Electronic Controls
The FuelMizer™ (SR501-OR) is a microprocessor-based control designed to regulate
the supply water temperature of a single boiler, based on the outdoor temperature. The
FuelMizer is a boiler reset control and switching relay in one unit; it is ideal for retrofit
application, but may also be used in new installations as well.
©Taco Catalog #100-100
Supersedes: New
Effective Date: 06/12/12
Printed in USA
SR 501OR-
6
AMP
INPUT
120 VAC
RELAY
ZONE 1
120 VAC
N H N H
Submittal Data Information
FuelMizer™
Instruction Sheet # 102-420
Supersedes: New
N
POWER
INPUT
(120 VAC)
Effective: 06/12/12
SYSTEM
CIRCULATOR
(OPTIONAL)
H
ONE ZONE INSTALLATION W/O INDIRECT DHW
Application
The FuelMizer (SR501-OR) includes
functions such as automatic reset
ratio calculation, warm weather shut
down (WWSD), minimum boiler
temperature setting, and boiler
differential setting. The control
also includes both boiler and
outdoor sensors.
24 VAC
THERMOSTAT
THERMOSTATS
(24VAC)
24 VAC ZONE VALVES
PUMP END
SWITCH
X
X
BOILER
CONTROL
DESIGN OUTDOOR
TEMPERATURE
FOR 180°F SUPPLY
TEMPERATURE
-10 0 10
-20
20
POT1
-30
30
OFF
X X R W C R W OUTDOOR
BOILER
TSTAT
SENSOR
DHW
ONE ZONE
SWITCHING RELAY
WITH OUTDOOR RESET
40
DESIGN OUTDOOR
TEMPERATURE
FOR 180°F SUPPLY
TEMPERATURE
-10 0 10
-20
20
POT1
-30
30
OFF
40
X X R W C R W OUTDOOR
BOILER
TSTAT
DHW
VALVE 3
ZONE 2
1 2 3 4
ZONE 3
1 2 3 4
1
2
3
1
2
3
TACO 3 WIRE
ZONE VALVE
TACO 3 WIRE
ZONE VALVE
DHW
OVERRIDE
BOILER
RELAY
ZONE 1
120 VAC
N H N H
POWER
INPUT
(120 VAC)
SYSTEM
CIRCULATOR
(OPTIONAL)
Configuration OUTDOOR
Dip SwitchEs TEMPERATURE
CONTROL
ADJUSTMENT
A
DHW
AQUASTAT
SENSOR CONNECTIONS
ZONE 3
PRIORITY
R W C R W C R W C
ZONE 1 ZONE 2 ZONE 3
THERMOSTATS
PRIORITY
SYSTEM
CIRCULATOR
(OPTIONAL)
DEMAND INPUT CONNECTIONS
BOILER CONTROL
CONNECTIONS
THERMOSTATS
(24VAC)
N
H
MULTI-ZONE INSTALLATION WITH
ZONE CONTROL, WITH INDIRECT DHW
ONE ZONE INSTALLATION W/O INDIRECT DHW
FUSE
5 AMP
6
AMP
INPUT
120 VAC
ZONE 1
120 VAC
H
POWER IN
24 VAC
LED
INDICATORS
TSTAT
BOILER
RELAY
X
X
ISOLATED
END SWITCH
SUPPLY
SENSOR
POWER
N
POWER
INPUT
(120 VAC)
SENSOR
ONE ZONE
SWITCHING RELAY
WITH OUTDOOR RESET
SR 501OR-4
SR 501OR-4
INPUT
120 VAC
ON
OFF
LED
INDICATORS
POWER
EXISTING
ZONE VALVE CONTROL
24 VAC ZONE VALVES
PUMP END
SWITCH
X
Relays: .....................Boiler Relay ..................................1 amp @ 24 VAC
X
ZONE 1
1 2 3 4
ZONE 3 PUMP
END SWITCH
N/O COM N/C
BOILER
CONTROL
T STAT 1
VALVE 1
T STAT 2
VALVE 2
T STAT 3
VALVE 3
EXTERNAL DIAGNOSTIC LED'S
PRIORITY
ZONE 2
1 2 3 4
JUMPER
3&4
2 WIRE ZONE VALVE
(NO END SWITCH)
MUST USE JUMPER
ZONE 3
1 2 3 4
1
2
3
1
2
3
TACO 3 WIRE
ZONE VALVE
TACO 3 WIRE
ZONE VALVE
Savings from 5% to 30%
OUTDOOR
SENSOR
$900
BOILER
SUPPLY
SENSOR
OFF ON
$800
SW1
40
X X R W C R W OUTDOOR
BOILER
TSTAT
DHW
SENSOR
ONE ZONE
SWITCHING RELAY
WITH OUTDOOR RESET
$700
SUPPLY
SENSOR
Savings
DESIGN OUTDOOR
TEMPERATURE
FOR 180°F SUPPLY
TEMPERATURE
-10 0 10
-20
20
POT1
-30
30
OFF
LED
INDICATORS
POWER
Sensors: ..................NTC thermistor, ..................................10 kΩ @ 77°F
