Commercial kitchen gfi problem

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eds

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I have wired a small bakery per N.E.C 2002 code wich requires all 15 and 20 amp 125v receptacles be gfi protected. This has not been a problem untill today. The owner has a proof box (place bread dough and such in this) this box has a heating element and 2 small lights that light to say power on and a light that shows when the element is heating. I also believe it has a timer and a thermastat. This box is box has been plugged into a multi wire circut one circut for a mixer and one circut for the proof box for 2 weeks with out a glitch. Today the gfi receptacle button pops out, she tries the gfi receptacle for the mixer it pops, she tries all other receptacles and they pop, she closes for the day, and takes the proof box back to the manuf. The manuf plugs it into a non gfi recep and it works she comes back and it pops the gfi again.I get there tonight plug it in the power light comes on, but as soon as I turn on the stat the gfi trips. I take my wiggy and check continuity from phase to ground and from neutral to ground both ring when timer is turned on. I then replace gfi with outlet and read amps 6.8 amps on phase 6.5 on neutral (fluke digital) Call manuf they claim that gfi are not required (they sell to all the big grocery stores and they don't have gfi, or maybe my gfi is weak) I then ask them will they check it on a gfi protected out if she brings it back to them, their response dont have to since gfi are not required and they dont have gfi in the building (this was a used proof box) I have informed her that a new box may be needed, what other steps can be taken to check this out further. Thank you and it is nice to sit down and relate your problem to some one
 
Buy a new proof box... You don't have a choice but to keep your kitchen receptacles GFI protected, so if they trip when a piece of equipment is plugged in, then you have a problem with that piece of equipment...
 
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eds said:
I then replace gfi with outlet and read amps 6.8 amps on phase 6.5 on neutral (fluke digital)
Click to expand...
You've got a 300ma leakage current, most likely in the heating element. Of course, any GFCI will trip.

Get the manufacturer to write a letter of exception to the code that the NEC and AHJ will accept. :rolleyes:
 
you are very close to your answer

you are very close to your answer

By measuring the outgoing current and the returning current you are doing the job of the gfci device. So if you are sending out 6.8 amps and only returning 6.5 amps via the neutral the job of the gfci device is to stop all current when what is going out is not coming back. The next question is of course where is this current going????and the obvious answer is it is going to ground via the ground conductor. I will bet you if you hook up your recept non gfi for testing purposes you will find out where your .3 amps is going coming back on the ground wire . if you want to get involved in fixing this machine you can probably easily trace where the current is going to ground it may be a pinched wire or a rotted out light socket or the manufacturer may have intentionely grounded the neutral side of the switch to make it operate something... well intentional or not the gfci will not hold when current is going to ground. Good luck finding a solution
 
Commercial kitchen gfci problem

Commercial kitchen gfci problem

In some cases my inspectors let us use a single outlet on a seperate circuit for such appliances. If the counter is set up for this appliance only. I realize they could use it for anything but most people don't expecially in a commercial situtation. I will probably get bashed for this but what do you all think about this. Semper Fi.
 
Commercial electrical work

Commercial electrical work

I forgot to say before that I change the gfci for a new one and make sure I use a 20A instead of a 15A and most of the time this works. Sorry. Would like to know what you decide to do to fix this problem. Semper Fi
 
I spoke to the AHJ yesterday while I was looking at this problem, he informed me that I could take this proof box off of the gfi. This is not a local ammendment to the code , but he understands the nusiance tripping that is associated with some equipment. At this time I don't know if I will go that route as this seems to be a direct violation.
 
eds said:
I spoke to the AHJ [...] informed me that I could take this proof box off of the gfi. This is not a local ammendment to the code , but he understands the nusiance tripping that is associated with some equipment.
Click to expand...

Don't go this route. We are not talking about nuisance tripping here; the proof box is _broken_ and is leaking 200mA-300mA to the chassis. If the equipment grounding conductor in the cord or ground pin gets damaged, then the chassis could very well become energized to a significant level.

-Jon
 
eds said:
The manufacturer plugs it into a non GFCI receptacle and it works. . . .
Click to expand...
No it doesn?t!

That is the key point. The manufacturer is wrong in saying it works. The manufacturer used an incomplete testing process to determine whether or not it works.

The concept of ?does this thing work or does it not work? involves more than just ?well, I don?t see a problem with it.? To be said to ?work,? the device must meet several criteria. One is that it fulfills the functions for which it was designed (i.e., the lights come on, the heater comes on, the thing automatically turns off when it reaches temperature, etc.).

