22awg fused or not

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slick 50

slick 50

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I have a power supply that will be mounted directly to the load center via 3/4" chase nipple. The supply needs to be 240v. The smallest 2 pole breaker I can find is 10amp and the 22 awg is only rated at 7 amps. Question is.....Does anywhere in the NEC say that conductors that do not leave the enclosure has to be fused? Basically the 22 awg will come out of 2 pole 10 amp breaker and into a 4" square box mounted directly to loadcenter with chase nipple. I cannot get any bigger conductor to fit in terminal of power supply. Thanks
 
slick 50 said:
I have a power supply that will be mounted directly to the load center via 3/4" chase nipple. The supply needs to be 240v. The smallest 2 pole breaker I can find is 10amp and the 22 awg is only rated at 7 amps. Question is.....Does anywhere in the NEC say that conductors that do not leave the enclosure has to be fused? Basically the 22 awg will come out of 2 pole 10 amp breaker and into a 4" square box mounted directly to loadcenter with chase nipple. I cannot get any bigger conductor to fit in terminal of power supply. Thanks
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Newark sells two pole brkr din-rail mountable down to one amp - feed it with #14 and use a bigger box.
 
slick 50 said:
The smallest 2 pole breaker I can find is 10amp and the 22 awg is only rated at 7 amps.
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I do industrial control panel design and wiring ... no way would we allow 7A with 22AWG wire; where did you get that rating?

FYI ... we use 10A for #16, and 6A for #18. Anything smaller is ASSUMED to be protected by the equipment ... we don't run it except in cable. If I needed to do so, I'd protect #20 at 4A and #22 at 3A.
 
slick 50 said:
I have a power supply that will be mounted directly to the load center via 3/4" chase nipple. The supply needs to be 240v. The smallest 2 pole breaker I can find is 10amp and the 22 awg is only rated at 7 amps. Question is.....Does anywhere in the NEC say that conductors that do not leave the enclosure has to be fused? Basically the 22 awg will come out of 2 pole 10 amp breaker and into a 4" square box mounted directly to loadcenter with chase nipple. I cannot get any bigger conductor to fit in terminal of power supply. Thanks
Click to expand...

Look in the NFPA 79. A curiosity is that in the NFPA 79, it said that 22 AWG conductors (Cu) with either 60 or 75 degrees C insulation is only good for 3 amps. Where did the 7 amps come from?
 
In the 08 NEC. Go to 725.49 ( size and use ) then 402.5 ( allowable ampacity ) then 724.43 ( overcurrent protection )

The power supply that I am feeding is .07 amp. #16 good for 10amp and #18 good for 7 amp
 
slick 50 said:
In the 08 NEC. Go to 725.49 ( size and use ) then 402.5 ( allowable ampacity ) then 725.43 ( overcurrent protection )

The power supply that I am feeding is .07 amp. #16 good for 10amp and #18 good for 7 amp
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Again, where is the 7 amps coming from?? Yes, 7 amps is for 18 AWG, but not 22.

In your first post, you said that you were using 22 AWG wire, not 18 AWG. Which is it? Is it 18 or 22?
 
doesn't matter how you protect that 22awg wire hooking up a class 2 power supply with conductors smaller then 18 is a violation of code:

725.51 Wiring Methods on Supply Side of the Class 2 or Class 3 Power Source.
Conductors and equipment on the supply side of the power source shall be installed in accordance with the appropriate requirements of Chapters 1 through 4. Transformers or other devices supplied from electric light or power circuits shall be protected by an overcurrent device rated not over 20 amperes.
Exception: The input leads of a transformer or other power source supplying Class 2 and Class 3 circuits shall be permitted to be smaller than 14 AWG, but not smaller than 18 AWG if they are not over 12 in. (305 mm) long and if they have insulation that complies with 725.27(B).
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What is this that your trying to hook up and maybe we can help find a code compliant way of doing it?
 
slick 50 said:
I told you I googled it. Try googling amoacity of 22 awg
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Aside from the fact that the code does not allow using 22 AWG conductors for the wiring of the power supply, I am still stuck on the 7 amps.

I did Google it. Yes, one of the websites that I found did list 22 AWG conductors as having an ampacity of 7 amps. However, directly from one of the websites (www.powerstream.com):

As you might guess, the rated ampacities are just a rule of thumb. In careful engineering the voltage drop, insulation temperature limit, thickness, thermal conductivity, and air convection and temperature should all be taken into account. The Maximum Amps for Power Transmission uses the 700 circular mils per amp rule, which is very very conservative. The Maximum Amps for Chassis Wiring is also a conservative rating, but is meant for wiring in air, and not in a bundle. For short lengths of wire, such as is used in battery packs you should trade off the resistance and load with size, weight, and flexibility. NOTE: For installations that need to conform to the National Electrical Code, you must use their guidelines. Contact your local electrician to find out what is legal!

I was not aware that the rules that electricians live by were titled "Google Electrical Code". There is no reference to 22 AWG wire in the NEC. There is a reference to 22 AWG wire in the NFPA 79, which I suggested in the first place, which you also obviously did not check. In the NFPA 79, in table 12.5.1, the ampacity of 22 AWG wire is listed as 3 amps.

I also asked you if you were using 18 or 22 AWG wire, becuase you initially said 22, but then you changed to 18. You did not answer. If it is 18 AWG, then 7 amps would be correct. Again, are you using 18 or 22 gauge wire?
 
Take a look at Table 522.22 for the ampacity of 22 AWG.
Come out of you panel with a 14 AWG, at 15 amps, run to a small Hoffman enclosure with backpanel, install a DIN rail and DIN rail mount fuse holder, and terminal blocks the N and G.
 
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