Nest


  #1  
Old 03-25-17, 08:55 AM
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Nest

Are there any Nest T/S "experts" available here to answer a question or two?
 
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Old 03-25-17, 09:08 AM
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That is a loaded question. Some "experts" will tell you to stay away from them. Others will say that they are OK as long as you have a C wire. I recommend a relay on anything feeding a contactor to protect the electronics. They are regularly getting software updates and don't always do what you expect so are OK if you can live with that.
 
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Old 03-25-17, 09:41 AM
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Feel free to post your questions.
 
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Old 03-25-17, 10:28 AM
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Wiring

Got a customer with hydronic radiant heat, multiple zones,and A/C, we are now using Nest stats. On the heat/cool stats we are wired Rh, W on the heating side, Rc,C, and Y on the cooling side, two systems with two xformers. Uponor (Wirsbo) zone control modules for the radiant loops with actuators. The Nest is back feeding the zone module causing the yellow light, which is a signal that the stat is calling and opening the actuator, to flash, should be solid yellow on a call for a heat,can't be good for the module. Even if the Nest is turned off I get a backfeed situation unless I totally disconnect the Rc wire. Nest can't seem to help me, they have no idea what the zone control module is even if I explain it as if it were a Taco ZVC.
 
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Old 03-25-17, 10:49 AM
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One thing you can try is to reverse the Rh and W wires and see what happens.

What I would do is install a relay right at the zone control module. The relay would get its power from the zc board and its control from the nest. Any basic 24v N.O. relay will work.
 
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Old 03-25-17, 11:04 AM
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I've never known a Nest to function well with zoning controls, be it hydronic or forced air.
 
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Old 03-25-17, 11:09 AM
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The nest doesn't use relays to control loads. It uses electronic switches which can cause problems. A relay is used to isolate the switched outputs.

You'll find this with any wifi stat that doesn't require a C connection.

One plus for the honeywell stats that use relays.
 
  #8  
Old 03-26-17, 11:12 AM
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Going to use a RIB relay for isolation purposes. That should solve the issue.
 
  #9  
Old 03-26-17, 11:41 AM
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A RIB is perfect. Any 24vac S.P. normally open relay will work for you.
 
 

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