And whether you're using basic priority switching, Taco Plug-In PowerPort Cards or add-on power controls, tailoring the system has never been easier. All is good, the Nest has a constant 3.93 volts. When a zone calls, the the appr … read more My hot water source is a Takagi TK-3 tankless water heater. SR501-845RP 1 Zone Switching Relay Replacement PC Board for Honeywell R845,RA89A,RA832 or Comparable Relay SR502 2 Zone Switching Relay with Priority SR503 3 Zone Switching Relay with Priority SR504 4 Zone Switching Relay with Priority SR506 6 Zone Switching Relay with Priority Switching Relays with PowerPort Options and Expandable to 20 Zones $180.00. The Taco SR503-4 Zone Switching Relay has a built-in 24V transformer that is only sufficient in rating to supply voltage to the Zone Control. It is a closed system with a heat exchanger. Active 2 years, 2 months ago. I just bought a home with a three-zone radiant heat system controlled by Nest thermostats. Hi, I have a (slightly older style) Taco SR503, wired with a newer SR503 and an SR504, as shown on p.10 of the 100-9.0 Taco zone controls wiring guide (10 zones total). Switching Relay. I removed the Honeywell RA89A (even though it's working fine) and installed the Taco SR501-4 Single Zone switching relay. View and Download Taco SR503-EXP-4 instruction sheet online. ... Taco ZA024Q4A2 Zone Sentry Replacement Actuator Head, NC, 24V . $105.99. There's only two wires (red and white) going to each thermostat. I have 1 thermostat per zone and 1 pump per zone. Free shipping . Picture Information. Small Relay Panel, (2x) 2-Pole Featuring a NEMA 1 indoor enclosure and clearly Featuring a NEMA 1 indoor enclosure and clearly labeled terminals to facilitate installation, the RLY-4PL small relay panels are designed for use with snow melting, slab heating, and roof deicing applications. TACO SR-601B 4-6 Circulator Relay - end switch & ZC/ZR Terminals 120VAC * New. I ran new 18/3 wire from the Nest to the Taco. Taco SR504 Pump Switching Relay 4 Zone W/Priority. Boilers - Home Heating Steam and Hot Water Systems - Taco SR 503 Relay Switching Unit - [TABLE= width: 500 ] [TR] [TD]I use this relay unit to turn on the hot water heat to my basement, bath and Taco SR 503 Relay Switching Unit - DoItYourself.com Community Forums I used the Taco supplied cross reference chart to wire it up. Taco SR503-2 - 3 Zone Switching Relay - Taco Switching Relays combine clearly-labeled PC board layouts with advanced features that allow you to completely customize your system. Viewed 4k times 1. Taco SR503-4 3-Zone Switching Relay. For larger jobs, switching relays can be expanded up to 20 zones with priority. Battery powered thermostats do not steal power from this control, therefore the 1 amp rating will be sufficient. $152.78 + shipping . Free shipping . Ask Question Asked 2 years, 3 months ago. SR503-EXP-4 relays pdf manual download. Taco SR503 switching relay and common wire? Appropriate for use with 120, 208, 240 or 277 Vac cables, they are virtually silent during operation. Taco SR 503 switching relay runnning circulator pump; Author: yduohs (WA) I am currently using a Taco SR503 to run a 3 zone radiant heating system. The Taco SR503-4 switching relay is UL listed, use standard replaceable relays and are compatible with conventional and programmable thermostats.