Here's my layout as it stands:

200A disconnect, neutral and ground bonded
mobile home main panel (200A main breaker, neutral and ground not bonded)

I would like to run another 100A panel outside, right next to the meter so that it runs like this:

meter -------- 100A Panel
200A disconnect
mobile home panel

My question is, do I need a main breaker for the 100A panel, and does the neutral need to be bonded with the ground?

I bought 1/0 wire to run from the meter to the new panel.

Edit: pictures of the current setup here with the new panel on the same pole https://imgur.com/a/eXDbVQ8

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    Is this 100A panel on the same pole/board as the meter and the 200A disconnect, or located remotely from it? Can you post photos of the meter and disconnect configuration? – ThreePhaseEel Sep 7 '19 at 23:40
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    Where will the overcurrent protection be which protects the wires between the meter and 100A panel? How about tapping the bottom of the 200A disconnect, and running 200A wire the short distance? – Harper - Reinstate Monica Sep 8 '19 at 0:28
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    That would be "designing the system for everything working perfectly". You don't need circuit breakers at all for that. You need breaker protection upline of the panel in case anything goes wrong. Spaces are cheap, regrets are expensive, explosions are very expensive. So how about getting a 200A subpanel (main lug is fine) and tapping that as mentioned last comment. Fully protected and only a few bucks more (mainly, for the 3-lug Polaris connectors you'd need to split the 200A, but you'll need those with any scenario). – Harper - Reinstate Monica Sep 8 '19 at 0:34
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    This is why we like to advise novices to buy wire as late as possible in the design-buy-educate-design-educate-buy cycle. – Harper - Reinstate Monica Sep 8 '19 at 1:05
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    Also, what make and model is your new panel, and what do you intend to power from it? – ThreePhaseEel Sep 8 '19 at 2:00

You must buy lugs either way. Do it right.

You can't double-tap a lug. You can buy "staircase" lugs that are 1-lug width but provide 2 lugs, but you can't torque one without removing the other. And they may not fit on your breaker. In that case, you'd use 3-lug Polaris connectors.

Regardless, these don't come in small-large-large, so you'll have enough for dual 200A connections.

Since you're stuck buying the lugs anyway, it's cost-neutral whether you tap the bottom or top of the main breaker (e.g. Service side or breaker-protected side). Tapping the service side is a) Very Super Mega Bad from a safety and Code POV, because it's sending power to the subpanel totally unfused, and even worse (if that's even possible) b) since the sub is main-lug, it has no protection whatsoever for the buses - another show-stopper. Other than that, Mrs. Lincoln, c) it will have worse issues with bending radius due to the smaller area there.

So "on the breaker-protected side" is the non-exploding answer.

The breaker protects the wires

Given that the cost of wire is not critical when only going a couple of feet, use wire rated for 200A, so the breaker protects this wire. (Failing to do so is a codevio).

As long as you tap the breakered side, and use 200A wire, the subpanel doesn't need a main breaker if it has 200A+ busing. Your baby panel doesn't, so it would need a 100A main breaker, plus likely another pair of 2-lug Polaris to step the 200A wire down to something that will fit on a 100A lug. Therefore, for this and so many other reasons, I recommend this baby panel go back to the store, and spend a few dollars more on a 200A-bused panel - main lug is fine.

Not least, you won't be back here going "My panel is full, what do I do now?" Spaces are cheap; regrets are expensive.

Oh, snap: 310.15(B)7

There's one other wrinkle.

Right now, all your service's wiring goes onto the mobile home via those wires. That qualifies you for an 83% friendly "De-rate" based on NEC 310.15(B)7, since NEC is basically calling this an extension of your service drop, and letting you use service-drop sized wires.

Once you split it to two different destinations, you lose your 310.15(B)7 discount. That means adding this subpanel may make your long-existing cabling to the RV too small.

First, check if that is so. If it is, this is where you'd want to throw yourself on the mercy of the local permitting authority, and ask them to "grandfather" it.

And if they won't, then you could pull the meter, replace that 200A main breaker box with a 200A main-breaker service panel (as small as you can get it), add a 150A? 175A? breaker feeding the mobile home on its existing wires. Then, this "main" panel will have gobs of extra spaces for whatever you're trying to do here.

Heck, a wise choice of panel might even make a generator interlock both feasible and affordable.

