Control wiring question

[Ira]

Hypothetically, let's say that I have a four zone irrigation system that I want to control from two different controllers (maybe a Rain8 and a Hunter Pro-C contoller). It's an either or situation. Either the Rain8 is controlling all four zones or the Pro-C is controlling all four zones. No other possibilities. Both controllers are powered by the same 24Vac power supply, and it has plenty of power to do the job. I can use a 4PDT relay to switch between controllers. A lead from each of the four zone valves connects to the "common" terminal for each of the four poles on the relay, e.g., zone one valve connects to pole one common, zone two valve connects to zone two common. The four zone valve outputs from the Rain8 are connected to the four N/C terminals on the relay. The four zone valve outputs on the Pro-C are connected to the N/O terminals on the relay. The coil side of the relay is controlled by a simple SPST toggle switch that provides 24Vac (from the same power supply) to the relay coil when the toggle switch is closed. So, when the toggle switch is closed, the coil is energized, the relay contacts are closed, and the four zone valves are under the control of the Rain8. When the toggle switch is open, the coil is not energized, the relay contacts are open, and the four zone valves are controlled by the Pro-C.

My question...does the 24Vac common wire from the controllers to zone valves need to be switched by a relay also, or can I simply connect the commons from both controllers to the common going to the valves, and leave it that way regardless of which controller is "on"? Note that both controllers will be powered up at all times.

Thanks,
Ira

 

[nov0798]

Dont know if this will help, but I think this guy already did this.

http://m1sprinkler.blogspot.com/2006_08_01_archive.html

 

[Ira]

Dont know if this will help, but I think this guy already did this.

http://m1sprinkler.blogspot.com/2006_08_01_archive.html

Unless there's more to the setup than his diagram shows, it looks like both of his controllers (the irritrol and the M1G) are "operational" at the same time, e.g., they can both send power to the zone one valve at the sime time. In my setup, I want to only have one controller physically connected to the zone valves at a time. That's done by the toggle switch and relay. Either the Rain8 is controlling all the valves or the Pro-C is controlling all the valves.

So my question remains...do I need to switch the common wires, too?

Thanks,
Ira

 

[Sandpiper]

Dont know if this will help, but I think this guy already did this.

http://m1sprinkler.blogspot.com/2006_08_01_archive.html

Unless there's more to the setup than his diagram shows, it looks like both of his controllers (the irritrol and the M1G) are "operational" at the same time, e.g., they can both send power to the zone one valve at the sime time. In my setup, I want to only have one controller physically connected to the zone valves at a time. That's done by the toggle switch and relay. Either the Rain8 is controlling all the valves or the Pro-C is controlling all the valves.

So my question remains...do I need to switch the common wires, too?

Thanks,
Ira

No. You do not need to switch the common wires. The commons can be tied together with a single common going to each of the two controllers, which should also be tied to the transformer common.

By the way. I assume the relay you have chosen has a 24VAC coil, correct?

 

[Ira]

No. You do not need to switch the common wires. The commons can be tied together with a single common going to each of the two controllers, which should also be tied to the transformer common.

By the way. I assume the relay you have chosen has a 24VAC coil, correct?

Yes, I'm using this relay "kit". The transformer I'm looking at is 100VA at 24Vac, so it should easily handle all of this.

Thanks,
Ira