table 310.15(B)(7)

[david]

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.

215.2 Minimum Rating and Size.
(A) Feeders Not More Than 600 Volts.
(3) Individual Dwelling Unit or Mobile Home Conductors. Feeder conductors for individual dwelling units or mobile homes need not be larger than service conductors. (Paragraph 310.15(B)(6) )shall be permitted to be used for conductor size.

Lets make it look something like this:

215.2 Minimum Rating and Size.
(A) Feeders Not More Than 600 Volts.
(3) Individual Dwelling Unit or Mobile Home Conductors. Feeder conductors for individual dwelling units or mobile homes need not be larger than service conductors. (Table 310.15 (B) (7)) ) shall be permitted to be used for conductor size.

Exception: when adjustments for temp or other corrections apply the feeder conductor size shall be adjusted according to those adjustments or correction factors

 

[david]

215.2 Minimum Rating and Size.
Lets make it look something like this:

215.2 Minimum Rating and Size.
(A) Feeders Not More Than 600 Volts.
(3) Individual Dwelling Unit or Mobile Home Conductors. Feeder conductors for individual dwelling units or mobile homes need not be larger than service conductors. (Table 310.15 (B) (7)) ) shall be permitted to be used for conductor size.

Exception: when adjustments for temp or other corrections apply the feeder conductor size shall be adjusted according to those adjustments or correction factors

Or maybe like this, eather way the isssue needs to be addressed by 215.2

215.2 Minimum Rating and Size.
(A) Feeders Not More Than 600 Volts.
(3) Individual Dwelling Unit supplied by one set of service conductors.
Feeder conductors for individual dwelling units or mobile homes need not be larger than service conductors.
Exception: when adjustments for temp or other corrections apply the feeder conductor size shall be adjusted according to those adjustments or correction factors]

 

[kwired]

215.2 Minimum Rating and Size.
(A) Feeders Not More Than 600 Volts.
(3) Individual Dwelling Unit or Mobile Home Conductors. Feeder conductors for individual dwelling units or mobile homes need not be larger than service conductors. (Paragraph 310.15(B)(6) )shall be permitted to be used for conductor size.

Lets make it look something like this:

215.2 Minimum Rating and Size.
(A) Feeders Not More Than 600 Volts.
(3) Individual Dwelling Unit or Mobile Home Conductors. Feeder conductors for individual dwelling units or mobile homes need not be larger than service conductors. (Table 310.15 (B) (7)) ) shall be permitted to be used for conductor size.

Exception: when adjustments for temp or other corrections apply the feeder conductor size shall be adjusted according to those adjustments or correction factors

I don't think 215.2 needs changed other than to reflect any changes that may be made in 310.15(B)(7). I see there is a mistake in the present wording of 2011. It refers us to 310.15(B)(7) when it should be (B)(6) this was probably overlooked, as I am pretty sure (B)(7) in 2008 was what is now (B)(6).

Anyway any changes IMO need to be made in 310.15(B)(7), as this applies to any supply conductor to a dwelling unit.

215.2 only applies to feeder conductors but not to service conductors.

 

[david]

I don't think 215.2 needs changed other than to reflect any changes that may be made in 310.15(B)(7). I see there is a mistake in the present wording of 2011. It refers us to 310.15(B)(7) when it should be (B)(6) this was probably overlooked, as I am pretty sure (B)(7) in 2008 was what is now (B)(6).

Anyway any changes IMO need to be made in 310.15(B)(7), as this applies to any supply conductor to a dwelling unit.

215.2 only applies to feeder conductors but not to service conductors.

I do not see a need for a feeder that carries the exact same load or a lesser load as the service conductors ever needing to be larger than the service entrance conductors. (not withstanding adjustment or correction factors) for a feeder.
Currently 215.2 directs you to the paragraph for 310.15(B)(6) rather than the table. Once directed to the paragraph you still need to define weather the feeder carries the total load for the allowance to use 310.15 (B) (6). This sentence should stand alone without referencing 310.15 (B) (6) as long as it is assured that the service conductors being referenced in the rule are carrying the total load for the dwelling.
(3) Individual Dwelling Unit or Mobile Home Conductors. Feeder conductors for individual dwelling units or mobile homes need not be larger than service conductors

 

[okeechobee0138@ces-us.net]

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

Dennis, we have a 200a rated Meter main with a 150a main and an 8-16 distribution panel (8-16 meter main combo), using feed through lugs at bottom of panel to feed (via conduit) the 150a panel in the trailer. Because the ac is branch fed before the trailer the inspector is stating a 3/0 aluminum has to be used to feed the trailer, (distance is only 60ft). The load calculation is 110 amps. By code the inspector is right, but this application doesn't make sense. So we lost and we had to remove the 2/0 al and replace with 1/0 copper.

