I am having trouble figuring out the wiring for a new programmable thermostat installation.

I moved into a barnd new house equipped with two Robertshaw Model 9400 Thermostats (one for each zone). I bought Honeywell RTH7500D programmable thermostats to replace them because I wanted programmable thermostats. I have two central AC units (one for upstairs, one for downstairs) and I have a gas furnace.

The curret thermostat is wired with the following:
Red Wire > RC (Jumped to RH)
Yellow Wire > Y
Green Wire > G
White Wire > W
Orange Wire > O
Blue Wire > B
There are also a brown wire and a black wire not used coming out of the wall.

The new honeywell has the following connections:

Conventional --- HP
C --- C
G --- G
Y --- Y
W --- O/B
RC (jumped to R) --- RC (jumped to R)
R --- R
W2 --- AUX
Y2 --- E
--- L

Any ideas on what wire goes to what? I can't figure out the orange wire and the blue wire and I don't know if I need the brown or the black.

Thanks!
Paul

Post this in the "Heating and Air Conditioning" forum... Labman will answer it.

Usually there is a 24 volt AC transformer in the furnace with the secondary winding connected to a red wire running to the thermostat and a blue wire, common, to the gas valve, A/C relay, and fan relay. From the thermostat there will be white wire to the gas valve, yellow to the A/C, and green to the fan. The thermostat is wired to switch the power from the red to the white, yellow, and green as needed with the blue completing the circuit. Most thermostats and furnaces have the contacts labeled R, B or C, W, Y, and G for the corresponding wire colors. It may be wired to have the A/C control wires return to the furnace and its controls and then a second wire goes to the A/C unit. Internal wiring may replace the green wire if the thermostat does not give you the option of fan only or continuous fan. Digital or programmable thermostats may need the blue wire connected to them.

The C terminal on the thermostat may be common, needing the blue wire to complete the circuit to power the thermostat. One side of the transformer is connected to the red. The R and RC is jumpered to provide power to the thermostat and power to be switched to the load selected. To figure out the rest of the wires, you need to look at the furnace and maybe its installation manual. If it has a white wire connected to a W terminal, you need to connect the white wire to the W terminal of the thermostat. The black and orange wires may not be used. Are they connected at the furnace, and if so, how are the terminals marked? Some furnaces have more than one firing rate, and terminals that allow a thermostat to call for either a high or low firing rate. If the furnace has terminals similar to the
W --- O/B,
W2 --- AUX
Y2 --- E
--- L,

You could try connecting the black or orange wires each to the same terminals at both ends. If the markings aren't the same, you would need to study the installation manuals of both to have the thermostat control the firing rate.

I have a simple thermostat that tells my dual rate furnace we need heat. The furnace has a program that chooses a firing rate mostly based of recent heat cycles. Some systems also have an outside temperature sensor. The Y2 terminal is likely for a multiple speed air conditioner.

This site appears helpful, but I didn't see my situation, and I tried the Honeywell wiring wizard but it doesn't include my model.
I currently have a White Rodgers (9510E7) rectangular thermostat and I am trying to replace with Honeywell 5-2 Day Programmable RTH230B.

Currently there are 8 wires coming out of the wall
Blue- not connected to anything
Black- not connected to anything
Red- R
Brown- C
Yellow- Y
White- W2
Green-G
Pink- O

The new thermostat only has room for 5 wires. Some are straight forward, but others are confusing. The outlets are:
Rh- Heating Power
Rc- Cooling Power
W- Heating Signal
Y- Cooling Signal
G- Fan
*Jumper wire between Rh and Rc.

Can someone please tell me what wires connect to the Rh,Rc,W,Y,G Honeywell outlets and which are not used (and possibly why not used). Thanks in advance!

Rh/Rc represent a 24 volt power supply to either the heating or the cooling circuit,hence the "c" or the "h" after the R. That would only apply to you if you had a separate 24 volt power supply for both your heating and cooling. If your equipment is newer than 20 yrs I would say you have a single 24 volt power supply so you need to have a jumper connecting the two together. The wire that connects to Rc/Rh comes from the "R" terminal on your furnace. According to your letter designations on the old thermostat it looks as if you have a heat pump. "C" is the common terminal and completes the 24 volt circuit to power up your thermostat. "Y" brings 24 volts back to your furnace to energize the cooling circuit. "G" brings 24 volts back to energize the fan/blower circuit. Now this is where it gets tricky, the "O"terminal brings 24 volts back to energize a reversing relay in your air conditioner/heatpump which allows the air conditioner to dump the heat it absorbed from outside into your house, you can consider this action your first stage of heating. So when the outdoor conditions are not favorable for absorbing any more heat i.e an outdoor temperature cut off, the thermostat then sends 24 volts down the W2 terminal to the "W/W1" terminal on your furnace to bring either gas or electric heat, I am assuming gas . So, you first need to know if you have a heatpump or not, if you do the new thermostat you have will not work, you will need to get a heatpump thermostat. If you have an air conditioner with a single stage furnace pull the panels off for your furnace and idetify where the thermostat wires go to. Verify and write down what color wire comes off each terminal R=red, W=white, Y=yellow, G=green, C=typically blue, but whatever color you want to use. Also remember that if you have to get a heatpump thermostat, you will have to get in to the internal configuration mode and configure the thermostat for heatpump operation. Hope this helps

I have a honey programmable thermostat and it has a five wire with rh rc w y g. There is a line coming up from the furnace with 5 wires blue white red yellow and green. As of right now I have it wired with red going to rh blue going to rc white to w yellow to y and green to g. My air conditioner is not working what is my solution to this

Rc= Red
Rh= Jumper to Rc
G = Green Blower
Y = Yellow Cool
W = White Heat

I just bought a Honeywell RTH7500D programmable thermostat to replace an old Carrier (or Honeywell) LR1620 thermostat. Could someone please help me figure out what wires go where on the new RTH7500D thermostat?

Thank you very much.

need wiring matches to remove Honeywell LR1620 and replace with RTH6350 thermostat.
Landed wires on LR1620 are : W3-W2-O-G-Y-R-X
there are no jumpers on old thermostat
This is a heat pump set up for heat and cooling

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I just bought Honeywell RTH7600D 7-day programmable thermostat. There is a battery-free option noted on the box and nothing in the installation steps that describes how to opt out of batteries. How do I install with no battery option?