table 310.15(B)(7)

[okeechobee0138@ces-us.net]

Table 310.15(B)(7) clearly shows 2/0 XHHW-2 aluminum for a single phase dwelling being rated for 150a. Per the manufacturer the Aluminum is rated 90deg at 150a. Now the inspector claims the lugs of the load center (1st means of disc after meter can) are rated 60deg or 75deg. Because of this the inspector claims the 2/0 aluminum is now rated using 310.15(B)(16) 75deg column now 2/0 XHHW-2 is only rated for 135amps.

What is the rating for 2/0 XHHW-2 al when used as feeder wire to a building? And if the 1st means of disc is a meter main combo (ie feeding the ac from that panel before feeding the building) does that change anything?

 

[david luchini]

The (unadjusted) ampacity of @2/0AWG XHHW-2 Al used with 75deg terminations is 135.

Table 310.15(B)(7) permits this to be used as 150A, 120/240V, 1ph, 3w service conductors or main power feeder for an individual dwelling unit

 

[gndrod]

Service/feeders

Service/feeders

And if the 1st means of disc is a meter main combo (ie feeding the ac from that panel before feeding the building) does that change anything?

Depends if the meter main combo is to a single family dwelling or part of multi-family units. A single meter main would be a 3-wire service using Table 310.15(B)(7) sizing for 150A. If the meter main combo is to a building multi-family configuration, then the 3-wire service requires using the Table 310.15(B)(16) ampacities to the meter center and then after the tenant disconnect, the tenant feeder is permitted to use Table 310.15(B)(7) for conductor sizing to the dwelling unit. I hope this helps.

 

[augie47]

Table 310.15(B)(7) clearly shows 2/0 XHHW-2 aluminum for a single phase dwelling being rated for 150a. Per the manufacturer the Aluminum is rated 90deg at 150a. Now the inspector claims the lugs of the load center (1st means of disc after meter can) are rated 60deg or 75deg. Because of this the inspector claims the 2/0 aluminum is now rated using 310.15(B)(16) 75deg column now 2/0 XHHW-2 is only rated for 135amps.

What is the rating for 2/0 XHHW-2 al when used as feeder wire to a building? And if the 1st means of disc is a meter main combo (ie feeding the ac from that panel before feeding the building) does that change anything?

Unfortunately it does. 310.15(B)(7) addresses SERVICE conductors and feeder conductors that serve as MAIN POWER FEEDERS.
You will note in that Section it describes the main power feeder as one that supplies ALL loads associated with the dwelling.
Once you supplied the HVAC from the combo, the feeder to the inside panel does not qualify under 310.15(B)(7)

You might perform a load calulation on the remaining dwelling unit load (less the HVAC) and if its' less than 135 amps, convince the incpector that you are using 240.4(B), "next size up" rule.

 

[gndrod]

You might perform a load calulation on the remaining dwelling unit load (less the HVAC) and if its' less than 135 amps, convince the incpector that you are using 240.4(B), "next size up" rule.

Augie,

You are worth your salt.

Okeechobee,

Let us know what the inspector says. Tx

 

[okeechobee0138@ces-us.net]

Is a wires ampacity rating determined by the cecius rating of the lugs used to connec

Is a wires ampacity rating determined by the cecius rating of the lugs used to connec

The local inspector is trying to force us to size wire according to the celcius rating of the lugs we are connecting to, and if a lug is not physically stamped with a degrees celcius rating then he is using the 60 deg column of 310.15(B)(16). He is using this argument for meter cans and load centers. My argument of using table 310.15(B)(7) to size main feeder wires for a single family dwelling (as long as the application fits the requirements of this table) is falling on deaf ears. I thought table 310.15(B)(7) superceeded 310.15(B)(16) if the application fit. The inspector claims that wire sizing has to be sized according to the lugs because it is the weakest point of the connection. From what i have found if the aic rating is below 25Kaic then lugs are rated 60deg or 75deg, and if 25kaic or higher the the lugs are rated 90deg. If this inspector is right this changes the wire sizing for every job less than 25kaic that is not a main feeder that falls under 310.15(B)(7). Why even give the wire a rating if the rating is determined by lugs?

