Locating C for Ecobee Install with zone valves


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Old 11-01-17, 06:57 PM
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Locating C for Ecobee Install with zone valves

Surely I have enough wires/power to replace two of my five thermostats on my boiler/hot water heating system with Ecobees. My system has five thermostats/Honeywell zone valves V8043 and a Honeywell L8148E Aquastat. The thermostat wires are 3-wire with red, white and green where the green is unused. I would like to replace the thermostats on zones 2 and 4 with the Ecobees. I have diagrammed to the best of my ability the rat's nest that is my systems wiring in hopes that someone can tell me if/how I can utilize the spare green thermostat wires as the C wires required by the Ecobees. If not, is there any way I can use Ecobees in my system?

Diagram posted as an attachment.

Thanks in advance for your assistance!
 
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Old 11-01-17, 07:59 PM
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Welcome to the forums.

Why such a confusing diagram ?

OK.... let me explain what needs to happen and then you can see how to change your wiring. When you have a basic two wire thermostat controlling zones valves...... there is no polarity. It doesn't matter which wire is R and which is W. To operate the zone valve..... R and W are shorted together.

Now.... enter the proper wiring world. When you have a powered thermostat like the Ecobee.... the 24vac power MUST appear on the R terminal. The W terminal is the switched 24vac out to the zone valve. R is basically one side of the transformer. C is the opposite side of the transformer.

Your diagram shows the red wire going to the zone valve. It should be the white wire.

The two red wires on the Honeywell zone valves all get connected in parallel. Then they connect to TT on the aquastat. There is NO zone valve power on those wires. The transformer that powers the zone valves does not connect to those red wires at any place.

With five zone valves and two wifi stats you will need to increase your transformer to a 75 watt (va) model. A 40 watt model is too small.

Just as an example.... Class-Transformer-75VA-120VAC-24VAC

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Actually shows all as wifi stat. Pink is red but used to differentiate from TT lines.
 

Last edited by PJmax; 11-01-17 at 08:31 PM.
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Old 11-01-17, 08:38 PM
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Yep that diagram could have been drawn in a manner that is a little easier to read.
I would not have drawn in all the unused wires, just green.
I would have kept XFMR common blue all the way to the valves ( or at least almost all the way)



So you have 2 yellow wires to each valve. These are W and C.
Your existing thermostats are only using W between the stat and valve.
The remaining yellow wire runs to transformer C.

You also have 2 red wires to each valve. They are the end switch T wires.

Connect your green wire from the thermostat C terminal to the valve yellow wire that is not connected to stat W.
 
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Old 11-01-17, 08:44 PM
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PJ you are too fast for me...

GO ASTROS...
 
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Old 11-03-17, 02:56 PM
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Thanks for the quick responses. Swapped white and red wires from the thermostats and at RC, connected C wire to location you identified and smart thermostat is working!!!

Sorry for the confusing diagram. I’m a software, not electrical engineer.

Thanks again!!!

Also, transformer was already 75VA, but appreciate your mentioning it. I would not have known to check.
 
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Old 11-03-17, 04:05 PM
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Good job ! Thanks for letting us know how you made out.
These threads on finding a C are highly scrutinized and are a popular topic.
 
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Old 10-06-19, 06:28 PM
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I'm joining this party a couple years late, but hoping I could get some input from the very smart people on this forum.

I too have a multi-zone radiant boiler system. 3 wires to the thermostats. 24vac transformer powering the White/Rogers 1311valves and Honeywell aquastat. I made a schematic of my current wiring and attached 1311. In total I have 4 zones, but guessing I only need to know how the first is wired.

I've been doing my best to interpret the comments above, but afraid I need a little more handholding.

Thanks for any input!
Josh

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Last edited by PJmax; 10-07-19 at 12:04 AM. Reason: imported/split link into two pictures
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Old 10-07-19, 12:04 AM
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Not sure what you are trying to do. Install wifi stats ?

To check motor operation without thermostat connected.....
jumper 4 to 5 to open valve; jumper 5 to 6 to close valve.


Those zone valves require three wire thermostats to operate. You cannot sub regular thermostats in for the three wire type. You'd need to add a relay for each zone valve supplying the open and close connections.

To answer your question directly....in the 1311 diagram..... terminal 1 is common.
 
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Old 10-07-19, 05:34 AM
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Hi, I'm trying to replace my old dial thermostats w/ecobee thermostats.
 
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Old 10-08-19, 08:27 AM
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Hi, so I'm still trying to get a handle on what I need to do...

My zone valves requires a wire each to call for heat and a wire to turn heat off. Plus a wire that has something to do w/power through the valve and transformer.

In order to use an Ecobee, I need a C wire directly off the transformer. Since there are only 3 wires currently, I need to get a relay switch so that I can call/cancel heat from the thermostat with one wire and free up a wire to run as C off a transformer.

Did I get this right?
 
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Old 10-08-19, 09:41 AM
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Aftermarket thermostats only supply power to open the valve.... not close it.
The relay is used to open and close the valve. Your three wires between the stat and valve is ok.

I just read you have four zones. If there is a single 40va transformer running those valves it may need to be increased. The motors in your valves run approx a minute to open or close the valve. If all were active at one time.... the transformer could cook. Just to make you aware of possible problem.
Each zone valve requires 10va. of power.
The Ecobee requires 3.5va each

In addition to your stats you will need three relays. White-Rodgers-90-293Q is a good choice.

White-Rodgers-90-293Q
 
 

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