Taco Comfort Solutions FuelMizer SR501-OR-4 User manual

Instruction Sheet
FuelMizer®SR501-OR-4 Switching Relay with Outdoor Reset
A Taco Family Company
102-431
SUPERSEDES: March 1, 2013 EFFECTIVE: December 20, 2013
Plant ID# 9300-2871
MULTI-ZONE INSTALLATION WITH ZONE CONTROL
AND WITH INDIRECT DHW
ONE ZONE
SWITCHING RELAY
WITH OUTDOOR RESET
SR 501OR-4
LED
INDICATORS
POWER
TSTAT
DHW
OVERRIDE
BOILER
RELAY
NH
INPUT
120 VAC
ZONE 1
120 VAC
NH
6
AMP
XR
BOILER TSTAT
WCR W
DHW
OUTDOOR
SENSOR
SUPPLY
SENSOR
X
DESIGN OUTDOOR
TEMPERATURE
FOR 180°F SUPPLY
TEMPERATURE
OFF
-30
-20
0
-10 10
20
40
30
ON
SW1
OFF
SYSTEM
CIRCULATOR
(OPTIONAL)
N
H
POWER
INPUT
(120 VAC)
BOILER
CONTROL
OUTDOOR
SENSOR
BOILER
SUPPLY
SENSOR
POT1
1234
ZONE 1
1234
ZONE 2
1234
ZONE 3
EXISTING
ZONE VALVE CONTROL
POWER IN
24 VAC
N/O COM
N/C
PUMP END
SWITCH
FUSE
5 AMP
ZONE 3 PUMP
END SWITCH
THERMOSTATS
(24VAC)
TSTAT 1 VALVE 1
T STAT 2 VALVE 2
T STAT 3 VALVE 3
POWER
LED
INDICATORS
ZONE 1 ZONE 2 ZONE 3
ISOLATED
XX RW RW RW
END SWITCH THERMOSTATS PRIORITY
24 VAC ZONE VALVES PRIORITY
XX
ZONE 3
PRIORITY
OFF
ON
CCC
2 WIRE ZONE VALVE
(NO END SWITCH)
MUST USE JUMPER TACO 3 WIRE
ZONE VALVE
1
2
3
JUMPER
3 & 4
TACO 3 WIRE
ZONE VALVE
1
2
3
DHW
AQUASTAT
A
CONTROL STRATEGY:
Outdoor Reset:
In order to properly control a hot water heating system, the heat sup-
plied to the building must equal the heat lost by the building.
• The heat supplied to a building is proportional to the temperature of
the supply water and the surface area of the heating element. A
small surface area such as baseboard radiators requires a higher
water temperature than a larger surface area such as radiant floors.
• The heat lost from a building is dependent on the outdoor tem-
perature, as well as other factors. As the outdoor temperature
drops, the building heat loss increases.
Reset Ratio:
Operation of a hot water heating system can generally be improved by
modulating the supply water temperature as the outdoor temperature
changes. Using this approach, the heat lost from the building is
matched by the heat input to the building. The SR501-OR boiler reset
control utilizes a reset ratio to set the relationship between outdoor tem-
perature and supply water temperature. The reset ratio determines the
amount the supply water temperature is raised for every 1° drop in out-
door air temperature, and it is determined from the starting point and
the system design conditions. In order for the control to automatically
determine the reset ratio, outdoor design conditions must be estab-
lished. This is usually the typical coldest outdoor temperature or it can
be set by using AS ARE standards for Design Outdoor Temperature
for specific geographic locations.
APPLICATION:
The SR501-OR is a microprocessor-based control designed to regulate
the supply water temperature of a single boiler, based on the outdoor
temperature. The SR501-OR is a boiler reset control and switching relay
in one unit. The SR501-OR is ideal for retrofit application, but may also
be used in new installations as well.
The SR501-OR includes functions such as automatic reset ratio calcu-
lation, warm weather shut down (WWSD), minimum boiler temperature
setting, and boiler differential setting. The control also has boiler sensor
and outdoor sensor error checking.
