knob & tube ampacity

[al hildenbrand]

. . . as of 1956 the rules in section 2127 of the 1956 NEC prohibit a breaker larger than 15A on a multi-outlet branch circuit. I was inspecting a house built in 1955 [1953 NEC] that was protected with a 20A OCPD; it would appear they are not in violation of over fusing the 14 AWG circuit wiring.

:-?

How is the 20A OCPD compliant with 2127?

 

[480sparky]

Follow 2127 forward, then.
In 1959, it is 210-25. In 1975, it becomes 210-24. It ends up as our current 210.24. That's not the small conductor rule of 240.4(D).

 

[dana1028]

:-?

How is the 20A OCPD compliant with 2127?

oops... you had referred to the 1956 code as having section 2127....I looked in the 1956 and found it....but I didn't bother checking the 1953 NEC [which also has that code section; I improperly thought 2127 was new to 1956.

 

[480sparky]

:-?

How is the 20A OCPD compliant with 2127?

2127 states that a branch circuit with more than one outlet must have a minimum conductor size of 14. If there is only one outlet on the circuit, then the OCD can be sized according to ampacity in Tables 1 or 2, Chapter 10.

See note 3 to the tables.... it states that concealed K&T must use Table 2. Table 2 shows various ampacities of 14, starting at 20.

 

[al hildenbrand]

Follow 2127 forward, then.
In 1959, it is 210-25. In 1975, it becomes 210-24. It ends up as our current 210.24. That's not the small conductor rule of 240.4(D).

So?

You, yourself, pointed out that the "small conductor rule" is not in existance in '53. New Code is new code.

 

[dana1028]

2127 states that a branch circuit with more than one outlet must have a minimum conductor size of 14. If there is only one outlet on the circuit, then the OCD can be sized according to ampacity in Tables 1 or 2, Chapter 10.

See note 3 to the tables.... it states that concealed K&T must use Table 2. Table 2 shows various ampacities of 14, starting at 20.

You are correct and I don't think either of us [Al & I...don't mean to be speaking for Al] disagree with what you are saying.

However, as Al did point out, it's not very likely to see single outlet circuits; and I at least am referring to a multi-outlet circuit.

I do wish to that both of you for the time you have taken to research these code sections and assist me.

 

[al hildenbrand]

2127 states that a branch circuit with more than one outlet must have a minimum conductor size of 14. If there is only one outlet on the circuit, then the OCD can be sized according to ampacity in Tables 1 or 2, Chapter 10.

See note 3 to the tables.... it states that concealed K&T must use Table 2. Table 2 shows various ampacities of 14, starting at 20.

Again, why talk about a possibility that was very rare in the common single family dwelling wired with K&T in 1955?

99+% of the 15 and 20 Amp branch circuits in single family dwellings built in 1955 had two or more outlets.

 

[al hildenbrand]

I do wish to that both of you for the time you have taken to research these code sections and assist me.

You're most welcome.

The Ampacity in the Tables (1953 Chapt. 10 & today's 310.16) still are much larger than the OCPD can be set at, with some noteable exceptions. For the generic multioutlet dwelling general lighting circuit, the difference between the OCPD and the conductor ampacity in the table provides the buffer for various deratings . . . . may not be the most concise statement, but it helps me keep it straight.

 

[480sparky]

Again, why talk about a possibility that was very rare in the common single family dwelling wired with K&T in 1955?

99+% of the 15 and 20 Amp branch circuits in single family dwellings built in 1955 had two or more outlets.

Oh, I agree. Dedicated circuits probably weren't even required in resi in '53, at least that I can see. Unlikey, yes. Impossible, no.

 

[al hildenbrand]

. . . Dedicated circuits probably weren't even required in resi in '53, at least that I can see. . .

That is something, isn't it?

2127 refers one back to 2115 b which states that a single 20 A circuit (minimum) is to be installed "for the small appliance load in kitchen, laundry, pantry, dining-room and breakfast-room of dwelling occupancies. . . "

One could install more than a single 20 A circuit, but, at minimum, one is required.

My how things have changed.