"Here's the "code book" for HUD." LOL. Although labeled differently, I see we posted the identical link. I, too, live in an area (rural Maine) that effectively requires no permit and no inspection for electrical work. When I asked my local "Code Inspection Officer" (a gravel and concrete guy), he said, "Oh, I verify set-backs and once or twice I've failed buildings for using 16' 2 x 4 rafters, but I don't do electrical." So I pushed him a bit and he agreed to inspect my new garage/workshop building. He had no clue what to look for so I even walked him around, pointing out the various things an inspector might look for (passing each one, naturally) and got him to sign off. That way, I can honestly tell my insurance company that the electrical work was inspected. We both thought the exercise was pretty funny. Anyway, back on topic. Perhaps I shouldn't doubt you, but are you sure you need a service upgrade? A 100-amp service is typically plenty for a mobile home unless there is a lot of electrical heat (e.g., baseboard heaters or heat pump). Have you done a load demand calculation that includes the proposed wall oven? The reason I ask is that I think if you can forego a service upgrade (to 200A?) and replace the panel with physical dimensions not too much larger than the original, you'd be in a pretty good position to argue that, although you've replaced a part (the panel) and added a circuit or two, you haven't voided the "HUD sticker." I think that position is much less defensible if you've upgraded the entire service. But do I know this for certainty? Nope, sure don't.

Questions?-- We are converting it to a dwelling by adding 3 BR & 2 baths which leaves a 24x32 shop/garage in the back 1/3 of the structure.All the wiring already installed is in flexable conduit,but the 200A panel is up front & I want to rework the 70A sub panel by installing a 100A panel about 40' back from the 200A main and replace the existing 70A breaker with a 100A to feed the new sub panel. Whether you can protect the #4 individual conductors (I'm assuming they're THHN) with a 100A breaker is "iffy" because it may depend on local code interpretations. In some jurisdictions you can use #4 for 100 amps for indoor subpanels. In others you'd need to upsize to #3 copper. (The latter would be true where I live, BTW.) Best to check with your AHJ (authority having jurisdiction--the local permit/inspections office) to be sure. This will allow me to make short runs to feed the additional rooms and have the panel in the shop/garage where I want to have a 220V welder plug close to the 100A sub panel.I'm trying to avoid making all those homeruns from the front of the building to the back as well as having control over the shop feeds right in the shop area. Makes sense to me. The existing 70A sub panel is three #4 separate copper (AWG) wires...Will this feed the 100A sub panel? I also have a good amount of #3 copper of the same type,if that will be better. If I had sufficient #3 on hand, that's what I'd use. (If I'm interpreting your info correctly, you'll be moving the subpanel further to the rear of the building. Thus, I'm also factoring in the advantage of not having to splice the old wires in an junction box located in the middle of the run. However, I'm not certain I understand your plan. When say "rework", does that mean you'd leave the existing 70A subpanel in place and have it feed a second subpanel? Or do you plan to move it altogether? Just want to be sure...) Would it be better(correct) to run 4 wires (H-H-N-G) or 3 wires? This is all inside the structure. Yes, it would be better (correct) to use 4 wires with separate neutral and grounding conductors. So called 3-wire feeds are legal only in certain circumstances for detached buildings. But even in that context, they are being phased out by the 2008 National Electric Code. The grounding conductor can be smaller than the hots and neutral. In this case you should be able to use #8 bare or green, although that's also worth verifying with your AHJ. Whether you reuse the old subpanel or buy a new one, when wiring a 4-wire feed, you need to fully separate the neutral (grounded) conductor from the grounding conductor. The neutral feed and all branch neutrals should land on the neutral bar. The grounding conductor and all branch equipment grounds should connect to a separate ground bar. (You may have to purchase a ground bar separately--usually under $10.) You also need to remove any bonding connector from the neutral bar to the box and/or...

Wayne, Thanks for replying. 1) I was adding another circuit to the main panel later in the day of my original posting, so I checked the heater circuit. It was 5kW, not the 3kW I originally posted, but it's in addition to the heating element installed as part of the HVAC (probably wasn't clear in my original post)... the cost was $100 if I had the extra circuit installed by the time they put in the main HVAC unit, so I said "why not". This is the circuit I think I can now do away with as it's not needed with the new pellet stove keeping us warm. The "standard" heating element in the HVAC is now the "emergency" element, if you will. 2) So you're suggesting bringing a short main panel circuit outside to the transfer switch, thereby allowing for a single long run from the switch to the subpanel. Hmmm, that idea has a lot of merit. I would definitely want to go with an ATS, then, so I don't have to walk outside to swap things out (and shoveling snow to get to that side of the house... like the 4' we had in 3 days last year :( ). 3) I'll read it after posting this... 4) I was thinking of a Kohler or a Cummins-Onan, though I hear Kohler is often more expensive in the long run because they do their best to force you into using their own guys for general service. In that case, Cummins-Onan has a serious edge.

I removed the cover to double check. The only back areas thickly covered by wires and questionable are between the ground bars and sides. I searched around them as best I could with a flashlight for the bumped in holes that would allow mounting screw back clearance but didn't see anything. The rest of the box interior is easy to see. There were a couple small holes here and there but they were punched flush, not bumped in. This box is fairly new, installed in 1-12 if that matters. I did an internet search but came up dry. If you find the spot(s) where these holes are located in the 200A box please post it. Thanks