40 30 20 10
0
-10
-20
-30
70
-20
90
130
110
150
170
180
190
210
90 80 70 60 50 40 30 20 10 0 -10
OUTDOOR TEMPERATURE (°F)
BOILER SUPPLY TEMPERATURE vs. OUTDOOR TEMPERATURE (°F)
FOR OUTDOOR DESIGN TEMPERATURES
BOILER SUPPLY TEMPERATURE (°F)
For information on Taco’s
Switching Relays (SR)
including catalog sheet,
instruction sheets, Visio sten-
cils and our highly praised
Zone Controls Wiring Guide,
scan the QR code above or
go to our website:
http://www.TacoComfort.com.
ONE ZONE INSTALLATION W/O INDIRECT DHW
ONE ZONE
SWITCHING RELAY
WITH OUTDOOR RESET
SR 501OR-4
LED
INDICATORS
POWER
TSTAT
DHW
OVERRIDE
BOILER
RELAY
NH
INPUT
120 VAC
ZONE 1
120 VAC
NH
6
AMP
XR
BOILER TSTAT
WCR
DHW
OUTDOOR
SENSOR
SUPPLY
SENSOR
X
DESIGN OUTDOOR
TEMPERATURE
FOR 180°F SUPPLY
TEMPERATURE
OFF
-30
-20
0
-10 10
20
40
30
ON
SW1
OFF
SYSTEM
CIRCULATOR
(OPTIONAL)
N
H
POWER
INPUT
(120 VAC)
24 VAC
THERMOSTAT
BOILER
CONTROL
OUTDOOR
SENSOR
BOILER
SUPPLY
SENSOR
POT1
See NOTE
NOTE: Resistor
(1KΩ, 1⁄2W)
may be needed
between Wand C
terminals.
W

Boiler Operation:
The supply water temperature from a boiler can be controlled by
cycling the boiler on and off. Modulation of the boiler’s operating tem-
perature in hot water heating systems not only provides more comfort
but also offers significant energy savings. The cooler the boiler runs,
the more efficient it is due to less heat losses up the flue and reduced
boiler jacket losses.
Differential:
An on / off boiler must be operated with a differential in order to pre-
vent short cycling. When the supply water temperature drops below
the bottom rail of the differential, the boiler is turned on. The boiler is
then kept on until the supply water temperature rises above the top
rail of the differential. If the differential is too wide, there can be large
supply water temperature swings; however, if the differential is too
narrow, the boiler short cycles and operates inefficiently. This control
can be set for two different boiler differentials, 10°F (6°C) or 20°F
(12°C). This setting will help to achieve an appropriate balance
between temperature swings and boiler efficiency.
Minimum Boiler Supply:
Most boilers require a minimum supply water temperature in order to
prevent corrosion from flue gas condensation. The control should
therefore only modulate the boiler supply water temperature down to
the boiler manufacturer’s minimum recommended operating temper-
ature. Some boilers are designed to condense and should be operat-
ed at low water temperatures as much as possible for maximum effi-
ciency.
SUPPLY WATER TEMPERATURE
TIME
Differential = 10°F (5°C
)
165 °F(74°C)
155°F (68°C)
160°F (71°C)
BOILER ON BOILER ON
BOILER OFF BOILER OFF
OUTDOOR AIR TEMPERATURE
50
(10)
30
(-1)
10
(-12)
-10
(-23)
70
(21)
90
(32)
WWSD
TEMPERATURE
°F( °C)
SUPPLY WATER TEMPERATURE
110 (43)
70 (21)
90 (32)
210 (99)
170 (77)
150 (65)
130 (54)
190 (88)
RESET
RATIO
BOILER
MINIMUM
SEQUENCE OF OPERATION:
Powering Up the Control:
After the SR501-OR is powered up, the green power LED light will be on.
Heating Demand:
The SR501-OR receives a heating demand from thermostat or zone
control end switch closure on the R and W thermostat terminals. The
thermostat red LED light will also be turned on. The control can be
setup for boiler temperature reset or ON – OFF boiler operation.