But it must also fulfill those functions without presenting a danger to its operator. If it has a leakage current, that does present a danger. Plugging the device into a non-GFCI outlet will not reveal whether or not there is a leakage current. In order to trip the breaker feeding the non-GFCI receptacle, there would have to be a leakage current well beyond 20 amps. Point in fact, if the device does not trip a non-GFCI receptacle circuit, and if it does trip a GFCI receptacle, that constitutes very strong evidence that it does have an unacceptable level of leakage current.

Tell the client to get a new device. If this is a new device, the manufacturer should replace it for free.
 
eds said:
... I spoke to the AHJ yesterday ... he informed me that I could take this proof box off of the gfi ... he understands the nusiance tripping that is associated with some equipment.
Click to expand...
Clearly, there seems to be a awful lot about this particular case which the AHJ doesn't understand.
 
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eds said:
Call manuf they claim that gfi are not required (they sell to all the big grocery stores and they don't have gfi, or maybe my gfi is weak) I then ask them will they check it on a gfi protected out if she brings it back to them, their response dont have to since gfi are not required and they dont have gfi in the building (this was a used proof box)
Click to expand...


If they don't have GFCI's in the building then ask him to use the alternative method of testing. ( take shoes off, then stand on wet floor and operate the equipment ).

You can probably have the piece of equipment repaired by a restaurant equipment repair company. Let the people that normally work on the equipment deal with it. Our job stops at the receptacle.
 
This is an interesting thread.

I can see that most of the people who are responding understand what is actually happening with this piece of equipment, and they are giving good advice.

On the other hand is the "AHJ" out in the field who has a "misperception" of what is happening. There are still many people in the field who dismiss the fact that something may be wrong with equipment if the GFCI trips open. They do not even conceive of the fact that there could be a potential life safety hazard, so they say replace the GFCI device.
This is another item on the list of what further training needs to be done to help this industry.
 
I agree with Pierre. Many times I get contractors in the office telling me that the GFCI or AFCI is tripping. I always tell them good, then it's doing it's job, now do yours and find out why. Probably 9 out of 10 times I get them back with, bad equipment or a nail in the wire, wired wrong, etc.
 
I have in the past, while discussing this topic, suggested the following. I've not brought it up with any standards body or CMP; just an idea that I've thrown out there.

For equipment fastened in place, in commercial kitchens, a different standard of GFCI should be permitted. This GFCI would have normal feature of tripping on 4-6mA of 'unaccounted for' current, but would also measure current flow on the equipment grounding conductor, and would permit up to 50mA of EGC current to 'count' for imbalance between hot and neutral.

The idea is that in a 'reasonably functioning' system, there will always be _some_ leakage through imperfect insulation systems, and thus some current flow on the EGC. As long as this current flow is low and not through a person, it really isn't a problem. By differentiating between current flowing to the chassis of the appliance and then back through the EGC, versus current going 'somewhere else', apparatus with minor insulation faults could continue to operate, while still providing protection for human users.

-Jon
 
Just because the inspector allows or overlooks a violation does not mean that it is not a violation. All it means is that you may have the inspector with you while you are being sued if a problem occurs because of the violation. Of course the inspector would deny giving permission for this exception, which is why "special permission" is now defined to mean written permission. This piece of equipment is broken, period. It needs to be repaired or replaced. There is no such thing as a minor insulation fault. The circuit is either good or bad, and this one is bad. Equipment grounding conductors are not meant to carry current, except when they are clearing a fault. Any current on a grounding conductor indicates a problem. Also remember that there are many appliances that use only two conductors with no equipment ground, GFCI is the only protection available for these appliances. Check the GFCI receptacle with the push button and/or an inexpensive GFCI tester; if it passes the test your work is done - the problem is in the equipment.
 
haskindm said:
There is no such thing as a minor insulation fault. The circuit is either good or bad, and this one is bad. Equipment grounding conductors are not meant to carry current, except when they are clearing a fault.
Click to expand...

I have to disagree, but on doing further reading, my disagreement is reduced to a minor quibble :)

There is most certainly such a thing as a minor insulation fault. Insulation is _never_ perfect, and there will always be _some_ current flow to ground from energized parts. _Always_. Thus to determine the state of an insulation system, you must specify an allowed threshold of current flow, or a required insulation resistance.

