Originally Posted By: rpalac This post was automatically imported from our archived forum.
Your right, I did mention the six foot rule from years ago. I guess I did that out of habit. The code does require GFI’s almost every where compared to back then.
I have a question for all you vetrans.
A fellow engineer who was building his on residence had a 200 Amp service disconnect feeding two panels. Each of these panels had a 200 amp main. The 1st panel was for A/C, heat, dryer, water heater, lighting and a feed to another sub pannel in a work shop. The 2nd 200 Amp panel was all of his general appliance outlets. THIS PANEL HAD A 200AMP GFI BREAKER.
Now leave it to an architecht to do that....he had good ideas but do you see the problems created?
Originally Posted By: rpalac This post was automatically imported from our archived forum.
it was an architect
and yes, that is what we warned him about.....now to do one better he later came to us telling us he kept triping the main.....When I inspected it all of the breakers were 20,000 interuping ampacity and the main was only a 10,000.
As I siad to him, He needed to go back to the drawing board.....with his crayons....
Well he did learn alot, but I'd rather get his bucks.
Originally Posted By: jpeck This post was automatically imported from our archived forum.
Robert,
Reminds of when I was up in Gainesville, Florida.
It was, I guess, around the mid 1970s, the electrical contractor I was working for was wiring a large mall. The architect had this habit of specifying 200 amp services for the stores, which then fed 400 amp mains and 600 amp panels.
Originally Posted By: Bob Badger This post was automatically imported from our archived forum.
rpalac wrote:
The 2nd 200 Amp panel was all of his general appliance outlets. THIS PANEL HAD A 200AMP GFI BREAKER.
Curious was this a GFCI breaker as used for 210.8 Ground-Fault Circuit-Interrupter Protection for Personnel. or a GFP breaker as used for 230.95 Ground-Fault Protection of Equipment?
Not saying either was a good idea for this use.
The difference is a GFP breaker can have the trip settings adjusted to a point where false trips should not be an issue.
That fact makes it unusable to protect the circuits in 210.8
I only ask as I have never seen a 200 amp 2 pole GFCI breaker and did not think they would be available.
Originally Posted By: jpeck This post was automatically imported from our archived forum.
Bob,
I guessed (because I wondered the same thing) that it was for equipment, with a protection level of 50 ma.
Otherwise, it would likely never stay on, the total ground faults added together from all circuits in that panel would be exceeded quickly the 5 ma for personnel protection, I would suspect.
Originally Posted By: roconnor This post was automatically imported from our archived forum.
Sounds like it “was” a good plan … on paper at least …
I am assuming it was an upgraded 200A, which on paper sounds good because if you have to upgrade in the future only the service feeders and possibly the MD may need to be swapped out. I am assuming that the two panelboard feeders were rated for 200A, and that the neutral/ground bond was only in the MD.
But talking about GFCI's, I have something else to throw in the mix here.
I have heard that GFCI outlets/breakers have a tendency to trip for no apparent reason ... called "phantom" trips, in addition to having a likelihood of tripping under heavy start up load. Are GFCI outlets not recommended for things like a refrigerator because of these "phantom" trips, or because of the additional load when the compressor kicks on? Any thoughts, or more importantly any good links to articles that discuss that?
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: Bob Badger This post was automatically imported from our archived forum.
Well I will go out on a limb here and give it a shot.
When starting a motor you do get, and I do not know the correct way to put this other than leakage through the magnetic field.
That is a real rough way to put it but it is not a false trip, the GFCI does see the 5 ma difference between the phase conductors.
The NEC requires all commercial kitchen 125 volt 15 and 20 amp outlets to be on GFCIs so the NEC expects refrigerators to be on GFCIs.
I have gotten in some heated discussions about this with guys that want exceptions for the refrigerators, I disagree, spoiled food is not a good argument to remove an effective personal protective device.
The bigger problem this is causing in the commercial kitchens is the interconnected computer equipment (order screens, printers etc) trips the GFCIs.
Sorry I have no great links, I suggest a search at Holt's.
Originally Posted By: roconnor This post was automatically imported from our archived forum.
Bob Badger wrote:
I have gotten in some heated discussions about this with guys that want exceptions for the refrigerators, I disagree, spoiled food is not a good argument to remove an effective personal protective device.
Good point ... but will Harry Homeowner try to "fix" any nuisance trip problems so the milk doesn't spoil, which may be more of a hazard? Also, have you heard about "phantom" GFCI trips as they tend to be sensitive, or do ya think that is a "myth" picked up from things like refrigerators tripping GFCI outlets?
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: Guest This post was automatically imported from our archived forum.
GFCI’s trip from the difference in voltage between the two legs of a circuit. This fact makes them prone to tripping when certain items are plugged into them.
When you have windings, like in motors and relays, and energize them, they create magnetic fields. When you turn them off by flipping the switch, the field collapses. When the one side of field is turned off by the switch and the collapse occurs, the energy that was in stored in the winding sends a brief, high voltage, low current spike to ground. If conditions are right that spike can trip the GFCI.
The appliances that are most prone to creating a problem have relays and also vibrator style motors like in hair clippers. These motors and relays too, collapse immediately in one strong spike. Some of these can be corrected by using diodes to act like a check valve. Most of the time though, diode protection isn’t necessary unless it concerns computers that can be damaged by the spike.
Conventional motors that use brushes or are induction, dissipate the spike into several smaller spikes that get past the GFCI.
