Hi all,
So we recently bought a property that has a number of out-buildings in addition to the main home.
In one of these buildings is a horrific mess of a sub-panel that needs to go.
I wanted to add a kill switch upstream of the new panel I am putting in so I could shut off all power to the downstream sub-panel (and thus the entire building) with a simple throw of the lever. Otherwise it is about a 50-yard dash back to the main panel if I have to execute an emergency shut-off on the out-building.
When I went to the local electrical supply store they told me that this was a needlessly expensive addition and instead advised me to backfeed the sub-panel through a 100A 2-pole breaker (and yes, 100A is far more than I need in this building) so if I need to shut power off to the panel I could just manually trip the breaker.
They said as long as 100A is far and away more than I would ever need in the building, and to make sure to split my circuit loads evenly, that back-feeding like this is perfectly safe.
So they sold me the breaker and I installed it as suggested. (supply is 6 AWG threaded that come from 60 AMP breakers in the main panel)
A carpenter that is working on an unrelated project on the property happened to pass by the panel as I was working on adding a few light circuits and flipped the freak out. He said that no one should ever back-feed a sub-panel, that it was a huge fire risk should the 100A breaker ever fail, and that I should immediately disconnect and feed the box properly.
Am I missing something? Who is right? The electrical guys down at the supply store, or the carpenter? If there is a danger, what is it?
Image for clarity:
Note: sub-panel is 200-amp.
So we recently bought a property that has a number of out-buildings in addition to the main home.
In one of these buildings is a horrific mess of a sub-panel that needs to go.
I wanted to add a kill switch upstream of the new panel I am putting in so I could shut off all power to the downstream sub-panel (and thus the entire building) with a simple throw of the lever. Otherwise it is about a 50-yard dash back to the main panel if I have to execute an emergency shut-off on the out-building.
When I went to the local electrical supply store they told me that this was a needlessly expensive addition and instead advised me to backfeed the sub-panel through a 100A 2-pole breaker (and yes, 100A is far more than I need in this building) so if I need to shut power off to the panel I could just manually trip the breaker.
They said as long as 100A is far and away more than I would ever need in the building, and to make sure to split my circuit loads evenly, that back-feeding like this is perfectly safe.
So they sold me the breaker and I installed it as suggested. (supply is 6 AWG threaded that come from 60 AMP breakers in the main panel)
A carpenter that is working on an unrelated project on the property happened to pass by the panel as I was working on adding a few light circuits and flipped the freak out. He said that no one should ever back-feed a sub-panel, that it was a huge fire risk should the 100A breaker ever fail, and that I should immediately disconnect and feed the box properly.
Am I missing something? Who is right? The electrical guys down at the supply store, or the carpenter? If there is a danger, what is it?
Image for clarity:
Note: sub-panel is 200-amp.