A 'minor' insulation fault is thus a defect in the insulation which permits current flow that is below your threshold for acceptability.

_However_ I did some reading, and apparently the standards for appliances are on the order of 1mA, well below the threshold of a normal GFCI. If an appliance trips a GFCI, then its leakage current exceeds that normally allowed for appliances.

-Jon
 
I am so glad that their are people that understand the purpose and intent of a gfi and the problems more often are with the equipment and not that "damn" gfi receptacle
 
50 ma current

50 ma current

50 ma current is not an acceptable level in humans unless you think respiratory paralysis is acceptable. It is substantially lower in women and even lower in children.
 
shock hazard

shock hazard

I could not get the charts to copy but i think you get the idea. 11
The Hazards of Electricity ? Do You Know What They Are?
Dennis K. Neitzel, CPE
Senior Member, IEEE
AVO Training Institute, Inc.
4271 Bronze Way
Dallas, Texas 75237
Abstract - OSHA statistics show that several hundred
deaths occur annually as a result of electrical shock. Over
one-half of these deaths are the result of contact with lowvoltage,
primarily 120-volts. Residential, commercial,
industrial, farm, and utility accidents are included in these
statistics. NIOSH statistics show that electrical contact
results in 4,000 non-disabling and 3,600 disabling injuries
annually in the United States, plus ONE death in the
workplace every day.
Many of the electrical shock accidents that occur in
commercial and industrial facilities are the result of contact
with 277-volts. This is due to the extensive use of 277-volt
fluorescent lighting. Employees generally perform
maintenance on these light fixtures without performing a
proper lockout/tagout of the circuit.
Studies also show that 10-15 employees are hospitalized
every day with arc-flash burns, which are often catastrophic
to the victims physically, psychologically, and financially. In
reality, the hazards associated with the use of electricity are
real and can affect anyone.
The three main hazards of electricity; electrical shock,
electrical arc-flash, and electrical arc-blast, along with the
physiological effects on the human body must be
understood by everyone working on or near electrical
circuits and equipment.
I. Introduction
Electricity is often referred to as a ?silent killer? because it
cannot be tasted, seen, heard, or smelled. It is essentially
invisible. Electricity has long been recognized as a serious
workplace hazard, exposing employees to electrical shock;
which can result in electrocution, serious burns, or falls that
result in additional injuries or even death; as well as
electrical arc-flash and electrical arc-blast.
It is a well known fact that electricity is essential to everyday
life, both at home and on the job. Perhaps because it has
become such a familiar part of daily life, most people don?t
give much thought to it or how much our work depends on
a reliable source of electricity. More importantly, people
tend to overlook the hazards that electricity poses and fail
to treat it with the respect it deserves.
Electricity is no respecter of persons; it will injure or kill a
custodian, manager, president, or office worker just as fast
as it will injure or kill an electrician. The laws of physics for
electricity apply to everyone. Some employees work with
electricity directly as part of their everyday jobs while others
work with it indirectly, primarily by the use of cord- and plugconnected
equipment and tools.
As was noted above, there are several hundred workers
injured or killed each year due to inadvertent contact with
energized conductors. Surprisingly, over half of those killed
are not in tradition electrical fields (i.e. linemen, electricians,
technicians, etc.), but are from fields such as painters,
laborers, and drivers. [Detailed surveillance data and
investigative reports of fatal incidents involving workers who
contacted energized electrical conductors or equipment are
derived from the National Traumatic Occupational Fatalities
(NTOF) surveillance system maintained by the National
Institute for Occupational Safety and Health (NIOSH)].
This paper will address the three hazards of electricity
mentioned above along with the physiological effects of
each.
II. Electrical Shock
A basic understanding of the shock hazard, along with the
physiological effects on the human body, is vital to an
understanding of electrical safety. The following discussion
will address the most common effects of electrical shock.
Electrical shock occurs when a person?s body completes
the current path between two energized conductors of an
electrical circuit or between an energized conductor and a
grounded surface or object. Essentially, when there is a
difference in potential from one part of the body to another
current will flow.
The effects of an electrical shock can vary from a slight
tingle to immediate cardiac arrest. The severity depends on
several factors:
? Body resistance (wet or dry skin are major factors of
resistance)
? Circuit voltage
? Amount of current flowing through the body
? Current path through the body
? Area of contact