  • I don't think he can do what he's doing to Code anyway, because he'd then have two feeders to the same structure in violation of 225.30... – ThreePhaseEel Sep 8 '19 at 23:11
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    @ThreePhaseEel well... OP didn't ask about that, I figured it was for outdoor loads like a well or RV stand. Perhaps this is an XY problem and the X is "my in-the-house panel is too small"... see, OP, this. This is why we are kraaaaazee about getting people to install gigantic panels. The cure here may be upgrading the "sub" panel in the home to a 42-space, or or adding a 42 "sub, sub" panel in the home. – Harper - Reinstate Monica Sep 8 '19 at 23:23
  • @ThreePhaseEel and Harper to answer you both, I have 4-5 spaces left in the panel in the mobile home, but it's fed its 2/0 from the buried conduit in the ground we installed in the first place. That means I would have to remove the siding, drill a hole on the floor, feed more conduit etc. Installing another panel outside just made more sense. Not to mention the critters under the mobile home. – Krimo Sep 12 '19 at 12:43
  • @Krimo -- one more thing: is the pressure tank/switch/... for this well pump in the house, or at the wellhead? – ThreePhaseEel Sep 13 '19 at 0:39
  • Also, how far is the wellhead from the house? – ThreePhaseEel Sep 13 '19 at 3:34

One bond. That's already in your meter/disconnect. Everything else is a subpanel, ground & neutral separated.

Slightly debatable whether the main disconnect nearby trumps the "six motions of the hand" to shut everything off rule for this panel, sometimes interpreted as 6 breakers. Wait, you were planning to take off ahead of the main disconnect? No, don't do that...

Me, I'd choose a panel with a main breaker and remove the bonding screw - they are often no more expensive than those without a main, and sometimes less expensive since they move in volume. And there's no debate...

  • Thank you for your answer. Is it any at all dangerous if I forego the 100A main breaker in the new panel? My understanding would be hot to hot, neutral to neutral, and a separate ground for the new panel. As long as I don't put more than 100A worth of breakers in the new panel, the new short wires would be safe? – Krimo Sep 8 '19 at 0:33

Two different problems, two different solutions, but only one circuit from the pole to the house

Your problem here is that you are trying to solve two different problems (the porch circuit and the well pump) in the same, incorrect way. As it turns out, since the porch is attached to the trailer (and thus part of the same structure), you cannot do what you are asking to do, as the extra branch circuit from the pole to the house/porch violates NEC 225.30. However, you can still get what you need by splitting this problem into its component parts; namely, the porch circuit and the well-pump circuit.

Tap power at the house for the porch

For the porch, what I would do is bring power from the mobile home's panel out to a weatherproof junction box in the porch-facing wall of the house, then run surface-mounted UF cable from that junction box out to the other outlets and the ceiling-fan boxes. This keeps you from having to do the "submarine dive" through the floor of the mobile home, and also allows you to tap an existing circuit for this if loading permits vs. running a dedicated circuit for these receptacles and fixtures.

The well pump can be run from the pole, but not the way you've described it

On the other hand, presuming that the pump controller lives at the wellhead, the well pump circuit can be run from a panel at the pole. However, double-lugging the meter base to feed a second panel is generally not the correct move here. If I had free reign in hardware, I would fit a dedicated "mobile home feeder" panel in place of the existing 200A disconnect; this type of panel has a 200A main breaker feeding an 8-space loadcenter that is also fitted with a set of feed-through lugs that allow a full 200A feeder to be brought out to the mobile home.

If you are dead-set on using the existing panel (what looks to be an 8-space, 100A or 125A Square-D Homeline unit) instead of going back and getting a 200A panel (which lends itself to the approach mentioned above), I would get a QOM100VH main breaker kit for your panel (as it's convertible from main lug to main breaker), install that, then adjust things so that a 1" pull elbow can be fitted to go "around the corner" between the disconnect and the panel. Once the pull elbow is fitted (this may require a chase nipple or two), the load-side wires can then be tapped using short lengths of 2/0 copper as jumpers from the load lugs to 3-port mechanical set-screw (Polaris™) connectors, which then have the existing and new wires connected to their remaining ports. The new panel is then wired up as a subpanel with the green bonding screw pulled and a PK7GTA ground bar kit fitted to it, and the well pump circuit can be run normally from there.


With all these lug connections being undone, done, and redone, it is vital that you use an inch-pound torque wrench and/or torque screwdriver to torque all lugs (loadcenter, breaker, connector) to their manufacturer-specified torques. Not only is this required under the latest NEC (110.14(D)), it means you won't have to ever worry about your electrical system losing its lugnuts on you!

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