Manufacturer: Johnson Controls |
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Description: CIRCULATING PUMP SEQUENCER
Category: Electrical Controls
S-7300 Circulating
Pump Sequencer
The Johnson Controls S-7300
Circulating Pump Sequencer* is
an automatic electric switching
device designed to automatically
activate a “standby” circulating
pump whenever the operating
pump fails. By cutting in the
standby unit, the S-7300
provides added protection
against potential damages from
coil freeze-ups, equipment
overload strain and other such
related problems.
The S-7300 employs a solidstate
time delay relay and low
voltage control circuitry. It is
housed in a sturdy, surface
mounted cabinet, with knockouts
on the top and bottom. The face
plate has a “Lead Pump” manual
selector switch, a “Reset” button,
and green “Flow-Normal” and
red lead pump “Failure” pilot
lights mounted on it. Both pilot
lights have a “Press-to-Test”
feature.
The Sequencer is also equipped
for the addition of an outdoor air
thermostat. The thermostat will
open the circuit on a rise in
temperature, stopping the
operating pump. Operation is
automatically resumed when the
temperature drops down below
the set point.
Operation
In a circulating pump application
two circulating pumps are
ordinarily used in the water line:
a lead or main operating pump
and a standby or backup pump.
The “Lead Pump” manual
selector switch is placed in
either the “P-1” or “P-2” position
for selection of the lead pump.
The green pilot light indicates a “Flow-Normal” condition
whenever either pump P-1 or
P-2 is operating. If the lead
pump should fail, the SPDT
pressure differential or flow
switch alerts the sequencer and
energizes its time delay relay,
turning off the green “Flow-Normal”
pilot light. If the flow is
interrupted for more than thirty
seconds, the time delay relay will
simultaneously deenergize the
lead pump, energize the standby
pump, activate the red “Lead
Pump Failure” pilot light, and
trigger the optional alarm, if
included.
*The S-7300 Circulating Pump
Sequencer was tested under
Underwriters Laboratories, Inc. Standard 873, Temperature
Indication and Regulating
Equipment, and is U.L. listed
(Guide XAPX, File E27734).
When normal flow has been
restored, the green “Flow-
Normal” pilot light will be
activated, indicating both a
return to normal flow conditions,
and that the standby pump has
replaced the lead pump.
After the cause of the
interruption has been eliminated,
by repairing or replacing the lead
pump, the “Reset” button must
be depressed to reestablish the
initial lead-standby sequence
and turn off the red “Lead Pump
Failure” pilot light. The
continuous indication of thegreen“Flow-Normal” pilot light
again indicates lead pump
operation.
The “Lead-Pump” manual
selector switch can be placed in
either the “P-1” or “P-2” position.
In case of lead pump “Failure”,
the sequencer will always index
to the standby pump, P-2 or P-1,
no matter which pump is
selected as the lead pump, P-
or P-2. In the event of power
failure, the sequencer will
immediately start the lead pump
when power is restored. If the
lead pump has failed, the
standby pump will begin
operating after the 30 second
flow interruption.
Mounting
The Johnson Controls S-7300
Circulating Pump Sequencer
may be mounted in any position
on a flat, relatively smooth
surface, with four #10 screws.
Wiring
The S-7300 Sequencer is
provided with line voltage and
relay connections in the top of
the cabinet. A low voltage seven
station terminal strip is located in
the bottom of the cabinet. The
S-7300 U.L. approved wiring
barriers are assembled to permit
line voltage wiring to enter
through the top and low voltage
wiring to enter through the
bottom, remove barrier No. 1;
when low voltage must be routed
through the top, remove barrier
No. 2. Whenever both barriers
are removed, all wires must
have a 600 volt insulation rating.
All wiring must be in accordance
with applicable national and
local electrical codes.
Replaces Part Numbers: S-7300-3, CARS-7300-3