Question about Honeywell CT87B ROUND HEATING&COOLING MECHANICAL THERMOSTAT - WHITE Heater

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Hot air does not come on

I am trying to install a Lux mechanical heating and cooling thermostat that has G, Y, W, and Red wires.

When I have the switches on Cool and Auto, and move the temp control to a low setting, it comes on just fine.

But when I have the switches on Heat and Auto, nothing happens.

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Common color code is as follows:
Terminal Wire Color
R RED
W White
G Green
Y Yellow or Blue

This does not guarantee your thermostat was wired to common color code. Assuming it is a single transformer forced air heating and cooling system the following is likely your problem there should be a RC & a RH termial on your new thermostat incase you need a split sub-base for multiple transformers. My guess is that you are connected to RC, if there is not a wire to RH the heat function will not work. the thermostat should have been supplied with a jumper to connect RC & RH together for single transformer applications. If not any small gage piece of wire will work, if I have assumed incorrectly please give me more info about your system.

Posted on Dec 18, 2008

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I recently installed a Honeywell RTH6350D to replace a 2 year old LUX and can get everything to work but the heat(reason for replacing the LUX). Works sometimes but not consistantly. Have the common red(R)...


R represents power supply for the heat system.
RC represents power supply for cooling system.
G represents fan (neutral).
W represents heat system.
Y represents cooling system.
Y2 represents 2nd stage cooling.
W2 represents 2nd stage heating.
AUX represents heat pump.
Try calling 1-800-468-1502.
Their english is "REALLY BAD"!!!

Jan 02, 2011 | Honeywell Electronic Programmable...

Tip

Lux Thermostat 500


The Lux 500 Thermostat is an affordable programmable thermostat that gives you a very easy way to customize your heating and cooling temperatures to your schedule. The programming of this thermostat is easily the simplest that I have found in a programmable t-stat.

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The Lux 500 series thermostats are a great economical way to reduce energy and utility expenses by raising or lowering your temperature settings a the times you set. The installation is so easy that most any DIY’er can install this thermostat. It has an easy to read display and the rotary dial makes the programming very user friendly.

A few of the other great features of this unit are, a keyboard lockout, and an air filter reminder.

This thermostat can be used on any 24v AC or 750mV single stage conventional heating/cooling system. Single stage heat pumps without auxiliary heat will also work with this thermostat.

Here is a summary of the features of this thermostat

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  • 5 - 2 Day programming
  • 4 Periods per day
  • Large easy-to-read display
  • LUX patented user-friendly Speed Dial®
  • Filter usage monitor and alert
  • Default Energy Star approved program
  • Temporary Temperature Override
  • Temperature Hold
  • Keyboard Lockout
  • Temperature Calibration
  • Swing Settings #1 - #9
  • Fahrenheit or Celsius temperature Scale
  • 12/24 Time Format
  • Low Battery Warning Indicator
  • Mercury Free


As you can see this thermostat will give you a lot of great features at an affordable price.

on Jan 16, 2010 | Heating & Cooling

1 Answer

I have a Goodman PHK036-1 unit outside and it had a Lennox Thermostat. I want to replace it with a Lux DMH110 Thermostat and I need to know the wiring for this. I had someone help me last night but the...


Disconnect all wires to start.
1)Go out to unit shut off power and remove electircal panel.

2) Locate the terminal board where thermostat wires are connected. Write down where each color goes to
each letter and then try to do this at the thermostat.

R= Red wire= Power
G= Green Wire= Fan Leg
W or W1= White Wire= Heat Leg
Y1 or Y2= Blue or Yellow Wire= Cool Leg
C=Brown or Black or Orange= Common if used

Jun 27, 2010 | Heating & Cooling

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I paid $20 last night to talk to someone. He told me how to hook up the Lux DMH110 but when i hooked it up this morning the heater came on when i put it on COOL and the fan just come on when i put it on...


If you have this type of system your thermostat will not work;
  • Multi-Stage Heat Pumps
  • 3 Wire Hydronic Systems
  • Line Voltage Systems (120/240 VAC)

  • This thermostat is only for this type of HVAC systems;
  • Most 24V Heating and A/C Systems
  • 1 Stage Heat/1 Stage Cool: Gas, Oil, Electric, or Single Stage Heat Pump Systems
  • 2 Wire Heat Only Hydronic Systems (Hot Water Baseboard & Radiator)
  • Millivolt Systems (Wall Heaters / Furnaces & Gas Fireplaces)