 

[Smart $]

Dennis, we have a 200a rated Meter main with a 150a main and an 8-16 distribution panel (8-16 meter main combo), using feed through lugs at bottom of panel to feed (via conduit) the 150a panel in the trailer. Because the ac is branch fed before the trailer the inspector is stating a 3/0 aluminum has to be used to feed the trailer, (distance is only 60ft). The load calculation is 110 amps. By code the inspector is right , but this application doesn't make sense. So we lost and we had to remove the 2/0 al and replace with 1/0 copper.

No, the inspector is not right. Dennis is correct. 2/0 XHHW-2 Aluminum would have been compliant.

 

[david]

Dennis, we have a 200a rated Meter main with a 150a main and an 8-16 distribution panel (8-16 meter main combo), using feed through lugs at bottom of panel to feed (via conduit) the 150a panel in the trailer. Because the ac is branch fed before the trailer the inspector is stating a 3/0 aluminum has to be used to feed the trailer, (distance is only 60ft). The load calculation is 110 amps. By code the inspector is right, but this application doesn't make sense. So we lost and we had to remove the 2/0 al and replace with 1/0 copper.

I do not believe it matters what the load calculations are when it is a manufactured home. They come with a tag from the manufacture stating what the supply and overcurrent protection has to be.

I assume the 60 ft is the length of the conductors.

 

[david]

By code the inspector is right, but this application doesn't make sense. So we lost and we had to remove the 2/0 al and replace with 1/0 copper.

Your inspector is trying to apply the paragraph for Table 310.15(B)(6) you have a manufactured home with a tag on it that says something like the supply 4 wire 150 amp. In addition to being federally regulated it has state regulations.

Table 310.16 2008 NFPA-70 gives you a range of conductor sizes with 75 deg. temp rating that you would commonly use to size a feeder. Table 310.15 (B) (6) has a range of conductors for alum. Wire that increases there common use to a range in table 310.16 that normally would be in the 90 deg temp coulomb range. The allowance is given for load diversity and the idea is that the activity is such in a single family dwelling the conductors will have sufficient time to cool and will not effect the 70 deg C. rating of the conductors / terminals.

To qualify for the 90 deg C. range the conductors must carry the full load of the dwelling. Not because of the load but they want load diversity. As I said before I do not see a need for a feeder to ever be larger than the service entrance conductors when the service entrance conductors have been sized and judged sufficient to safely carry the total load.

You inspector is not judging if this makes sense this is currently what the paragraph says.

 

[George Stolz]

I do not believe it matters what the load calculations are when it is a manufactured home. They come with a tag from the manufacture stating what the supply and overcurrent protection has to be.

I assume the 60 ft is the length of the conductors.

What it can not exceed, not a minimum. There is no reason not to feed the dwelling unit at 125A.

 

[david]

What it can not exceed, not a minimum. There is no reason not to feed the dwelling unit at 125A.

550.10 (I)
(I) Mast Weatherhead or Raceway. Where the calculated load exceeds 50 amperes or where a permanent feeder is used, the supply shall be by means of either of the following:
2) A metal raceway or rigid nonmetallic conduit from the disconnecting means in the mobile home to the underside of the mobile home, with provisions for the attachment to a suitable junction box or fitting to the raceway on the underside of the mobile home [with or without conductors as in 550.10(I)



(1)]. The manufacturer shall provide written installation instructions stating the proper feeder conductor sizes for the raceway and the size of the junction box to be used.

i do not see it as a max or a min but what is required it most likely is a min since service entrance conductors are sized to handle the calculated load. The manufacture calculated the load and posted it with a proper size

 

[George Stolz]

David, see 2011 550.11(D) exception.

 

[ActionDave]

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 get it now. Somebody needs to educate those wires, like they did us in health class, and let them know that once you loose your diversity you can never get it back.

 

[david]

What it can not exceed, not a minimum. There is no reason not to feed the dwelling unit at 125A.

David, see 2011 550.11(D) exception.

Exception: For manufactured homes, the manufacturer shall provide in its written installation instructions or in the data plate the minimum ampere rating of the feeder assembly or, where provided, the service-entrance conductors intended for connection to the manufactured home. The rating provided shall not be less than the minimum load calculated in accordance with 550.18

Under 2008 I?ll check Monday 2011 at our office to see if it is different in 2011
So in this case you must provide at least a 150 amp feeder to the mobile home.

The point I was attempting to make was others suggested that you could do load calculations for the mobile home and reduce the feeder size to a 125 amp feeder. I was trying to point out that does not work for dwellings when they are manufactured or mobile homes.

 

[George Stolz]

Exception: For manufactured homes, the manufacturer shall provide in its written installation instructions or in the data plate the minimum ampere rating of the feeder assembly or, where provided, the service-entrance conductors intended for connection to the manufactured home. The rating provided shall not be less than the minimum load calculated in accordance with 550.18

Under 2008 I?ll check Monday 2011 at our office to see if it is different in 2011
So in this case you must provide at least a 150 amp feeder to the mobile home.

