Trailer House Service & Panel

[FACB25]

Given a 60 Amp fused disconnect, 6 gauge wire, does code allow for a panel with a 100 Amp main breaker in a trailer house. Where in the NEC is the right answer?

 

[dpc]

I don't think so. It may depend on whether this is a "mobile home" or "manufactured home". See Article 550 for specific information on mobile homes.

Basic sizing criteria for single-phase dwelling services is given in Article 310, Table 310.15(B)(6). This shows #4 copper required for a 100A service.

Basic ampacity of #6 copper from Table 310-16 is only 55 amps (for 60 deg C terminations) or 65 amps for 75 deg C terminations. Since this is a 100A panel, you need to assume 60 deg C terminations unless marked otherwise.

 

[FACB25]

Thanks dpc. I usually do industrial work, but I have a friend who inherited 2 dissimilar trailers stuck together for a homemade double wide by an old boy who had his own ideas on wiring. After a quick look at section 550, I think I'll go back to the pole and do 100 amps all the way in, unless...
The local electric co-op is likely to want upgrades if I try to change the pole disconnect, and the ground is a tad bit hard for trying to drive a new ground right now. I may have to run the 4 gauge for now and wait 'til spring to upgrade the disconnect. The things we get ourselves into!

 

[dpc]

FACB25,

I actually didn't read your first post quite closely enough. With the 60A fused disconnect ahead of the 100A main breaker, you're probably OK. Provided he actually had fuses in there and not pieces of copper pipe, the fuses will protect the #6 copper. It just means you won't be able to load up the panelboard to 100A.

I think from the utility's view, the fused disconnect is your service entrance, so they're probably OK with it.

In the long run, you may want to upgrade, especially if you have air conditioning.

 

[skiier]

The 100A panel is fine with a 60A fuse in front of it.
The combination of bkr's u need for your loads might not have fit in a 60A panel. So who ever did the original install used the next size up - a 100A panel.
Think about it. If you had 30 120VAC loads each drawing 1/2 A would you rate the service needed as 30X15A or 30X1/2A? Could you fit 30 bkr's in 60A panel?
Look at the "tap rule" in your code book. Understand this rule and you understand most of what u need to know about fusing.
Leave your service as is and save some money.
Do a load calculation and determine what u have. I 'll bet your ok.

 

[jbartos]

Suggestion: Contact the local Utility having jurisdiction for their practices often stated in a "Utility Book ..."
Please, notice that standard or preferred services are 100A, 200A, 400A, etc.
60A service is fine if the load is small, e.g. trailer, mobile home, etc.
If the homes are prefabs and doubled, the peak hour load will probably increase, and 100A service will become a matter of convenience.
NFPA 70-2002 National Electrical Code, Annex D includes load calculations and service sizing for dwelling. This can be used as guidance for the mobile home load calculation. The peak load may include an electric range, refrigerator and heating in the cold winter, or electric range, refrigerator and air conditioner in the hot summer. (Small loads like laptops, low watt hi-fi, plasma TV, etc. may be neglected.)