Taco SR502 User manual

Operation: Wh n any th rmostat calls for h at, th appropriat circu-
lator is n rgiz d and th isolat d nd switch (X and X) will start th
boil r.
Priority Operation: Wh n zon 3 is switch d to th priority s tting
and is actuat d, all oth r zon s will stop op ration until zon 3 is sat-
isfi d. Wh n zon 3 is not switch d to priority, all zon s will op rat
ind p nd ntly.
Priority Protection Operation: Wh n th priority switch is s t to ON,
and if th priority zon calls continuously for mor than on hour,
pow r is r turn d to all th oth r zon s, allowing ach zon to function
ind p nd ntly. Onc th priority zon is satisfi d, th control’s auto-
r s t is activat d and th priority zon is again allow d to hav priority
for up to on hour starting from wh n it calls n xt.
Jumper Placement: Th jump r should b plac d b tw n t rminals
ZC and ZR. Conn ct th isolat d nd switch to th aquastat control on
th boil r.
Power Input: Conn ct 120 volt ac pow r input to t rminals N and H.
N utral wir to t rminal N. Hot wir to t rminal H.
Operation: Wh n any th rmostat calls for h at, th boil r is giv n a
signal to start. Th appropriat circulator is n rgiz d only wh n th
boil r t mp ratur is abov th s t low limit.
Priority Operation: Wh n zon 3 is switch d to th priority s tting
and is actuat d, all oth r zon s will stop op ration until zon 3 is sat-
isfi d. Wh n zon 3 is not switch d to priority, all zon s will op rat
ind p nd ntly.
Priority Protection Operation: Wh n th priority switch is s t to ON,
and if th priority zon calls continuously for mor than on hour,
pow r is r turn d to all th oth r zon s, allowing ach zon to function
ind p nd ntly. Onc th priority zon is satisfi d, th control’s auto-
r s t is activat d and th priority zon is again allow d to hav priority
for up to on hour starting from wh n it calls n xt.
Jumper Placement: REMOVE th jump r b tw n t rminals ZC and
ZR. Conn ct t rminal ZC to ZC on th aquastat control. Conn ct t r-
minal ZR to ZR on th aquastat control. Confirm polarity is consist nt
b tw n boil r aquastat and switching r lay.
Power Input: Conn ct 120 volt ac pow r input to t rminals N and H.
N utral wir to t rminal N. Hot wir to t rminal H.
Cold Start Boiler
Application:
Tan less Coil Boiler Application:
(Alternative Wiring)
Instruction Sheet
SR503-4 Switching Relay
102-379
SUPERSEDES: December 20, 2013 EFFECTIVE: January 18, 2017
Plant ID# 9300-2867
WARNING: Wh n using Alt rnativ Wiring diagram, wiring instruc-
tions must b follow d so pow r originat s from th boil r aquastat.
Failur to follow th s wiring instructions may r sult in a s condary
sourc of pow r b ing conn ct d to th boil r that may activat it
und r c rtain circumstanc s, causing injury or d ath.
Specifications:
P ODUCT NUMBE INPUT MAXIMUM TYPE 1 ENCLOSU E
NUMBE OF ZONES VOLTAGE COMBINED LOAD WIDTH HEIGHT DEPTH
S 503-4 3 with Priority 120/60/1 VAC 15 amps 121/4" 8" 3"
All circulator relay connections, including ZC/Z , are rated 1/3hp (6 FLA, 36 L A) at 120 VAC.
End switch connections are rated 24 VAC, 1 amp.
All thermostat connections supply a 24 VAC class 2 output.
WARNING: Wiring conn ctions must b mad in accordanc with all
applicabl l ctrical cod s. Us copp r wir only. 120 VAC wiring must hav
a minimum t mp ratur rating of 75°C. Failur to follow this instruction
can r sult in p rsonal injury or d ath and/or prop rty damag . 12-18 gaug
wir r comm nd d for 120 VAC conn ctions, 14-22 gaug wir for th rmo-
stat conn ctions, and 14-22 gaug wir for 24 VAC sourc conn ctions.
This device complies with part 15 of the FCC ules. 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.
