Can a line to ground fault cause a backfeed?
4.10.4 Backfeeds During a line-to-ground fault where a single-phase device opens, current may backfeed through a three-phase load. It is a common misconception that this type of backfeed can only happen with an ungrounded transformer connection. Backfeed can also occur with a grounded three-phase connection.
When do you need a back feed for a transformer?
This is incorrect as it is also a statement used where the main supply has been disconnected and a temporary supply is connected to keep equipment running eg When you have a HV supply you may need to work on the transformer and to keep the LV equipment running you would connect a generator to the LV side and this is known as back feeding.
How does a back feed light fitting work?
Prove, test, prove… He has got a bunch of wires in his hand, feeding them through the base of new light fitting.
Why does LC circuit have high back feed voltage?
The capacitance of underground cable usually plays a key role in the LC circuit resulting in the back feed. This back feed voltage can be quite high, higher than the normal phase-to-ground voltage, but has little power behind it: The voltage will collapse when grounded, with a bolted fault current of under 10 amperes.
4.10.4 Backfeeds During a line-to-ground fault where a single-phase device opens, current may backfeed through a three-phase load. It is a common misconception that this type of backfeed can only happen with an ungrounded transformer connection. Backfeed can also occur with a grounded three-phase connection.
Where is a backfeed main breaker at an electric panel?
The breaker is usually, but not always, in the upper left position, and required to be clearly marked as “MAIN BREAKER.” A backfeed main breaker must also be mechanically secured in place. The red tab at the breaker above is a rated securing device, and it will only be visible with the dead front removed.
How many amps can you put in a backfeed breaker?
If you backfeed a panel with a 100-amp service breaker, and the maximum allowed by the manufacturer is 125 amps per stab, then the max you can install on the other side of the stab is 20 amps. This is why the slots opposite a backfeed main breaker are often blank.
How many amps does a stab backfeed panel need?
A stab is another name for a bus bar finger. This maximum is listed in the data plate. If you backfeed a panel with a 100-amp service breaker, and the maximum allowed by the manufacturer is 125 amps per stab, then the max you can install on the other side of the stab is 20 amps.