Distribution panel in separate building

For a three wire feed to a panel in a detached building, power supplied from a main panel in the house: This distribution panel is protected by a 40 amp breaker feeding this panel, located in the main panel in the house. No main breaker present in this distribution panel. Because it’s in a separate building, is there a requirement for a main disconnect? Can a distribution panel be installed in a detached building separate from the main panel? This was installed in 1985. This panel supplies power to two 220 volt baseboard heaters.

There is a second panel in this detached building supplying power for circuits, and it does have a main disconnect in the panel box.

Yes, there is no bonding screw or jumper, a defect reported. The 220 volt junction box cover was also reported.


Yes, you need a means of disconnect. But I do believe the 6 throws rule would apply.

Was that solid copper conductor going to a Ground rod? Building should have its own EGS. I assume thats what it is from, or is it coming from the main panel? If it is the EGC, then it needs to be isolated from that neutral. (Not like it matters much with no neutral branch wires)

Are both panels in the detached structure being served separately from the main in the house? Or is one of the panels feeding the other?

To a ground rod at this outbuilding.

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Install a bonding jumper from the neutral to the enclosure and it’s code compliant if there are no other metallic paths between the two structures.


Thats what I was thinking, because those are big conductors for a 40 amp disco

Two panels in the house, two in the detached building, served by separate feeds. This is a reduced rate, two meter service. Electric heat is on a separate meter, separate panels.

As far as I know, both feeds will need a means of disconnect in the detached structure. I do believe the 6 throws rule applies though.

Yes, bigger than needed for the 40 amp breaker present in the main service panel located in the house.

Unless it meets the special conditions a separate structure can have only one supply.

225.30 Number of Supplies. A building or other structure that is served by a branch circuit or feeder on the load side of a service disconnecting means shall be supplied by only one feeder or branch circuit unless permitted in 225.30(A) through (E). For the purpose of this section, a multiwire branch circuit shall be considered a single circuit. Where a branch circuit or feeder originates in these additional buildings or other structures, only one feeder or branch circuit shall be permitted to supply power back to the original
building or structure, unless permitted in 225.30(A) through (E).


Not familiar with that rule; This distribution panel has 2 breakers, so my take is no disconnect required???

The other panel is totally separate from this one and does have a main disconnect, and does have more than 6 breakers in the panel.

This is a two meter service to this property. One meter is general service, second meter is reduced rate, interruptable power. Reduced rate powers electric heat, with propane heat backup for when power is interrupted. We have a lot of these systems where I am located. The buildings are thus served by two service panels, two meters. Electric heat on one, general service on the other.

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That is good info to know! I didn’t go view the exceptions yet, but do you know if load control is one of them?

So as I understand this, breezing through your link; If there were 7 breakers in this heat distribution panel, then a main disconnect would be required?? Because there are 2 breakers, no main disconnect is required??

Very popular in my area as well. I have multiple components on load control.

That is how I understand it. Unless this is a new build under 2020 NEC Code. I do believe the 2020 changes eliminated the 6 throws rule.

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Not to be “that guy,” but I think you meant GES. Dang electricians and all their acronyms. :joy: :grin: :man_shrugging: :ok_hand: :laughing:

Haha, Yes, thankyou

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