Yet Another C Wire Issue

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  #1  
Old 11-05-20, 12:13 PM
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Yet Another C Wire Issue

Hello All,

Attached is a schematic of my current 2 zone heating system setup. The boiler uses a Honeywell L7224U 1002 Electronic Aquastat:

From what I can tell Its the same setup (with some additional splices) as the taco 571 schematic shown at the following link (image attached):

https://www.doityourself.com/forum/t...ifi-tstat.html

When I tried to follow the advice within this thread post to add the C wire by attaching the C wire to the transformer labeled R or "Load", I was receiving 24V from both the R to C as well as the W to C.

Should I simply rewire my system to duplicate what PJmax mentioned in a different thread (attached), or is there a simple way to add the C wire to my existing setup?

https://www.doityourself.com/forum/t...no-c-wire.html




 

Last edited by PJmax; 11-06-20 at 07:49 PM. Reason: replaced incorrect forum diagram
  #2  
Old 11-05-20, 02:29 PM
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Welcome to the forums.

My diagram is what you need to follow.
You must send 24v to R not Rc on the stat.
The W on the stat must feed terminal 1 on the zone valves.

If you didn't want to change all the wiring..... reverse the R and W wires at the stat and add a C wire.
 
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  #3  
Old 11-06-20, 06:41 PM
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Thermostat RC is for cooling. RH is for heating and used to activate heat, burner, circulators or whatever.

AAK123 should review his setup. Some modern thermostats have options that flip things.

The blue wire at transformer is C. Connect it with 3rd wire directly to all thermostats C terminals.

Picking it up from some other device can lead to confusion and miss wiring.

RC is for C from separate air conditioners that have transformers. If AC does not have one, RH and RC are commonly jumper-ed. Some new thermostats come with jumpers. If no AC, nothing will happen if jumper ed.
 

Last edited by doughess; 11-06-20 at 07:20 PM.
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Old 11-06-20, 06:55 PM
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@ AAK123 .....

Thanks for posting that link image from this site.
The additional wiring that my forum partner drew in is not correct. (I'll be changing that)

When using three wires.....
You must power the stat via R and the switched 24v out must come from W.
That diagram is strictly a basic two wire diagram and C should not be on it.

Diagram in liked thread and posted in this thread corrected.
 
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Last edited by PJmax; 11-06-20 at 07:50 PM.
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Old 11-06-20, 08:27 PM
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Most techs are trained on classic wiring and would stick with that. C to C, R to RH and W to activate heat, G for fan.

I post wiring diagrams and manuals on walls so outside tech will see them.

Also have labels and 120 or 24 volt LED pilot lights on everything.

On cold, snowy, winter night can just see at glance status of things and easily diagnose any issues. Battery activated alarm sounds if oil burner control locks out. Better that awakening to cold house.
 
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Old 11-07-20, 07:57 PM
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PJmax,

Many thanks for the help. Your diagram was straightforward and very easy to follow. Took about an hour to rewire w/ testing along the way.

No clue why it was wired up the way it was, but I'm happy everything works the way it should now.

Thanks Again!
 
  #7  
Old 11-07-20, 08:10 PM
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Awesome job. .... Thanks for letting us know how you made out,
 
 

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