The terminal where both the start and run windings on a motor are connected is called common. All of the diagrams I've seen have a contractor on that line as well as the on its way to the other line. Of course you could just use one.
Step one. Understand Line and Neutral in an AC system. Step two, understand that DC terms change to identify that it is different from AC power but the circuit has to function the same regardless. They is a constant line of power on one side, regarded as “line” in AC and “+ 24V” in a DC circuit. The “neutral” in AC, is the “-“ or “OVDC” in DC. And just like AC power, the neutral (- or 0VDC) is bonded to GND at the panel
funny you mention this. Instead of hooking up the common on a 240V single phase PSC motor - I hooked up one of the speed taps - motor got pretty toasty. so I was using the hi and med-lo speed taps for 240v. Cost me $100 bill. Good video.
+Robert Munguia On 120 volts, There is the hot (black) and the neutral (white). The hot is usually switched because you would get shocked if you touched it. You will not get shocked when you touch an unconnected white. Hope this helps. GFM
Good video, I'd like to see one on properly setting an adjustable head pressure contoller and why you picked the temps/pressures to cycle the fan. Seems fitting being that's is winter.
What if there's only two black wires? I'm trying to replace a switch to an existing box w/ a dimmer light switch & a receptacle, I using a piggy back for ground, can anyone just tell me which screw to use for ground? There's no green screw
common is called common because it is common to something. usually a common source. common in a 3 way switch, relay, i/o module ect. are most of the time hot or ungrounded and unswitched. could be a common feed, a center tap, or a common ground. depending on the circuit.
It sounds like the common wire as you describe it is in a 24 volt DC circuit is : 1. Connected to the chassis 2. Is unscathed That sounds like the wire down side from a load, exhausted of volts, reading 24 volts voltage drop across the load directed to a ground and that is why it is attached to the chassis. I'm not telling you, I'm asking you So what would be the wire that has switches typically in series , thrmostat, pressure switches not connected to the chassis and upstream from the load. Or leading to the load
Not sure of your meaning. This circuit has no 24 volt portion. The 24 volt circuit in a furnace is produced by a transformer that changes 120 volts to 24 volts. GFM
This comment Not this one the one above about a neutral grounded conductor could of never been type by me, I ''m no where near that smart. It's an interesting read but I already have an understanding of the netural . And Grayfurnaceman just told me how to idenyify the neutral using a multmeter. Now how can I identify a common using a multmeter. The common wire
Strike this comment out . It reference a comment that no longer is on this thread the referenced comment on my tablet originally was on the neutral video and some how appeared on this video section
grayfurnaceman could you get rid of all my comments posted on this comment section. I'm so confused with my numerous comments I do not know to continue
IMO The common in a 24vlt circuit is not switched through the safety's because if R was direct and C was switched if a short to ground were to happen anywhere along the common path the unit would still be able to operate without the safety's between the short and transformer.being able to shut unit down. This is not a safe way to wire the low voltage circuit.
6 years down the line, this video still helped me understand common, thank you!
The terminal where both the start and run windings on a motor are connected is called common. All of the diagrams I've seen have a contractor on that line as well as the on its way to the other line. Of course you could just use one.
Step one. Understand Line and Neutral in an AC system. Step two, understand that DC terms change to identify that it is different from AC power but the circuit has to function the same regardless. They is a constant line of power on one side, regarded as “line” in AC and “+ 24V” in a DC circuit. The “neutral” in AC, is the “-“ or “OVDC” in DC. And just like AC power, the neutral (- or 0VDC) is bonded to GND at the panel
Lol not only is Mr Grayfurnaceman funny ( the way he acts lol) but he's also informative and knowledgeable. Thumps up I like this fellow.
funny you mention this. Instead of hooking up the common on a 240V single phase PSC motor - I hooked up one of the speed taps - motor got pretty toasty. so I was using the hi and med-lo speed taps for 240v. Cost me $100 bill. Good video.
what do you mean by unswitched side of line for the common? great info just need to fully understand concept.
+Robert Munguia On 120 volts, There is the hot (black) and the neutral (white). The hot is usually switched because you would get shocked if you touched it. You will not get shocked when you touch an unconnected white. Hope this helps.