The text is the same in 2008 and 2011.

I do not see a requirement on the installer to adhere to the manufacturer's data plate. It appears to me to be an aid to "mobile home installers", who do everything from leveling the house to connecting the supply/waste and electrical hookup.

The section explains that the load calculation in 550.18 determines the minimum feeder size. If an electrician does the calculation and finds the factory overestimated, I see no section requiring the electrician to conform to the manufacturer's error.

Since we're talking about 60' of 150A wiring here, and changing from 150A feed-through to 125A OCPD might be problematic, I would of course advise the OP that the simplest solution is to use 310.15(B)(16) (since 310.15(B)(7) can't be applied after losing the A/C) reinstall the feeder and call it a day.

 

[jumper]

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?

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.

MH proposed a change to this section, it was rejected.:rant:

This is what I meant to post.

 

[david]

The text is the same in 2008 and 2011.

I do not see a requirement on the installer to adhere to the manufacturer's data plate. It appears to me to be an aid to "mobile home installers", who do everything from leveling the house to connecting the supply/waste and electrical hookup.

The section explains that the load calculation in 550.18 determines the minimum feeder size. If an electrician does the calculation and finds the factory overestimated, I see no section requiring the electrician to conform to the manufacturer's error.

Since we're talking about 60' of 150A wiring here, and changing from 150A feed-through to 125A OCPD might be problematic, I would of course advise the OP that the simplest solution is to use 310.15(B)(16) (since 310.15(B)(7) can't be applied after losing the A/C) reinstall the feeder and call it a day.

In this state you after have specific certification to work on the installation of a manufacture home. And the installer must follow the manufactures written instructions for first time installations. There is currently legislation addressing manufacture homes that are moved and it looks like the certification requirements will extend to all manufactured dwellings in this state.

I also believe for an electrician to change the manufactures required min. service or feeder conductors sixes to a smaller conductor size he would void the Hud certification.

After the electrician applied different load calculations who would certify the installation?

 

[kwired]

In this state you after have specific certification to work on the installation of a manufacture home. And the installer must follow the manufactures written instructions for first time installations. There is currently legislation addressing manufacture homes that are moved and it looks like the certification requirements will extend to all manufactured dwellings in this state.

I also believe for an electrician to change the manufactures required min. service or feeder conductors sixes to a smaller conductor size he would void the Hud certification.

After the electrician applied different load calculations who would certify the installation?

HUD certification means it met those requirements when it left the manufacturer. Changes will be made at some point down the road, even if it is only maintenance issues that are the source of the change.

Just like a piece of equipment has a UL listing, that means it is listed as it is when it leaves the manufacturer. Many field modifications are made to listed equipment, simple drilling of a mounting hole or raceway or cable entries are real common modifications.

 

[david]

HUD certification means it met those requirements when it left the manufacturer. Changes will be made at some point down the road, even if it is only maintenance issues that are the source of the change.

Just like a piece of equipment has a UL listing, that means it is listed as it is when it leaves the manufacturer. Many field modifications are made to listed equipment, simple drilling of a mounting hole or raceway or cable entries are real common modifications.

in this state it means to the location of first sale

Commonwealth of Pennsylvania New Manufactured Home Installation
Requirements for Retailers & Installers

The Pennsylvania Manufactured Housing Improvement Act (Act 158 of 2004) requires that all new
manufactured homes installed in the Commonwealth be subject to certain provisions of the law and
regulations all designed to assure proper installation and completion of every new manufactured home.
Listed below are the key elements of the law:

?Every new manufactured home must be installed consistent with the manufacturers? approved
designs and instructions for installation of the home.

 

[George Stolz]

In this state you after have specific certification to work on the installation of a manufacture home. And the installer must follow the manufactures written instructions for first time installations. There is currently legislation addressing manufacture homes that are moved and it looks like the certification requirements will extend to all manufactured dwellings in this state.

Sounds as though your state congress wastes almost as much time as ours. :lol:

I also believe for an electrician to change the manufactures required min. service or feeder conductors sixes to a smaller conductor size he would void the Hud certification.

I believe that to be wildly speculative. I've made inspected deviations on HUD projects quite frequently. It's not exactly like voiding the listing of a piece of electrical equipment.

After the electrician applied different load calculations who would certify the installation?

In my state, that would be the building department and inspector.

 

[david]

In my state, that would be the building department and inspector.

Commonwealth of Pennsylvania New Manufactured Home Installation
Requirements for Retailers & Installers

Code officials, operating under the Pennsylvania Uniform Construction Code, may not reject the
manufacturers? approved designs or require review, approval or a seal by engineer or architect
licensed in Pennsylvania.
.
our department must insure the manufactures design we do not have the right to check their calculations.
It is different from state to state. Here no electrician has the right to change those calculations either