I have 3 mobile home lots that will be fed from a central meter stack. Each mobile home will have a 125 amp main breaker and meter off a 3 stack meter pack. I just want to verify my calculations. 125 amp x 3 = 375 amps. Using Table 550.31 (Demand Factors for Services and Feeders) number of mobile homes is 3 so that would be a 44%. 375 amps x 44% = 165 amps. So the service conductors to this meter stack should be sized to 165 amps. Which would be 1/0 THHN. Does that sound correct?
Multi Family Meter Bank service conductor sizing
- Thread starter ddaut
- Start date
letgomywago
Senior Member
- Location
- Washington state and Oregon coast
- Occupation
- residential electrician
Why such small mobile home feeders?
And never go smallest and copper for feeders. Smallest I'd do is 250 AL to the pedestals. Is this sn actual mobile home park or is this something else. Remember that you have to use the largest of the options. 16000va per unit or go by the table. 16000 ×3 is 48000/240 is 200a in 75° column you need 250 for your lines.
And never go smallest and copper for feeders. Smallest I'd do is 250 AL to the pedestals. Is this sn actual mobile home park or is this something else. Remember that you have to use the largest of the options. 16000va per unit or go by the table. 16000 ×3 is 48000/240 is 200a in 75° column you need 250 for your lines.
14x70 older mobile homes. Currently on 70 amp breakers. All electric. Did load Calcs came out to 101 amps.
letgomywago
Senior Member
- Location
- Washington state and Oregon coast
- Occupation
- residential electrician
Ok you still have to go with the largest which is 16000va each.
- Location
- Illinois
- Occupation
- retired electrician
16000/240 = 66.7 amps. I believe the OP is saying that load calculations show a load of 24,240va per unit.
Elect117
Senior Member
- Location
- California
- Occupation
- Engineer E.E. P.E.
550.32(C) requiring each mobile home having a service of 100A just adds to the confusion.
The way I understand it is that that the park must have the larger of the following:
1) Minimum of 16kVA for each mobile home. In this case that is 3x16,000 / 240 = 200A. So no less than 200A service conductor and service equipment.
2) The largest calculated load that a lot could have for a mobile home with 550.18 and multiple that by the number of mobile homes on the lot.
The confusing part, and I imagine the reason for the question, is the language for using the demand factor.
"It shall be permissible to calculate the feeder or service load in accordance with Table 550.31. No demand factor shall be allowed for any other load, except as provided in this Code."
The section does not specify if you can apply that to option 1. It also does not say if you are allowed to have a calculated load less than option 1 or option two after demand factors.
I am assuming they mean to apply the demand factors to both options and that no load should be less than option 1 before the application of demand factors.
So your math looks sound. Though the conductor selection was incorrect.
1/0 is only good to 150A. So you would need 2/0 Cu or 250kcmil Al.
The way I understand it is that that the park must have the larger of the following:
1) Minimum of 16kVA for each mobile home. In this case that is 3x16,000 / 240 = 200A. So no less than 200A service conductor and service equipment.
2) The largest calculated load that a lot could have for a mobile home with 550.18 and multiple that by the number of mobile homes on the lot.
The confusing part, and I imagine the reason for the question, is the language for using the demand factor.
"It shall be permissible to calculate the feeder or service load in accordance with Table 550.31. No demand factor shall be allowed for any other load, except as provided in this Code."
The section does not specify if you can apply that to option 1. It also does not say if you are allowed to have a calculated load less than option 1 or option two after demand factors.
I am assuming they mean to apply the demand factors to both options and that no load should be less than option 1 before the application of demand factors.
So your math looks sound. Though the conductor selection was incorrect.
1/0 is only good to 150A. So you would need 2/0 Cu or 250kcmil Al.
letgomywago
Senior Member
- Location
- Washington state and Oregon coast
- Occupation
- residential electrician
Thanks for adding in the explanation I don't think I was conveying it well.