NOTE: R sistor (1KΩ, 1⁄2W) may b n d d
b tw n Wand Ct rminals.
Troubleshooting:
• Problem: Digital th rmostats do not work corr ctly wh n conn ct d
to a switching r lay.
• Solution: Som th rmostats ar a “Pow r St aling” typ which m ans
th y ar pow r d by th switching r lay with just 2 wir s (R& W). A
r sistor may b n d d in ord r to hav th th rmostat work prop rly.
This r sistor should b plac d b tw n th W& C(common) t rmi-
nals of th switching r lay. If th th rmostat manufactur r do s not
supply a r sistor, a 1000 ohm ½ watt r sistor has prov n to work with
most mod ls and is r adily availabl at l ctronic supply outl ts ( .g.
Radio Shack). If th th rmostat is batt ry pow r d, th n ch ck that
th batt ri s ar fr sh and install d corr ctly.
• Problem: No h at in a zon or room of building.
• Solution: LED diagnostic lights will h lp find a compon nt that is not work-
ing prop rly. Th gr n LED should always b on, indicating that pow r is con-
n ct d and th solid-stat fus is good. Wh n th r is a call for h at, th r d
LED will com on indicating pow r to th zon circulator. This indicat s th
th rmostat is working corr ctly. If th r d LED do s not com on, th n ch ck
th th rmostat and th rmostat wiring for rrors.
For information on Taco’s Switching R lays (SR)
including catalog sh t, instruction sh ts, Visio
st ncils and our highly prais d Zon Controls
Wiring Guid , scan th QR cod to th l ft or go to
our w bsit : http://www.taco-hvac.com.

Taco, Inc. will repair or replace without charge (at
the company’s option) any product or part which
is proven defective under normal use within three
(3) years from the date of start-up or three (3)
years and six (6) months from date of shipment
(whichever occurs first).
In order to obtain service under this warranty, it is
the responsibility of the purchaser to promptly
notify the local Taco stocking distributor or Taco
in writing and promptly deliver the subject prod-
uct or part, delivery prepaid, to the stocking dis-
tributor. For assistance on warranty returns, the
purchaser may either contact the local Taco
stocking distributor or Taco. If the subject product
or part contains no defect as covered in this war-
ranty, the purchaser will be billed for parts and
labor charges in effect at time of factory exami-
nation and repair.
Any Taco product or part not installed or operat-
ed in conformity with Taco instructions or which
has been subject to misuse, misapplication, the
addition of petroleum-based fluids or certain
chemical additives to the systems, or other
abuse, will not be covered by this warranty.
If in doubt as to whether a particular substance is
suitable for use with a Taco product or part, or for
any application restrictions, consult the applica-
ble Taco instruction sheets or contact Taco at
[401-942-8000].
Taco reserves the right to provide replacement
products and parts which are substantially simi-
lar in design and functionally equivalent to the
defective product or part. Taco reserves the right
to make changes in details of design, construc-
tion, or arrangement of materials 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
FITNESS 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
STATUTORY, OR ANY OTHER WARRANTY
OBLIGATION ON THE PART OF TACO.
TACO WILL NOT BE LIABLE FOR ANY SPE-
CIAL, INCIDENTAL, INDIRECT OR CONSE-
UENTIAL DAMAGES RESULTING FROM THE
USE OF ITS PRODUCTS OR ANY INCIDENTAL
COSTS OF REMOVING OR REPLACING
DEFECTIVE PRODUCTS.
This warranty gives the purchaser specific rights,
and the purchaser may have other rights which
vary from state to state. Some states do not
allow limitations on how long an implied warranty
lasts or on the exclusion of incidental or conse-
quential damages, so these limitations or exclu-
sions may not apply to you.
LIMITED WARRANTY STATEMENT
Two Standard Switching Relays Connected Together (SR502 – SR506)
Optional power stealing thermostat resistor part number: S T -001 P
(Value: 1000 Ohms, 1/2 watt or higher)
eplacement Switching elay fuses part number: S 6A-001 P
(Manufacture: Littlefuse, Part Number: 229006)
A Taco Family Company
2017