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What is the common terminal on a device - Electrical Supplies

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The common terminal is where wires 'common' to a circuit of several devices connected together have the same wire or part of the circuit attached. In AC circuits, this is usually the neutral wire- neutral is usually color-coded white, the hot (live or active) single phase wires are black in most household circuitry. In DC circuits, the common terminal is usually the ground. Neutral and ground are NOT the same thing. Three wire circuits have a green ground wire connected to a ground lug on the switch which is separate from the neutral circuit. You can get serious voltage between the ground and the neutral wire in AC house circuitry. Always keep these two circuits separate.

Posted on Apr 25, 2015

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If you are speaking of a light switch or an outlet it is white or chrome and the hot is brass in color

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SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

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Thermostat fuse keeps blowing

The fuse protects the transformer from being damaged due to too much amperage, this is typically due to the circuit having a short or a device in that circuit being shorted.
See below the transformer's relationship to the thermostat.
The RED wire is the "hot leg" of the 24 volt power provided by the transformer to the thermostats R or RED terminal as pictured below.
The 24 volt hot leg enters the thermostat on R or RED.
The various other terminals White = heat, Yellow = cool ,
Green = fan and Common is the side of the 24 volt power source that every 24 volt circuit terminates or return to complete the circuit.
Thus the common name designated, note hoe everything returns to Common.
Well if we jumped Red directly to Common that is a short and will blow the fuse as you observe.
See the 2 diagrams in red describing a notrmal circuit then a short circuit.




Mar 03, 2015 | Heating & Cooling


How to wire your new themostat

0a9962f0-eea8-41fa-881b-a1074d6aa966.pngThe heater has a transformer that steps down the line voltage supplied either 115v or 230v to 24 volts,a safe voltage to use for the thermostat's control voltage and a voltage which requires no license to install.
The most important thing to remember before you begin is that ,
Red or R is the "hot leg" of the 24 volts provided by the transformer and
Common or C is the "neutral leg" of the 24 volts provided by the transformer and
Common is the side of power which EVERY 24 volt circuit will terminate or return to in completing the circuit, thus the "Common " designation, note after each circuits device, be it AC or Heat or Fan,every 24 volt circuit returns to Common or it's circuit is not completed.
Every electric circuit ,regardless of voltage or polarity requires a device ,
without a device in a circuit, upon energizing that circuit it will be a direct short!
Red to Common, this will blow the fuse or worse the transformer if not protected by a fuse which some are not. If you have a device in the circuit you can energize a circuit, my point being do not let Red touch Common and as Common is grounded at the transformer, do not let Red touch any metal, as it is likely grounded too, so turn off power before doing anything.
Note the color of the wiring attached to your existing thermostat's terminals and make a diagram so you will not forget.
The new thermostat may have different terminals or more that you will not be using.
All thermostats have an R or Red terminal, it may be RC and an RH 2 separate terminals designating RC as red cool and RH as red heat.
There 2 terminals RC and RH are for 2 transformer systems which are obsolete old GE units so if you do have both RC and RH use a small jumper wire and connect the 2 terminals and wire the Red "hot leg" from the transformer to either RC or RH it will not matter if both are jumpered together, otherwise you will only have cooling or heating but not both available.
The Red hot leg of the 24 volts enters the thermostat on R and most modern thermostats are parasitically powered meaning they derive power from the heaters transformer, as a result the Common 24 volt neutral leg must be ran to the thermostat.
Note, the new NEST thermostats say they do not require Common to be wired, however 50% of the time the NEST will go dead in time and require a Common wire be used to power the thermostat satisfactorily.
Upon a call for heat the switch between the Red and White circuit closes making white electrically hot with the 24 volts which it sends out the white wire to the heater gas valve etc and return to common to complete the heat circuit.
Upon a call for AC the switch to Yellow closes and as you will notice the Fan switch on the thermostat has an AUTO and ON switch, in the AUTO position, upon a call for AC
the Yellow becomes hot with the 24 volts and as a result of the AUTO switch being closed, the indoor blower will automatically cycle as required.
The fan control for ON fan or AC is High speed, the fan control for heat is Low speed and controlled by a time or temperature delay at the initiation and termination of the heat cycle, this is to eliminate cold air from blowing until the heater warms up and upon termination it extracts the residual heat to not overheat the unit and be most efficient.
Green is the Fan circuit, it is the High speed fan and only used for heating with electric heaters as resistive heat strips or heat pumps and will be controlled in both heat and cool modes by the thermostat, this is designed in to the thermostat or part of the thermostats set up and programming if a universal type thermostat.
Common as explained is there to power the thermostat it being the other side of 24 volt power opposite from the red 24 volt hot leg.
Heat pumps will have an O and a B terminal, this gets the Orange wire on O if the reversing valve is energized in cool mode, if you get heat in the cool mode switch the Orange wire from O and put it on B, B is energized in the Heat mode.

This was not written for just heat pumps or any brand I had to pick a specific brand however this applies to all brands and types gas furnaces , heat pumps and electric heat.

on Oct 13, 2013 | Aube TH144HPN2H1C Thermostat: Heat-Pump...

1 Answer

3 way switch wiring diagram

There are several possibilities depending on where the power source enters the circuit. I am currently teaching lessons on Basic electrical circuits. I will add my "Rules of Thumb for wiring switches" I use in my class. You MUST follow the instructions exactly.
Wiring three-way switches.

