Connecting Taco SR503-4 Three Zone Switching Relays and Ecobee Thermostats

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Connecting Taco SR503-4 Three Zone Switching Relays and Ecobee Thermostats

Here are instructions for connecting Taco SR503-4 Three Zone Switching Relays and Ecobee thermostats.

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Dave H_2

Unfortunately, this answer doesn't really answer the original poster's question. If you only have two wires connected to your thermostat that has batteries, you will need a third wire or a "common-maker" as I have seen available to make this work.
This does help with wiring hi power-stealing stats with switching relays.

Erin Holohan Haskell

Thanks, @Dave H_2. Please let me know if you have more resources that we can share here.

Dave H_2

You are so welcome and thanks for posting this. We get a lot of calls regarding this and I hope this can help.

sjamz

The ecobee instructions are misleading (especially about the 1 amp rating). Taco documentation has been updated to show where to connect common. See page 56 of their wiring guide (https://www.tacocomfort.com/documents/FileLibrary/100-92.pdf). FAQs on the Taco site also address this. (And yes you do need the third wire.)

lost11

i think argo really explains it best in their manual (https://argocontrols.com/sites/default/files/240005129 ARGO ARM Series IOM REV E.pdf) all these controllers are NOT designed to work power robbing thermostats without additional power. you need the additional transformer for MORE power than the boards were originally designed for.