I am renting a home and the landlord just put in a new programable thermostat. I know that she has messed up installing other items in the house and I think she might have messed this up. Here is why, when I turn on the heat the air conditioner unit out side also turns on (maybe it is just acting like a fan?). Is this supposed to happen? Also when the thermostat gets to the temperature set it doesn't turn off, instead it just turns the heat off and blows cool air in through the ducts until it turns back on to heat the place up agian, I am quite sure this is abnormal. The AC unit outside stays on the entire time. I toof off the cover of the thermostat and there are 5 wires, one green, blue and yellow and two reds. Ther appear to be hooked up to the letter that corrosponds to their coloe (ie Green is hooked up to G, Yellow to Y). Both reds are hooked up to RC. I have no clue what it was like on the old thermostat. Does this sound correct? And does the AC part sound normal? This is the first time I am living in a house so I just don't know.

Thanks
Mike

labman

If a programmable thermostat is hooked up right, the heating system should work the same except for the thermostat taking care of details like turning itself up and down as needed. If you got heat without the outside unit running before, you should now.

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.

Does the thermostat have an RH terminal? RH and RC are for separate hot wires from 2 transformers. Usually there is just one transformer and one red wire is connected to both. Where is the blue wire connected, the W terminal? If there are HE and HG jumpers, you need to select the one for electric or gas heat. You may need look at the furnace and see where the wires are connected at that end. If you just connect the blue wire to the W terminal at both ends, and connect everything else as above, it should work unless you have a heat pump system.

sailblue5

I looked agian and there and here are the hook ups,

Red wire to RC and RH.
Blue to B
White to W
Green to G

I looked near the furnace and I don't really know where the wires are running too. If the AC unit is running outside is it just the fan or is it conditioning the air? Is that going to make my electric bill go up as much as it does when the AC is running? I don't know what the unit did before the thermostat was replaced.

The other thing that really confusses me is that the fan still blows after it has reached the correct heat. Is this a problem of the thermostat? I would prefer if it just turned off.

Thanks
Michael

Kender

It sounds like you just need to move the blue wire to the "Y" terminal on the T-stat

sailblue5

What is the Y terminal for? What would that change?

Thanks for all of your help.

Michael

Kender

Red wire to RC and RH.
Blue to B
White to W
Green to G

Is that how is hooked up now?
if so then the blue wire is to turn on the outside system.

The "B" terminal on the T-Stat is always on when the t-stat is switched into heat regardless if it is calling for heat or not.

The "Y" terminal is what turns the outside system ON and OFF in cooling mode

sailblue5

That is how it is hooked up (Blue to B). So if I put it to Y then the unit outside won't turn on when it is on heat? It is just a normal ac unit outside most housed, does it need to be on to push air in to the furnace?

Kender

The wire should be YELLOW but it is common to use a BLUE wire in is place.
The furnace should run with the outside system off.
The only time the outside system should run in heating is if it is a HEAT PUMP.
if it is a heat pump then there would be more wires going into the t-stat.

sailblue5

Thanks for your help. I am going to move it over. I definitly don't have more wires running in to the T-stat. Is there anything I should look for after I move the wire that might signify a problem becuase the outside unit is off when it should be on?

Thanks

Michael

Kender

Just make sure the A/C system still works when you finish ( in cooling mode ). But wait for when it is warmer in the day time to check because it is bad for the outside system to run when it is cold outside