Increasing Breaker for Increased Cable Size

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philly

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If a cable size is increased to account for volage drop for a particular circuit and load, do you need to increase the size of the OCPD as well?

As an example if I have a load of 80A but rather than using a #4AWG I increased the cable size to a #2 AWG, then do I need to increase the OCPD size as well?
 
philly said:
If a cable size is increased to account for volage drop for a particular circuit and load, do you need to increase the size of the OCPD as well?

As an example if I have a load of 80A but rather than using a #4AWG I increased the cable size to a #2 AWG, then do I need to increase the OCPD size as well?
Click to expand...

No. Increasing conductor size for voltage drop does not change the OCPD. In fact, you may create a violation by putting too large an OCPD for the load.

An extreme example would be using 2/0 for lot lighting, but it's still on a 20a breaker.
 
philly said:
If a cable size is increased to account for volage drop for a particular circuit and load, do you need to increase the size of the OCPD as well?

As an example if I have a load of 80A but rather than using a #4AWG I increased the cable size to a #2 AWG, then do I need to increase the OCPD size as well?
Click to expand...

It would depend on the application. If you are feeding a sub panel then I would increase the breaker size because then art. 250. 122(B) will not come into play. But as Ken said sometimes that is not an option.
 
Dennis Alwon said:
It would depend on the application. If you are feeding a sub panel then I would increase the breaker size
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If you up sized for voltage drop you must have known the load. Now if you increase the breaker size thinking the load will increase then you get back into voltage drop so you will have to increase the conductors size. It kind of goes in a never ending circle.

IMO size the breaker for the load, size the wire for the voltage drop.
 
480sparky said:
In fact, you may create a violation by putting too large an OCPD for the load.

An extreme example would be using 2/0 for lot lighting, but it's still on a 20a breaker.
Click to expand...

what if you use a larger breaker in order to have larger terminals to land the wire in, and then install properly sized overcurrent protection where the wire is reduced in size in the bases of the poles in a parking lot?
 
ultramegabob said:
what if you use a larger breaker in order to have larger terminals to land the wire in, and then install properly sized overcurrent protection where the wire is reduced in size in the bases of the poles in a parking lot?
Click to expand...

That's fine, but I don't see any advantage to it.

Besides, if I up-size wires for lot lighting, I still run 12 from the 20a breaker to the contactor so the terminals in the breaker aren't a problem. If the wires are going to be too big for the contactor, I install an over-size box and put the contactor(s) and splices in the same box.
 
480sparky said:
That's fine, but I don't see any advantage to it.

Besides, if I up-size wires for lot lighting, I still run 12 from the 20a breaker to the contactor so the terminals in the breaker aren't a problem. If the wires are going to be too big for the contactor, I install an over-size box and put the contactor(s) and splices in the same box.
Click to expand...

I guess I was picturing an entire panel that is feed from a contactor, many ways to do the same thing....
 
iwire said:
If you up sized for voltage drop you must have known the load. Now if you increase the breaker size thinking the load will increase then you get back into voltage drop so you will have to increase the conductors size. It kind of goes in a never ending circle.

IMO size the breaker for the load, size the wire for the voltage drop.
Click to expand...

There are some situations where this is not an issue. For instance on some home I may want to upsize the feeder to a subpanel because of distance but with NM cable upsizing the EGC cannot be done so it is advantangeous to just change the breaker size esp. when it feeds a sub panel that is between floors and would be difficult to add to.

I try to look for future expansions but I don't always have that flexibility.
 
Dennis Alwon said:
There are some situations where this is not an issue. For instance on some home I may want to upsize the feeder to a subpanel because of distance but with NM cable upsizing the EGC cannot be done so it is advantangeous to just change the breaker size esp. when it feeds a sub panel that is between floors and would be difficult to add to.
Click to expand...
True. We've had that discussion before. A #6 NM os okay on a 50a breaker, but not a 30a breaker.
 
Dennis Alwon said:
There are some situations where this is not an issue. For instance on some home I may want to upsize the feeder to a subpanel because of distance but with NM cable upsizing the EGC cannot be done so it is advantangeous to just change the breaker size esp. when it feeds a sub panel that is between floors and would be difficult to add to.

I try to look for future expansions but I don't always have that flexibility.
Click to expand...

Are you saying that because the larger conductor does not have a larger EGC you can not use a larger size breaker?
 
philly said:
Are you saying that because the larger conductor does not have a larger EGC you can not use a larger size breaker?
Click to expand...

Article 250.122(B) says if you increase the ungrounded conductors then you must increase the EGC proportionately. So if a lighting circuit needs a #12 wire circuit and you decide that a #8 must be pulled for VD then a #8 EGC is required.
 
philly said:
Are you saying that because the larger conductor does not have a larger EGC you can not use a larger size breaker?
Click to expand...
Imagine, if you will ...

Someone comes along and sees existing conductors that are large enough for his new load. Voltage drop is not as important as saving money, so he uses them closer to their rated ampacity.

The existing EGC is not large enough for the circuit's new rating.
 
LarryFine said:
Imagine, if you will ...

Someone comes along and sees existing conductors that are large enough for his new load. Voltage drop is not as important as saving money, so he uses them closer to their rated ampacity.

The existing EGC is not large enough for the circuit's new rating.
Click to expand...
Were you using your best Rod Serling voice when you typed this?
 
Dennis Alwon said:
Article 250.122(B) says if you increase the ungrounded conductors then you must increase the EGC proportionately. So if a lighting circuit needs a #12 wire circuit and you decide that a #8 must be pulled for VD then a #8 EGC is required.
Click to expand...

250.122(B) states that you must increase the size of the EGC in proportion to the ungrounded feeders. Does this necessarily mean that we need to have the same size ECG as the ungrounded feeders or just select a size larger in proportion?

Nevermind, after I typed this I found that for smaller circuits the EGC size is proportional to the ungrounded conductor size 1:1
 
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philly said:
250.122(B) states that you must increase the size of the EGC in proportion to the ungrounded feeders. Does this necessarily mean that we need to have the same size ECG as the ungrounded feeders or just select a size larger in proportion?

Nevermind, after I typed this I found that for smaller circuits the EGC size is proportional to the ungrounded conductor size 1:1
Click to expand...

It must be proportional but for wire sizes #14-10 the egc is equivalent to the ungrounded conductors. When you do the ratio you will see that whatever size you change the ungrounded conductors to the EGC will be that size also (1:1). This will not be true for when you increase from #8 and larger. It is proportional but not 1:1 in those cases.
 
iwire said:
If you up sized for voltage drop you must have known the load. Now if you increase the breaker size thinking the load will increase then you get back into voltage drop so you will have to increase the conductors size. It kind of goes in a never ending circle.

IMO size the breaker for the load, size the wire for the voltage drop.
Click to expand...

Here is another possibility. Use the larger OCP 100 amp at the beginning of the feeder and then use an 80 amp breaker as a main on the sub panel at the other end. This will protect the circuit from the issue Bob mentioned above.
 
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