Reset Demand:
When the SR501-OR receives a heating demand the controls enable
the boiler based on the reset curve. The Boiler Relay red LED light
will be turned on when the boiler relay is energized.
DHW Demand:
When the SR501-OR receives a D W demand the controls enable
the boiler and ignore the boiler reset curve. The D W Override red
LED light will also be turned on.
Warm Weather Shut Down (WWSD):
When the outdoor temperature rises above 70°F (21°C), the control
turns off the boiler and blinks the Thermostat LED light. This function
only applies for space heating and does not affect D W operation.
Boiler Operation:
When the SR501-OR has a reset demand, the system supply water
temperature is controlled by turning the boiler on and off. The control
calculates the target supply water temperature based on the outdoor
temperature, and the settings that were entered. The boiler operates
around a differential that is manually set by dip switch number 2. The
control includes a minimum on and off time for the boiler, in order to
minimize short cycling.
Maximum Boiler Supply:
The SR501-OR does not allow the boiler target temperature to
exceed the boiler design temperature setting plus 10°F (6°C) up to a
maximum of 225°F (107°C).
Minimum Boiler Supply:
The SR501-OR has a 140°F minimum boiler setting which is used in
order to prevent corrosion from flue gas condensation. During mild
outdoor conditions, the boiler cycles around the minimum boiler set-
ting. This programmed function can be set to the OFF setting for con-
densing and electric boilers.
INSTALLATION:
Step One:
Check the contents of this package. If any of the contents listed are
missing or damaged, please contact your sales representative for
assistance. The SR501-OR includes:
SR501-OR Boiler Reset Control and Switching Relay Combination
One Outdoor Sensor
One Strap on Sensor
Instruction Sheet
Replacement sensors are available from Taco, Inc.:
Strap on Sensor – 9300-2044RP
Outdoor Sensor – 9300-2052RP
Note: Carefully read the details of the Sequence of Operation section
in this brochure to ensure that you have chosen the proper control for
your application.
Step Two:
Installing the Control:
The enclosure is to be mounted flush onto a wall or any ridge surface.
• The mounting holes in the enclosure accept #6 screws.
• Line voltage to enter from bottom of control and low voltage to
enter from top of control.
Installing the Outdoor Sensor:
Note: The temperature sensor (thermistor) is built into the enclosure.
• Use one round or pan head screw to attach the base of the sen-
sor to the wall.
• The sensor is wall mounted and the wiring enters through the
bottom of the enclosure. The hole for the cable entry must face
downward in order to prevent water from entering and filling the
enclosure.
CAUTION: Improper installation and operation of this control
could result in damage to the equipment and possibly even
personal injury. It is your responsibility to ensure that this con-
trol is safely installed according to all applicable codes and
standards. This electronic control is not intended for use as a
primary limit control. Other controls that are intended and cer-
tified as safety limits must be part of the control circuit.

• The sensor should be mounted on a wall which best represents
the heat load on the building (i.e. a northern wall for most build-
ings and a southern facing wall for buildings with large south fac-
ing glass areas). The sensor should not be installed near heat
sources such as ventilation or window openings.
• The sensor should be installed at an elevation above the ground
that will prevent accidental damage or tampering.
• Install the Outdoor Sensor and run the wiring back to the control
mounting location.
Installing the Boiler Sensor:
Note: This sensor is designed to mount on a pipe or in a temperature
immersion well.
• The sensor can be strapped directly to the pipe using the cable
tie provided. Insulation should be placed around the sensor to
reduce the effect of air currents on the sensor measurement.
• The Boiler Sensor should be placed downstream of a pump or
after an elbow or similar fitting. This is especially important if
large diameter pipes are used because the thermal stratification
within the pipe can result in erroneous sensor readings. Proper
sensor location requires that the fluid is thoroughly mixed within
the pipe before it reaches the sensor.
Step Three:
Wiring to the Zone Control:
Line Voltage Connections –
Connect 120VAC incoming line voltage; ot to the terminal and
Neutral to the N terminal.
Connect 120VAC circulator; OT lead of circulator to Zone ter-
minal and Neutral lead of circulator to Zone N terminal.
