Product Overview

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.
Specifications
Control: ................. Microprocessor
..................................control. This is not
........................... a safety (limit)
........................... control.
Enclosure: ..............TYPE 1
Dimensions: ..........4-1⁄4" W x 5-1⁄4" H
..................................x 2-3⁄4" 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
..................................1⁄3 HP
..................................(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)
Instruction Sheet # 102-420 Effective: 06/12/12
Supersedes: New
Submittal Data Information
FuelMizer™
Taco Inc., 1160 Cranston Street. Cranston, RI 02920 / [phone] / Fax [phone]
Taco (Canada) Ltd., 8450 Lawson Road, Unit #3, Milton, Ontario L9T 0J8 / [phone] / Fax [phone]
www.taco-hvac.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
N H
INPUT
120 VAC
ZONE 1
120 VAC
N H
6
AMP
X
R
BOILER TSTAT
W
C R
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)
24 VAC
THERMOSTAT
BOILER
CONTROL
OUTDOOR
SENSOR
BOILER
SUPPLY
SENSOR
POT1
MULTI-ZONE INSTALLATION WITH
ZONE CONTROL, WITH INDIRECT DHW
ONE ZONE
SWITCHING RELAY
WITH OUTDOOR RESET
SR 501OR-4
LED
INDICATORS
POWER
TSTAT
DHW
OVERRIDE
BOILER
RELAY
N H
INPUT
120 VAC
ZONE 1
120 VAC
N H
6
AMP
X
R
BOILER TSTAT
W
C R
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
1 2 3 4
ZONE 1
1 2 3 4
ZONE 2
1 2 3 4
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)
T STAT 1
VALVE 1
T STAT 2
VALVE 2
T STAT 3
VALVE 3
POWER
LED
INDICATORS
ZONE 1 ZONE 2 ZONE 3
ISOLATED
X X R W R W R W
END SWITCH THERMOSTATS PRIORITY
24 VAC ZONE VALVES PRIORITY
X X
ZONE 3
PRIORITY
OFF
ON
C C C
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
The installer must ensure that this control and its wiring
are isolated and/or shielded from strong sources of elec-
tromagnetic noise. This device complies with part 15 of the
FCC Rules. Operation is subject to the following two con-
ditions: (1) This device may not cause harmful interference,
and (2) this device must accept any interference received,
including interference that may cause undesired operation.
Features
•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%
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
N H
INPUT
120 VAC
ZONE 1
120 VAC
N H
6
AMP
X
R
BOILER TSTAT
W
C R
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)
24 VAC
THERMOSTAT
BOILER
CONTROL
OUTDOOR
SENSOR
BOILER
SUPPLY
SENSOR
POT1
MULTI-ZONE INSTALLATION WITH
ZONE CONTROL, WITH INDIRECT DHW
ONE ZONE
SWITCHING RELAY
WITH OUTDOOR RESET
SR 501OR-4
LED
INDICATORS
POWER
TSTAT
DHW
OVERRIDE
BOILER
RELAY
N H
INPUT
120 VAC
ZONE 1
120 VAC
N H
6
AMP
X
R
BOILER TSTAT
W
C R
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
1 2 3 4
ZONE 1
1 2 3 4
ZONE 2
1 2 3 4
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)
T STAT 1
VALVE 1
T STAT 2
VALVE 2
T STAT 3
VALVE 3
POWER
LED
INDICATORS
ZONE 1 ZONE 2 ZONE 3
ISOLATED
X X R W R W R W
END SWITCH THERMOSTATS PRIORITY
24 VAC ZONE VALVES PRIORITY
X X
ZONE 3
PRIORITY
OFF
ON
C C C
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
Configuration
Dip SwitChES
tranSforMEr
EXtErnaL DiagnoStiC LED'S
fuSE
outDoor
tEMpEraturE
ControL
aDJuStMEnt
BoiLEr ControL
ConnECtionS
powEr input
ConnECtionS
SEnSor ConnECtionS
$0
$0
$1000 $2000 $3000 $4000
$100
$200
$300
$400
$500
$600
$700
$800
$900
Savings
Yearly Amount Spent on Fuel
Savings Range
Savings from 5% to 30%
DEManD input ConnECtionS
CirCuLator
output
ConnECtionS