Nothing would happen if a thermostat is wired backwards. The thermostat will NOT be damaged in any way, including a the screen being black. That is because the thermostat's relay is “normally open”, meaning there is no path for electricity to travel, so voltage would be present, but would stop there.
If you put wires into the wrong thermostat connectors during setup can, this can cause your system to malfunction or possibly damage it.
This is the most typical thermostat wiring style, and it applies to systems that regulate both heat and air conditioning. The wires are typically arranged as follows: red for 24-volt hot, white for heat, yellow for cooling, green for the fan, and blue for common (although the common wire may be a different color).
TH1120, TH1121, TH1123, and TH1124 series thermostats have two unpolarized wires, meaning that either thermostat wires can be connected to either electrical box wires. TH1500 series thermostats have four polarized wires.
A 2-wire thermostat is almost always for a system with heat but without air conditioning, controlled by a digital thermostat. The two wires are most often red for power and white for heat.
Get an Adaptor. Older thermostat connections sometimes have only two wires, and because the power is split so few times, it is too strong for your smart thermostat. You cannot run a new device through these wires without an adaptor that accounts for the wires' higher voltage.
Thermostat Wiring Tips
If your thermostat controls your heat, you will have a white wire. The Y wire is yellow and connects to your air conditioning compressor. The G wire is green and connects to the fan. Rc and Rh: The red wire(s) are the power source for your thermostat.
A basic two-wire thermostat can be compared to a simple single-pole switch that you will find throughout your home, only instead of you turning the switch on and off as required, a mechanical or electronic temperature controlled mechanism is the operator of the switch. The terminals are usually marked 'R' and 'W'.
White, W wire: This wire signals when it's time to use conventional heating to heat your home. Green, G wire: It operates your HVAC fan. Yellow, Y wire: This wire signals your air conditioner to start the cooling process when needed. Black or Blue, C-wire: It provides continuous power to the smart thermostat.
Place the multimeter's red probe onto the thermostat terminal marked R for red; you can place the black probe onto any of the other terminals. The multimeter reading should be at or close to the thermostat's voltage level.
Some cords come with grooves/ribs along one side and smooth on the other. The ribbed side is your neutral/white wire. The s. ooth side is the hot.
In this case, you'll want to check for the following: Tripped Circuit Breaker: The main issue here is not with the thermostat itself but with the electrical panel. Go to the breaker panel and locate the circuit breaker for your thermostat. If it's off, try to reset the breaker switch.
Nothing would happen if a thermostat is wired backwards. The thermostat will NOT be damaged in any way, including a the screen being black.
Connecting a positive (black) wire to a negative (white) wire, or reversing the live and neutral wire, can cause short circuits and even fires, given the disruption in the flow of electricity.
Upside down and backwards thermostats seem to be a common thing. When replacing your thermostat, make sure the little air bleeder is facing up, the spring is pointed towards the head, and that your surfaces are super flat and clean for your gasket. Using good quality parts is also a good idea!
The blue wire—also called the C, or “common,” wire—is required to power any thermostat and ensure proper system function. Your HVAC system and thermostat configuration will determine what color the C wire will be. The C wire in homes with a heat pump is always blue.
Connect white wires together. Connect black wires together. Connect the lighting wire, typically blue, to the black fan wire and the black ceiling wire. Tuck the wires back into the box.
O/B: This option selects the type of reversing valve for heat pump systems. An “O” reversing valve is energized when cooling and a “B” reversing valve is energized when heating. Most systems use an O type reversing valve.
Yes, thermostat color code wiring does matter a great deal. The color coding indicates which wire goes to which port. In some cases, the color of the wire doesn't necessarily mean it connects to the same color on the board.
As you examine the wiring, you will probably see two wire jackets, also called wire bundles. One of them, with Rc, G, and Y, comes from the cooling system. The other one, with Rh and W1, comes from the heating system.
If there is no hidden C-wire, you can use a G-wire instead. However, you will not be able to use your fan independently when the heating or cooling isn't running. Also, many HVAC systems are incompatible with this solution, including: HVAC systems using electric heat.
Then there's the obvious answer: air-source heat pumps have reversing valves while basic A/C units do not.
If the thermostat is located near a heat source, such as a lamp, an electronic device, the kitchen, the laundry room, a bathroom or an air vent, the temperature in those areas will be higher than it is in other parts of the house.