1. Product Overview
The Tekmar 303P Switching Relay is designed to manage up to three thermostats and operate circulators within a zoned hydronic heating system. This device facilitates efficient heat distribution by connecting to various zones and prioritizing heating demands as configured. Zone 1 offers an optional priority function, making it suitable for applications such as indirect domestic hot water tanks.
Key functionalities include optional pump exercising to prevent circulator seizure during periods of inactivity, and an optional post-purge operation for the last active zone to enhance energy efficiency. The 303P also provides a RoomResponse signal, which can optimize boiler efficiency and comfort when integrated with modulating-condensing boilers.
Figure 1: Front view of the Tekmar 303P 3-Zone Priority Switching Relay. The blue enclosure features a white label indicating the brand "tekmar", model "Switching Relay 303P", and LED indicators for Power, RoomResponse, Priority, Zone 1, Zone 2, and Zone 3.
2. Features
The Tekmar 303P Switching Relay incorporates several features designed to optimize hydronic heating system performance and user convenience:
- Away Signal Sharing: Compatible with Tekmar thermostats for shared away signals.
- Safety Approvals: CSA approved for reliable operation.
- Thermostat Compatibility: Works with all low voltage thermostats.
- Grounding: Equipped with four ground screws for secure installation.
- Circuit Protection: Fuses protect both transformers and pumps from electrical overloads.
- Status Indicators: LED indicators for each zone, priority status, end switch, and RoomResponse™ activity.
- Post Purge: Optional feature to run the last operating zone's circulator for a short period after the call for heat ends, maximizing energy transfer.
- Priority Override: Allows Zone 1 to take precedence over other zones, typically for domestic hot water.
- Pump Exercising: Periodically activates circulators to prevent seizure during extended periods of inactivity.
- RoomResponse™ Signal: Provides a signal to modulating-condensing boilers to optimize comfort and improve boiler efficiency.
- Conduit Knockouts: Top, bottom, and back conduit knockouts for flexible wiring installation.
- Spare Fuses: Includes two spare fuses for convenience.
- Zone Expansion: Supports unlimited zone expansion with additional relays.
- Zone Priority: Configurable priority for specific heating zones.
3. Technical Specifications
| Specification | Value |
|---|---|
| Product Type | Controller |
| Number of Zones | 3 |
| Enclosure Material | Cover: ABS plastic, Base: galvanized steel |
| Enclosure Type | NEMA type 1 |
| Approvals | CSA C US |
| Ambient Conditions | Indoor use only, 32 to 122°F (0 to 50°C), RH 90% non-condensing |
| Power Supply | 115 V (ac) ±10%, 60 Hz, 16 A |
| Transformer | 40 VA, expandable to 80 VA with additional transformer M3069 (sold separately) |
| Fuses | T5A 250 V slow blow (two spare fuses included) |
| Pump Relays | 115 V (ac), 5 A, 1/3 hp, 16 A combined |
| Boiler End Switch (XX) | 24 V (ac), 5 A |
| DHW End Switch | 24 V (ac), 5 A |
| Modulating Boiler Output | 0-10 V (dc) 500 ohm min load impedance / 4-20 mA 1 k ohm max load impedance |
| Connector Type | Screw |
| Mounting Type | Surface Mount |
| Operation Mode | Automatic |
| Wattage | 5.22 watts |
| Coil Resistance | 50 Ohms |
| Coil Voltage | 115 Volts |
| Minimum Switching Voltage | 105 Volts (AC) |
| Maximum Switching Voltage | 115 Volts |
| Maximum Switching Current | 5 Amps |
| UPC | 384929979532 |
4. Installation and Setup
WARNING: Electrical installation should only be performed by qualified personnel. Ensure power is disconnected before beginning any wiring procedures to prevent electric shock.
4.1 Mounting
- Select a suitable indoor location for surface mounting, away from direct sunlight, heat sources, and excessive moisture.
- Ensure adequate space for wiring and ventilation.
- Secure the relay to a wall or suitable surface using appropriate fasteners through the mounting holes.
4.2 Wiring Connections
The Tekmar 303P features screw terminals for all electrical connections. Refer to the wiring diagram provided with the product packaging for detailed connection points. General connections include:
- Power Supply: Connect the 115 V (ac) power supply to the designated terminals.
- Thermostats: Connect up to three low-voltage thermostats to their respective zone terminals (Zone 1, Zone 2, Zone 3).
