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On my therostat it show and talks about the R wire and the Rc wire. What is the differet?

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If you would have a two transformer system..... The power wire from the furnace transformer would hook up on R and the power wire from the Air Conditioner transformer would hook up to Rc....

BUT most systems now only have one transformer...... So if you are using this thermostat you will need to put a jumper wire from R to Rc. So the Air Conditioner will work. Furnace is the source of the transformer. R/Rc,W,Y, C, on the Thermostat will Hook up to R,W, Y,C on the furnace and Two wire from the Air Conditioner would hook up on Y and C on the furnace.....Good Luck.

Posted on Apr 02, 2011


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I have 4 wires green blue red and white my red is connected to the rh rc with jumper green connect to g blue to y1 and white is connected to w1 my new thermostat has no rc rh or a jumper

Paulette, if your new thermostat has no Rc and Rh thats fine. The Red wire should simply go to the R terminal. The Rc and Rh terminals on the old one was for the old 'two transformer' systems. The vast majority of systems now have no need for the Rc Rh terminal and jumper. The rest of your wires connect as on the old stat also.

Jul 31, 2015 | Heating & Cooling

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I am wiring a Honeywell wifi unit and I used a separate 24v transformer and connected to the c and rc terminal. My system is ac and heat and uses both and rc and rh wire. I wired the rc to the r ter

A thermostat is a switch. It connects 24vac from one terminal to another depending on the request. The 24vac comes from a transformer, usually located in the furnace and connects to the R terminal. Since you are using RH and RC without a jumper between it means there are two transformers, one in the furnace for heating (RH) and one in the air conditioner condenser used for cooling (RC).
Your old thermostat was probably mechanical and did not have a C (24vac common) terminal. Your new thermostat requires power to operate therefore needs a wire connected to a C terminal. I would get rid of the transformer you added and look for an unused wire in the bunch at the thermostat. If it's there connect it to C on the thermostat and to C on the furnace. Remove any jumper from R to RC or from RH to RC depending on your thermostat and connect wires same as the old thermostat.

Jul 04, 2014 | Heating & Cooling

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How do I connect the two thermostat wires from a Honeywell R8184G4009 to a programable thermostat. My old thermostat is not marked.

On the Protectorelay Oil Burner Control R8184G4009, you connect the two thermostat wires @ "T" and the other "T". On the ACE Smart Temp Universal programable therostat, connect one wire to "Rh" and the other wire to " "W". Be careful if you are using this thermostat for A/C. In that case, make sure there is no jumper between "Rh" to "Rc".

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Sounds like the control board or the wiring running to the unit from the main system has been damaged some how. Inspect the therostat wires running out of the system to the condenser (Outside Unit) to make sure that there is no damage to the wiring. Could also be that you have a bad relay that needs to be replaced, check to see if anything in the condenser outside looks to be burnt or enlarged. You will be able to tell the signs from the look of it.

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How to wire a therostat

You should have 4 wires, Red, Green, White, Yellow
On your thermostat just match up the Red to R, Green to G, White to W, Yellow to Y. sometimes the Yellow is blue instead. so Blue to Y.

If you have these four you are set.
Now some t-stats have Rc and Rh, If yours does put the Red to either one and add a small wire to connect the Rc to the Rh (jumper wire) this just tells the t-stat to use one power source for the A/C and Heat. No big deal. But if you don't jumper it you will only have A/C on Rc and Heat on the Rh depending where you put the Red wire.

If you have other colors just look in your furnace and see what colors are hooked to R,G,W,Y and do the same at the Thermostat. Good luck

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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,
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    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
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    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
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    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
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    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.
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