Yet, another C-Wire Question


  #1  
Old 04-16-18, 07:25 PM
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Yet, another C-Wire Question

I've read other threads, thought I knew what to do, but now have gotten myself confused. Any guidance would be most appreciated.

Background:
  • I have a 5-Zone boiler system center by a Aquastat Relay: L8148E
  • Zone Valves are Taco. I was not able to find Part#, but it says "3 Zones - 40VA transformer"
  • I recently successfully swapped-out 4 of 5 Boiler T-Stats from Mercury 2-wire to a Honeywell Wifi RTH6500, using Ventstar 2 Wire Kit at each of T-Stats.
  • Transformers are 24V - 40VA
  • I have 3-wire installed behind walls. G-wire is not attached to anything on either end, and I want to use this wire to now power my RTH6500's.
Here is my existing configuration: https://drive.google.com/open?id=1BZ...cEOIynhrQ5jbg5

Here is my proposed configuration: https://drive.google.com/open?id=1pQ...oMgFmze1ufZxXZ

Putting aside the Transformer sizing for now, is my proposed configuration correct? Many thanks in advance.
 
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Old 04-16-18, 08:23 PM
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In your pic the green at the stats would be C, Orange would be R, and red feeds W
 
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Old 04-16-18, 08:30 PM
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Old 04-16-18, 08:48 PM
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I closed your other thread. Way too confusing to be responding to the same topic in two threads.

You have 2) 40va transformers connected in parallel. You lucked out in getting the phasing correct or you would have had at least one in ashes. That setup has to go. Two transformers should not be connected together.
 
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Old 04-17-18, 07:17 AM
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OK, great. Thanks Pete and Astuff.

I have corrected my diagram per your suggestions, but haven't touched the XFormer configuration/mess just yet. Would you mind confirming this is now correct? https://drive.google.com/open?id=10P...78lo45kElLaJCw

I think now I understand why I'm so confused. Am I correct that whoever wired this up originally did it backwards? (granted, it didn't matter with 2 wire thermostats). Is it worth the effort to re-wire this to get the colors to line up correctly or would you just leave it?

Lastly, does polarity matter on the boiler (T vs TW)? My XFormers don't have indications of polarity, so I'm left to assume the red is hot, and white is common.
 
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Old 04-17-18, 08:30 AM
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There is not a standard color coding when dealing with boiler systems. Getting the R and W to red and white at the thermostat would help in the long run but not worth the effort to rewire everything.

Labels should be T and TV on the Aquastat and polarity doesn't matter.

PJ - I've never seen transformers in parallel outside of a class but is there an actual rule preventing it?
 
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Old 04-17-18, 08:58 AM
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Yup, double checked. You're correct it's "TV"...

Is this right? If something is wired in a series it combines the volts; if it's in parallel, it combines the Amps?
 
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Old 04-17-18, 09:20 AM
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If something is wired in a series it combines the volts; if it's in parallel, it combines the Amps?
Yes...that is correct.

No rule against paralleling transformers but they need to be matched and in phase... otherwise one fights the other.
 
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Old 04-17-18, 10:19 AM
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I'm a bit lost by that so will either have to research it, or just split the XFormers. If I were to split the XFormers, would it look something like this? If not, do you have a different more accurate diagram I should start with?
https://drive.google.com/open?id=1PT...RDKPVfAACotpL3
 
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Old 04-17-18, 10:40 AM
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That diagram is correct...............
 
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Old 04-17-18, 04:35 PM
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I bought two new 75VA XFormers, and since I'll be rewiring the XFormers to the thermostat wire junction anyway, I decided I will rewire the Boiler Control Relay terminal to the Taco Zone Valves and root portion of the Common wire. With the extra amps, should I increase the gauge wire? I think what is on there now is 22ga or 20-ga (standard thermostat 3-wire)

Thanks all for the help!
 
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Old 04-17-18, 05:29 PM
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#22 is too small. #18 thermostat wire is the preferred choice.
 
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Old 04-17-18, 06:45 PM
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I've got one more question... my understanding is that these Taco Zone Valves consume 0.9Amps/~21 Watts each. I have 5 of them (therefore totaling 105 Watts). With 5 Wifi Thermostats, even if they consume 100 Watts each (500 Watts), why doesn't one 40VA Transformer (24V x 40VA=960Watts) handle my power needs? What am I not considering?
 
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Old 04-17-18, 09:23 PM
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Va = watts or volts x amps.
A 40va transformer is 40 watts or 40va/24v = 1.7A.

Zone valves require from .3A (7.2va) to .9a (21va).
 
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Old 04-18-18, 05:54 AM
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Brilliant! Thank you very much for the assistance!!!
 
 

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