- Circulators: Connect the circulators for each heating zone to the corresponding pump relay terminals.
- Boiler Connections:
- Connect the boiler end switch (XX) to the boiler's call for heat input.
- If using for domestic hot water priority, connect the DHW end switch.
- For modulating boilers, connect the 0-10 V (dc) or 4-20 mA output to the boiler's modulation input.
- Grounding: Ensure all four ground screws are properly connected to the system ground.
After all connections are made, carefully review the wiring for correctness and security before restoring power.
5. Operation
Once installed and powered, the Tekmar 303P operates automatically to manage your hydronic heating system. The LED indicators on the front panel provide visual feedback on the system's status.
5.1 LED Indicators
- Power LED: Illuminates when the unit is receiving power.
- RoomResponse™ LED: Indicates when the RoomResponse signal is active.
- Priority LED: Illuminates when Zone 1 is active and operating in priority mode.
- Zone 1, 2, 3 LEDs: Each LED illuminates when its respective zone thermostat is calling for heat and the circulator is active.
5.2 Zone Priority
Zone 1 can be configured for priority operation. When a call for heat comes from Zone 1 (e.g., for domestic hot water), it will override calls from Zone 2 and Zone 3. This ensures that the priority zone receives heat first. Once the priority demand is satisfied, the relay will resume heating for other zones as needed.
5.3 Pump Exercising
The optional pump exercising feature periodically activates the circulators for a short duration, even when there is no call for heat. This prevents the circulator pumps from seizing due to prolonged inactivity, extending their lifespan and ensuring readiness.
5.4 Post Purge
With the optional post purge feature enabled, the circulator for the last operating zone will continue to run for a brief period after the thermostat's call for heat has ended. This helps to extract residual heat from the heating system, improving overall energy efficiency.
6. Maintenance
The Tekmar 303P Switching Relay is designed for reliable, long-term operation with minimal maintenance. However, periodic checks can help ensure optimal performance.
- Visual Inspection: Annually inspect the unit for any signs of physical damage, loose wiring, or corrosion.
- Cleaning: Keep the unit's exterior clean and free of dust. Use a soft, dry cloth. Do not use abrasive cleaners or solvents.
- Fuse Check: If a zone or the entire unit loses power, check the fuses. The unit includes two spare fuses. Always replace fuses with the correct type and rating (T5A 250 V slow blow).
- Ventilation: Ensure that the ventilation slots on the enclosure are not obstructed to prevent overheating.
CAUTION: Disconnect power to the unit before performing any maintenance or fuse replacement.
7. Troubleshooting
This section provides solutions to common issues you might encounter with your Tekmar 303P Switching Relay. For problems not listed here, or if issues persist, contact qualified service personnel.
| Problem | Possible Cause | Solution |
|---|---|---|
| No Power LED / Unit is off | No power supply; Blown fuse; Loose wiring. | Check circuit breaker; Replace fuse (T5A 250 V slow blow); Verify all power connections are secure. |
| Zone not heating / Circulator not running | Thermostat not calling for heat; Loose wiring to thermostat or circulator; Blown pump relay fuse; Zone priority active. | Check thermostat setting; Inspect wiring connections; Replace pump relay fuse; Verify if Zone 1 priority is active and satisfied. |
| Boiler not firing | Boiler end switch wiring issue; Boiler lockout; No call for heat from any zone. | Check boiler end switch connections; Consult boiler manual for lockout codes; Ensure at least one zone is calling for heat. |
| RoomResponse™ LED not active | Feature not enabled; Wiring issue to modulating boiler; Boiler not compatible. | Refer to installation manual for RoomResponse™ setup; Check wiring to modulating boiler; Confirm boiler compatibility. |
8. Warranty and Technical Support
8.1 Warranty Information
For detailed warranty information regarding your Tekmar 303P Switching Relay, please refer to the official warranty statement included with your product packaging or visit the official Tekmar website. Warranty terms typically cover defects in materials and workmanship for a specified period from the date of purchase.
8.2 Technical Support
If you require technical assistance, have questions about installation, operation, or troubleshooting that are not covered in this manual, please contact Tekmar customer support. You can usually find contact information, including phone numbers and email addresses, on the Tekmar website or in the documentation provided with your product.
When contacting support, please have your product model number (303P) and any relevant purchase information readily available to expedite assistance.
