I think it is probably not a good idea to reference a household light switch as a dry contact. At that point it is more perspective of what is intrinsic to the power system within a house. One could call it a wet contact because "under normal conditions" it always has a "source" voltage applied to one side of the switch which in the case of a house is typically "120VAC" in the U.S. To me a better example would be to use a multiple pole relay e.g. DPDT,3PDT or 4PDT. A source voltage controls when the relay is energized or de-energized. On one of the contacts, it could (but doesn't have to) have a voltage applied all the time waiting for the relay to energize to pass the voltage. This would be considered a "Wet Contact". Another contact on the same relay which by itself is not electrically connected to the other contact still mechanically closes when the relay coil is energized. This separate contact which is considered a "Dry Contact" has no voltage potential on it and can be used by another source voltage usually supplied by a customer or end user and can be a different potential than the source potential as long as the contact is rated for it e.g. (contact rated up to 240VAC at 10A or up to 48VDC @ 5A) Another example - A 3 phase contactor sends 480VAC to a compressor. [Auxiliary N.O. contact #1] located on that contactor that has 120VAC on it (WET CONTACT) so when the contactor is pulled in to send power to the compressor, it also sends 120VAC to a pilot light on the door saying it is running. [Auxiliary N.O. contact #2] has 2 wires to terminals and has no voltage (DRY CONTACT) for the end user to use (wire his own equipment) to notify or to control something else only when the compressor is running. The end user can wire to these terminals and place whatever voltage potential he likes as long as the contact is rated for it.
Man, apart from the poor English, your explanation answered more questions on this subject than two of the videos I have just watched (including this one).
True but you can’t use “any” voltage as, for example, a relay’s contacts may only take up to 240VAC @8A. You’re not wrong but there is always a maximum rating for what a potential free contact can take.
Let's say you have a relay with a 120v coil fed from circuit 1 on a panel. Then you also run a 120v circuit from breaker 3 and it goes through the normal open contact of the relay. So breaker 1 feed is closing the coil of the relay and making breaker 3 on the NO contact close. This would be a dry contact?
A light switch is an SPDT switch which is a perfect example of what is NOT a dry contact. Surprisingly you’re not alone, every video on RUclips seems to not know what a dry contract is and give exactly the wrong explanation.
So Can we say , Active (comes direct from CIRCUIT BREAKER ) is WET CONTACT and Switch wire which goes through switch to load (Light Fan) and turns the the load on when switch is on is called DRY CONTACT ???? Hope you will reply .....
Hi, you said " the temperature sensor for the controller that is switching the contact will be using the same power ....." What you mean " same power"? Same power to what?
Thanks for the video but you did not answer a questions you said you would answer - why or when we want to use either "dry" or "wet". What is advantage or disadvantage of each? Like I am choosing a in-wall relay to make my ordinary power socket "smart". I have a choice of "dry" and "wet" relays. Which one should I choose and why?
Thanks you RSP Supply for all such useful videos..! Can you explain how to use Dry and Wet Contact with a PLC. Also PL explain with some Diagram how to wire these Dry and Wet Contacts. PL help.. waiting for the reply a.s.a.p. Thanks in advance!!!
In the control world I was under the impression that dry contacts close a circuit that never has power on it. It is simply there to create a short or open to be detected by controls.
You are correct to a degree. The “wet contact” in this case would be the controls you mentioned detecting the status of the dry contact via some level of voltage applied to the line. 3.3v 5v 12v 24v ect……. Example a control relay could provide a dry contact for another device to detect via “wet” controls.
You are a great presenter. My only quibble is whether there is a way to use the exact same terminology in both explanations. I admit I am just learning so what I say might not be true. I always look at relays as being comprised of a control signal and an electrical load. The controller can remotely switch the load on or off. (Bearing in mind the NO/NC detail which indicates the default setting, plus the potential to switch power from one circuit to another). If my basic understanding is correct, than I think I’ve explained a dry contact scenario. Are you saying that the wet contact scenario is the same, with the sole difference that the control circuit just happens to get its power from the same source as the load? It still has to be isolated (in parallel) so it can operate independently of the load, right? It’s whole purpose is to switch the load, so I assume it’s still independent except for power source. Am I on the right path?
No. when wet relays pass electric through the coil is energized ie produces a magnetic field and then passes "in series" through the contacts. The process begins with heat bending/contracting the contact ribbon. When cooled the ribbon relaxes back into position. Opening the contact, braking the surface. This is one application, I'm sure there are many other. I think.
It sounds like even a dry contact has power supplied to it, so this is the hard part to get around. The switch cannot operate or send a signal without power, yet it's still considered dry?
