Receptacle Tap Question.

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sparkky302

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Hello I am working on a project where we are installing a freezer for some medical equipment. The freezer draws 15Amps. The electrical engineer specs us to run #6 THHN from a 20A breaker 175' away. My question is can we tap the #6 at the receptale with #10's so it will work on a 20A duplex receptacle? I think that 210.19 (a) (4) Exception 1 will cover me. Also we have another 20A circuit feeding some Refriderators which is calling for #6 THHN. Can we tap in a ceiling junction box and run #10's as long as it is within 25 feet? All the equipment has the standard U ground cord caps.
Thanks
 
These conductors would not be tap conductors and will not be limited in length by any code rule. There is no code reason not to make the connection from the #6 to the receptacle using #12 wire.
 
A definition of Tap Conductor

A tap conductor is a conductor, other than a service conductor, that has
overcurrent protection ahead of its point of supply that exceeds the value permitted for similar conductors that are ptotected as described elsewhere in 240.4 .
 
Look also at 210.3. The rating of a circuit is determined by the ampere rating of the overcurrent device. Since the overcurrent device is 20-amps, this is just a 20-amp circuit which happens to be using #6 wire. You are allowed to use #12 wire in a 20-amp circuit. You will just need to make sure that doing so is agreeable to the person that wrote the specs and how much of the smaller wire is acceptable to him. This has everything to do with specifications and little to do with the NEC.
 
I know #6 is over kill and I have questioned him on this. He is saying because it is a 175' run from the breaker to the device that because of the load attached I need #6. Now I don't mind doing what he wants its just going to cost more money.
 
He'll have a heck of a time getting the outlet back in the box. Or getting the #6 on a 20 amp breaker. It wouldn't go in a Siemens breaker.
 
buckofdurham said:
He'll have a heck of a time getting the outlet back in the box. Or getting the #6 on a 20 amp breaker. It wouldn't go in a Siemens breaker.
Click to expand...

That is why the OP is asking about using a smaller wire for the terminations. He was trying to justify it using tap rules. Tap rules don't apply as this is not a tap, it is just an over-sized conductor on a 20-amp circuit. It is perfectly code compliant to do so and to use #10 or #12 conductors in the circuit as needed. The OP will just have to make sure that the person writing the specs understands what he is doing, why he is doing it, and how much of the smaller wire he will allow in the circuit.
 
But wouldn't the smaller wire at the beginning of the circuit (at the breaker)
Would that be a weak link?
And would you not get a voltage drop useing a short piece of 10 or 12 at the breaker?
 
buckofdurham said:
But wouldn't the smaller wire at the beginning of the circuit (at the breaker)
Would that be a weak link?
And would you not get a voltage drop useing a short piece of 10 or 12 at the breaker?
Click to expand...


Short answer is no. The smaller wire could be anywhere in the circuit with the same effect on VD. The VD would be based on the entire circuit length and the ratio of the larger to smaller conductors used.
 
I wouldn't bother telling the EE anything. It's obvious why the wire is sized at #6 and as the installer, I should know how to accomplish what the EE wants in a practical and code compliant manner. If the EE has to spell out how to do the complete install for the installer, he will start looking for an installer who knows what he's doing. IMSO
 
I thought it was goofy too, but looking on a table the longest distance you can go on a 120v circuit with 15 amps and 2% drop is:

#12 47
#10 75
#8 120
#6 190

There must be other loads in the area... put in a transformer and load center... get a higher voltage freezer or something ...I won't be able to sleep knowing there are #6 wires on a 20 a circuit.:smile:
 
realolman said:
I thought it was goofy too, but looking on a table the longest distance you can go on a 120v circuit with 15 amps and 2% drop is:

#12 47
#10 75
#8 120
#6 190

There must be other loads in the area... put in a transformer and load center... get a higher voltage freezer or something ...I won't be able to sleep knowing there are #6 wires on a 20 a circuit.:smile:
Click to expand...


Do we really care if someone spec's #6 conductors for a 20 amp circuit? If they're paying for it why should it matter?
 
buckofdurham said:
But wouldn't the smaller wire at the beginning of the circuit (at the breaker)
Would that be a weak link?
And would you not get a voltage drop useing a short piece of 10 or 12 at the breaker?
Click to expand...

You will get a voltage drop using a short piece, but it will be unnoticable because it is short. It is the because of the length of the wire that the small resistance of each foot adds up into a larger resistance. ( which usually isn't very large either )

It's the larger current passing through that resistance that causes the voltage drop. The larger current passing through the short piece with the very small resistance isn't going to drop much voltage.

This isn't using large wire for heavy currents. The # 12 would be sufficient for the current, so it isn't really a "weak" link.
 
infinity said:
Do we really care if someone spec's #6 conductors for a 20 amp circuit? If they're paying for it why should it matter?
Click to expand...

I guess we don't really. You're absolutely right.:smile:

It just seems that running a 20 a. recept. circuit splicing #6 to # 10 or 12 at both ends is a bit awkward. That's all.
 
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