A/C runs when furnace runs?


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Old 03-15-06, 09:41 PM
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Angry A/C runs when furnace runs?

I have a Honeywell Chronotherm thermostat. It has 2 levers on top with blue & red lines, which select the temperature. Below is switch to select heating or cooling or off. The heating is a furnace in an indoor closet and the cooling is an A/C unit in back of the house.

If I select heating, I need to move both levers above to the temperature. When the thermostat activates, the furnace comes on immediately (no initial warmup by burner) and also the separate A/C unit comes on. Why do I need to move the lever with blue line to temperature, causing the A/C unit to come on?

Help!!
 
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Old 03-16-06, 05:02 AM
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Ok, something is up.

What happens if you move the blue one all the way down the lowest temp?

Have you made any changes to the t-stat like remove when painting?

If the outdoor unit still runs with the blue all the way down, and have not done any t-stat wire changes, i'd rule the t-stat needs to be replaced. But before you do that. remove the wire on Y at the t-stat sub base, and re try. if it stops, then replace.

If you can't do anything right away, turn the power off to the outdoor unit.

Make sure you turn off the power at the furnace.
 
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Old 03-17-06, 08:47 AM
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A/C runs when furnace runs?

Jay,

Thanks for replying. I thought something was up! Thanks for verifying that I must have a problem.

If I move the blue lever to lowest temp, the A/C unit in back and the furnace turns off, even if the red lever is much higher temperature than room temp.

I also suspected someone might have rewired it incorrectly. The house was a rental for 15 years before I moved in recently. The thermostat looks original. A renter might have installed a newer digital model, but took it with them and replacing the original or maintenance people on the furnace might have rewired it incorrectly while fixing something else. Ill check the wiring.

What do you think of the instant on of the furnace? Is this just an older model without heat sensor in burner area to turn on fan when it gets hot enough?

Thanks, 007
 
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Old 03-17-06, 09:46 AM
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As Jay stated, Either tstat faulty or miswired....remove stat from sub-base and take a look at the wiring...Which colors are on which terminal? Next go to furnace and see where corresponding wires are connected. I suspect it is wired wrong
 
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Old 03-22-06, 07:24 AM
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Angry A/C runs when furnace runs?

Thank you guys for your inputs. Ive checked the wiring and it doesnt agree with info I can get on todays thermostats. Mine has the following wiring:

R terminal Red wire (measures 24v to White)
W terminal White wire
Y terminal Yellow wire
G terminal Green wire
O terminal Orange wire

Only R to W has 24 volts. Is anyone familiar with this wire coding?

What I understand is that there should be 2 with 24v, RH and RC. Others are W, Y, and G.

My O is the difference. But, what? Should it have 24v and be equivalent to RC?

Im hoping for more understanding on the wiring before I look at furnace or A/C to see where wires go. That might be a tough task.

It doesnt appear that the unit has been tampered with.

Thanks, 007
 
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Old 03-22-06, 07:37 AM
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Originally Posted by justdoit007
R terminal Red wire (measures 24v to White)
W terminal White wire
Y terminal Yellow wire
G terminal Green wire
O terminal Orange wire

Thanks, 007

R is your "Hot" line of 24 volts.

W goes to the furnace to tell it to turn on the heat.

Y goes to your outdoor unit for cooling

G goes to the fan relay to run on the fan when you call for cool, and t-stat switch fan ON.

O goes to a valve for a heat pump....??

Do you have a heat pump? It didn't sound like you did?
 
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Old 03-22-06, 03:18 PM
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Heat Pump

I too suspect a heat pump. When set for heating & the outdoor unit is running, go outside & feel the large copper line (may be covered in black foam insulation). If it is warm to hot, you indeed have a heat pump & it seems to be operating as normal. The red & blue levers are for day & night settings.
 
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Old 03-22-06, 08:51 PM
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I believe the Chronotherm is an auto changeover mechanical stat. Its been a couple years since Ive seen one but I think the differential between heating and cooling with the levers touching is 5 degrees. The blue lever is the cool setpoint and the red is the heat setpoint. Its also a 2 stage stat for heat and cool.
 
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Old 03-24-06, 02:46 PM
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Red face A/C runs when furnace runs?

Thanks everyone. You were right. It is a Goodman Manuf Corp. Heat Pump, about 20 years old. I was even in the wrong section of doityourself. My second house with central air and first with a heat pump. Previous one had a single unit on the roof and I thought that was a heat pump. Turned out to be an A/C Furnace combination. Good thing I didnt take more of it apart.
 
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Old 03-24-06, 03:21 PM
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Is your furnace gas heat? or Electric strip back up?

If it's gas, the burners shouldn't be on when the heat pump it runing.
 
 

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