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Old 11-16-2009, 08:38 AM   #1
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Installing a breaker "backwards"

Well, not jamming it into the box backwards, but using it "backwards". Is this possible?? Here's what I mean:
I'd like to use a shed sub-panel as a loadcentre. Right now, I am feeding a Siemens sub-panel from the house to the shed - 20A, single phase. OK - I didn't do that part. that was the former owner. It's a nice panel though - appears new almost - and I want to upgrade to 30 A two phase to handle splits for power tools, lights, and a small, tankless water heater.
The idea:
  • run 8/3 off a 30A breaker in the house to the shed (roughly 25 metres away). I believe 8/3 is overkill.
  • connect the LINE from the house into the LOAD side of another 30A in this sub-panel
  • Have the sub-panel 30A breaker act as the panel disconnect
Sounds simple enough, and I am a very simple person I have been told. Can breakers work in this configuration tthe way they are intended to? Is it still the same protection? And, what would the neutrals + grounds need to look like in this situation (and why?). I am thinking that I should have a ground rod or plate at the shed.

Do-able or dumb?

Thanks for the truth.

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Old 11-16-2009, 08:43 AM   #2
Join Date: Jan 2009
Location: South of Boston, MA
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Installing a breaker "backwards"

You can back feed a panel by inserting a breaker in place

BUT the panel MUST be rated to handle the power
Does this panel have a main breaker, what is the breaker size ?

IE you can't back feed a 60a rated panel with 100a

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Old 11-16-2009, 08:59 AM   #3
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Installing a breaker "backwards"


If I follow you, this practice would appear to be do-able provided (i) I don't ask for too much from the house, and (ii) drive it into too small a panel in the shed.
  • The house main disconnect is 200A which I didn't do but it looks typical to me.
  • The big draws on that panel are AC, RANGE and DRYER. The usual suspects follow after that, a variety of lights and plugs, with the washing machine, microwave, dishwasher, shed, a panel plug (GFCI), and fire alarms being on distinct breakers. There are a couple of kitchen splits in there, too.
  • Looks to be around 10 years old and everything matches.
  • The sub-panel in the shed is rated at 100A.
I hope that helps you answer me.

Is there any special consideration I should give to Neutral and Ground in this application?

Thanks again.

PS By the way, I think I goofed when I said I wanted to ugrade to "two phase". Sorry - I'm using the language all wrong. What I meant - which you probably recognized - was to merely upgrade from a 120V to a 240 V service.
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Old 11-16-2009, 10:32 AM   #4
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Location: Newnan GA
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Installing a breaker "backwards"

You also need a breaker hold down kit to hold the backfed breaker in place!
Yes I am a Pirate, 200 years too late. "Jimmy Buffett"
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Old 11-16-2009, 10:38 AM   #5
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Location: South of Boston, MA
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Installing a breaker "backwards"

Does the sub-panel have a main breaker?
If so then you don't need another breaker IF you are feeding it from the house with a 30a 240v breaker
I have a 100a main breaker panel in my pool cabana fed with a 60a in the house
As long as the 100 panel lugs are rated to take #8 wire or #6

You might want to think about 6-3 & install a 50a or 60a breaker in the house
Seems you have plenty of power in the house with a 200a panel
If the garage is detached (seems like it?) then you also need (2) grounding rods at the garage
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