more vs less

[dicklaxt]

I read a lot of posts trying to get by with the minimums
it appears.

ie: calculating amps for conductor sizing using 115% or 125%,why not just take worst case and move on , does this 10% difference mean that much more in dollar outlay for copper or are there other ramifications,such as inspectors not accepting a larger value, etc?

Curious George,,,,,,,,,,,,,

 

[chris kennedy]

I read a lot of posts trying to get by with the minimums
it appears.

ie: calculating amps for conductor sizing using 115% or 125%,why not just take worst case and move on , does this 10% difference mean that much more in dollar outlay for copper?

Curious George,,,,,,,,,,,,,

It does if your bidding 100 units against 6 other contractors.

 

[peter d]

I read a lot of posts trying to get by with the minimums
it appears.

ie: calculating amps for conductor sizing using 115% or 125%,why not just take worst case and move on , does this 10% difference mean that much more in dollar outlay for copper or are there other ramifications,such as inspectors not accepting a larger value, etc?

Curious George,,,,,,,,,,,,,

Most of us do not wire to code minimum. However, knowing the code minimums can often be used to our economic advantage as Chris pointed out.

Furthermore, knowing what the NEC actually says (aka "code minimum") is what's important, not what your were told, what you heard, what the inspector told you, what they instructor told you, etc.

 

[peter d]

As an aside, the often maligned code minimum will produce an a safe installation. As the NEC's primary concern is electrical safety, it is very conservative and has a lot of "fudge factor" built into it. So code minimum is not such a bad thing. But as I said, very few of us wire to code minimum on a regular basis.

 

[dicklaxt]

Great answers for Curious George

 

[roger]

It does if your bidding 100 units against 6 other contractors.

Even against 1 other contractor.

It also changes things in long runs, 1000 feet x 4 runs of 600 MCM is a a lot of money compared to 1000 feet x 4 runs of 500 MCM if 500 MCM will do.


Roger

 

[peter d]

It also changes things in long runs, 1000 feet x 4 runs of 600 MCM is a a lot of money compared to 1000 feet x 4 runs of 500 MCM if 500 MCM will do.

I disagree, the contractor should just go ahead and eat the difference for the 600 because then he can say he did a better job and pat himself on the back.

 

[roger]

I disagree, the contractor should just go ahead and eat the difference for the 600 because then he can say he did a better job and pat himself on the back.

Well, this is true. :grin:

Roger

 

[iwire]

I read a lot of posts trying to get by with the minimums it appears.

ie: calculating amps for conductor sizing using 115% or 125%,why not just take worst case and move on , does this 10% difference mean that much more in dollar outlay for copper or are there other ramifications,such as inspectors not accepting a larger value, etc?

I agree with the reasons already given and will add that in my mind this is primarily an NEC forum so we focus on the actually requirements and less on what provides the best value for the job.

Many times given the choice the customer will want code minimum as they will see no added value in more copper if less copper is legal and will work.

 

[dicklaxt]

Thanks for the answers and let me add that from the design side of the fence economics tend to take a back seat after the contract is let and we will design to a less risky situation.We find it easier to go more because of constant change and the larger size keeps us away from rework as time in engineering is a minimal part of the contract compared to construction setting around waiting for move ahead documents

dick

 

[peter d]

Thanks for the answers and let me add that from the design side of the fence economics tend to take a back seat after the contract is let and we will design to a less risky situation.

dick

That makes sense, I think there is a tendency to "overdesign" to compensate for the risk factor that you speak of.

Case in point, I was involved with wiring a craft store (national chain.) They had a boiler plate spec that required all wiring to be in raceway and the minimum size conductor was #10.

The minimum #10 requirement certainly made sense for the 120 volt circuits, many of which were very long. But for the 277 volt lighting circuits it made no sense at all. The raceway requirement was quite unnecessary as the job could have been done faster and cheaper using a combination of raceways and MC cable at the EC's discretion.

 

[dicklaxt]

Its not always a case of over design as you call it, it is very often a client directive or specification.

There is never enough time to do it right but always enough time to do it over, once the blame has been placed.It seems someone has to be the whipping boy and then everyone is happy. It goes on record that the fault lies here and the profits are counted,,,,,,never have figured how the bean counters made sense of that.

dick