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Installing New Honeywell Wi-Fi Smart Thermostat with Old Aquastat L8148A

Installing New Honeywell Wi-Fi Smart Thermostat with Old Aquastat L8148A


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Old 03-31-14, 09:02 AM
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Installing New Honeywell Wi-Fi Smart Thermostat with Old Aquastat L8148A

I'm looking to install a new Honeywell Wi-Fi Smart Thermostat (Model # RTH9580WF) to replace a battery-operated thermostat I currently have in place.

At the moment I only have two wires going from "T" "T" on the Aquastat to my thermostat, the new wi-fi thermostats require a third C wire, so I'm going to run new 18/3 wire but I'm not sure where to tie this third C wire into my Aquastat L8148A.

Please see my diagram here for further details, I have spec'd out my entire environment.

Here is a link to the diagram I created:

http://www.nathanpoirier.com/thermostat.png

I appreciate any advice/suggestions anyone can provide, thank you!
 
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Old 03-31-14, 09:26 AM
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I also noticed that on the Taco SR501 there is an open COM spot, could I just run the two wires from my thermostat to the existing Aquastat and the "C" wire to the Taco to get its power?
 
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Old 03-31-14, 09:56 AM
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Yes. Refer to the R, W and C labels on the aqua stat.
With 2 wires it didn't matter but with 3 wires it is important to connect aquastat W and R to the correct stat locations as well.
 
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Old 03-31-14, 10:07 AM
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Houston204, thank you for your reply I really appreciate this.

The Aquastat only has "T" and "T" which is used for R and W on the thermostat, it does not have a third option for my C wire, can I use the Taco SR501 COM option for this? I only need the C wire for power correct?
 
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Old 03-31-14, 10:09 AM
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could I just run the two wires from my thermostat to the existing L8148A Aquastat and the "C" wire to the Taco SR501 to get its power
You can't take power from one controller and common from another.
 
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Old 03-31-14, 10:11 AM
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Ok, that is good to know, any suggestions how I can tie this "C" wire into the Aquastat if I'm not able to use the COM option on the Taco SR501?
 
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Old 03-31-14, 06:13 PM
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You may be able to connect Rh and W to the TT terminals of the Aguastat and Rc and C to the Taco SR501. You would NOT use the RH-RC jumper. You would need four wires from the thermostat to the controllers.

Wait for the forum pro, Houston, to stop by and see if this is a workable solution.
 
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Old 04-01-14, 10:03 AM
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Thanks PJ for the response, yeah that's the way I have it setup now RH and W (with the jumper in place) going to TT on the Aquastat. Just where to go with C on the furnace, will I even need Rc if I'm not using cooling, just heating? Again, I appreciate your help with this.
 
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Old 04-01-14, 07:11 PM
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I'd get a separate transformer and connect it to Rc and C on your thermostat.
Remove the jumper between RH and RC at the thermostat,
and connect RH to a T and W to the remaining T at the L8148A.

Amazon.com: Class II Transformer - 24 Volt AC, 40 VA, UL/CSA Approved : MGT-2440: Car Electronics
 
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Old 04-02-14, 05:22 AM
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It appears that there may be a C terminal on the SR501,why not set up the boiler as per the Dia for the control from Taco? Any questions call Taco tech support they are pretty helpful.
Just a thought
Geo
 
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Old 04-14-14, 12:01 PM
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Hi Houston,

Thank you for your reply, this may be the way to go, looks like the cheapest and easy option here.

Sounds fairly straight forward here.

Thank you for this suggestion! I appreciate all the help from everyone!
 
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Old 04-14-14, 12:57 PM
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Hi Geo,

I was actually thinking of this option earlier but PJmax suggested that this was not an option from what I recall in this thread.
 
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Old 04-14-14, 05:36 PM
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Right now your thermostat is tied to your aquastats TT terminals. You can't just move the thermostat to the the SR501 without making other changes.
 
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Old 04-14-14, 06:22 PM
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Just curious what is the SR501 controlling now?
Geo
 
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Old 04-15-14, 10:03 AM
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If you look at the link provided in this thread to my diagram the SR501 is controlling the Hot Water Tank, which both of those T-T connections are connected to. Then the 120 VAC connections are tied to the Hot Water circulator.

My original thought for installing this new thermostat was to use T-T on the Aquastat and then use the 24 VAC COM "port" on the SR501 to give the new thermostat power but that's what I was told wasn't possible.
 
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Old 04-15-14, 06:02 PM
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It appears that the hot water and the room Tstat are both connected to the TT on the aqua stat , is that correct? One other thing check between R and Common on the SR501 and see if there is 24vac there.
Geo
 

Last edited by Geochurchi; 04-15-14 at 06:05 PM. Reason: Another option
  #17  
Old 04-16-14, 04:46 AM
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After more thought the SR501 is for only 1 zone and can not be used to supply 24vac to your wifi Tstat,your best bet would be Houston's using a separate 24 VAC..
Sorry for the confusing.
Geo
 
 

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