Using relay to add common wire

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Old 12-07-16, 06:07 AM
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Using relay to add common wire

Hi,

I've been reading threads and I'm still a bit confused. Hope you don't mind looking at my unique situation.

I have a boiler with radiant water heat. Passed through taco valves controlling two zones.
I wired an Ecobee3 on the first floor easily because the wire in the wall contained 5 wires.

Second floor only has 3 wires. So I need to use a relay to add the 3rd common. I just don't know exactly were to put the relay? Before the taco valves or after?

Here is a drawing of the existing wiring.
Name:  before_relay.jpg
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And a drawing of my assumption of how this should be done. Please correct me if I'm wrong.
Name:  relay_before_valve.jpg
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Old 12-07-16, 06:16 AM
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If it helps I bought this relay.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Here are the wiring instructions from Ecobee. But it doesnt include the Taco valve. So I'm not sure.

Name:  E3 with Isolation relay.jpg
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Old 12-07-16, 07:42 AM
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Hi, you say you have 3 wires to the 2nd floor, and do you have only 1 transformer feeding all the zone valves? If so I don't see the need for the relay,what is Tstat you are replacing and where are the 3 conductors connected?
 
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Old 12-07-16, 08:27 AM
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Thanks Geo,

Current Thermostat only needs 2 wires. There are 3 wires in the wall.

Replacing with an Ecobee3. I tried to just pull the common wire from the transformer by jumping wires from the single transformer. It didn't work.
-From the "white" wire of the transformer which goes to Taco valve position 2. The Ecobee did not turn on.
-From the red wire of the transformer, which feeds the Thermostat, the Ecobee would power cycle when it requested heat.

Ecobee support helped me use two extra wires and do common from the white wire of the Transformer, and Red wire from transformer to Rc

They supplied the wiring diagram I mentioned below to use a relay to replace the Rc connection. (At least I assume)
 
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Old 12-07-16, 09:12 AM
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That setup will only turn on your boiler,if you connect the extra conductor from the 2 terminal on the valve and test between it and the R terminal at the stat you should get 24 vac,that should be your common wire,I am that familular with the Ecobee,I think they might work differently,one of the other may jump in to clarify.
 
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Old 12-07-16, 11:30 AM
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Appreciate the comments Geo.
 
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Old 12-07-16, 12:09 PM
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Here's a diagram you can follow....

Name:  before_relay.jpg
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Old 12-07-16, 12:13 PM
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I will try it PJmax. But it did not work downstairs.

Thank you for the comment!

Edit: I notice the change in transformer wiring. Doesn't Rh tell the Taco valve to power the boiler?
Can you explain the change?
 
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Old 12-07-16, 04:05 PM
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Does the stat not work at all ?
Try the Rc instead of Rh.

It's the W that controls the valve.

Name:  Taco - Copy.jpg
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Old 12-07-16, 05:11 PM
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RH should be power at the stat,with a volt meter check between RH &C, should be 24 VAC
 
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