sparkle5
Member
- Location
- California
This is a rudimentary question, what specifically is a "dry" contact as opposed to a "wet" contact.
contact terminology
- Thread starter sparkle5
- Start date
- Status
russ
Senior Member
- Location
- Burbank IL
Re: contact terminology
Dry contact has no power, just like a wall switch you have to supply power to it.
Dry contact has no power, just like a wall switch you have to supply power to it.
russ
Senior Member
- Location
- Burbank IL
Re: contact terminology
The dry contact is a normally closed or normally open set of switch contacts that open or close when a control coil is activated.
The dry contact is a normally closed or normally open set of switch contacts that open or close when a control coil is activated.
sparkle5
Member
- Location
- California
Re: contact terminology
thank you,I suspected that was the case, like a typical form "c" contact, i just have not seen a wet contact so i suspected the default is a dry that is "energized" from the coil supply or a seperate source.
thank you,I suspected that was the case, like a typical form "c" contact, i just have not seen a wet contact so i suspected the default is a dry that is "energized" from the coil supply or a seperate source.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: contact terminology
Dry contact would be a unpowered set of relay contacts. I am guessing, but a wet contact is probably a mercury relay. A mercury relay has mercury wetted contacts, or a plunger that operates in mercury. Mercury relays handle large amounts of power and last forever.
Dry contact would be a unpowered set of relay contacts. I am guessing, but a wet contact is probably a mercury relay. A mercury relay has mercury wetted contacts, or a plunger that operates in mercury. Mercury relays handle large amounts of power and last forever.
Re: contact terminology
As for wet contact it might applies for the breakers which uses liquids such as oil and sf6.
I've been in engineering field since 1989 but I never heard such terminolgy even in university we never heard such.Can you give give please where did you get the term.thanks.
As for wet contact it might applies for the breakers which uses liquids such as oil and sf6.
I've been in engineering field since 1989 but I never heard such terminolgy even in university we never heard such.Can you give give please where did you get the term.thanks.
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: contact terminology
I think we are letting our knowledge of the English language get in the way of understanding the language of our profession. In English, the terms ?dry? and ?wet? are opposites. I don?t think that there is a term in the language of electrical design and construction that is opposite to the term ?dry contact.? But even if there is, I believe it would not mean that a liquid is part of the component. Let the equipment vendors on this forum chime in, and tell me I am wrong, if they like.
My use of the term ?dry contact? carries the meaning that the circuit in which a decision is made is electrically isolated from the circuit in which a resultant action is taken. Consider a controller for an air compressor. Suppose its controller has a pressure switch in series with the motor starting coil (the ?M Coil?). As pressure gets too low, the switch changes states, allowing power to get to the M Coil, and the compressor motor begins to go roundy-roundy. That would not be a ?dry contact? arrangement.
Now change the circuit. Suppose that there is a power source that could drive current through the pressure switch, and (instead of then flowing through the M Coil) it sendis power through a relay coil. The power turns on the relay coil, and its ?a? contact (?normally open?) closes. Finally, suppose that this contact is in series with the M Coil, so that when the contact closes, the motor will start. The ?decision loop? includes the pressure switch, but the ?action loop? does not. The two loops are electrically isolated, and the isolation point is internal to the relay (i.e., the relay coil and the relay contact separate the two loops). In my view, the relay contact would fit the definition of a ?dry contact.?
Does anyone else use the term ?dry contact? in this sense?
I think we are letting our knowledge of the English language get in the way of understanding the language of our profession. In English, the terms ?dry? and ?wet? are opposites. I don?t think that there is a term in the language of electrical design and construction that is opposite to the term ?dry contact.? But even if there is, I believe it would not mean that a liquid is part of the component. Let the equipment vendors on this forum chime in, and tell me I am wrong, if they like.
My use of the term ?dry contact? carries the meaning that the circuit in which a decision is made is electrically isolated from the circuit in which a resultant action is taken. Consider a controller for an air compressor. Suppose its controller has a pressure switch in series with the motor starting coil (the ?M Coil?). As pressure gets too low, the switch changes states, allowing power to get to the M Coil, and the compressor motor begins to go roundy-roundy. That would not be a ?dry contact? arrangement.
