#2 wire on a 20A breaker

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sryan

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Location
omaha, ne
I am running a circuit of 5 amps 1800 feet away and calling for #2 XHHW. I know I can do the 10 foot rule at the device per 240.21(B)(1). But how can I make a #2 wire fit on a 20 amp breaker when only rated for #8 max? My thought is using a disconnect, but thoughts are limited.
 

GoldDigger

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Location
Placerville, CA, USA
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Retired PV System Designer
I am running a circuit of 5 amps 1800 feet away and calling for #2 XHHW. I know I can do the 10 foot rule at the device per 240.21(B)(1). But how can I make a #2 wire fit on a 20 amp breaker when only rated for #8 max? My thought is using a disconnect, but thoughts are limited.
Very simple. Use a butt splice or wire connector to put a short length of #8 on the end of your #2. You should be able to do that within the breaker enclosure.
If the #2 were there for ampacity this would not be allowed or safe. But since the size is just to minimize voltage drop a short (under 100 feet!) section of smaller wire will not be an issue.
 

Strathead

Senior Member
Location
Ocala, Florida, USA
Occupation
Electrician/Estimator/Project Manager/Superintendent
I am running a circuit of 5 amps 1800 feet away and calling for #2 XHHW. I know I can do the 10 foot rule at the device per 240.21(B)(1). But how can I make a #2 wire fit on a 20 amp breaker when only rated for #8 max? My thought is using a disconnect, but thoughts are limited.

The only way that I can think of easily is to use a polaris lug or a kerney with tape, to splice a piece of small wire right inside the panel. Nothing wrong with that. A short piece of #12 will cause almost no voltage drop difference. The tap rule doesn't apply to this situation. It is only for using a wire that has lower ampacity than the upstream breaker. Voltage drop isn't an NEC rule it is merely a fine print note.
 

templdl

Senior Member
Location
Wisconsin
I am running a circuit of 5 amps 1800 feet away and calling for #2 XHHW. I know I can do the 10 foot rule at the device per 240.21(B)(1). But how can I make a #2 wire fit on a 20 amp breaker when only rated for #8 max? My thought is using a disconnect, but thoughts are limited.
Mmmmm, only 5a? 1800' of #2 wire? $$$$.
Could stepping up to 480v and back down to 120v be more cost effective?
Have you priced (2) 1ph 1kva 480-120/240 transformers and compare that to the cost of 1800' of #2 wire? Then at 480v the amperes will be 1/4 or 1-1/4ⁿ8a. The voltage drop on 1-1/4a may be better to deal with.
 

Carultch

Senior Member
Location
Massachusetts
Don't forget that the EGC will also have to be #2 for this circuit.

Excellent point. Good luck terminating that. It is common for panels to have a ground bar capable of #4 thru #14, unless they expect larger ground wires, as is the case when larger branch breakers can be installed.

Are you permitted to "step down" ground wires with a splice to the smaller EGC size directly from Table 250.122, when you need to upsize them to match the upsize ratio of an upsized line conductor?
 

iwire

Moderator
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Location
Massachusetts
Good luck terminating that. It is common for panels to have a ground bar capable of #4 thru #14, unless they expect larger ground wires as would be the case for higher ampacities.

Are you permitted to "step down" ground wires when you need to upsize them to match the upsize ratio of an upsized line conductor?

I don't see anything prohibiting stepping the EGC down but i would just add a a lug to the panel.
 

GoldDigger

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Location
Placerville, CA, USA
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Retired PV System Designer
Good luck terminating that. It is common for panels to have a ground bar capable of #4 thru #14, unless they expect larger ground wires as would be the case for higher ampacities.

Are you permitted to "step down" ground wires when you need to upsize them to match the upsize ratio of an upsized line conductor?
Good question.
Electrically and in relation to the *reason* for that code provision the down splice should be fine.
Again it is fault current VD that is at issue rather than fault current ampacity.
But it comes down to the AHJ.
If you put in s terminal strip and transition the hot, neutral, and EGC all at the same point you have an excellent arguing point.
 

Carultch

Senior Member
Location
Massachusetts
Mmmmm, only 5a? 1800' of #2 wire? $$$$.
Could stepping up to 480v and back down to 120v be more cost effective?
Have you priced (2) 1ph 1kva 480-120/240 transformers and compare that to the cost of 1800' of #2 wire? Then at 480v the amperes will be 1/4 or 1-1/4ⁿ8a. The voltage drop on 1-1/4a may be better to deal with.

The performance and economic issues persist either way. Either you pay for and loose energy through the wire, or you pay for and loose energy through the transformer(s). It's a tradeoff.
 

iwire

Moderator
Staff member
Location
Massachusetts
Good question.
Electrically and in relation to the *reason* for that code provision the down splice should be fine.
Again it is fault current VD that is at issue rather than fault current ampacity.
But it comes down to the AHJ.
If you put in s terminal strip and transition the hot, neutral, and EGC all at the same point you have an excellent arguing point.

I think we may be overthinking things.

Of course you can reduce the EGC where you reduce the circuit conductor size.
 

ADub

Senior Member
Location
Midwest
Occupation
Estimator/Project Manager
Can you do that at a field-drilled hole?
Or factory holes that aren't indicated as grounding holes?

I don't know about you but I can. My taps are just as good as a factory tap.


Sent from my iPhone using Tapatalk
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
The performance and economic issues persist either way. Either you pay for and loose energy through the wire, or you pay for and loose energy through the transformer(s). It's a tradeoff.
Except with the wire you pay in energy loss only when running the load(s).
With a transformer you pay in idling (magnetizing) losses 24/7 whether the loads are on or not.
 
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