How do i wire nest to this old Lenox

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Old 08-02-20, 06:15 AM
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How do i wire nest to this old Lenox


Need to figure out how to hook up nest 3rd generation to this thermostat
 
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Old 08-02-20, 07:38 AM
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Those old thermostats are a nightmare. Similar, but different one here: https://www.doityourself.com/forum/h...cury-nest.html
  • Lennox - color - Nest
  • R - green - O/B
  • M - red - Y1
  • Y - white - W1
  • V - blue - Rc
  • F - yellow - G

Ideally go to the air handler and see what color connects there to verify connections.
 
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Old 08-02-20, 10:33 AM
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I would make one change.... put the white wire on W2/AUX terminal.
 
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Old 08-02-20, 02:50 PM
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Neither wiring diagram worked. It acts like no power. It says nest won't work with v/vr systems. Might have to give up.
 
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Old 08-02-20, 09:06 PM
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You will need to locate where the transformer is. Some have one inside, some outside and some have both.
Sometimes the nest can be finicky based on the amount of power it can steal.
You may ultimately need to get a C wire to the stat.
 
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Old 08-03-20, 09:03 AM
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I do not have a Nest but when I changed my unit out my Venstar t stat REQUIRED a constant hot. Which most of the older single stages t stats did not require. Check behind the t stat and see if you have an extra wire. If you do then you can terminate it on the control board and get the voltage you require.
 
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Old 08-03-20, 07:45 PM
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The R is constant hot. You mean a Common.

This is an old Lennox system and could use two transformers. They were NOT wired like systems are today and the ID lettering does not match.
 
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