Relay Panels
Relays are installed in a relay panel. Douglas panels for 6, 12, 24, 36, 48 and 72 relay capacity are available.
Size the panel to allow for future expansion.
Install the required amount of relays and add when necessary.
Douglas LitePak panels (8 relays, expandable to 16 relays with an Expansion Pak) are designed for small projects.
Panel Location
The load (lighting or other) must be connected to the relay.
In most cases, it is best to locate the relay panel adjacent
to the circuit breaker panel.
In some cases, though, there is less wiring if a small panel
is located nearer to the load. This can occur where several
rooms share the same circuit breaker.
Panel Wiring -Line Voltage
Relay panels have a line voltage compartment for the lighting loads and a low voltage compartment for the relay controls.
Install conduit to panels at the appropriate locations.
The line voltage compartment can be partitioned to support different voltages or voltage sources.
In the diagram above, a partition exists for 120V and 277V sections.
Connect from the breaker to the relay and then to the load. In some cases, one circuit breaker services several switched loads.
If so, parallel the breaker wire feed to several relays and then run the individual switch legs to the loads.
Neutral wires are routed back to the breaker panel and connect to the neutral terminals.
Low Voltage Controls -Panel Wire Types
Low voltage lighting control wiring for relays, switches
and transformers is class 2 rated, 18 AWG. Solid wire is recommended
as it is easier to terminate and there are no strands that
could cause shorts.
For panels that are digitally networked, conductors rated
for data signal connection are required. Refer to the product
specifications for data wire types.
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Low Voltage Controls -Panel Wiring Strategy
Relays only require power when they are switched. Switching a relay requires only one electrical sine wave (17 milliseconds).
Thus, one control transformer can be used for many relays.
When relays are switched as a group by a relay scanner device, the scanner sequences the relays ON or OFF.
Thus, only the relays connected to one scanner output are switched at any given moment.
In most cases a relay panel only has one transformer. A common wire is supplied to all of the remote switches and each
switch has a control wire that connects to the appropriate relay or scanner input.
If there are several panels interconnected and wire distances are less than 500 feet (150 meters) it may prove practical to use one transformer for all of the panels.
In larger projects, each panel usually has its own transformer. Local switches use this transformer to switch the relays.
If a relay scanner is installed in the panel, the scanner also uses the panel’s transformer to switch the relays.
The scanner’s switch inputs are an isolated circuit. This permits a transformer located elsewhere to be used to switch the inputs of
all scanners in all panels, permitting a building-wide control scheme.
Wire Distance from Panels
Allowable wire distances from the relay to the 2-wire switch
that controls it are shown in the following list.
1.5 A & 3.0A RATED SWITCHES
applies to all Douglas 2-wire wall switches, sensors and relay
control devices
1 relay/switch: 2000'/600m wire length
2 relays/sw: 1500'/450m wire length
3 relays/sw: 1000'/300m wire length
4 relays/sw: 500'/150m wire length
3.0A RATED SWITCHES
applies to Douglas WR-8001, WRK-8001 and élan 2-wire
switches only
6 relays/sw: 300'/90m wire length
8 relays/sw: 150'/50m wire length
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