    1. Never connect a low voltage thermostat to line voltage.
    Two wires control a heat only system.
    1. Connect one wire to W and the other to RH.
    Two wires control a cool only system.
    1. Connect one wire to RC and the other to Y.
    Three wires for forced air heat only system, where the previous thermostat
    did not have a clock or timer.
    1. The previous RH or RC wire is the 24-volt transformer wire. Connect it to RH. Leave jumper connecting RH to RC. Connect the forced air heat system to W, and the fan wire to G.
    Three wires for a heat only, forced
    water system that did NOT have a
    clock or timer.
    1. This system employ 3 wire zone valves. Currently no Lux controls are compatible with this system.
    Three wires control a heat only, forced water system that DID have a clock or timer.
    1. Tape off and do NOT install any clock or timer wire. Often they are labeled C or TC. Install the remaining two wires, one to RH and the other to W.
    Four wires control a heat only system,
    and two of the wires operate clock or timer. The other two wires operate the heater.
    1. Tape off and do NOT install any clock or timer wire. Often they are labeled C or TC. Install the remaining two wires, one to RH and the other to W. The jumper connecting RH to RC may remain or be removed.
    Two wires control heating AND cooling.
    1. Currently no Lux controls are compatible with this system.
    Three wires control heating and cooling. One wire operates heat, one operates cooling and the third provides 24 VAC.
    1. Connect the 24-volt power wire to RH. Install a jumper connecting RH to RC. This jumper is usually pre-wired. connect the heat wire to W, and the cooling wire to Y.
    Three wires control a cooling only system. One wire operates the compressor, one operates the fan and the third provides
    24 VAC.
    1. Connect the 24-volt power wire to RC. Connect the cooling wire to Y and the fan wire to G.
    Four wires control a heating and cooling, electric, gas or oil, forced air system that
    is NOT a heat pump.
    1. Connect the 24 VAC transformer wire to RH or RC. Install a jumper connecting RH to RC This jumper is often prewired. Connect the heat wire to W, the cooling wire to Y. and the fan wire to G.
    Four wires control a Single Stage Heat Pump. They were labeled: G, Y, R or
    RH or RC, With either B or was used.
    1. Do not connect wires to both B and O. Connect the reversing valve wire to B or O, just as the previous thermostat. Install a jumper wire from RH to RC. Connect 24 VAC wire to RH too. Install a second jumper wire from W to Y. Connect compressor wire to Y and the fan wire to G.
    More than 4 wires are connected to the
    old thermostat

    Jun 27, 2010 | Heating & Cooling

    1 Answer

    How do you wire a honeywell round mechanical thermostat


    What are you trying to wire up?
    Typical Thermostat Wiring for 4 or 5 wire Heat/Cool Thermostat (not heat pumps)
    4 Wire Termostat
    R = Red One Side of 24 volt Transformer
    G = Green Blower
    Y = Yellow Cool
    W = White Heat
    5 Wire Thermostat
    with one transformer for both units
    Rc One Side of 24 volt Transformer
    Rh Jumper Rc to Rh
    G = Green Blower
    Y = Yellow Cool
    W = White Heat
    5 Wire Thermostat
    With 2 transformers one for indoor unit
    And one for outdoor unit
    Rc = Red One Side of (outside) 24 volt (outside transformer)
    G = Green Blower (outside transformer)
    Y = Yellow Cool (outside transformer)
    Rh = Blue One side of (inside) 24 volt (inside transformer)
    W = White Heat (inside transformer)
    COOLING ONLY Thermostat
    R = Red One Side of 24 volt Transformer
    G = Green Blower
    Y = Yellow Cool
    HEATING ONLY
    R or Rh One Side of 24 volt Transformer
    W = White Heat

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    I have a mobile home with just heat but the air cond come with it


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    Thermostat


    Heat pump Thermastats have Terminals RYW/OW2 G C. I run into this a lot with people buying tStats at home depot. To wire three sages of heat you must have correct tstat. one stage cool and three stage heat. You have to have enough wires at the Tstat. I use white first stage brown second and grey or black third. Make a diagram where each wire goes. Remember to trun of air handler power or you will short the transformer or blow low voltage fuse. Yellow cool, green fan, most of the time blue is c unless it is a battery tstat. orange is O. Red R ot power wire. Rusty

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    Thermostat wiring


    Normal 0 MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman";} Thermostat wire color codes explained.
    Please note. Not all installers use the proper color codes when they install or replace equipment. It may be necessary go go to the furnace or outdoor unit to verify what wires are for what purpose. Also be sure there are no splices in the wire that could change the wire colors between components.
    • R (red) or Rh (Red heat) 24 volts from equipment.
    • Rc (Red cooling) 24 volts from transformer in cooling equipment.
    Note: If only furnace has a transformer and cooling equipment does not jumper Rc and Rh.
    • W (White) sends 24 volts to furnace control to start the heating cycle.
    • W2 (no standardized wire color, usually whatever wire color is available) controls second stage heat.
    Note: W2 is most often used for heat pumps to control what is called emegency heat or Auxillary heat, and most often will use the white wire.
    • Y (yellow) often (blue) is used, controls cooling unit (outdoor condensing unit) also is used for heat pump heat.
    • Y2 (no standardized wire color, usually whatever wire color is available) controls second stage cooling.
    • G (Green) controls the fan "on" operation of the furnace/air handler. Also often is used to start the blower for many electric furnaces.
    • C (common) most often brown but can also be black or other color available to installer.
    • O (orange) Energizes heat pump reversing valve for cooling (Trane and most other brands).
    • B (Blue) Energizes heat pump reversing valve for heating (Rheem, Ruud and Weatherking).

    Jun 02, 2009 | Carrier Heating & Cooling

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