Taco SR502

TACO ZONE CONTROLS WIRING GUIDE
Pages
Switching Relays – Single Zone Wiring 2 – 2
Switching Relays – Oil Boiler Wiring Safety Notice 2 3– 4
Switching Relays – N
ON EXP Connected Together with Priority 5 – 11
Switching Relays – EXP Connected Together with Priority 12 – 14
Switching Relays – Multiple Indirect Hot Water Heaters 15 – 16
Switching Relays – EXP Connected To Reset Controls (PC700, 702 & 705) 17 – 28
Zone Valve Controls – N
ON EXP Connected Together with Priority 29 – 34
Zone Valve Controls – EXP Connected Together with Priority 35 – 38
Zone Valve Controls – Connected To Reset Controls (PC700, 702 & 705) 39 – 46
Hydro Air Fan Controls (HAFC 101 & 201) 47 – 51
Specialty Thermostat and Zone Valve Wiring 52 – 56
Radiant Mixing Block 57 – 58
X-Pump Block 59 – 61
iSeries Mixing Valves 62 – 63
Low Water Cutoffs and Electric Water Feeders 64 – 79
Aquastat Wiring 80 – 86
Instruction Sheets 87 – 97
Standard Terms and Definitions – 98
Cross Reference 99 – 100
Do it once.
Do it right.
© Taco Catalog No. 100-9.0 Effective Date: July 1, 2010
Supersedes Date: July 1, 2007

Taco SR502 Specifications

General

Zones	2
Frequency	60 Hz
Relay Type	SPDT
Mounting	Wall mount
Input Voltage	120 VAC
Output Voltage	24 VAC
Enclosure Type	Plastic
Terminal Type	Screw terminal

Summary

TACO ZONE CONTROLS WIRING GUIDE

Switching Relays - Single Zone Wiring

Wiring configuration for single zone switching relays.

Switching Relays - Oil Boiler Wiring Safety Notice

Essential safety information for wiring switching relays with oil boilers.

Zone Valve Controls - NON EXP Connected Together with Priority

Wiring setup for non-EXP zone valve controls with priority functionality.

SR501 Switching Relay Wiring

TYPICAL WIRING (COLD START)

Standard wiring diagram for the SR501 relay in cold start applications.

ALTERNATIVE WIRING (TANKLESS COIL)

SAFETY NOTICE

How to check for two power sources

Procedure to verify and identify potential dual power sources for safety.

How to correct the wiring

Corrective wiring instructions to ensure safe operation and prevent hazards.

PC700 Boiler Reset Control Connected to SR501-EXP Switching Relay

PC700 Boiler Reset Control Connected to EXP Switching Relay

PC700 Boiler Reset Control Connected To EXP Zone Valve Control

Multiple HAFCs and Switching Relay

Radiant Mixing Block (RMB)

Radiant Mixing Block, Single Zone

X - Pump Block (XPB)

X - Pump Block, Single Zone

iSeries Mixing Valve

iValve, 2-Way Injection, Single Zone

Wiring Taco LN and LTA-2 Series Low Water Cutoffs Using Burner Circuit Power Source

Wiring Taco LN and LTA-2 Series Low Water Cutoffs Using Power Source Other Than Burner Circuit

Alternative wiring for LN/LTA-2 LWCOs using an external power source.

Aquastat Wiring

HONEYWELL L8124 A & C OR EQUAL

HONEYWELL L8124 M OR EQUAL

HONEYWELL L8124 B OR EQUAL

Wiring for Boilers with Honeywell Aquastat Model L8148 E or Equivalent

Wiring for Boilers with Honeywell Aquastat Model L8124 E or Equivalent

Wiring for boilers using Honeywell L8124E aquastats.

Aquastat Wiring to 24 VAC Low Water Cutoff

Aquastat Wiring to 120 VAC Low Water Cutoff

Instruction Sheet SR501 Switching Relay

Instruction Sheet SR501-845 RP Universal Replacement Relay

Instruction Sheet SR502 & SR503 Switching Relay

Instruction Sheet SR504 & SR506 Switching Relay

Instruction Sheet ZVC403 & ZVC405 Zone Valve Control

Instruction Sheet ZVC404 & ZVC406 Zone Valve Control

Instruction Sheet ZVC404-EXP & ZVC406-EXP Zone Valve Control

Instruction Sheet PC600 Post Purge Timer Plug-In PowerPort Card

Instruction Sheet PC605 Priority Protection Plug-In PowerPort Card

Instruction Sheet PC610 Pump Exercise and Timer Plug-In PowerPort Card