There are two sides to the 24-volt transformer: A high side and a secondary – or low-voltage – side. The high side is the line-voltage of the transformer and the electrical connection to the feeding voltage, generally a 120-VAC power. The secondary or low-voltage side is the power that is transformed into 24 volts.
What color is common on 24V transformer?
The usual practice is to connect the phase (usually blue) wire of the transformer secondary to the phase or ~ terminal and the common (usually brown) wire connected to the – or ground terminal.
What does the R and C stand for on a transformer?
In the case of HVAC/R systems, the power source is a low-voltage transformer (usually a 24 VAC transformer) and the two wires supplying the power are labeled C (common) and R.
What is the white wire on a transformer?
The black wire is “hot”, the white wire is “neutral”, and the green is earth ground. Connect the transformer’s two red wires to the neutral wire, and the two black wires to the side tab on the fuseholder, and your “hot” lead to the bottom terminal of the fuseholder. Adding a power switch is a good idea.
What is the common wire on a transformer?
The C wire, or “common wire” enables the continuous flow of 24 VAC power to the thermostat. Technically speaking, power flows from the R (red) wire, but not continuously (not on its own, anyway). To make it continuous requires a common wire to complete the circuit.
Should 24vac common be grounded?
On many hvac units the 24v or 120v control transformer common is grounded to the unit chassis. This brings the common to ground potential and helps with troubleshooting.
What is the C terminal on a transformer?
By definition the R terminal is one end of the transformer winding and the C terminal is the other end. Simple thermostats (bimetal strip, or battery-powered programmable) simply short R to W or G to call for heat or cooling.
Can I connect C wire to transformer?
If you have a heat-only system connected to your Sensi thermostat, an easy option for adding a common, or c-wire, is to install a 24 VAC wall plug-in transformer. Transformers with 150-400mA output are the most widely available online and easily provide sufficient power for the thermostat.
What is the difference between 208 and 240?
They require two legs of power from the power utility, whereas 240v motors and appliances only use one. You will commonly see 208v present in three-phase buildings when “single-phase” equipment (like an A/C condenser) is wired to two legs of three-phase wye power.