It sounds like you're saying a mercury switch that is mechanically actuated by heat to trigger the AC/heater is wet, but a light switch that is mechanically triggered by a human is dry? Other than the mercury I see no difference. If it's wet because it's Mercury then you should say so, but aren't there also mercury light switches and all new AC switches are solid state? If not for that specific reason, mercury, then I don't see the see the difference..... If you mean a solid state AC/heater switch, which I'm assuming uses an RTD to read temperature, then again I do not see the difference. I know electronics and more or less know AC systems, but I had never heard the term wet until last week. I actually thought it was a joke at first. It was mentioned by an industrial contractor I hired for some work, but when I asked wth wet meant he didn't really know. He called his resident expert who said a relay that uses power to actuate a switch (typical relay) was wet, and a switch that you mechanically flip, like a manual on/off, was dry. At least that how we took his explanation, which in my mind sounded like he wanted to appear like he knew, but did not. Excluding the use of Mercury, I cannot see any reason to use the word "wet", so help me/us out here. The way you worded it gave me the impression that a relay or transistor could be wet or dry depending on how it was wired. Meaning that if the power to actuate the relay was supplied by the same power the switch is controlling, then it's wet. If the relay was actuated by a different power supply then it's dry. That seems like a weak reason to call it wet as well. If that is the case, then what if the power to actuate is not directly, but ultimately from the same source? Like at home I'm using 120VAC to actuate a relay to control 120VAC elsewhere. They both feed from the same 240VAC fed box, but some relays the actuation and power are on the same 120 side of the 240, some opposite sides. Some on the same side are being fed from the same fuse. If fed from the same fuse would this not be wet? Or would this be a gray area and be a "moist" switch? I'm only half joking because I thought wet was a joke when I first heard it. Surely there's a better, clearer explanation for this, and a reason for the term wet. Is the source of the term lost to history, or it is a BS term used by people who don't really know what it means?
Check out the reply from punder30 down below, he clears it up a bit. The light switch is somewhat of a bad example for the dry contact as he points out.
It would be even better if a live demo was shown or atleast images are displayed
👍 yes😂
I think it is probably not a good idea to reference a household light switch as a dry contact. At that point it is more perspective of what is intrinsic to the power system within a house. One could call it a wet contact because "under normal conditions" it always has a "source" voltage applied to one side of the switch which in the case of a house is typically "120VAC" in the U.S. To me a better example would be to use a multiple pole relay e.g. DPDT,3PDT or 4PDT. A source voltage controls when the relay is energized or de-energized. On one of the contacts, it could (but doesn't have to) have a voltage applied all the time waiting for the relay to energize to pass the voltage. This would be considered a "Wet Contact". Another contact on the same relay which by itself is not electrically connected to the other contact still mechanically closes when the relay coil is energized. This separate contact which is considered a "Dry Contact" has no voltage potential on it and can be used by another source voltage usually supplied by a customer or end user and can be a different potential than the source potential as long as the contact is rated for it e.g. (contact rated up to 240VAC at 10A or up to 48VDC @ 5A)
Another example - A 3 phase contactor sends 480VAC to a compressor. [Auxiliary N.O. contact #1] located on that contactor that has 120VAC on it (WET CONTACT) so when the contactor is pulled in to send power to the compressor, it also sends 120VAC to a pilot light on the door saying it is running. [Auxiliary N.O. contact #2] has 2 wires to terminals and has no voltage (DRY CONTACT) for the end user to use (wire his own equipment) to notify or to control something else only when the compressor is running. The end user can wire to these terminals and place whatever voltage potential he likes as long as the contact is rated for it.
Man, apart from the poor English, your explanation answered more questions on this subject than two of the videos I have just watched (including this one).
Clear as mud.
That's true
😂👍
Is that you Stolle?!
Thank you very much for this explanation!!
Great Explanation Sir Thank You a lot .
Hi, Buddy. the explanation is clear and excellent. thanks
dry contact is also called potential free contact. because you can use any voltage irrespective of the device power.
True but you can’t use “any” voltage as, for example, a relay’s contacts may only take up to 240VAC @8A. You’re not wrong but there is always a maximum rating for what a potential free contact can take.
Let's say you have a relay with a 120v coil fed from circuit 1 on a panel. Then you also run a 120v circuit from breaker 3 and it goes through the normal open contact of the relay. So breaker 1 feed is closing the coil of the relay and making breaker 3 on the NO contact close. This would be a dry contact?
Highly appreciated 👍,
Is dry contact also called "volt free contact"???
yes it is
Great explanation
Glad you think so!
your explanation is amazing , can you please provide a video explaining the use of Signaling Contact coming with Manual Motor Starter for SK1-11 ABB ?
A light switch is an SPDT switch which is a perfect example of what is NOT a dry contact.
Surprisingly you’re not alone, every video on RUclips seems to not know what a dry contract is and give exactly the wrong explanation.
Nicely explained
Thank you so much 🙂
So Can we say , Active (comes direct from CIRCUIT BREAKER ) is WET CONTACT and Switch wire which goes through switch to load (Light Fan) and turns the the load on when switch is on is called DRY CONTACT ???? Hope you will reply .....
