Operation: When the thermostat calls for heat, the circulating pump
is energized and the isolated end switch (X and X) will start the boiler.
Priority Operation: When the priority dip switch is set to ON and the
zone is actuated, all other connected zoning panels will stop operation
until the zone is satisfied. When the priority dip switch is set to OFF
and the zone is actuated, all other connected zoning panels will oper-
ate independently.
Mode Operation: When the mode dip switch is set to NORMAL, the end
switch relay will be energized if any zone is in operation. When the mode
dip switch is set to RESET, the end switch relay will only be energized
through the operation of a plug-in reset control or closure of Priority Input.
Primary Pump Operation: When the dip switch is set to OFF, the pri-
mary circulating pump output will not energize when zone calls for
heat. When the dip switch is set to ON, the primary circulating pump
output will energize when zone calls for heat.
Post Purge Operation: When the dip switch is set to ON, the circula-
tion pump output will stay energized for 2 minutes after its thermostat
or aquastat is satisfied, but not operate the boiler.
Priority Protection Operation: When the dip switch is set to ON and
the zone (priority) on master zone panel calls for heat continuously for
more than one hour, then power is returned to the space heating zones
allowing all the zones to function independently. Once the zone (pri-
ority) on master zone panel is satisfied, the control’s auto-reset is acti-
vated and the zone is again allowed to have priority for up to one hour.
Pump Exercise Operation: When the dip switch is set to ON, the solid
state timer cycles all the circulating pumps that are attached to the
Expandable Switching Relay at the selected time interval. The time
interval can be set for the pumps to run for either 30 seconds every 2
weeks or for 4 minutes every 24 hours.
End Switch: The switch closes when the thermostat calls for heat and
the mode switch is set to NORMAL. The end switch also closes when
the mode switch is set to RESET and a PC Series boiler reset power con-
trol is calling for heat.
Expansion Connections: Set the expansion switch to MASTER on the
switching relay that has the designated priority zone or is utilizing the
PC Series plug-in option. Set all other daisy chained controls to SLAVE.
Using thermostat wire (18-22 gauge) connect between terminals A, B,
C on the master control to the corresponding A, B, C on the SLAVE
control(s). Controls may be daisy chained up to 20 zoning panels using
any combination of -EXP controls (120 zones if all are 6 zone panels).
Thermostat Input (24 vac):
RHot side of transformer. Connect to Ron thermostat.
WSwitched R signal from thermostat. Connect to W on thermostat.
CCommon side of transformer. Connect to COM on
thermostat (optional).
120 VAC Connections (N is Neutral, H is Hot):
Power Input Connect 120 Volt AC power.
Primary Primary Pump (optional)
N/O Zone Circulator Zone
N/C Zone Normally closed terminal for the Circulator Zone.
Will deactivate on a thermostat call.
NConnect to pump neutral leads.
External Diagnostics: Externally visible lights show full functionality of the
switching relay. The green light should always be on, indicating that power is
connected. When the thermostat calls for heat, both the appropriate circulator
and red indicating light are energized.
WARNING: Wiring connections must be made in accordance with all applicable electrical codes. Use copper wire only. 120 VAC wiring must have
a minimum temperature rating of 75°C. Failure to follow this instruction can result in personal injury or death and/or property damage. 12-18 gauge
wire recommended for 120 VAC connections, 14-22 gauge wire for thermostat connections, and 14-22 gauge wire for 24 VAC source connections.
Wiring Diagram:
Instruction Sheet
SR501-EXP-4 Switching Relay
102-385
SUPERSEDES: New EFFECTIVE: May 1, 2010
Plant ID# 9300-2872
Features:
Front External Indicator Lights
Ideal for Retrofitting
Primary Circulator Output
Simplified Wiring
Add-On Power Controls
Sealed Relays
Compact Design
Fuse Protected
100% Factory Tested
Isolated End Switch
UL Approved
Expandable to 20 Zoning Panels
(120 zones if all are 6 zone
panels)
Contractor Friendly PC Board
Layout
Universal Thermostat
Compatibility
24 volt Power Input or Output
Terminal
Extended 3 Year Warranty
Made in the USA