? Duration of contact
There have been many studies performed in this area with
different values of current that causes each effect. Table 1
illustrates average values of current and the effects as
taken from various published studies. [1] [2]. The values
listed are average and are not meant to provide specific
effects for every person.
Presented at the 2006 IEEE IAS Electrical Safety Workshop, February 7-10, 2006, Philadelphia, Pennsylvania
Table 1
Current Rang and Effect
Table 2 illustrates comparisons between AC and DC shock.
Direct current shocks can be as hazardous as shocks
received from alternating current. When working with
battery systems, as well as other DC sources, there is also
a potential for arc-flash burns or chemical burns.
Table 2
AC and DC Shock Comparison
Although the majority of electrocutions are the result of
ventricular fibrillation, burns are the most common shockrelated
injury. An electrical accident can result in an
electrical burn, arc burn, thermal contact burn, or a
combination of burns. Electrical burns are among the most
serious burns and require immediate medical attention.
They occur when an electric current flows through tissue or
bone, generating heat that causes tissue damage. The
body cannot dissipate the heat generated by current flowing
through the resistance of the tissue therefore, burns occur.
[1]
To further illustrate how easily a person can receive a fatal
shock, consider a voltage that is common to every location
in the United States, 120-volts. Under average working
conditions where the person is perspiring and has a
resistance of only 1000-ohms from hand-to-hand, using the
simple Ohm?s Law formula (current equals the voltage
divided by the resistance) the current flow will be 0.12
amperes or 120 mA. Examination of Table 1 shows that this
value of current will probably cause ventricular fibrillation
which is, in most cases, fatal.
Figure 1 summarizes the overall effects of resistance,
voltage, and current in a shock appraisal chart. Notice on
this chart that the resistance values are set at a maximum
of 1000 ohms at and beyond the 600-volt level. This is due
to the immediate penetration of the skin at the 600-volt
shock level, thus allowing the current to travel through the
body without the skin resistance being a factor. Entrance
and exit wound injuries are generally present when this
occurs.
Figure 1
A Resistance-Voltage-Current
Shock Appraisal Chart [1]
Some ways to prevent these accidents are through the use
of insulation, guarding, grounding, electrical protective
devices, and safe work practices.
It is very important that individuals exposed to the hazard of
electrical shock be cognizant of the physiological effects of
current flowing through the body. It is also important to
understand the factors which will reduce or increase the
body?s resistance. The best practice overall is to STAY
OUT OF THE CIRCUIT.
The ?Shock Hazard Analysis? required by NFPA 70E-2004
provides the guidance needed to determine the level of
shock hazard. This analysis also determines the shock
protection boundaries as well as the approach limits for
qualified and unqualified employees.
III. Electrical Arc-Flash
The second major hazard of electricity is the electrical arcflash.
Historically the shock hazard has been the most
understood and addressed hazard of electricity. The
physiological effects of current passing through the body
are well documented and accepted by the general industry.
However, studies on the causes of electrical injuries show
that a large number of serious electrical injuries involve
burns from electrical arcs.
There seems to be a serious misconception in the industry
that electrical arcs are a product of only high voltage.
Actually, the electrical arc-flash is not voltage sensitive but
is more a product of short-circuit current and clearing time
or arc duration. In some cases, it is possible to generate
higher arc energy from a low-voltage source than from a
high-voltage source. The amount of energy will in turn
determine the temperature of the arc, which can reach a
temperature of 20,0000K (Kelvin) or about 35,5400F. Some
studies report temperatures as high as 34,0000K (about
60,7400F). The only known source that can produce a
higher temperature is the laser, which can produce a
temperature of 100,0000K (about 179,5400F). [3]
There are actually three different issues with the arc-flash
hazard, the arc temperature, the incident energy, and the
pressure developed by the arc. The main concern with the
arc temperature is the flash flame and ignition of clothing.
At approximately 2030F (960C) for one-tenth of a second (6
cycles), the skin is rendered incurable or in other words a
third-degree burn (see Figure 2). The incident energy
threshold for the onset of a second degree burn is 1.2
cal/cm2. As can be seen by this, it does not take a very high
temperature or very much incident energy to cause severe
injury, which results in extreme pain and discomfort or
death to the worker.
Figure 2
Human Tissue Tolerance [3]
The flash hazard analysis, required by NFPA 70E-2004, is
used to determine the incident energy of an electrical arc
and to establish
 
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