from Omnilogic. So if both are on I think they would be added together and equal 48V on the sprinkler switch unless on was block somehow, right?

jocanon said:

It's very possible I am using the wrong term. I thought a 3-way switch, like when you are talking about light switches in your house, are where you can turn a light on from either one switch or another.

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Oh wait, you want to be able to override things with your phone? Then you need something a bit different than wiring multiple relay primary contacts in parallel and running the coils to separate control sources. Doing it that way means any control source can turn it on, and as long as one or more are commanding it to be on, it will stay on. It cannot be turned off unless all control sources say that it is turned off. The simplest way to override is to add in another relay in series with all the parallel primary relay contacts that can disconnect everything.

jocanon said:

There are two discrete 24V power sources, one from the control box and one from Omnilogic. So if both are on I think they would be added together and equal 48V on the sprinkler switch unless on was block somehow, right?

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No. Not unless you stacked the batteries in series somehow which won't be the case. At worst, when both batteries are connected they will be connected in parallel. So they won't "stack up" the voltage. More like each battery will share part of the load. If one battery is significantly discharged though, then the other battery will also drive current into it which isn't always good. But easily rectified with a diode which only allows current to flow in one direction. You wire it so current can only flow out of each the battery. That way, current can never flow from one battery and into the other battery.

Maybe review what connected things in series and parallel do before continuing. This is important and it's real tough to talk to you about things until you do.

Actually, what I was picturing is that any control source would be able to turn it on because I am more concerned about being able to turn it on when it is off and not so much about being able to turn it off when it is on, if that makes sense. However, that being said, if there is a simple way to wire it so my cell phone can override and turn it off even if the control box is on, that would probably be a good idea, wouldn't hurt to have that control. I am just not understanding in my mind how that would work. I mean say for instance the control box is set for the sprinklers to come on every night at 10pm, then wouldn't my Omnilogic have to also be set up to come on at 10pm or it would override and not allow the spriklers to go on. It would be nice if I could have an override button on my phone to turn it off if the control box has it turn on, but unless I select the override then the normal control box can turn it off and on without needing any input from the Omnilogic...I just don't see how that is possible in a simple set up. Maybe I am missing something and it is really very easy to do. Anyway, if all I can do is turn it on but not turn it off from my cell phone if the regular control box is turned on, then that is fine.

I need to verify something. You say the system has 24V relays. Do these relays actually connect to the 24V battery? Or are they just contacts that connect two points together than can handle 24V? There's a difference.

Go into chat please. Top of the page.

dknguyen said:

Maybe review what connected things in series and parallel do before continuing. This is important and it's real tough to talk to you about things until you do.

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Actually, now that you mention it, I totally get it. That makes sense.

As we discussed in chat:

The timer box and Omnilogic box each have one primary contact permanently connected to their own 24V source.
No external relays needed. Can use relays internal to boxes.
Only need to override things to be ON.
Override to turn things off not needed.

Sprinkler systems often operate from 24Vac.
Are we talking AC or DC here?

All the systems I've come across in Australia use 24Vac.

Mike.

crutschow said:

Sprinkler systems often operate from 24Vac.
Are we talking AC or DC here?

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He said they were being powered from batteries being charged from the line. But yeah, if AC, you can't mix unless they are in sync and equal (identical). Also no diodes. Best to disconnect one before connecting the other in that case.

dknguyen said:

He said they were being powered from batteries being charged from the line. But yeah, if AC, you can't mix unless they are in sync and equal (identical). Also no diodes. Best to disconnect one before connecting the other in that case.

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No where above does he mention batteries.

Mike.

Pommie said:

No where above does he mention batteries.

Mike.

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In our chat.

dknguyen said:

In our chat.

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Asking an OP to go to chat is really a crappy move for the rest of us.

gophert said:

Asking an OP to go to chat is really a crappy move for the rest of us.

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I understand. Problem is that in posts like this where there's a few ways things could be set up and the OP doesn't know the proper temrinology, there is so much back and forth trying to figure out what the poster actually has in front of him that the thread becomes 4 pages long just to get to that point where you think you know, but still can't be sure which is why I did what I did.

dknguyen said:

I understand. Problem is that in posts like this where there's a few ways things could be set up and the OP doesn't know the proper temrinology, there is so much back and forth trying to figure out what the poster actually has in front of him that the thread becomes 4 pages long just to get to that point where you think you know, but still can't be sure which is why I did what I did.

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Well then you may now why you did what you did, but we sure as heck don't.
If want to have you own little private chat, that's fine, but don't bring us back in the middle of it.
That's really poor form.