Uponor A3100101 with Taco SR503-EXP Zone Switching Relay Controller?

Peepers

Hey Guys, great site and thanks for the help in advance .....

I'm trying to install a Uponor A3100101 T-Stat for my infloor radiant heating. I'm trying to connect it to my Taco SR503-EXP Zone Switching Relay Controller. There's two wires coming from the Taco to the T-Stat. Image of the Taco below (Zone 1 is for infloor heat)



When I connected the R and W to the Rh & W on the T-Stat, the unit doesn't power up? My circulating pump turns on but no display. I tested voltage between the Rh & W and it's 4.6V (and that's probably why it's not powering up?). I then checked for voltage at the Taco and getting the same 4.6V between R & W, However C & W is giving 29V

The T-Stat came with a 10K Ohm 0.25watt resistor and the manual states this:
This thermostat works effortlessly with other Uponor components.
However, some commonly used third-party devices (e.g., relays, zone valves, etc.) may have compatibility issues with this thermostat. If connecting the thermostat to a third-party control device, refer to that device’s installation instructions for specific information regarding operation with a power-sharing thermostat. A 10K Ohm, 0.25 Watt resistor is included in the packaging when compatibility issues arise



I did read somewhere (can't find the link) that Taco states:
"Some thermostats are a “Power Stealing” type which means they are powered by the switching relay with just 2 wires (R& W). A resistor may be needed in order to have the thermostat work properly. This resistor should be placed between the W& C(common) terminals of the switching relay. If the thermostat manufacturer does not supply a resistor, a 1000 ohm ½ watt resistor has proven to work with most models and is readily available at electronic supply outlets (e.g.8the batteries are fresh and installed correctly."


Is this where that supplied Uponor resistor goes to help power up the unit?

Any thoughts / advice on how to get this working?

Oh ya, I have a floor probe installed and will be connecting that which I think is pretty straight forward.

FYI - Here's a picture of the Uponor T-stat

Jamie Hall

Oh dear. Yet another power stealing thermostat. Life was so simple when the thermostat was a simple swirh... Figure 7n on page 9 of your manual shows the bypass resistor installed on a relay. It may work...

Zman

I have installed dozens of those connected to taco zone controllers with no resistor. I wonder if you just got a bad one?

Peepers

Hi @Jamie Hall , what manual are you referencing? Taco or Uponor? I can't find a manual with page 9?
Hi @Zman, do you recall how you wired them up to the Taco?

Zman

Just connected to R and W. Why does your zone 2 have 2 wires on each terminal?

Peepers

@Zman I have two air handlers hooked up to zone 2

Shane_2

Before you go too far troubleshooting, double check all your wiring connections. Is the white wire on the Taco controller inserted correctly?

Peepers

Hi @Shane_2, yes the two wires are connected to the Taco correctly. Reason I know this is for about a year I had a basic Honeywell (battery powered) two wire t-stat hooked up running the system. However this basic unit only reads air temp and I wanted to start using my floor probe thus why I purchased the Uponor T-Stat

Shane_2

Peepers said:

Hi @Shane_2, yes the two wires are connected to the Taco correctly. Reason I know this is for about a year I had a basic Honeywell (battery powered) two wire t-stat hooked up running the system. However this basic unit only reads air temp and I wanted to start using my floor probe thus why I purchased the Uponor T-Stat

Just saw the extra copper exposed for the white wire on zone 1, worth checking the easy stuff first.

twinax

Hi Peepers, did you ever get this working?