 

[kwired]

The local inspector is trying to force us to size wire according to the celcius rating of the lugs we are connecting to, and if a lug is not physically stamped with a degrees celcius rating then he is using the 60 deg column of 310.15(B)(16). He is using this argument for meter cans and load centers. My argument of using table 310.15(B)(7) to size main feeder wires for a single family dwelling (as long as the application fits the requirements of this table) is falling on deaf ears. I thought table 310.15(B)(7) superceeded 310.15(B)(16) if the application fit. The inspector claims that wire sizing has to be sized according to the lugs because it is the weakest point of the connection. From what i have found if the aic rating is below 25Kaic then lugs are rated 60deg or 75deg, and if 25kaic or higher the the lugs are rated 90deg. If this inspector is right this changes the wire sizing for every job less than 25kaic that is not a main feeder that falls under 310.15(B)(7). Why even give the wire a rating if the rating is determined by lugs?

110.14(C)(1) tells us that if the temperature rating of a termination is not marked then we must use 60 deg C for conductors 1 AWG and smaller or 100 amps and below. For over 100 amps or larger than 1AWG conductors we must use 75 deg C conductors. This is only if there is no other rating marked. Most newer equipment is marked 75 deg C.

 

[Lectricbota]

The local inspector is trying to force us to size wire according to the celcius rating of the lugs we are connecting to, and if a lug is not physically stamped with a degrees celcius rating then he is using the 60 deg column of 310.15(B)(16). He is using this argument for meter cans and load centers. My argument of using table 310.15(B)(7) to size main feeder wires for a single family dwelling (as long as the application fits the requirements of this table) is falling on deaf ears. I thought table 310.15(B)(7) superceeded 310.15(B)(16) if the application fit. The inspector claims that wire sizing has to be sized according to the lugs because it is the weakest point of the connection. From what i have found if the aic rating is below 25Kaic then lugs are rated 60deg or 75deg, and if 25kaic or higher the the lugs are rated 90deg. If this inspector is right this changes the wire sizing for every job less than 25kaic that is not a main feeder that falls under 310.15(B)(7). Why even give the wire a rating if the rating is determined by lugs?

If you have to use adjustment factor for any reason(ambient,wire bundling,etc.) you use the wire rating to start your adjustment calculations.

 

[david luchini]

The local inspector is trying to force us to size wire according to the celcius rating of the lugs we are connecting to, and if a lug is not physically stamped with a degrees celcius rating then he is using the 60 deg column of 310.15(B)(16). He is using this argument for meter cans and load centers. My argument of using table 310.15(B)(7) to size main feeder wires for a single family dwelling (as long as the application fits the requirements of this table) is falling on deaf ears. I thought table 310.15(B)(7) superceeded 310.15(B)(16) if the application fit. The inspector claims that wire sizing has to be sized according to the lugs because it is the weakest point of the connection.

For what it's worth, I agree with you (if I understand your application correctly.)

310.15(B) says that the ampacity for conductors rated 0 to 2000 volts shall be as specified in the allowable ampacity tables as modified by 310.15(B)(1) through 310.15(B)(7.)

There is nothing in 310.16(B)(7) about the temperature ratings of the terminations...Only Conductor types and sizes, service/feeder rating (amperes), and the requirements that the conductors be the 120/240V, 3 wire, single phase service conductors or main power feeder to an individual dwelling unit.

 

[okeechobee0138@ces-us.net]

The local inspector is trying to force us to size wire according to the celcius rating of the lugs we are connecting to, and if a lug is not physically stamped with a degrees celcius rating then he is using the 60 deg column of 310.15(B)(16). He is using this argument for meter cans and load centers. My argument of using table 310.15(B)(7) to size main feeder wires for a single family dwelling (as long as the application fits the requirements of this table) is falling on deaf ears. I thought table 310.15(B)(7) superceeded 310.15(B)(16) if the application fit. The inspector claims that wire sizing has to be sized according to the lugs because it is the weakest point of the connection. From what i have found if the aic rating is below 25Kaic then lugs are rated 60deg or 75deg, and if 25kaic or higher the the lugs are rated 90deg. If this inspector is right this changes the wire sizing for every job less than 25kaic that is not a main feeder that falls under 310.15(B)(7). Why even give the wire a rating if the rating is determined by lugs?