Rule 1: The incoming hot conductor goes to the nearest common terminal.

Rule 2: The conductor attached to the other common terminal goes to the device. This conductor must be black.

Rule 3: The neutral conductor goes to the device. This conductor must be
white or gray.

Rule 4: Traveler conductors are connected to the remaining terminals on the 3-way switches.

Rule 5: The grounding conductor must be continuous throughout the

May 02, 2014 | Electrical Supplies

1 Answer

Rockwell 34 345

Assuming the power cord is 15 amp, 120 VAC, let's start with the green wire. It is a ground for human protection. It should be connected to the metal parts of the saw. Next, the white wire is a "neutral" and should be connected to one side of the motor windings. While a "neutral" is tied to ground at the power panel, it does carry electrical current.

The black "hot" wire should connect to a common or normally open terminal of the power switch. The remaining normally open terminal should connect to the common terminal of the "reset button". The reset is actually a thermal overload protection device. The three terminals should be common, normally open, and normally closed. Connect the normally closed terminal to the remaining motor winding.

P.S. The reset device may have been bypassed because it failed. Replacements can be hard to find.

Nov 02, 2013 | Saws

1 Answer

Replacing a double light switch, the old switch has 6 terminals. The new metal double switch has the same but both commons are at the top where as the old one had common top and bottom. The L1 and L2 are...

You question invites guessing.

Switch is not identified.
Screw terminal colors are not identified. Load is not described.
Maybe you have double switch where 1 switch is single pole and 1 switch is 3-way.
This type switch is wired differently depending on location of hot wire supplying power to 3-way switch.

Electricians don't guess, they test.
Use multi-meter and continuity tester from home center.
Screw color is very important for wiring electrical devices.
First step is to note where each wire is located on old switch, hopefully doing that before removing wires on old switch.
And note what color screw that wire connected to.
Take a photograph.
Then determine what each wire does by testing and process of elimination.

Compare screw colors on old device to screw colors on new device.
Use continuity tester on old device and on new device to check screw-terminal relationships.

For additional help, add a comment after testing the screw terminals as described above.

Sep 02, 2011 | Cooper Industries Cooper Wiring CS220W AC...

1 Answer

I have an 12QZ22TA model. It's blowing warm air. How do you put in freon?

Only an EPA certified Technician can add refrigerant. There are other possibilities why it is blowing cold air.
1. Thermostat is bad (disconnect the power, remove the thermostat, place a jumper wire on the two terminals) Unit starts to cool bad thermostat.

2. Capacitor is bad (look for oil or swelling) looks like a can with terminals.

You can test with a meter.
Instructions Things You'll Need
  • Standard multimeter
  • A/C compressor capacitor
    • 1 Turn the A/C unit off along, and unplug it from, the wall to prevent any power surge to the unit when handling the internal devices. Locate the capacitor inside the unit. Capacitors will come in varying shapes; some will look like either a round or oval cylinder with two or three power terminals on the top. Air conditioners can have two capacitors -- one for the condenser fan and one for the compressor -- and are called dual-run or dual-rated capacitors.
    • 2 Place the probes on the terminals for a run capacitor with two terminals. If the capacitor is a dual-run capacitor with three probes, connect one probe to the herm terminal and the other to the common terminal. You can check the capacitance of the fan for a dual-run capacitor by connecting the probes to the fan and common terminal.
    • 3 Turn on the multimeter and read the display screen. You will see two readings, one for the condenser fan and the other for the compressor. Readings will be in micro farads and seen as the letters "mfd" or "uf."
    • 4 Replace a capacitor if the reading is below manufacturer standards. You can find the required micro farad for the capacitor either marked on the device or in the air conditioner's installation manual. Refrain from testing any capacitor if it is leaking, has corroded terminals or the capacitor unit bulges. Replace it immediately.


Aug 01, 2011 | Amana Quiet Zone 12M12TA Air Conditioner

2 Answers

Need wiring info for hooking up 3 -way switches

Open following link to view general drawing for 3-way switches.

Add a comment with information about wires and what you have done so far for more help

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Jun 01, 2011 | Cooper Wiring Devices INC #C7503W-SP WHT...

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I have a P&S illuminated toggele switch 660islg.. There are two termial on the switch, one of which is martked "common." What does COMMON mean?

Common in electrical terms means shared: belonging to or shared by two or more circuits.

The hot wire is connected to the "common" terminal on this device because it is "common" to both the little light that illuminates the switch and the hot side of the switch. If you connect the hot wire to the opposite terminal the switch will not be illuminated until the switch is in the ON position.

Nov 08, 2010 | Pass & Seymour #660ISLGCC10 Ivory LGTD SP...

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Need diagram for compressor terminals .need to know what is common,start and run terminal

As you are looking at the terminals
The nine 'o clock terminal is the common
The 2 'o clock terminal is the run,
The four 'o clock terminal is the start

I hope that this will help you to solve your problem!

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Dec 18, 2009 | Migali Refrigerators

1 Answer

Common terminal location on a goodman furnace

White wires are commonly the common connection (sorry for the pun). L2 is also considered the common leg. You did not mention if you are looking for high voltage or low voltage common. L2 is your high voltage leg. If the power venter ties into the thermostat circuit, W on the circuit board is the common terminal.

Dec 01, 2009 | Goodman GMS90703BXA Heater

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