phase converter GFCI protected

[elec58]

Have a 240V panel with 20amp breaker feeding a phase converter for a 3 phase motor that is used on a conveyor for produce. There is water involved to wash fruit. Was curious if I should install a GFCI breaker to feed the converter for safety. Also since this is a production line was curious if it would cause nuisance tripping. Any thoughts. Reason for concern is there is metal framing on conveyors with numerous people leaning on to sort fruit, some have hands in water as fruit gets washed /waxed. TIA

 

[retirede]

A GFCI on the single phase side likely isn’t going to protect anything on the 3 phase side depending on the type of converter.

 

[elec58]

A GFCI on the single phase side likely isn’t going to protect anything on the 3 phase side depending on the type of converter.

Thanks for the input any advice on making it safe, or am I over thinking this?

 

[elec58]

Thanks for the input any advice on making it safe, or am I over thinking this?

FYI I am unsure due to the sub panel being an old 3 wire installation. No isolated ground bar, PVC conduit fed from a pole mounted metered panel about 150 ft away

 

[MasonF]

I assume a gfci on the 3 phase side would nuisance trip due to imbalance from the generated phase. Is there a spot in the facility that you can get to that has a good ground electrode and single bond to neutral or is the whole place 3 wire?

 

[elec58]

I assume a gfci on the 3 phase side would nuisance trip due to imbalance from the generated phase. Is there a spot in the facility that you can get to that has a good ground electrode and single bond to neutral or is the whole place 3 wire?

There is a ground rod GEC to the sub panel it is a large awning on metal poles so I could find out about poles, depth, concrete etc. Ideas?

 

[elec58]

I assume a gfci on the 3 phase side would nuisance trip due to imbalance from the generated phase. Is there a spot in the facility that you can get to that has a good ground electrode and single bond to neutral or is the whole place 3 wire?

everything is ran correctly to equipment, but Equipment grounds and neutrals all land on same buss in sub panel

 

[MasonF]

Can you get an egc back to where the feeder originates? Then you can separate it safely.

 

[winnie]

1) what sort of phase converter is this? Rotary, static, VFD/synthesized, motor/generator? Lots of choices, and they will behave differently.

2) is system grounding done correctly? Remember ground/ neutral isolation, except at the service and after SDS devices such as isolation transformers or some types of phase converters.

3) how isolated is the conveyor electrical from people. Are all electrical components enclosed by bonded metal?

Jon

 

[elec58]

Can you get an egc back to where the feeder originates? Then you can separate it safely.

would have to pull out 150ft of feeders then pull back with added egc underground pvc no pull boxes looks difficult

 

[elec58]

1) what sort of phase converter is this? Rotary, static, VFD/synthesized, motor/generator? Lots of choices, and they will behave differently.

2) is system grounding done correctly? Remember ground/ neutral isolation, except at the service and after SDS devices such as isolation transformers or some types of phase converters.

3) how isolated is the conveyor electrical from people. Are all electrical components enclosed by bonded metal?

Jon

1) would have to go to site and look at types not sure
2) yes everywhere, all equipment and metered panel is correct but sub panel is not isolated possibly done pre 2008 code change
3) problem is conveyor is metal framed and motor is mounted on frame so a fault could energize frame people are near and touching at times.

 

[ptonsparky]

Thanks for the input any advice on making it safe, or am I over thinking this?

Over thinking.

Was three wire to the existing legal when it was installed? At one time, outside you were good to go.

 

[ptonsparky]

The rotophase is a single phase load. It will not have an imbalance that would cause a GFCI to trip. It may trip for some other reason but that shouldn't be the cause.

 

[winnie]

Not only is a rotary phase converter a single phase load, the three phase output is not isolated from the input, and a GFCI on the input will protect the output.

Unfortunately we don't know if this is a rotary phase converter or something else.

If the 'phase converter' is really a VFD, then the switching noise on switching frequency current will almost certainly cause the GFCI to trip.

Back to the OP.

IMHO if the concern is energizing a metal frame which encloses electrical equipment, then I believe the correct solution is bonding.

There should already be an EGC bonding the frame. If you are concerned that the location needs more than this, then I'd look at a redundant EGC. The shock hazard you describe requires two failures: insulation failing so some exposed metal gets energized, and bonding failure so that it stays energized.

My guess is that this conveyor has many parts, bolted together and subject to vibration. It wouldn't surprise me if the existing EGC connects reliably to only one portion of the machine.

Jon