We finally got the inspectors to agree to use table 310.15(B)(7) for a 200a service, regardless of lug deg rating. 150a meter to 150a main breaker (with no branch ckts) to 150a mb panel inside the single phase single resi dwelling. He will allow 2/0 aluminum to be used as main feeder for 150a. Thank you for your insights.

However, if we change the scenario a little bit: 150a 1ph service to a 150a meter combo (with 8 branch circuits) to a 150a mb panel inside the 1ph single resi dwelling. And the meter combo now feeds the ac with a 2pole 60a on the panel outside. Now we have to use a 3/0 aluminum to feed that same 150a panel inside that has less of a load because the ac is fed from outside. I understand that the 3/0 is no longer a main feeder so 310.15(B)(7) is out, but does it make sense that the wire is larger for a smaller load, and all because the lug is 75 deg rated. It's the same 75 deg lug used with 2/0 in the previuos example.

Also if we decide to feed the ac from the panel inside we now have to use metal ridgid pipe attached to the bottom of the structure all the way back to the ac unit. We are talking about a service for a trailer, mobile home. New inspector changing the way the town has done things for decades, frustrating.

 

[david]

(New) inspector changing the way the town has done things for decades, frustrating.

Inspectors here that all the time I have been doing this for (10, 20 , 30 ) years.

Here we see 700.12(F) being considered in the past the only thing looked at was placement of EM lights not how they where wired.

Swimming pools : we now have barriers that prevent young children from entering the water un-attended. We now see a # 8 bond to wet- nitch lighting. GFCI rec. alarms on patio doors that access the pool area.

Inner –connected smoke detectors

Transformer neutral (SDS) being bonded to grounding electrodes.

Equipment grounds for taps based on the supply side over current protection

Last month I had the head of the meter department call and chew me out for approving a meter height at 6 ? ft center first one since 1990 when I started inspecting. Yes I was aware that the utility reg. it between 4 ? ft to 5 ? ft center but this was a service repair.
To day a temp. service meter was 7 ft to center construction site they piled two feet of dirt and made a flat surface in front of the meter.

It sounds like to me you have an inspector trying to do a good job. Not throwing his weight around, work with him, learn with him, grow with him it is a changing code. Give him time you said he is new!!!!!!!!!!!

 

[weressl]

The local inspector is trying to force us to size wire according to the celcius rating of the lugs we are connecting to, and if a lug is not physically stamped with a degrees celcius rating then he is using the 60 deg column of 310.15(B)(16). He is using this argument for meter cans and load centers. My argument of using table 310.15(B)(7) to size main feeder wires for a single family dwelling (as long as the application fits the requirements of this table) is falling on deaf ears. I thought table 310.15(B)(7) superceeded 310.15(B)(16) if the application fit. The inspector claims that wire sizing has to be sized according to the lugs because it is the weakest point of the connection. From what i have found if the aic rating is below 25Kaic then lugs are rated 60deg or 75deg, and if 25kaic or higher the the lugs are rated 90deg. If this inspector is right this changes the wire sizing for every job less than 25kaic that is not a main feeder that falls under 310.15(B)(7). Why even give the wire a rating if the rating is determined by lugs?

The weakest link - in a chain - principle guides here. You must size for the lowest rating, make adjustment to the highest ambient, etc.

There are lugs that are rated for different temperatures, including 90Centigrade rise.

The ratings are not only applicable to the items you've listed above, but a broad variety if industrial and commercial devices.

Somewhat surprised by your questions. If you're installing as a Contractor - presuming from the Inspectors involvement - all this information should be of no news to you.

 

[rbalex]

...
There is nothing in 310.16(B)(7) about the temperature ratings of the terminations...Only Conductor types and sizes, service/feeder rating (amperes), and the requirements that the conductors be the 120/240V, 3 wire, single phase service conductors or main power feeder to an individual dwelling unit.

Laszlo has it right. There may be nothing in 310.15 but there definitely is in the opening statement of Section 110.14(C) Temperature Limitations.:


The temperature rating associated with the ampacity of a conductor shall be selected and coordinated so as not to exceed the lowest temperature rating of any connected termination, conductor, or device. Conductors with temperature ratings higher than specified for terminations shall be permitted to be used for ampacity adjustment, correction, or both.


Both Sections 310.15 and 110.14 must be properly addressed.