Hi, you said
" the temperature sensor for the controller that is switching the contact will be using the same power ....."
What you mean " same power"? Same power to what?
Thank very much
Thanks for the video but you did not answer a questions you said you would answer - why or when we want to use either "dry" or "wet".
What is advantage or disadvantage of each?
Like I am choosing a in-wall relay to make my ordinary power socket "smart". I have a choice of "dry" and "wet" relays.
Which one should I choose and why?
Thanks you RSP Supply for all such useful videos..!
Can you explain how to use Dry and Wet Contact with a PLC.
Also PL explain with some Diagram how to wire these Dry and Wet Contacts.
PL help.. waiting for the reply a.s.a.p.
Thanks in advance!!!
May be he doesn't know, for this reason he didn't reply.
In the control world I was under the impression that dry contacts close a circuit that never has power on it. It is simply there to create a short or open to be detected by controls.
You are correct to a degree. The “wet contact” in this case would be the controls you mentioned detecting the status of the dry contact via some level of voltage applied to the line. 3.3v 5v 12v 24v ect……. Example a control relay could provide a dry contact for another device to detect via “wet” controls.
nice video.thanx.
You are a great presenter. My only quibble is whether there is a way to use the exact same terminology in both explanations. I admit I am just learning so what I say might not be true. I always look at relays as being comprised of a control signal and an electrical load. The controller can remotely switch the load on or off. (Bearing in mind the NO/NC detail which indicates the default setting, plus the potential to switch power from one circuit to another). If my basic understanding is correct, than I think I’ve explained a dry contact scenario. Are you saying that the wet contact scenario is the same, with the sole difference that the control circuit just happens to get its power from the same source as the load? It still has to be isolated (in parallel) so it can operate independently of the load, right? It’s whole purpose is to switch the load, so I assume it’s still independent except for power source. Am I on the right path?
No. when wet relays pass electric through the coil is energized ie produces a magnetic field and then passes "in series" through the contacts. The process begins with heat bending/contracting the contact ribbon. When cooled the ribbon relaxes back into position. Opening the contact, braking the surface. This is one application, I'm sure there are many other. I think.
These are really nice, could you please create one for multifunction realy
It sounds like even a dry contact has power supplied to it, so this is the hard part to get around. The switch cannot operate or send a signal without power, yet it's still considered dry?
Thanks for the info, but some diagrams might help deepen the understanding of the subject.
Thanks Bro Explanation
Happy to help
It sounds like you're saying a mercury switch that is mechanically actuated by heat to trigger the AC/heater is wet, but a light switch that is mechanically triggered by a human is dry? Other than the mercury I see no difference. If it's wet because it's Mercury then you should say so, but aren't there also mercury light switches and all new AC switches are solid state? If not for that specific reason, mercury, then I don't see the see the difference..... If you mean a solid state AC/heater switch, which I'm assuming uses an RTD to read temperature, then again I do not see the difference.
I know electronics and more or less know AC systems, but I had never heard the term wet until last week. I actually thought it was a joke at first. It was mentioned by an industrial contractor I hired for some work, but when I asked wth wet meant he didn't really know. He called his resident expert who said a relay that uses power to actuate a switch (typical relay) was wet, and a switch that you mechanically flip, like a manual on/off, was dry. At least that how we took his explanation, which in my mind sounded like he wanted to appear like he knew, but did not. Excluding the use of Mercury, I cannot see any reason to use the word "wet", so help me/us out here.
The way you worded it gave me the impression that a relay or transistor could be wet or dry depending on how it was wired. Meaning that if the power to actuate the relay was supplied by the same power the switch is controlling, then it's wet. If the relay was actuated by a different power supply then it's dry. That seems like a weak reason to call it wet as well. If that is the case, then what if the power to actuate is not directly, but ultimately from the same source? Like at home I'm using 120VAC to actuate a relay to control 120VAC elsewhere. They both feed from the same 240VAC fed box, but some relays the actuation and power are on the same 120 side of the 240, some opposite sides. Some on the same side are being fed from the same fuse. If fed from the same fuse would this not be wet? Or would this be a gray area and be a "moist" switch? I'm only half joking because I thought wet was a joke when I first heard it.
Surely there's a better, clearer explanation for this, and a reason for the term wet. Is the source of the term lost to history, or it is a BS term used by people who don't really know what it means?
I am also confused about that.
Check out the reply from punder30 down below, he clears it up a bit. The light switch is somewhat of a bad example for the dry contact as he points out.
Thank you !
Born and raised in Florida, so I have no familiarity with a furnace in a home..
Спасибо. Пожалуйста, допилите субтитры к Вашим видое.
Sourcing/sinking
*Another way to think about it: Chubby dude's wedding ring wasn't supplied from an outside source - he bought it himself - he's a DRY source*
❤️🇮🇳👍🏻
Outdated way to teach. Just pointless talking. Modern pedagogy is wasted on this channel
Clear as mud.