Old 06-30-04, 08:11 PM
keith fore
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My husband and I are new to DIY and we love this web site. We are seeking anyones help with a heating and cooling question. We have a 3 year old Carrier Weathermaker 8000 two-speed furnace. We are looking into adding a central air conditioning unit to it. However, when the heating unit was installed, the booklet was not placed in or near the furnace. We are in need of a diagram to wire a new thermostat with the new cooling unit.. I know we could contact Carrier for it, however, it would take time to recieve it. If anyone can help us, we would greatly appreciate it.
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Old 07-01-04, 05:14 AM
Spark Chaser
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Old 07-01-04, 09:00 AM
Join Date: Feb 2002
Location: port chester n y
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This presumes the existing furnace/blower unit is equipped with a 24-volt gas-valve, a fan-relay, and a control-power transformer. One terminal of the control-power transformer is indentified "R", and the other terminal "C".

For the existing "heat-only" operation there is a 2-wire thermosat cable with Red and White wires between the thermosat and the furnace/blower, with the Red wire connected to the "R" control-power transformer terminal , and the White wire connected to the gas-valve.

On a "call-for-heat", the thermostat completes the internal circuit between the Red & Whire wires, and the gas-valve operates.

To progress to both heating and cooling, a heating/cooling thermostat with "R", "W", "Y" and "G" terminals is connected. The heating circuit is connected as before to the "R" & "W" terminals. If the thermosat has "Rh" (heat) and "Rc" (cool) terminals, the Red thermostat wire "jumps" between the terminals.

There is a 2-wire, low-voltage, control-power cable connected to a contactor inside the out-door condensing section of the cooling system.One wire of this cable connects to the "C" terminal of the control-power transformer, and the other wire connects to a Yellow wire that connects to the "Y" terminal of the thermostat. For cooling, the thermostat completes an internal circuit between the Red & Yellow wires, and the control-contactor in the condensing section operates and switches 220-volt power to the fan/compressor motors.

One wire of the control-coil of the fan-relay connects to the "C" terminal of the control-power transformer, and the other wire connects to a Green wire that connects to the "G" terminal of the thermosat.For cooling.the thermostat completes an internal circuit to the Green wire and the fan-relay operates and switches power to the blower which circulates internal air across the evaporator (cooling) coil.

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