TSTAT
SR 501OR-4
DHW
OVERRIDE
..................................(25°C ±0.2°C) ..................................ß=3892
WWSD: ..................70°F (21°C)
VALVE 2
T STAT 3
SW1
SUPPLY
SENSOR
LED
INDICATORS
6
AMP
Power Supply: .......120/60/1 VAC, ..................................12 amps maximum
Differential: ............10°F or 20°F ..................................(6°C or 12°C)
VALVE 1
T STAT 2
BOILER
SUPPLY
SENSOR
N H N H
Enclosure: ...............TYPE 1
Boiler ......................
Minimum: ...............70°F or 140°F ..................................(21°C or 60°C)
LED
INDICATORS
T STAT 1
SW1
Control: ..................Microprocessor ..................................control. This is not ........................... a safety (limit) ........................... control.
Outdoor ................
Design Temp.: ........-30°F to 40°F ..................................(-35°C to 5°C)
OFF
PRIORITY
OFF ON
DHW
OVERRIDE
Thermostat: ...........24 VAC ..................................Class 2 Output
ON
OUTDOOR
SENSOR
OFF ON
TSTAT
..................................Circulator Relay ..................................1⁄3 HP ..................................(6 FLA, 36 LRA)
ZONE 1
1 2 3 4
ZONE 3 PUMP
END SWITCH
N/O COM N/C
2 WIRE ZONE VALVE
(NO END SWITCH)
MUST USE JUMPER
BOILER
SUPPLY
SENSOR
BOILER
CONTROL
DHW
AQUASTAT
POWER
JUMPER
3&4
OUTDOOR
SENSOR
Specifications
Approvals: ..............UL listed for ..................................US and Canada, ..................................Temperature
..................................Indicating and ..................................Regulating ..................................Equipment.
R W C R W C R W C
ZONE 1 ZONE 2 ZONE 3
THERMOSTATS
PRIORITY
EXISTING
ZONE VALVE CONTROL
POWER
Dimensions: ...........4-1⁄4" W x 5-1⁄4" H ..................................x 2-3⁄4" D
A
ZONE 3
PRIORITY
X
X
ISOLATED
END SWITCH
FUSE
5 AMP
•Full outdoor boiler reset control
•Can control system or zone valve circulator
•Over-ride of outdoor reset when DHW tank is calling
•Easy to install and set; will not affect boiler’s warranty
•Front mounted LED lights for full diagnostic information
•Ideal for retrofit applications of just about any hot water boiler
•Typical energy savings is about 14% with some customers experiencing up to 30%
POWER IN
24 VAC
Features
6
AMP
INPUT
120 VAC
$600
$500
Savings Range
$400
$300
BOILER
RELAY
$200
$100
ZONE 1
120 VAC
$0
N H N H
$0
$1000
$2000
$3000
$4000
Yearly Amount Spent on Fuel
POWER
INPUT
N
(120 VAC)
H
TRANSFORMER
POWER INPUT
CONNECTIONS
CIRCULATOR
OUTPUT
CONNECTIONS
SYSTEM
CIRCULATOR
(OPTIONAL)
MULTI-ZONE INSTALLATION WITH
ZONE CONTROL, WITH INDIRECT DHW
FUSE
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 interference,
and (2) this device must accept any interference received,
including interference that may cause undesired operation.
Taco Inc., 1160 Cranston Street. Cranston, RI 02920 / (401) 942-8000 / Fax (401) 942-2360
Taco (Canada) Ltd., 8450 Lawson Road, Unit #3, Milton, Ontario L9T 0J8 / (905) 564-9422 / Fax (905) 564-9436
www.taco-hvac.com