Taco SR502-4 User manual

120 VAC INPUT
TWO ZONE SWITCHING RELAY
CIRCULATORS
ZC
INPUT
120 VAC
ZONE 1 ZONE 2
PRIORITY
ZONE1
ZONE2
PRIORITY
THERMOSTATS
(24 VAC)
SR 502-4
FUSE
6AMP
FUSE
6AMP
FUSE
6AMP
XX RWRW
ISOLATED
END
SWITCH THERMOSTATS
120 VAC
ZR
HHNHNH NH
ZONE 2
POWER
ZONE 1
LED
INDICATORS
ZONE 2
PRIORITY
OFF
ON
TO: "TT" ON
BOILER
JUMPER
24 VAC
COM
120
VAC
See NOTE
120 VAC INPUT
TWO ZONE SWITCHING RELAY
CIRCULATORS
ZC
INPUT
120 VAC
ZONE 1 ZONE 2
PRIORITY
ZONE1
ZONE2
PRIORITY
THERMOSTATS
(24 VAC)
SR 502-4
FUSE
6 AMP
FUSE
6AMP
FUSE
6AMP
XXRWRW
ISOLATED
END
SWITCH THERMOSTATS
120 VAC
ZR
HHNHNH NH
ZONE 2
POWER
ZONE 1
LED
INDICATORS
ZONE 2
PRIORITY
OFF
ON
120
VAC
TO: "ZC"
ON BOILER
TO: "ZR"
ON BOILER
24 VAC
COM
See NOTE
O eration: When any thermostat calls for heat, the appropriate circu-
lator is energized and the isolated end switch (X and X) will start the
boiler.
Priority O eration: When zone 2 is switched to the priority setting
and is actuated, all other zones will stop operation until zone 2 is sat-
isfied. When zone 2 is not switched to priority, all zones will operate
independently.
Priority Protection O eration: When the priority switch is set to ON,
and if the priority zone calls continuously for more than one hour,
power is returned to all the other zones, allowing each zone to function
independently. Once the priority zone is satisfied, the control’s auto-
reset is activated and the priority zone is again allowed to have priority
for up to one hour starting from when it calls next.
Jum er Placement: The jumper should be placed between terminals
ZC and ZR. Connect the isolated end switch to the aquastat control on
the boiler.
Power In ut: Connect 120 volt ac power input to terminals N and H.
Neutral wire to terminal N. Hot wire to terminal H.
O eration: When any thermostat calls for heat, the boiler is given a
signal to start. The appropriate circulator is energized only when the
boiler temperature is above the set low limit.
Priority O eration: When zone 2 is switched to the priority setting
and is actuated, all other zones will stop operation until zone 2 is sat-
isfied. When zone 2 is not switched to priority, all zones will operate
independently.
Priority Protection O eration: When the priority switch is set to ON,
and if the priority zone calls continuously for more than one hour,
power is returned to all the other zones, allowing each zone to function
independently. Once the priority zone is satisfied, the control’s auto-
reset is activated and the priority zone is again allowed to have priority
for up to one hour starting from when it calls next.
Jum er Placement: REMOVE the jumper between terminals ZC and
ZR. Connect terminal ZC to ZC on the aquastat control. Connect ter-
minal ZR to ZR on the aquastat control. Confirm polarity is consistent
between boiler aquastat and switching relay.
Power In ut: Connect 120 volt ac power input to terminals N and H.
Neutral wire to terminal N. Hot wire to terminal H.
Cold Start Boiler
A lication:
Tankless Coil Boiler A lication:
(Alternative Wiring)
Instruction Sheet
SR502-4 Switching Relay
102-377
SUPERSEDES: March 1, 2013 EFFECTIVE: D c mb r 20, 2013
Plant ID# 9300-2866
WARNING: When using Alternative Wiring diagram, wiring instruc-
tions must be followed so power originates from the boiler aquastat.
