Difference between Class 1, 2, 3

[brother]

I want to finally get this straight, what is the real difference in class 1, 2, and 3 systems. I know that some say its the voltage, i always thought class 2 and 3 were 30 volts or less. Class 1 was more like 120 volts or less.

725.55 says they have to be seperated unless its soley to connect the equipment associated with it. and 300.3(C)(1) says it can be together if the insulation is high as the highest voltage present. I just make sure i got it straight, had a fellow journeyman ask me about this and wanted to know if there was a code violation.

 

[iwire]

I want to finally get this straight, what is the real difference in class 1, 2, and 3 systems. I know that some say its the voltage, i always thought class 2 and 3 were 30 volts or less. Class 1 was more like 120 volts or less.

Take a look at Table 11(A) and 11(B) in the rear of the code book. In the 2005 they are on page 70-638

725.55 says they have to be separated unless its soley to connect the equipment associated with it. and 300.3(C)(1) says it can be together if the insulation is high as the highest voltage present.

Both statements are correct.

Basically when the NEC allows different voltages to be mixed 300.3(C) must be met. But there are many times when the NEC prohibits different systems in the same raceway.

 

[brother]

Take a look at Table 11(A) and 11(B) in the rear of the code book. In the 2005 they are on page 70-638

Thanks for the info, however reading the table and looking at the definition of class 1 725.21(A) actually throws me off a little. It looks like class 2, and 3 can be at the same rating according to this table.

 

[iwire]

Thanks for the info, however reading the table and looking at the definition of class 1 725.21(A) actually throws me off a little. It looks like class 2, and 3 can be at the same rating according to this table.

See 725.41

 

[tom baker]

Take a look at Table 11(A) and 11(B) in the rear of the code book. In the 2005 they are on page 70-638





Both statements are correct.

Basically when the NEC allows different voltages to be mixed 300.3(C) must be met. But there are many times when the NEC prohibits different systems in the same raceway.

But 300.3(C)(1) has a FPN to 725.55, which does not allow class 2 or 3 in the same raceway, OK in enclosures for connection as long as maintain 1/4" separation.

 

[tom baker]

I want to finally get this straight, what is the real difference in class 1, 2, and 3 systems. I know that some say its the voltage, i always thought class 2 and 3 were 30 volts or less. Class 1 was more like 120 volts or less.

725.55 says they have to be seperated unless its soley to connect the equipment associated with it. and 300.3(C)(1) says it can be together if the insulation is high as the highest voltage present. I just make sure i got it straight, had a fellow journeyman ask me about this and wanted to know if there was a code violation.

PM me with your email and I will send you a chart that compares the wiring methods.

Think of class 2 and 3 as low voltage - limited energy really.

Class 1 is a system thats wired with a chapter 3 wiring method. Power limited C1 typically is a electrical unit heater control system. Non power limited would typically be a motor control circuit.

 

[brother]

PM me with your email and I will send you a chart that compares the wiring methods.

Think of class 2 and 3 as low voltage - limited energy really.

Class 1 is a system thats wired with a chapter 3 wiring method. Power limited C1 typically is a electrical unit heater control system. Non power limited would typically be a motor control circuit.

Ill do that and get in contact with ya.