A side note

[david]

I have just recently attained my ICC certification for electrical inspector and hope to be starting new job soon. I have been doing lots of research in the 2017 NEC and the IRC. My question relates to mobile home service conductor sizing. After the meter if one uses a Mobile Home disconnect with the usual 4 circuits, and let's say they come out of there to get the well pump and the outside condenser. Now let's say this is a 200 amp service. From the disconnect into the mobile home wouldn't you be required to use 3/0 copper which would make your incoming service conductors 3/0 since no feeder conductor can be larger than incoming service conductor. It seems to me you can't use the 83 percent here because the disconnect with the circuits. Everyone around here uses 2/0 in this example. Thanks

When a manufacture tags a home the manufacture of the home has declared the calculated load of the home. In the manufacturer’s instructions or on the tag it states 200 amps. The instruction state by table 200-amp 3/0 copper feeder.

The home has a service panel in the basement or on a pole adjacent to the home. Sometimes the service panel is attached to the outside of the home.

The manufacture’s instructions apply to the feeder.

If a distribution panel is installed for such loads as a pad mount HVAC unit or a shed or well pump. The service needs to consider these as additional loads to the manufactures load calculation

For a 200 amp manufactured home a 200 amp service with additional breaker spaces intended for additional loads would be undersized

 

[augie47]

The only instructions I have ever seen say "supplied by a 200 amp service" and 550.33(B) states 310.15(B)(7) can be employees which would allow a 2/0.
If there are loads connected to the service disconnect other than the mobile home feeder it gets into the discussion just posted:

Mobile Home Service Conductors

I have just recently attained my ICC certification for electrical inspector and hope to be starting new job soon. I have been doing lots of research in the 2017 NEC and the IRC. My question relates to mobile home service conductor sizing. After the meter if one uses a Mobile Home disconnect...

forums.mikeholt.com

 

[ptonsparky]

When a manufacture tags a home the manufacture of the home has declared the calculated load of the home. In the manufacturer’s instructions or on the tag it states 200 amps. The instruction state by table 200-amp 3/0 copper feeder.

The home has a service panel in the basement or on a pole adjacent to the home. Sometimes the service panel is attached to the outside of the home.

The manufacture’s instructions apply to the feeder.

If a distribution panel is installed for such loads as a pad mount HVAC unit or a shed or well pump. The service needs to consider these as additional loads to the manufactures load calculation

For a 200 amp manufactured home a 200 amp service with additional breaker spaces intended for additional loads would be undersized

Why? What is the calculated load for the house? It could very well be 151, or 126. The additional calculated loads could be less than 49. Each with a 100 amp feeder from the 200 amp service entrance. The SE conductors would be required to be full size.

 

[david]

This is the actual manufacture's instructions from one out of Ohio "the current rating (in amperes) of the home can be found on the tag"
When the manufacturer states 200 amps is the current rating ofthe home ,we are kind of stuck with that. we cant do the load calculations our selves

 

[Greentagger]

Interesting. Where is this Table 25?

 

[david]

Interesting. Where is this Table 25?

see attached

 

[Greentagger]

3/0 copper for 200A feeder? Oh and same for 225A?

 

[david]

3/0 copper for 200A feeder? Oh and same for 225A?

The manufacturer showing the equipment ground sizes being the only difference #6 verses #4

 

[Greentagger]

So 2/0 copper is a no-no ?

 

[david]

So 2/0 copper is a no-no ?

according to this manufacturer . But more on point how would the pole service, for example be sized

 

[david]

The only instructions I have ever seen say "supplied by a 200 amp service" and 550.33(B) states 310.15(B)(7) can be employees which would allow a 2/0.
If there are loads connected to the service disconnect other than the mobile home feeder it gets into the discussion just posted:

Mobile Home Service Conductors

I have just recently attained my ICC certification for electrical inspector and hope to be starting new job soon. I have been doing lots of research in the 2017 NEC and the IRC. My question relates to mobile home service conductor sizing. After the meter if one uses a Mobile Home disconnect...

forums.mikeholt.com

I hear you 550.33(B) feeder capacity not less than the load supplied, not less than 100 amp and allowed to be sized 310.15 (B) (7)

 

[Greentagger]

according to this manufacturer . But more on point how would the pole service, for example be sized

How would you size it knowing what the manufacturer has stated how the feeder is to be sized?

 

[david]

We know that 83% is .83 as a multiplier. The inverse of .83 is 120% (1.205)

2/0 copper has an ampacity of175 amps 175 x1. 2 = 210amps

3/0 copper 200 amps X 1.2 = 240 amps

The manufacturer from Ohio states the ampacity for the home is 200 amps

I would have to decide are the additional loads going to be 10 amps, 40 amps or exceeding 40 amps

 

[Greentagger]

There are no calculations to perform. The manufacture has simply stated that if the main breaker in the mobile home is 200A , then a 3/0 copper feeder is required. According to the chart , calculated loads were not given , only main breaker sizes and their appropriate sized feeders approved by the manufacture?

 

[david]

"the current rating( in amperers) of the home can be found on a tag" No the manufacturer states the 200 amps is the current rating of the home that the 200 amp breaker (panel) provided by the manufacturer and 3/0 copper supply conductors are to be installed according to a 200 amp current rating

 

[david]

The point is a majority of the time if the tag says 200 amps, we provide a service sized accordingly (200 amp), we provide a feeder from a service sized for 200 amps. The additional breakers spaces are utilized most of the time after the initial installation is over. We know what the most likely additional loads might be.

A pad mount HVAC unit, perhaps a pump for a well, a security light common for manufactured homes,

And sometimes an out building like a small shed with lighting a receptacle or two and maybe an air compressor

If the tag is simply directing us to the correct feeder supply that is one thing. But if the manufacturer is stating the current rating of the home that is another thing when sizing a service that is going to provide additional loads.

 

[david]

There are no calculations to perform. The manufacture has simply stated that if the main breaker in the mobile home is 200A , then a 3/0 copper feeder is required. According to the chart , calculated loads were not given , only main breaker sizes and their appropriate sized feeders approved by the manufacture?

If you’re suggesting there are no loads to consider when providing a service for a manufactured home feeder and additional loads. You might be suggesting some rule of thump that would be a hit and miss type approach to getting the service size correct