The drawing below is used to isolate two controllers when
the same common wire is connected to both controllers. This
is referred to as a "looped" common. Be
aware that interconnecting the controller transformers is
in violation of National Electric Code, do not do this!
Other than the fact that this is a code violation, it can
also damage the controllers.
How Can This Happen
The most widespread cause of a looped common is connecting
the remote control valves to multiple controllers. Other ways
to loop the common are with accessory devices connected to
the controllers. Any device that uses the common wire and
is connected to multiple controllers will result in a looped
common. These devices include: master valves, pump start relays,
rain sensors, freeze sensors, soil moisture sensors, and remote
controls. These devices must use a relay or relays to isolate
the common wire.
What Does The Relay Do
A relay in this design allows only one controller at a time
to be connected to the common. If controller A is on, its
master valve circuit energizes the relay so contacts 4 and
7 are now connected, this disconnects the common from controller
B. When controller A turns off, the relay connects the common
to controller B through contacts 9 and 3. If both controllers
operate at the same time, the common will be connected to
controller A, and controller B will not operate.
What Components To Use
The drawing is designed around components that should be
readily available at your local electronics store or from
Newark Electronics. The installation will be easier if a relay
socket is used, this allows for easier mounting and replacement..
Device
Description
Part Number
NTE
Part Number
Newark
Relay
24 VAC coil
DPDT
10 amp contacts
R10-11A10-24
24F2611
Socket
11-Pin
Panel/Surface Mount
R95-105
57F3430
Wiring
For ease of installation, it is recommended that relay sockets
are used. The sockets have tabs for mounting purposes, and
allows easy replacement of a defective relay. The drawing
below details the terminal screw positions for the specified
sockets. This is the top view of the socket.
What Other Designs Are Available
Many additional designs are available by calling the Rain
Bird Specification Hotline 1-800-458-3005.