Refrigerators are likely to trip the GFCI not from the collapse of the windings in the compressor motor, but from the relays involved in the defrost and ice making schedules.
Originally Posted By: roconnor This post was automatically imported from our archived forum.
Thanks for the explanation Chad.
Am I reading that post right that commercial refrigerators and ice boxes may not have the same relays that could trip a GFCI on a home refrigerator ... which might explain why the GCFI protection is required for all commercial kitchen outlets, but not for dedicated residential kitchen outlets?
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: Guest This post was automatically imported from our archived forum.
Hi Robert,
I don't know. Commercial stuff might be engineered better, GFCI parameters might be higher. Most commercial refrigerators are just that...no freezers so there'd be no need to have defrost cycles.
The other thought is and I'm guessing here, but I bet most commercial units are 220/240 volt and GFCI would be in the form of a breaker in the service panel. The additional resistance of the wiring could dissipate the spike to inoccuous levels.
Originally Posted By: jpeck This post was automatically imported from our archived forum.
chad fabry wrote:
GFCI's trip from the difference in voltage between the two legs of a circuit.
Chad,
That is incorrect. Voltage, or difference in voltage, has nothing to do with a GFCI tripping.
A GFCI trips based on current, not voltage.
This is the most easily understood way to visualize what is happening when a GFCI trips:
Assume that a circuit has 10 amps going out the 'hot' wire through the GFCI device and 10 amps coming back in the 'neutral' wire. That means there is no problem, all the current is coming back.
Now, assume that something happened, there is still 10 amps going out the 'hot' wire through the GFCI device, but only .995 amps coming back in the 'neutral' wire. The GFCI senses that difference and trips off.
Quote:
This fact makes them prone to tripping when certain items are plugged into them.
When you have windings, like in motors and relays, and energize them, they create magnetic fields. When you turn them off by flipping the switch, the field collapses. When the one side of field is turned off by the switch and the collapse occurs, the energy that was in stored in the winding sends a brief, high voltage, low current spike to ground. If conditions are right that spike can trip the GFCI.
The appliances that are most prone to creating a problem have relays and also vibrator style motors like in hair clippers. These motors and relays too, collapse immediately in one strong spike. Some of these can be corrected by using diodes to act like a check valve. Most of the time though, diode protection isn't necessary unless it concerns computers that can be damaged by the spike.
Conventional motors that use brushes or are induction, dissipate the spike into several smaller spikes that get past the GFCI.
Refrigerators are likely to trip the GFCI not from the collapse of the windings in the compressor motor, but from the relays involved in the defrost and ice making schedules.
You've lost me there.
Motors will sometimes trip a GFCI because of leakage current to ground in the motor windings. If that leakage current reaches 4-6 ma, it will trip a GFCI used in the house. Brain fart here (can't remember which is which), but they are either Class A or Class B GFCI protection, one trips at 5 ma and the other trips at 50 ma (I think it's 50 ma). One is for protection of people (5 ma trip) and the other for protection of equipment (50 ma trip). Dang it, brain, work will ya ... Toto, we're not in Kansas anymore ... oops, wrong channel ...
Originally Posted By: Bob Badger This post was automatically imported from our archived forum.
roconnor wrote:
Thanks for the explanation Chad.
Am I reading that post right that commercial refrigerators and ice boxes may not have the same relays that could trip a GFCI on a home refrigerator ... which might explain why the GCFI protection is required for all commercial kitchen outlets, but not for dedicated residential kitchen outlets?
Here is the explanation I have been given on the commercial kitchen requirements and it has nothing to do with the likelihood of false tripping.
It had to do with injury's and fatality's occurring in commercial kitchens.
Take all the grounded metal surfaces combined with the fact much of the equipment is often moved for cleaning the cords end up damaged caused unsafe conditions.
I really have a lot of faith in GFCIs I hear people say they can not be used for motor loads, just for the heck of it I run my sump pump on a GFCI, it runs a a few times an hour during rain and has never tripped.
Originally Posted By: roconnor This post was automatically imported from our archived forum.
Bob Badger wrote:
I really have a lot of faith in GFCIs I hear people say they can not be used for motor loads, just for the heck of it I run my sump pump on a GFCI, it runs a a few times an hour during rain and has never tripped.
That gives me the warm and fuzzy about a lot of installs that I didn't comment on, but wondered about the practical application of a GFCI on a motor load circuit. I tend to think that GFCI outlets/breakers are the best thing since sliced bread.
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: Bob Badger This post was automatically imported from our archived forum.
Hi Robert,
I have never understood the reluctance to put motors on GFCI circuits.
I am not blind to the fact that some motors will trip GFCIs.
But on the other hand a great many more motors run just fine on GFCIs.
Pools and Spas are good examples of larger HP motors that work on GFCIs.
It is my belief that many of the times GFCIs trip is from equipment that is starting to have insulation breakdown.
All the outlets on construction sites have or should have GFCIs, we regularly have many motor loads on these.
High HP chop saws, power threaders, table saws, etc. When we have a GFCI that is tripping the problem is most times caused by a bad cord or wet equipment. Both of these conditions the GFCI is doing just what it should be doing, shutting down the circuit and bring a problem to our attention. 
Originally Posted By: rray This post was automatically imported from our archived forum.
We have a lot of newer house construction and condo conversions that have the bathroom outlets run from a GFCI outlet in the garage. I just note it as extremely inconvenient and hazardous if it’s 2:00 in the morning and they have to go down flights of stairs into the garage to turn the circuit back on.