Failure to follow these wiring instructions may result in a secondary
source of power being connected to the boiler that may activate it
under certain circumstances, causing injury or death.
S ecifications:
PRODUCT NUMBER INPUT MAXIMUM TYPE 1 ENCLOSURE
NUMBER OF ZONES VOLTAGE COMBINED LOAD WIDTH HEIGHT DEPTH
SR502- 2 with Priority 120/60/1 VAC 15 amps 103/" 7" 23/"
All circulator relay connections, including ZC/ZR, are rated 1/3hp (6 FLA, 36 LRA) at 120 VAC.
End switch connections are rated 2 VAC, 1 amp.
All thermostat connections supply a 2 VAC class 2 output.
This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device
may not cause harmful interference, and (2) this device must accept any interference received, including interference
that may cause undesired operation.
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. 12-1 gauge
wire recommended for 120 VAC connections, 14-22 gauge wire for thermo-
stat connections, and 14-22 gauge wire for 24 VAC source connections.
NOTE: Resistor (1KΩ, 1⁄2W) may be needed
between Wand Cterminals.
Troubleshooting:
• Problem: Digital thermostats do not work correctly when connected
to a switching relay.
• Solution: Some thermostats are a “Power Stealing” type which means
they are powered by the switching relay with just 2 wires (R& W). A
resistor may be needed in order to have the thermostat work properly.
This resistor should be placed between the W& C(common) termi-
nals of the switching relay. If the thermostat manufacturer does not
supply a resistor, a 1000 ohm ½ watt resistor has proven to work with
most models and is readily available at electronic supply outlets (e.g.
Radio Shack). If the thermostat is battery powered, then check that
the batteries are fresh and installed correctly.
• Problem: No heat in a zone or room of building.
• Solution: LED diagnostic lights will help find a component that is
not working properly. The green LED should always be on, indicating
that power is connected and the solid-state fuse is good. When there
is a call for heat, the red LED will come on indicating power to the
zone circulator. This indicates the thermostat is working correctly. If
the red LED does not come on, then check the thermostat and ther-
mostat wiring for errors.
For information on Taco’s Switching Relays (SR)
including catalog sheet, instruction sheets, Visio
stencils and our highly praised Zone Controls
Wiring Guide, scan the QR code to the left or go to
our website: http://www.taco-hvac.com.

Do it Once. Do it Right.®
TACO, INC., 1160 Cranston Str t, Cranston, RI 02920 T l phon : [phone] FAX: [phone].
TACO (Canada), Ltd., 8450 Lawson Road, Unit #3, Milton, Ontario L9T 0J8. T l phon : 905/564-9422. FAX: [phone].
Vi it our web ite at: http://www.taco-hvac.com
Print d in USA
Copyright 2013
TACO, Inc.
Taco, Inc. will r pair or r plac without charg
(at th company’s option) any product or part
which is prov n d f ctiv und r normal us
within thr (3) y ars from th dat of start-up or
thr (3) y ars and six (6) months from dat of
shipm nt (which v r occurs first).
In ord r to obtain s rvic und r this warranty, it
is th r sponsibility of th purchas r to promptly
notify th local Taco stocking distributor or Taco
in writing and promptly d liv r th subj ct prod-
uct or part, d liv ry pr paid, to th stocking dis-
tributor. For assistanc on warranty r turns, th
purchas r may ith r contact th local Taco
stocking distributor or Taco. If th subj ct prod-
uct or part contains no d f ct as cov r d in this
warranty, th purchas r will b bill d for parts
and labor charg s in ff ct at tim of factory
xamination and r pair.
Any Taco product or part not install d or op rat-
d in conformity with Taco instructions or which
has b n subj ct to misus , misapplication, th
addition of p trol um-bas d fluids or c rtain
ch mical additiv s to th syst ms, or oth r
abus , will not b cov r d by this warranty.
If in doubt as to wh th r a particular substanc
is suitabl for us with a Taco product or part, or
for any application r strictions, consult th
applicabl Taco instruction sh ts or contact
Taco at [401-942-8000].
