Upgrading Thermostat Issue


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Old 11-30-22, 10:04 PM
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Upgrading Thermostat Issue

Hello!

Like many others, I am looking to replace my old thermostat with a smart thermostat. I have reviewed several threads others have had regarding this issue, but couldn't find anything to specific to my exact setup. I will admit that I am not super knowledgeable when it comes to heating and electrical, so am hoping someone with expertise in this area can help me understand what the issue is and how to fix it.

I have a Burnham boiler that provides heat. No air conditioners or heat pumps. I have an Aquastat Relay Type L8124A with three Taco 571-2 valves and a thermostat for each zone.

I am looking to replace one of my old Honeywell round thermostat with an Amazon Smart Thermostat. Would like to potentially upgrade the other two at some point, but want to troubleshoot this first one before doing so.

When I removed the old Honeywell thermostat, there were only 2 wires connected to it: Red and White. In the brown wire that included the red and white wires, I did find an unused blue wire.

When I connected the red wire to the R slot, the white wire to the W slot, and then the blue wire to the C slot, the new thermostat did not power on. From reading other threads on this topic, it sounds like the way the wiring is setup is backwards or not setup to support the C wire.

Question is why is the thermostat not powering on? Am I able to use the unused blue wire as the C wire? If so, how can it be done?

Here are some pictures of my current setup. If there is additional information or pictures needed to help with troubleshooting the issue, please let me know. Again, not very savvy when it comes to this sort of stuff, so will greatly appreciate any help I can get. Thanks in advance!





 

Last edited by PJmax; 12-01-22 at 03:26 PM. Reason: resized pics/labeled
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Old 12-01-22, 09:40 AM
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Welcome to the forums.

I need to see the splices between the thermostats and the zone valves.
Hopefully they aren't all jammed in that 4" round box at the ceiling.
Post some splice pictures for me.
 
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Old 12-01-22, 10:08 AM
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Thanks for the quick response!
You were right, they were in the 4" round box at the ceiling.
Luckily, I was able to divide them to get a clear picture of them.
Here is the picture:
 

Last edited by PJmax; 12-01-22 at 04:38 PM. Reason: labeled pic
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Old 12-01-22, 04:43 PM
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I labeled your picture. Obviously you can see where the C splice is.
That's where your third wire to the stat will connect.
I put W? because I can't tell which is which.
I would highly recommend labeling the three zone valves.
Follow the wires up and label them just before they enter the box.
Using the blue/white W? splice...... identify and label the three thermostat cables.
Label the aquastat TT cable.
Labels the transformer cable.
Always good to know this.

Any questions ?
 
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Old 12-02-22, 07:58 AM
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Thanks! I will label those wires.

Just to make sure I am fully understanding what you mean by the C-Spice - is that the group of wires that you labeled on my picture "C/TT"?

In terms of next steps, what do I need to do to connect the new thermostat so that it gets power and works? Am I able to use the unused blue wire that is with the red and white wire at the thermostat? Do I need to swap any of the connections on the zone valves? Or swap connection at the thermostat?

I apologize for all the questions as this is all unfamiliar to me!
 
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Old 12-02-22, 07:42 PM
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You need red to R at the stat.... you have that.
You need white to W at the stat.... you have that.
All you need to do is to strip the cable insulation back. Connect the blue to C at the stat end and at the zone valve end connect blue to the splice that I've labeled C/TT. You'll end up with five white wires plus the new C wires.
 
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Old 12-02-22, 09:32 PM
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So, do I take the blue wire from the appropriate blue/white wire splice for that thermostat and connect it to the splice you labeled C/TT? What do I do with the white wire that's left from the blue/white splice?
 
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Old 12-03-22, 01:47 AM
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You have a three wire cable to each thermostat.
The red wire of that cable goes to the R splice.
The white wire of that cable goes to the blue wire (W?) which then goes down to the zone valve.

The blue wire from the thermostat is not in view. It's still in the cable.
You need to strip the cable jacket to expose it.
Apparently some thoughtful installer cut it off.

The three blue wires we see in that box are the three blue wires that go to #1 on the zone valves.
 
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Old 12-06-22, 01:00 PM
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I did what you said, and it worked! Thank you so much!

One last question: As I mentioned in my initial post, I would like to eventually upgrade all 3 thermostats. I got this one done, but wanted to know if my current setup would support having 3 smart thermostats? At the least, would it be able to support 2 smart thermostats and one (non-smart) battery operated thermostat?
 
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Old 12-06-22, 06:56 PM
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Yes... you can connect all three the same way.
 
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Old 12-07-22, 07:51 AM
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Great! Thank you again for all your help! I greatly appreciate it!
 
 

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