LRB
Member
- Location
- Interior Alaska
This is my first so bear with me
I recently did a service call on a new 10 KW 3 ph generator which would only build 20 volts phase to phase. The generator is a 12 lead Y connected for 208/120 V. The common / neutral connection is not bonded to frame. The dealer had an electrical contractor install a 1 phase breaker panel, one 208V 1 phase receptacle and 2-120 V duplex receptacles. The electrical contractor had installed a 50 A 2 pole GFCI which he was back feeding to serve as a main disconnect.
I found a phase conductor on the terminal marked N load of the GFCI breaker.
The white pigtail from the GFCI, generator neutral, receptacle neutrals, receptacle EGC?s, AND also a bonding jumper to the frame of the generator were all landed on the Neutral buss bar of the panel.
This was essentially shorting one phase to neutral. After moving the phase lead to the correct terminal the generator worked fine, however the GFCI would not trip when tested, so I moved the Generator neutral from the neutral buss to the GFCI N terminal. When the GFCI was tested it did trip, but then started to smoke. The breaker can still be reset but the GFCI sensing circuitry is toasted. I recommended to the dealer to replace the 50 A GFCI with a standard breaker and the install individual GFCI breakers for each circuit, since the goal was to have all circuts GFCI protected.
This incident has raised several questions in my mind.
1. Can GFCI breakers be back feed?
2. Is 50 A 1 phase breaker the correct protection for this generator? It is a 3 phase generator with one phase not being utilized. For 3 phase operation we would have utilized a 30 A 3 pole breaker.
3. How does a 2 pole GFCI work and what is its applications? ? on a multi wire circuit, the only neutral current is the unbalanced current. If you wanted GF protection on a 208 or 240 V load you would not have neutral.
4. The grouping of neutral, EGC, bonding jumper all on the same buss bothered me however this would be the service disconnect for the generator . ( my preference would have been to bond generator neutral to frame in the junction box for generator windings and to run separate EGC and grounded conductor (neutral) to the panel.
I recently did a service call on a new 10 KW 3 ph generator which would only build 20 volts phase to phase. The generator is a 12 lead Y connected for 208/120 V. The common / neutral connection is not bonded to frame. The dealer had an electrical contractor install a 1 phase breaker panel, one 208V 1 phase receptacle and 2-120 V duplex receptacles. The electrical contractor had installed a 50 A 2 pole GFCI which he was back feeding to serve as a main disconnect.
I found a phase conductor on the terminal marked N load of the GFCI breaker.
The white pigtail from the GFCI, generator neutral, receptacle neutrals, receptacle EGC?s, AND also a bonding jumper to the frame of the generator were all landed on the Neutral buss bar of the panel.
This was essentially shorting one phase to neutral. After moving the phase lead to the correct terminal the generator worked fine, however the GFCI would not trip when tested, so I moved the Generator neutral from the neutral buss to the GFCI N terminal. When the GFCI was tested it did trip, but then started to smoke. The breaker can still be reset but the GFCI sensing circuitry is toasted. I recommended to the dealer to replace the 50 A GFCI with a standard breaker and the install individual GFCI breakers for each circuit, since the goal was to have all circuts GFCI protected.
This incident has raised several questions in my mind.
1. Can GFCI breakers be back feed?
2. Is 50 A 1 phase breaker the correct protection for this generator? It is a 3 phase generator with one phase not being utilized. For 3 phase operation we would have utilized a 30 A 3 pole breaker.
3. How does a 2 pole GFCI work and what is its applications? ? on a multi wire circuit, the only neutral current is the unbalanced current. If you wanted GF protection on a 208 or 240 V load you would not have neutral.
4. The grouping of neutral, EGC, bonding jumper all on the same buss bothered me however this would be the service disconnect for the generator . ( my preference would have been to bond generator neutral to frame in the junction box for generator windings and to run separate EGC and grounded conductor (neutral) to the panel.