Taco r s rv s th right to provid r plac m nt
products and parts which ar substantially simi-
lar in d sign and functionally quival nt to th
d f ctiv product or part. Taco r s rv s th right
to mak chang s in d tails of d sign, construc-
tion, or arrang m nt of mat rials of its products
without notification.
TACO OFFERS THIS WARRANTY IN LIEU OF
ALL OTHER EXPRESS WARRANTIES. ANY
WARRANTY IMPLIED BY LAW INCLUDING
WARRANTIES OF MERCHANTABILITY OR FIT-
NESS IS IN EFFECT ONLY FOR THE DURATION
OF THE EXPRESS WARRANTY SET FORTH IN
THE FIRST PARAGRAPH ABOVE.
THE ABOVE WARRANTIES ARE IN LIEU OF ALL
OTHER WARRANTIES, EXPRESS OR STATU-
TORY, OR ANY OTHER WARRANTY OBLIGA-
TION ON THE PART OF TACO.
TACO WILL NOT BE LIABLE FOR ANY SPE-
CIAL, INCIDENTAL, INDIRECT OR CONSE-
QUENTIAL DAMAGES RESULTING FROM THE
USE OF ITS PRODUCTS OR ANY INCIDENTAL
COSTS OF REMOVING OR REPLACING
DEFECTIVE PRODUCTS.
This warranty giv s th purchas r sp cific
rights, and th purchas r may hav oth r rights
which vary from stat to stat . Som stat s do
not allow limitations on how long an impli d war-
ranty lasts or on th xclusion of incid ntal or
cons qu ntial damag s, so th s limitations or
xclusions may not apply to you.
LIMITED WARRANTY STATEMENT
Two Standard Switching Relays Connected Together (SR502 – SR506)
BOILER
H
N
AAQUASTAT ON
DHW HEATER
TT T
120 VAC INPUT
JUMPER
TT T
120 VAC INPUT
TO: "TT" ON BOILER
JUMPER
DHW
HEATER
CIRCULATOR
OUTPUT
NOT
USED
FOUR ZONE SWITCHING RELAY
120 VAC CIRCULATORS
ZC
INPUT
120 VAC
ZONE 1 ZONE 2 ZONE 3 ZONE 4
ZONE1 ZONE2 ZONE3
SR 504-4
FUSE
6AMP
FUSE
6 AMP
FUSE
6 AMP
FUSE
6AMP
FUSE
6AMP
XX RW RW
RW
RW
ISOLATED
END
SWITCH THERMOSTATS (24 VAC)
PRIORITY
120 VAC
ZR
HHNHNHNHNH NH
ZONE4
ZONE 2
POWER
ZONE 1
ZONE 3
ZONE 4
LED
INDICATORS
ZONE 4
PRIORITY
OFF
ON
PRIORITY
FOUR ZONE SWITCHING RELAY
120 VAC CIRCULATORS
ZC
INPUT
120 VAC
ZONE 1 ZONE 2 ZONE 3 ZONE 4
ZONE1 ZONE2 ZONE3
SR 504-4
FUSE
6 AMP
FUSE
6AMP
FUSE
6AMP
FUSE
6 AMP
FUSE
6 AMP
XX RW RW
RW
RW
ISOLATED
END
SWITCH THERMOSTATS (24 VAC)
PRIORITY
120 VAC
ZR
HHNHNHNHNH NH
ZONE4
ZONE 2
POWER
ZONE 1
ZONE 3
ZONE 4
LED
INDICATORS
ZONE 4
PRIORITY
OFF
ON
PRIORITY
TO: "TT" ON BOILER
24 VAC
COM
24 VAC
COM
Optional power stealing thermostat resistor part number: SRTR-001RP
(Value: 1000 Ohms, 1/2 watt or higher)
Replacement Switching Relay fuses part number: SR6A-001RP
(Manufacture: Littlefuse, Part Number: 229006)