GFM
HVAC terminology. Common, the un-switched side of the 24 volt transformer. (usually white wire)
Helped me understand it better. Thanks. Looking forward to the next videos on the neutral and transformers
+Steve Bitschy Thanks for the support.
GFM
Good video, I'd like to see one on properly setting an adjustable head pressure contoller and why you picked the temps/pressures to cycle the fan. Seems fitting being that's is winter.
+Matt Rodriguez I will be doing one on using head pressure to control high and low side pressures. Just have not gotten around to it yet.
GFM
Example: common in a high bay light ballast for commercial can be neutral for 120 or L2 for 208/240/277
refrigeration tech yeah but he just said it supposed to be unswitched. So if it turns into L2 then you would get shocked right!
What if there's only two black wires? I'm trying to replace a switch to an existing box w/ a dimmer light switch & a receptacle, I using a piggy back for ground, can anyone just tell me which screw to use for ground? There's no green screw
I checked out your favor video list. I didn't get very far because @ the top of the list was home made power hammer . Love that video
Lior Holtslag Kind of cool huh.
GFM
common is called common because it is common to something. usually a common source. common in a 3 way switch, relay, i/o module ect. are most of the time hot or ungrounded and unswitched. could be a common feed, a center tap, or a common ground. depending on the circuit.
thanks for the info very intesrsting have a good new year
So the common is just the continuing part of the hot line. Like it comes into the hot and goes out the common? Am I on the right track?
It is. If there is no connection from the common to the source of power, the common will be hot.
GFM
Yes u r
Basically 120 volts stepped down to 24 volts instead of hot and neutral you have hot and common thats what i took away
GFM, this video helped me understand this concept a little better, thank you!
Welcome
GFM
It sounds like the common wire as you describe it is in a 24 volt DC circuit is :
1. Connected to the chassis
2. Is unscathed
That sounds like the wire down side from a load, exhausted of volts, reading 24 volts voltage drop across the load directed to a ground and that is why it is attached to the chassis. I'm not telling you, I'm asking you
So what would be the wire that has switches typically in series , thrmostat, pressure switches not connected to the chassis and upstream from the load. Or leading to the load
Fooled by auto correct. Number 2 above should read
2. Unswitched
Not sure of your meaning. This circuit has no 24 volt portion. The 24 volt circuit in a furnace is produced by a transformer that changes 120 volts to 24 volts.
GFM
This comment Not this one the one above about a neutral grounded conductor could of never been type by me, I ''m no where near that smart. It's an interesting read but I already have an understanding of the netural . And Grayfurnaceman just told me how to idenyify the neutral using a multmeter.
Now how can I identify a common using a multmeter. The common wire
Strike this comment out . It reference a comment that no longer is on this thread the referenced comment on my tablet originally was on the neutral video and some how appeared on this video section
grayfurnaceman could you get rid of all my comments posted on this comment section. I'm so confused with my numerous comments I do not know to continue
Thanks for video very informative. Also Good to see the man behind the camera
+keith richards Pretty ugly huh?
GFM
grayfurnaceman but now everybody knows why you call yourself the Gray furnace man!
IMO
The common in a 24vlt circuit is not switched through the safety's because if R was direct and C was switched if a short to ground were to happen anywhere along the common path the unit would still be able to operate without the safety's between the short and transformer.being able to shut unit down.
This is not a safe way to wire the low voltage circuit.
+John Heritage However it is sometimes done by manufacturers for several reasons.
GFM
good video with nice and simple info
+gonz garr Thanks for the support.
GFM
Love your videos
Made it more understandable thanks
👑 for simple explanation for that can you just say it's a hot/live line 😮
Ur a very smart guy. That’s all he’s basically saying. Thanks to u both.
thanks for help us, awsome videos, and happy New year GFM
+Rolando Guajardo Welcome
GFM
Thanks very much. Certainly helpful.
+Ah H Thanks for the support.
GFM
Perfect answering...Geesh!
Thanks!
Welcome
GFM
Nice👍
Good info
+deanmartin1966 Thanks for the support
GFM
Common is not a bad word.
wonderful explanation, but what a ridiculous concept haha. why does such a simple word need to have such a convoluted definition
that was not explained at all
I do have a grounding and bonding playlist that may help on my channel.
GFM