I want to intasll a new Rheem system. My old Rheem unit has 5 low voltage wires. Contractors that want to install Carrier/Bryant units say I need 7 wires but the Rheem dealer said 5 wires are do able. What is going on? Please help!
Thanks, Mo

Is this a conventional gas forced air unit, or a heat pump? If conventional gas forced air with central air conditioning, five will do just fine, actually can get by with four, but safest to run five, as some thermostats require a fifth wire for common to power stat if batteries in stat die.

Thanks. The unit that I am getting is a Rheem heat pump RPQL-*AZ Series. When I looked the old unit's thermostat I saw 6 wires attached to circuit board and extra unused wire (blue), but when I looked at the condenser part I saw 5. Help please!

Sorry, we just don't do heat pumps in my area, so I just don't have enough experience with the low voltage wiring of them. Wouldn't want to steer you in the wrong direction. However, there are a few other pros here that seem familiar with these units, so hopefully one or more of them will pop in and help you out. Good luck.