Taco SR501-4 Switching Relay
Instruction Sheet
Manufacturer: Taco Comfort Solutions
Effective Date: December 20, 2013
Product Overview
The Taco SR501-4 is a single-zone switching relay designed for HVAC applications. It controls a circulator based on signals from a thermostat.
Features
- External Indicator Lights
- Universal Replaceability
- Snap-in PC Board
- Simplified Wiring
- Sealed Relays
- Fuse Protected Outputs
- 100% Factory Tested
- Contractor Friendly PC Board Layout
- Universal Thermostat Compatibility
- UL Approved
- Extended 3 Year Warranty
Operation
Connect a thermostat to the "T T" terminals on the switching relay. When the thermostat calls for heat, the relay is energized and power is supplied to the circulator.
Power Input
Connect 120 Volt AC power to terminals N (Neutral) and H (Hot).
Jumper Placement
The jumper is factory installed between terminals H and 3. This jumper switches power on terminals 4 normally open (n/o) and 4 normally closed (n/c).
Terminal Description
| Terminal | Description |
|---|---|
| T & T | Thermostat Connection |
| COM | Common side of transformer, to power some setback thermostats |
| N | Neutral wire of power input |
| H | Hot wire of power input |
| 3 | Common terminal for 4 n/o and 4 n/c |
| 4 n/o | Normally open terminal |
| 4 n/c | Normally closed terminal |
| 6 n/c | Normally closed terminal |
| 6 n/o | Normally open terminal |
| 5 | Common terminal for 6 n/o and 6 n/c |
Specifications
| Product Number | Number of Zones | Input Voltage | Maximum Combined Load | Type 1 Enclosure | Width | Height | Depth |
|---|---|---|---|---|---|---|---|
| SR501-4 | 1 | 120/60/1 VAC | 12 amps | 4 7/8" | 6 5/8" | 2 3/8" |
All circulator relay connections, including ZC/ZR, are rated 1/3 hp (6 FLA, 36 LRA) at 120 VAC.
The thermostat connection supplies a 24 VAC class 2 output.
Wiring Diagrams
Typical Wiring Diagram
This diagram illustrates the standard connection for the SR501-4. It shows a thermostat connected to the 'T T' and 'COM' terminals, providing 24 VAC. The 120 VAC power input connects to 'N' and 'H'. The circulator is connected to terminals '6 n/o' and 'COM'. The relay has indicator LEDs for Power and Zone 1. A note indicates that a resistor (1kΩ, 1/2W) may be needed between the W and C terminals of the thermostat if it is a 'power stealing' type.
Alternative Wiring Diagram
This diagram shows an alternative wiring setup. Similar to the typical wiring, but it highlights the connection of the boiler operating control's ZC terminal to the relay's ZC terminal. This setup requires careful adherence to instructions to avoid unintended boiler activation.
Master/Slave Configuration Diagram
This diagram depicts the SR501-4 (Master) controlling two SR504-4 (Slave) four-zone switching relays. The SR501-4 receives thermostat inputs and controls the circulators via the SR504-4 units. It shows how multiple zones can be managed, with priority switching options.
Replacement Cross-Reference
| Manufacturer | Model | Taco SR501-4 Connections | Compatibility | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| HN | 3 | 4 NO | 4 NC | 5 | 6 NO | 6 NC | R/T | W/T | C | ||||||||
| Taco | SR501-4 | HN | 3 | 4 | NO | 4 | NC | 5 | 6 | NO | 6 | NC | R/T | W/T | C | ||
| Argo | AR821 | 1 | 2 | 3 | 4 | NO | 4 | NC | 5 | 6 | NO | 6 | NC | R/T | C | ||
| Argo | AR822 | 1 | 2 | 3 | 4 | NO | 4 | NC | 5 | 6 | NO | 6 | NC | R/T | G/T | C | |
| Colombus | MR10 | L1 | L2 | 3 | 4 | NO | 4 | NC | 5 | 6 | NO | 6 | NC | R/T | G/T | C | |
| Erie | SR100 | L1 | N | 3 | 4 | NO | 4 | NC | 5 | 6 | NO | 6 | NC | R/T | G/T | C | |
| Honeywell | RA89A | 1 | 2 | 3 | 4 | T | T | ||||||||||
| RA832A | 1 | 2 | 3 | 4 | X | X | T | T | |||||||||
| R845A | 1 | 2 | 3 | 4 | 5 | 6 | T | T | |||||||||
| White-Rogers | 889-189 | 1 | 2 | 3 | 4 | T | T | ||||||||||
| 829-845 | 1 | 2 | 3 | 4 | 5 | 6 | T | T | |||||||||
Important Information
Wiring Warnings
WARNING: Wiring connections must be made in accordance with all applicable electrical codes. Use copper wire only. 120 VAC wiring must have a minimum temperature rating of 75°C. Failure to follow this instruction can result in personal injury or death and/or property damage. Use 12-18 gauge wire for 120 VAC connections, 14-22 gauge wire for thermostat connections, and 14-22 gauge wire for 24 VAC source connections.
Alternative Wiring Note
NOTE 2: When using the Alternative Wiring diagram, the boiler operating control's ZC terminal will see the load of the circulator(s). Failure to follow these wiring instructions may result in a secondary source of power being connected to the boiler that may activate it under certain circumstances, causing injury or death.
Digital Thermostat Note
NOTE 1: Resistor (1kΩ, 1/2W) may be needed between the W and C terminals on the thermostat if it is a 'power stealing' type to ensure proper operation.
Troubleshooting
Digital thermostats do not work correctly
Problem: Digital thermostats do not work correctly when connected to a switching relay.
Solution: Some thermostats are 'Power Stealing' types, powered by the switching relay using only 2 wires (R & W). A resistor may be needed between the W and C (common) terminals of the switching relay. A 1000 ohm 1/2 watt resistor is recommended and widely available. If the thermostat is battery-powered, ensure batteries are fresh and installed correctly.
No heat in a zone or room
Problem: No heat in a zone or room of a building.
Solution: Check the LED diagnostic lights. The green LED should be on, indicating power and a good solid-state fuse. The red LED should illuminate when there is a call for heat, indicating power to the circulator. If the red LED does not come on, check the thermostat and its wiring.
FCC Compliance
This device complies with Part 15 of the FCC Rules. Operation is subject to 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.
Limited Warranty Statement
Taco, Inc. warrants its products against defects in materials and workmanship for a period of three (3) years from the date of start-up, or three (3) years and six (6) months from the date of shipment, whichever occurs first. This warranty covers repair or replacement of defective products at Taco's option. The purchaser is responsible for delivering the product to the stocking distributor or Taco, prepaid. The warranty does not cover products misused, misapplied, or operated contrary to Taco instructions. Taco is not liable for incidental or consequential damages. This warranty provides specific legal rights, which may vary by state.
Contact Information
Taco Comfort Solutions
Taco, Inc.
1160 Cranston Street, Cranston, RI 02920
Tel: (401) 942-8000
FAX: (401) 942-2360
Website: www.taco-hvac.com
Taco (Canada), Ltd.
8450 Lawson Road, Suite #3, Milton, Ontario L9T 0J8
Tel: (905) 564-9422
FAX: (905) 564-9436
Visit our web site: www.TacoComfort.com
Printed in USA ©2015 Taco, Inc.