Low Voltage Connections –
Connect thermostat or zone control end switch to the R and W
thermostat terminals.
Connect the D W aquastat to the R and W D W override terminals
(optional).
Connect boiler’s T and T terminal to the X and X boiler end switch
terminals.
Wiring the Sensors:
Do not apply power to these terminals as this will damage the
control.
Outdoor Sensor
Connect the two wires from the Outdoor Sensor to the Outdoor
Sensor terminals. The Outdoor Sensor measures the outdoor air
temperature.
Boiler Sensor
Connect the two wires from the Boiler Sensor to the Supply
Sensor terminals and insulate. The Boiler Sensor measures the
supply water temperature going from the boiler to the system.
SETTINGS:
Before adjusting the settings, read through the sequence of operation
to ensure that you understand how the control operates. The following
page describes how to program these settings into the control once it
has been powered up.
Step Four:
Outdoor Design Temperature:
The Outdoor Design setting is the outdoor tem-
perature used in the heat loss calculation. It is
set to the typical coldest outdoor temperature.
Using a small screwdriver adjust the reset ratio
knob to appropriate Outdoor Design
Temperature. When set to OFF, the boiler tem-
perature will not be reset and boiler will fire to
high limit when there is a call for heat.
Boiler Minimum Supply Temperature (Dip Switch #1):
Most boilers require a minimum operating temperature to prevent cor-
rosion from flue gas condensation. The minimum boiler dip switch
should be set to ON (140°F) supply water temperature so boiler can
operate without causing the boiler flue gases to condense. Consult
the boiler manufacturer for recommended minimum boiler supply
temperatures. The dip switch can also be set to OFF (70°F) when
condensation is not a concern.
Differential (Dip Switch #2):
The differential adjustment sets how far the actual boiler supply water
temperature may deviate from the desired temperature before the boil-
er is turned on or off. This is a function of the water content of the boiler
and the flow rate through the system pump relative to the heat output
of the boiler. The differential can be set by dip switch #2, set to OFF for
10°F (6°C) or set to ON for 20°F (12°C).
Pump Operation (Dip Switch #3):
The pump operation is controlled by dip switch #3. When the dip
switch is set to ON, the pump output will energize when thermostat or
D W calls for heat. When set to OFF, the pump will only come on
when the thermostat calls for heat not the D W.
Warm Weather Shut Down:
When the outdoor temperature rises above 70°F (21°C), the control
turns off the boiler and blinks the Thermostat LED light. This function
only applies for space heating and does not affect D W operation.
TROUBLESHOOTING:
Step Five:
As in any troubleshooting procedure, it is important to isolate a prob-
lem as much as possible before proceeding. The blinking error LED
light greatly simplifies troubleshooting of the SR501-OR. If you sus-
pect a wiring fault, return to step three and carefully check all external
wiring and wiring connections.
Sensor Errors:
• If an outdoor sensor fault occurs, the SR501-OR will assume a
fixed outdoor temperature of 32°F (0°C) and will target the
appropriate supply water temperature. The Boiler light will blink
twice every 5 seconds to indicate the outdoor sensor error.
• If a boiler sensor fault occurs, the SR501-OR turns the boiler off
and the Boiler light will blink once every 5 seconds to indicate the
boiler supply sensor error.
Adjustment of Settings:
• If the outdoor temperature is cold and the rooms are cold,
increase the Outdoor Design setting by 5°F (3°C) per day.
• If the boiler is cycling too often, increase the Differential setting.
Testing the Sensors:
A good quality test meter capable of measuring up to 5,000 kΩ(1 k =
1000 Ω) is required to measure the sensor resistance. In addition to
this, the actual temperature must be measured with either a good
quality digital thermometer, or, if a thermometer is not available, a sec-
Ω
Do not apply voltage to a sensor at any time
as damage to the sensor may result.
Note: When the outdoor temperature rises above 70°F (21°C), the
control turns off the boiler and blinks the Thermostat LED light.
DHW will still operate.