This is not to say the inspector is correct; as has been pointed out in other posts, terminals greater than 110A have a 75C rating whether marked or not. This may also be found in the UL White Book under Category Code AALZ.

 

[kwired]

We finally got the inspectors to agree to use table 310.15(B)(7) for a 200a service, regardless of lug deg rating. 150a meter to 150a main breaker (with no branch ckts) to 150a mb panel inside the single phase single resi dwelling. He will allow 2/0 aluminum to be used as main feeder for 150a. Thank you for your insights.

However, if we change the scenario a little bit: 150a 1ph service to a 150a meter combo (with 8 branch circuits) to a 150a mb panel inside the 1ph single resi dwelling. And the meter combo now feeds the ac with a 2pole 60a on the panel outside. Now we have to use a 3/0 aluminum to feed that same 150a panel inside that has less of a load because the ac is fed from outside. I understand that the 3/0 is no longer a main feeder so 310.15(B)(7) is out, but does it make sense that the wire is larger for a smaller load, and all because the lug is 75 deg rated. It's the same 75 deg lug used with 2/0 in the previuos example.

Also if we decide to feed the ac from the panel inside we now have to use metal ridgid pipe attached to the bottom of the structure all the way back to the ac unit. We are talking about a service for a trailer, mobile home. New inspector changing the way the town has done things for decades, frustrating.

By dropping some loads at the service panel, you changed the load diversity on the feeder to the remainder of the house. 310.15(B)(7), is there because they assume the entire load of a dwelling will never have 100% diversity.

 

[ActionDave]

By dropping some loads at the service panel, you changed the load diversity on the feeder to the remainder of the house. 310.15(B)(7), is there because they assume the entire load of a dwelling will never have 100% diversity.

Are you saying that the load on the wires to the inside panel is now greater because the circuit for the air conditioner is not in it?

 

[augie47]

Are you saying that the load on the wires to the inside panel is now greater because the circuit for the air conditioner is not in it?

As mentioned back in post 4:
Ironic as it may sound, the Code does infer similar, Perhaps, not that it's greater but it's lost the diversity that allowed the reduction.

 

[kwired]

Are you saying that the load on the wires to the inside panel is now greater because the circuit for the air conditioner is not in it?

As mentioned back in post 4:
Ironic as it may sound, the Code does infer similar, Perhaps, not that it's greater but it's lost the diversity that allowed the reduction.

That is a simple way to say it - it lost the diversity that allowed the reduction.

I personally wouldn't have a problem with the only load that gets dropped from a dwelling feeder to be the AC or an electric space heating unit and still apply the smaller feeder conductor, but I still see that it is not permitted to do it this way as is written.

 

[Smart $]

As mentioned back in post 4:
Ironic as it may sound, the Code does infer similar, Perhaps, not that it's greater but it's lost the diversity that allowed the reduction.

I realize that's the popular rationale... but for the sake of argument, say two dwellings have an identical calculated load with the exception one has an additional A/C load which is fed ahead of the main dwelling feeder, as posed by this thread. The calculated load of the main feeders are identical. How does one have the necessary diversity while the other one doesn't?

 

[kwired]

I realize that's the popular rationale... but for the sake of argument, say two dwellings have an identical calculated load with the exception one has an additional A/C load which is fed ahead of the main dwelling feeder, as posed by this thread. The calculated load of the main feeders are identical. How does one have the necessary diversity while the other one doesn't?

I agree with you, you want to submit a change proposal? This section is supposed to change in 2014, but I think we will still have same question for the example you gave if using 2014 language.

 

[Dennis Alwon]

I realize that's the popular rationale... but for the sake of argument, say two dwellings have an identical calculated load with the exception one has an additional A/C load which is fed ahead of the main dwelling feeder, as posed by this thread. The calculated load of the main feeders are identical. How does one have the necessary diversity while the other one doesn't?

Of course the whole situation is ridiculous esp. if an a/c is involved. The load to one panel is less but needs a larger wire while the load to the other can use Table 310.15(B)(7).

That is the way it is by code since it is impossible to cover all scenarios.

IMO, the inspector is correct to enforce using 310.15 (B)(16) if the a/c comes from the main panel.

One way around this is to run conduit from the meter main to the sub panel and install 2/0 alumin at 135 amps. As long as the load is not greater than 135 amps you can use a 150 amp breaker