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Replacing AC Distribution Boxes/Panels


JCTex

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I need to remove my Main AC and sub AC panels and replace them when the ones of different sizes. Has anyone done this? Any references to RV repair people who could do it? Any idea where to buy RV type boxes/panels?

 

JC

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You can get them from RV parts suppliers. Here is just an example not a recommendation necessarily. http://rvpowerpartsplus.net/index.php?main_page=index&cPath=4 They sell DC distirbution boxes, AC boxes and combination boxes. If you want something that matches then you can probably find the same brand you have by just looking it over closely.

 

I do want to back up and ask you why you want to do this becuase we may have an alternative recommendation? Also, you really can use residential boxes from home depot if it is something that is going to be hidden and save a lot of money.

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RV type or residential AC Distribution Panels can be made to work (for the AC distribution) if wired properly PROVIDED HOWEVER you DO NOT,,,,,,,,,, I REPEAT DO NOT bond the Neutral Buss and Equipment Ground Buss together as is typically done in a homes main distribution panel. The RV panel is treated as a Sub Panel fed from the power pedestal. The RV's Neutral Buss must be electrically insulated and isolated from the Equipment Ground Buss and the tubs metal case/frame. Same holds true if you were to serve a smaller sub panel fed from your main panel. IE to it you would carry the non grounded (HOT) Conductor(s),,,,,,,,,,The GrounDED (Neutral) Conductor,,,,,,,,,,,,The Equipment GroundING Conductor and at the Sub again the Neutral is isolated and insulated from the Equipment Ground and case/frame. In some cheap residential 120/240 Single Phase Three Wire Main Panels there is only one single common Buss for Neutrals and Grounds alike,,,,,,,,,,,Others have a separate Neutral Buss and a Ground Buss with a tie bar you bond together if its used as the main panel.

 

 

Of course if you have a typical 120/240 Volt 50 Amp RV (Larger motorhomes and fifth wheels) it could have a two pole 50 amp main circuit breaker, while if you only have a 30 amp 120 volt RV it only requires a single pole 30 amp main breaker.

 

Clear as mud??????

 

John T Too long retired AC Power Distribution Engineer and rusty as an old nail on the NEC SO NO WARRANTY LOL

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With my soon to be installed 600A lithium bank and 1,440W of solar, I can run many more things off the inverter when boondocking (or anytime, for that matter). I can move out of my Main 120V panel: Splendide combo, refrigerator, front A/C, and fireplace. All can be doubled except probably the A/C. I have only once space left on my sub panel, leaving me short 2 spaces. The then almost empty mIn panel will then be taking up real estate that could be done in a smaller panel.

 

My Main has 2-120VAC 50A cables coming in, one for each leg. Currently, it has a 30A breaker for,the inverter. Magnum requires that be 50A.

 

I KNOW I can't run everything I want in the sub inverter panel at once. The Magnum can pass 63A through to the sub if the coach is plugged in; but the system's size limits that to 50A. The 3000W inverter can produce 25A of AC for the sub when boondocking. I'm very fine w that. My res Samsung won't use more than 4.75A and the roof A/C while protected for 20A never needs that, even on start up. I don't plan to,use the air unless I have to. I can be disciplined enough to make 25A work.

 

On your idea of leaving the existing panels in,place and adding a small satellite panel tied to the sub, that could work. It may be possible to cut another opening in my existing cabinet. How would,that be connected to the sub? Run jumpers between the bus bars and add a breaker? Or . . .

 

JC

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For clarity sake: to the best of my knowledge, my "sub panel" is not connected to the Main panel at all, except perhaps for sharing a ground. It could be called an Inverter AC panel and be more descriptive. It's located directly under the Main, probably for convenience of bringing all the AC lines to one place. So, John, it's not a sub panel off the Main in the usual residential sense. The inverter does get its AC from the Main panel to pass through when hooked to shore power. Otherwise, I don't think the inverter sub has access to AC.

 

I do know about the requirement to make neutral, or common, float. Having said that, knowing it and making sure I do that if I replace either panel are different matters.

 

JC

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Pebble, yep its getting a bit complicated to configure over the net absent diagrams etc. so I will just stick to the basics which it appears you have a good handle on.

 

If a panel is fed from an Inverter or Genset etc that would likely be considered and configured as a "Separately Derived Source" In that case the source WOULD HAVE a Neutral to ground Bond (usually within the source internal wiring) just like at a utility transformer (where N bonds to G) and the homes main distribution panel (N again bonds to G and Neutral is bonded to a Grounding Electrode (like mother earth) in panel or riser or meter base).

 

The trick comes if you're using a Transfer Switch such that you choose/switch one of the sources to serve a common main panel. For 120/240 residential/commercial if you use a two pole (switch the two Hots) transfer switch the Neutrals bond and are NOT switched and the Gensets Neutral to Ground bond is opened (Neutral is floated), but if you use a three pole transfer switch Neutrals are switched and at the Genset N bonds to Ground (Separate Derived Source). I believe some Inverters use a relay to bond N and G when required. I'm some RV's having a genset you accomplish Hot and Neutral switching by plugging the RV power cord into a generator receptacle so Hots and Neutrals are switched in which case the Gensets Neutral is bonded to case/frame/ground IE NOT floating.

 

NOTE, Pebble you state: "So, John, it's not a sub panel off the Main in the usual residential sense"

 

Thanks,Good information, its NOT a Sub Panel fed from a Main Panel. Again an Inverter or Genset considered/configured as a

"Separately Derived Source" would have its own Neutral Ground Bond, otherwise the Equipment GroundING Conductor couldn't serve its

intended purpose of providing a dedicated low impedance return path for FAULT CURRENT to trip the breaker and clear the fault.

 

NOT being there and not having any schematics and diagrams you best go with manufacturers recommendations NOT what anyone here tells you, but its my best good faith effort to explain the general theory of main and sub panels, transfer switching, separate derived sources and Neutral Ground bonding. It becomes most important when you bare footed grandchild is standing in the rain and comes up and touches the RV!!!!!!!!!!!

 

Keep safe yall

 

John T Too long retired EE but believe the above is still accurate

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