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Can I use DHW Aquastat line as constant 24V C to power Smart T-stat?

Can I use DHW Aquastat line as constant 24V C to power Smart T-stat?

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  #1  
Old 08-25-19, 09:37 AM
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Can I use DHW Aquastat line as constant 24V C to power Smart T-stat?

Hi - new to the site, so apologies if this is a dumb question (or a repeat, however I looked and couldnít find this exact question) but...I have a Weil-McLain Gold CGa boiler with 2 zones heating my baseboards. I also have 2 nest thermostats, which have recently been losing battery power after a recent upgrade. I have both Rh and Rc connected (we have independent air conditioner units), however the nest is only recognizing the Rc connections. Iíve done enough research to know I need to connect a constant 24V C from the boiler unit (Rh line).

However, the Weil-McLain doesnít seem to have stand along ports I can run the C line too (the Blue wire runs to my basement, but its cut off so I just need to connect it). However, I do have an unused Aquastat power line + constant (what I believe to be constant anyway) and was wondering if I could use that as my C line? Iíve been studying the wiring on this, and know the lines from the transformer runs into the unit via connector, and then there is a t-stat output connector which currently has a t-stat neutral line (black), a hot line (also Black but split three ways: to T-stat (black), to unused DHW Aquastat (blue capped line), and to Guard Dog Low Water Cut Off (red)), a ground (green), another neutral (black - going to guarddog LWCO) and what I believe is a constant wire for the DHW aquastat (blue wire) I attached pictures of the wiring diagram on the boiler itself and how its wired, trying to show all the above.

Iím obviously not a professional, so just wanted to A) see if my above understanding is correct; B) if I am correct on the wiring, will it work if I use the the DHW constant as my T-stat constant ; and C) make sure this wonít be unsafe for my boiler.

Thanks in advance
 
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Old 08-25-19, 11:49 AM
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Without looking at all your stuff...... the C connection on any wifi thermostat is referenced to the cooling system. That means the C must come from the A/C system as well as Rc.
 
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Old 08-25-19, 01:06 PM
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That solves that, thanks for the quick reply. Will start over up at the air handlers and see what I have.

Thanks again, appreciate it
 
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