Typically, the "hot" wires, or those that supply electricity to the machine, are the heating and cooling wires, denoted by the letters "Rc" and "Rh," respectively. They offer the source of 24V electricity that powers the main HVAC control board. The black wire is usually called the "grounding" conductor because it must be connected to something safe (i.e., earth) for the HVAC system to function properly.
If you have a programmable thermostat, it may have its own small battery inside it that provides power when the switch is closed. When the switch is opened, the battery prevents current from flowing through it, so it cannot charge up. Programmable thermostats with internal batteries are more efficient than simple on-off switches because they do not need to use as much electricity when you are not using the heat or air conditioning.
Some modern HVAC systems include a remote sensor that can transmit data to an indoor unit, allowing for some level of automation. These systems are often called "smart devices."
Heating and air-conditioning systems operate based on two principles: compression and vaporization. Compression refers to the process by which heat is transferred from one object to another by means of pressure. So, in order for heat to be transferred from one object to another, there needs to be pressure put on that object to be heated or cooled.
The R Terminal is connected to the Red Wire, sometimes known as the R Wire, which supplies 24-volt power to the thermostat and other regulated equipment. Is the control transformer, followed by the R Terminal The G Terminal is linked to the Green Wire, or G Wire, which powers the air handler's blower fan. The Y Terminal is connected to the Yellow Wire, which provides 120-volt AC power to the thermostat's internal display panel and other miscellaneous functions.
These are the only three terminals on a typical two-wire wall-mounted thermostat. Some low-cost models omit the G Terminal altogether. Other terminals may be named L1, L2, and HV (for heater valve). These names will be explained later in this article.
The purpose of the R Terminal is to connect the red wire from the energy source to the red wire on the thermostat. The green wire from the energy source connects to the green wire on the thermostat. And the yellow wire from the energy source connects to the yellow wire on the thermostat. This way, if any part of the system needs repairing, it can be done from just one of these three wires. No other parts of the system need to be shut off during repairs.
Repairs for these thermostats can only be done by a qualified technician. If you try to repair this type of thermostat yourself, you could break it further causing a fire hazard!
Rep with the red wire, attaching it to the "R" terminals on both the furnace and the thermostat. The c wire, also known as the common wire, allows for the continuous transmission of 24 VAC electricity to the thermostat. A "c" wire, which is normally blue, is not present in all thermostat systems. A c wire is not always present on a two-wire thermostat. When this happens, the red wire becomes the c wire and will be attached to one of the "R" terminals.
So, when you turn off the power at the main panel switch, the heater shuts off too. If you want the furnace to run when you turn off the power, connect it to a separate timer that turns it on at a later time. This can be done by buying a separate timer or by using something like smart thermostats. Of course, you could also just leave the heat on all day every day, but that's not very efficient is it?
The presence of a c wire on a furnace thermostat indicates the ability to control the temperature from a separate panel. This means that the homeowner can turn off the power to the whole house, but still have the furnace run so that they can keep a room at a certain temperature. These types of thermostats are usually found in larger houses or those that have been split up into apartments.