Alwayslearningelec
Senior Member
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- NJ
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- Estimator
Getting replaced in same exact location.
Temping Out Panel
- Thread starter Alwayslearningelec
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petersonra
Senior Member
- Location
- Northern illinois
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- Semi-retired engineer
If it is in the exact same place you should be able to turn off power, and swap transformers without a lot of down time with a little preparation.
Alwayslearningelec
Senior Member
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- NJ
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- Estimator
Also replacing primary and secondary feeds. Most of the feeds are less then 15'.
First thing needs to be done is turn the breaker off on the primary side. From this moment there is no power to panel B on the secondary side.
Now we have to:
1. Disconnect the existing primary and secondary feeds.
2. Remove the existing xfmr
3. Install new xfmr along with prim/sec feeds.
4, Energize.
When doing 1-3 there is no power to panel B.
I think the way I'm thinking about it is correct.
It is.
The previous 3 pages of advice were given in the event you could have zero downtime. As petersonra points out, with proper planning downtime could be kept to a minimum but some operations want zero down,.
Alwayslearningelec
Senior Member
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- NJ
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- Estimator
I didn't quite understand the back feed( previous pages) hence my post #39.
Alwayslearningelec
Senior Member
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- NJ
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- Estimator
Understood. Downtime per my post #43 steps could be 2-3 hours for a 45 kva xfrmr even with the new xfrmr in the vicinity.
A back feed breaker is a normal, non main, breaker installed on the bus where load breakers go. The power source is connected to what is normally the output of that breaker, and the panel is feed through that breaker. The breaker is feed "backwards", thus a back feed breaker.
If the panel is permanently feed with a back feed breaker the breaker is required to have a bolt holding it in place, and can typically only be installed in a specific location in the panel, usually at the top of the bus. For temporary use, like your case, you can skip the retaining bolt.
This would normally be used, for example, if you have a panel that does not take a main breaker, or that you don't have a main beaker kit for, and you want or need a main disconnect in the panel.
Normal, thermo/mag breakers, don't care which way power flows through them, and will work when back feed. AFCI/GFI beakers will not work when reverse feed.
kwired
Electron manager
- Location
- NE Nebraska
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- EC
I think what you are misunderstanding is feeding the panel with a position other than the conventional main breaker position. A normal thermal magnetic breaker is not a directional restricted item to voltage/current. You put voltage on what is typically the output lugs and it will feed through to the other side (the bus connector in this case) if the switch is closed, overcurrent protection components still work as well.
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