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    Proper Wiring Help Needed (13 Posts)

  • Wiring Wiring @ 4:52 PM
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    Proper Wiring Help Needed

    I purchased a Honeywell RTH8580WF Wi-Fi Thermostat and now I am not sure if I can use it on my system.  The current thermostat has only two (2) wires on it connected to the RH + W terminals.  I spoke with Honeywell and they tell me I need a third wire (24V) to power the display.  I checked the boiler and the thermostat is connected to a TACO SR503 Zone Control.  I only see two terminals where the current thermostat is connected and I am trying to figure out where the third would connect?
    Can anyone help me out here please or would I be better off just returning the new thermostat?
    Thanks in advance!
  • SWEI SWEI @ 5:09 PM
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    Those two terminals

    above the transformer have 24VAC on them.
  • Paul48 Paul48 @ 9:20 PM
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    I think he needs a Common wire SWEI. Oh...I see what you're talking about now. There's a "C" there.
    This post was edited by an admin on April 12, 2014 9:30 PM.
  • Techman Techman @ 11:08 AM
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    You have a major miswiring problem here. Is that low volt (24v) wiring  going into the same BX as the line volt (120v) wirers? If I'm seeing that correctly , then you have a big problem looming ahead of you and anyone who adjusts the t'stat.
  • Wiring Wiring @ 3:38 PM
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    I thought it strange

    I noticed that when I first opened the cover that the low voltage wires were fed in along with the AC.  I have already disconnected and removed them, feeding them in from the knockout on the opposite side.  I am glad I started this project or I would have never noticed it.  This was installed by a licensed contractor 2-3 years ago and has been that was since.  I have to pull a new wire from the thermostat down in order to get the third wire and just have not had the time as yet.  Thanks all for the info!  If I understand everything correctly, all I need to do is add the wire from the Common terminal of the 24VAC in order to get the new thermostat functioning.
  • STEVEusaPA STEVEusaPA @ 11:16 AM
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    End switch

    @ techman..Looks like those 2 wires are going to the end switch
    This post was edited by an admin on April 16, 2014 11:17 AM.
  • Buster Buster @ 8:21 AM
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    Proper wiring

    The 24vac terminals on the Taco control will go to the RC & C terminals in the thermostat, the existing wires from the Taco control (old thermostat wires) will go to the R & W terminals of the thermostat and remove the metal jumper between R & RC.
  • Wiring Wiring @ 8:28 AM
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    Thank you Buster!  Clear and concise!
  • Techman Techman @ 4:04 PM
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    Hi Steve, the low volt wirers being for the end switch makes good sense. The problem is the insulation value for the lo volt is 300V and 600v for the line volt wirers. So the line volt can "jump " thru any cracks , wear, or worn spots in the insulation , therefore "line volt wire " should have been used for the lo volt circuit if both are run thru the same conduit. We do that all the time. Plus if done on electronic control circuits there can be "interference" in the lo volt wiring due to magnetism.
    This post was edited by an admin on April 16, 2014 9:24 PM.
  • Techman Techman @ 7:14 PM
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    This post was edited by an admin on April 16, 2014 9:24 PM.
  • STEVEusaPA STEVEusaPA @ 2:18 AM
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    ahhhhh.....good point

    I didnt even look at that because i've never put low and line voltage in the same conduit.
  • heatpro02920 heatpro02920 @ 9:03 PM
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    Everyone does things their own way...

    I see the lv and bx ran like that all the time, I don't do it myself because I do it the way I always did it, kind of stuck in my ways. I get on a job and it seems to go super fast when I do it the way I always did it...

    And I as well as a lot of other guys will look at a different than our own practice and think its wrong or not as rite, but if its up to code, performs as intended, and the customer is happy with it, then its good...

    I had people comment about how I wire in a zone valve control on a retrofit, since the wries are never long enough to reach the control I mount my control, then run 18-5 up to the zone valves, tie red and white into the t-stat wires and tire the blue, green, and yellow into 1, 2, and 3 on the zone valve... I strip the 18-5 back around 8 inches and put a couple screwdriver loops in the r,w and then the b,g,y it looks good when its done, IMO, its fast, convenient, and works well for me... Now a tech that works for me and a friend of mine in the field like to put a handy box in the ceiling and connect all the t-stat wires in there with new longer extensions that go to the control, then run 18-2 for that and 18-3 to each zone valve.... To me it takes too long, doesn't look as good, costs more in materials, and gets confusing when servicing...

    I know a contractor that runs all his t-stats in one cable up to the ceiling {no box} then connects them all to a single cable and then runs 18-3 to each zone valve, so if he has 5 zones he runs 18-10 {10 different wires} for all the tstats and then wires each one, the wire he uses has double colors, so it for 18-10 it will be blue and then blue with a white stripe, then orange and orange with a white stripe, ect so each color is its own zone, then he puts a piece of that color electric tape on the zone that corresponds to it so the zone valve that he used for the orange wires gets some orange tape....

    To me it all works, but I like my way...
  • Techman Techman @ 6:44 AM
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    Lo volt vs line volt

    But it is against code to run both wirers in the same conduit. Put the 24v into "line volt wirers " and it is legal. Look inside control panels, relays boxes , zone panels and there is a "divider" (usually gray colored cardboard) between the two voltages separating them from each other. Look at the RIB relays, they use all "line volt" wirers.Look at AC cond units, lo volt wirers(24v) connect to line volt wirers(24v) then the lo volt circuit goes thru hi/lo press switches, the Copeland "staging control" or "time delay relays" or any other controls.
    This post was edited by an admin on April 22, 2014 6:46 AM.
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