Now change the circuit. Suppose that there is a power source that could drive current through the pressure switch, and (instead of then flowing through the M Coil) it sendis power through a relay coil. The power turns on the relay coil, and its ?a? contact (?normally open?) closes. Finally, suppose that this contact is in series with the M Coil, so that when the contact closes, the motor will start. The ?decision loop? includes the pressure switch, but the ?action loop? does not. The two loops are electrically isolated, and the isolation point is internal to the relay (i.e., the relay coil and the relay contact separate the two loops). In my view, the relay contact would fit the definition of a ?dry contact.?
Does anyone else use the term ?dry contact? in this sense?
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: contact terminology
The terms Dry and Wetted contacts, have been used for many years in process control industries in my locale, including utilities. In most cases there is no difference between these contacts until they have been installed into a circuit. All dry contacts can be wired as wetted.
Dry contacts are totally isolated, like the previous example of a light switch.
Wetted contacts have at least one side of the contact shared with a different circuit (typically a common "hot"). A mechanical 24 hour time switch is a good example of a wetted circuit.
The terms Dry and Wetted contacts, have been used for many years in process control industries in my locale, including utilities. In most cases there is no difference between these contacts until they have been installed into a circuit. All dry contacts can be wired as wetted.
Dry contacts are totally isolated, like the previous example of a light switch.
Wetted contacts have at least one side of the contact shared with a different circuit (typically a common "hot"). A mechanical 24 hour time switch is a good example of a wetted circuit.
Ed MacLaren
Senior Member
Re: contact terminology
As others have stated, "dry contact" means that it controls a circuit completely isolated from it's actuating coil, for example, a contact on a 24 volt fire alarm auxilliary relay wired to shut down a 480 volt HVAC supply fan.
Another example, the GF contact in the sketch below.
Ed
As others have stated, "dry contact" means that it controls a circuit completely isolated from it's actuating coil, for example, a contact on a 24 volt fire alarm auxilliary relay wired to shut down a 480 volt HVAC supply fan.
Another example, the GF contact in the sketch below.
Ed
sparkle5
Member
- Location
- California
Re: contact terminology
Thanks for the clarification, my curiosity as to the specific nomenclature of "dry" versus "wet" arises from hearing the term used by others (foreman, general foreman). Although never heard of a "wet" contact used in the field was curious as to the opinions and experiences that the members of this forum held.
Unfortunately i have not had extensive control work in my career, however knowing basic concepts and procedures one can usually break down complicated control processes to the their elementary function and understand the overall processes. Thanks again.
Thanks for the clarification, my curiosity as to the specific nomenclature of "dry" versus "wet" arises from hearing the term used by others (foreman, general foreman). Although never heard of a "wet" contact used in the field was curious as to the opinions and experiences that the members of this forum held.
Unfortunately i have not had extensive control work in my career, however knowing basic concepts and procedures one can usually break down complicated control processes to the their elementary function and understand the overall processes. Thanks again.
B
bthielen
Guest
Re: contact terminology
As others have mentioned, I have understood a "dry" contact to be one that is electrically isolated. An example that comes to mind is a PLC output card (module). Relay output modules would be using "dry" contacts vs. transistor outputs where the module's supply voltage is not isolated and the output devices then must be at the same voltage level.
Bob
As others have mentioned, I have understood a "dry" contact to be one that is electrically isolated. An example that comes to mind is a PLC output card (module). Relay output modules would be using "dry" contacts vs. transistor outputs where the module's supply voltage is not isolated and the output devices then must be at the same voltage level.
Bob
Re: contact terminology
Thanks to all of you.Now it is clear in my mind what are those two terminolgy means.I agree that wet does not incorporated in electrical as contact being done in liquid areas such as i mention.
I am sorry even i am in this field I never heard this term even in our designed we never designate as such wet and dry.
Thanks once again.
Thanks to all of you.Now it is clear in my mind what are those two terminolgy means.I agree that wet does not incorporated in electrical as contact being done in liquid areas such as i mention.
I am sorry even i am in this field I never heard this term even in our designed we never designate as such wet and dry.
Thanks once again.
- Status