OFF
-30
-20
-10
0
10
20
30
40

Taco, Inc. will repair or replace without charge
(at the company’s option) any product or part
which is proven defective under normal use with-
in 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 prod-
uct or part contains no defect as covered in this
warranty, the purchaser will be billed for parts
and labor charges in effect at time of factory
examination 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
applicable 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 T IS WARRANTY IN LIEU OF
ALL OT ER EXPRESS WARRANTIES. ANY
WARRANTY IMPLIED BY LAW INCLUDING
WARRANTIES OF MERC ANTABILITY OR
FITNESS IS IN EFFECT ONLY FOR T E
DURATION OF T E EXPRESS WARRANTY
SET FORT IN T E FIRST PARAGRAP
ABOVE.
T E ABOVE WARRANTIES ARE IN LIEU OF
ALL OT ER WARRANTIES, EXPRESS OR
STATUTORY, OR ANY OT ER WARRANTY
OBLIGATION ON T E PART OF TACO.
TACO WILL NOT BE LIABLE FOR ANY SPE-
CIAL, INCIDENTAL, INDIRECT OR CONSE-
QUENTIAL DAMAGES RESULTING FROM
T E USE OF ITS PRODUCTS OR ANY INCI-
DENTAL COSTS OF REMOVING OR REPLAC-
ING 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
ond sensor can be placed alongside the one to be tested and the read-
ings compared. First measure the temperature using the thermometer
and then measure the resistance of the sensor at the control. The wires
from the sensor must not be connected to the control while the test is
performed. Using the chart below, estimate the temperature measured
by the sensor. The sensor and thermometer readings should be close.
If the test meter reads a very high resistance, there may be a broken
wire, a poor wiring connection or a defective sensor. If the resistance is
very low, the wiring may be shorted, there may be moisture in the sen-
sor or the sensor may be defective. To test for a defective sensor, mea-
sure the resistance directly at the sensor location.
The installer must ensure that this control and its wiring are isolated
and/or shielded from strong sources of electromagnetic noise. 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 inter-
ference, and (2) this device must accept any interference received, includ-
ing interference that may cause undesired operation.
TECHNICAL DATA:
SR501-OR Boiler Reset Control Relay:
Control: Microprocessor PI control. This is not a
safety (limit) control.
Enclosure: TYPE 1
Dimensions: 41⁄4" W x 51⁄4" x 23⁄4" D
Approvals: UL listed for US and Canada, Temperature
Indicating and Regulating Equipment.
Power Supply: 120/60/1 VAC, 12 amps maximum
Relays: Boiler Relay 1 amp @ 24 VAC
Circulator Relay 1⁄3P (6 FLA, 36
LRA)
Thermostat: 24 VAC Class 2 Output
Sensors: NTC thermistor, 10 kΩ@ 77°F
(25°C ±0.2°C) ß=3892
Outdoor Design Temp.: -30°F to 40°F (-35°C to 5°C)
Boiler Minimum: 70°F or 140°F (21°C or 60°C)
Differential: 10°F or 20°F (6°C or 12°C)
WWSD: 70°F (21°C), blinks TSTAT light when
>70°F
WARNING: Wiring connections must be made in accordance with all applicable electrical codes. Use copper wire only. 120 VAC wiring must have a min-
imum 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 rec-
ommended for 120 VAC connections, 14-22 gauge wire for thermostat connections, and 14-22 gauge wire for 24 VAC source connections.
TEMPERATURE RESISTANCE
°F °C Ω
-30 -34 234,196
-20 -29 165,180
-10 -23 118,018
0 -18 85,362
10 -12 62,465
20 -7 46,218
TEMPERATURE RESISTANCE
°F °C Ω
30 -1 34,558
40 4 26,099
50 10 19,900
60 16 15,311
70 21 11,883
80 27 9,299
TEMPERATURE RESISTANCE
°F °C Ω
90 32 7,334
100 38 5,828
110 43 4,665
120 49 3,760
130 54 3,050
140 60 2,490
TEMPERATURE RESISTANCE
°F °C Ω
150 66 2,045
160 71 1,689
170 77 1,403
180 82 1,172
190 88 983
200 93 829
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)
A Taco Family Company
2016