5mA vs. 30mA sensitivity GFCI breaker

[synchro]

Thank you so much for all your responses! My situation is still not solved. I guess it's a complex one. Non-motor-rated GFCI or motor rated 5mA sensitivity GFCI is tripping on a food warming equipment, but we don't really know what the cause of this is. ...

Can you provide more information about the food warming equipment? For example, is it 120V or 240V? Does it heat with resistive elements or with microwaves, and if the latter does it use an internal transformer (which is typically quite heavy) or a switching supply aka inverter? Does it have a motor, possibly variable speed? I'm asking because sometimes an appliance can produce electrical noise or interference that can make a GFCI susceptible to tripping. I'm not saying this is the problem, just that more details like this are needed as winnie mentioned in his post #35 above.

 

[Fred B]

Thank you! Yes, I think they tested that the food equipment worked correctly on other GFCI. They need somebody on the site to analyze the situation. Who is usually responsible for this? The manufacturer of the food equipment, the manufacturer of the breaker/panel or the engineer of record or all?

Thank you so much for all your responses! My situation is still not solved. I guess it's a complex one. Non-motor-rated GFCI or motor rated 5mA sensitivity GFCI is tripping on a food warming equipment, but we don't really know what the cause of this is. 30mA sensitivity GFCI is being considered, but not decided if it's okay to be used and if it would solve the situation. I really think somebody should do a thorough analysis of the situation. It's actually multiple sites where this is occurring. Does anybody know whose responsibility it is to investigate situations like this: food warming equipment manufacturer, GFCI breaker manufacturer, panel manufacturer or engineer of record or all of the mentioned? How can this be done in practical life? Thank you so much, and have a great day!

What sort of food heating equipment is it? Is it something that has a surge loading when it comes on? Did anyone test the load amperage? Your response in post #18 seems to be at odds with comment in post #34 that this equipment is having issues in multiple sites. Does this mean similar equipment at different buildings? Or, that one piece moved about?

Ps does the equipment trip immediately or after some time running?

 

[jap]

In the end it may come down to getting a warmer that doesn't require GFI proection, or, move the warmer to a location where GFI protection
is not required.

JAP>

 

[mbrooke]

In other words, keep that EGC in tact and corrosion free regardless of what ground fault protection you have in place.

Correct?

Jap>

Correct.

 

[mbrooke]

Here is an article from 2014. Since this is an actively developing part of code, I am sure things have changed in the last 7 years. But it provides some useful history.

Now that industrial GFCIs are here, inspectors have a proactive option for shock protection

UL Class A ground-fault circuit interrupters (GFCI) began to be required in kitchens, bathrooms and outdoor outlets in the early ’70s, and have saved many lives over the years: According to...

iaeimagazine.org

-Jon

Industrial GFCIs are merely assuring rapid disconnection times, which CAN BE done with an EGC.

That curve is not ULs, but right out of IEC 61200 413.

 

[winnie]

mbrooke,

You might find it interesting to look at the difference between Class D and Class E GFCIs as described in the report I linked. Class D requires a full size EGC with one standard for tripping time and sensitivity, class E requires a standard size EGC with a different standard for tripping time and sensitivity.

-Jon

 

[mbrooke]

mbrooke,

You might find it interesting to look at the difference between Class D and Class E GFCIs as described in the report I linked. Class D requires a full size EGC with one standard for tripping time and sensitivity, class E requires a standard size EGC with a different standard for tripping time and sensitivity.

-Jon

They all are trying to do the same. Trip for a line to frame fault in 0.8 seconds at a touch of 60 volts, 0.4 seconds at 120 volts.

The only reason the NFPA has been requiring GFCIs since the 2000s is to cover their own liability over 250.4 A 5.

 

[winnie]

Industrial GFCIs are merely assuring rapid disconnection times, which CAN BE done with an EGC.

That curve is not ULs, but right out of IEC 61200 413.

I disagree to the following extent: an EGC, and in particular a larger reduced impedance EGC will reduce clearance times for 'solid' faults. But in the case of a fault with impedance (say a fault in the middle of a resistive load, or a fault making poor contact), the impedance of the EGC makes little difference in fault clearing time. This is because overcurrent protection cannot distinguish between normal operating current and fault current at normal levels.

Residual current detection (including GFCI devices) will distinguish between normal operating current and fault current, even with low levels of fault current.

-Jon

 

[mbrooke]

I disagree to the following extent: an EGC, and in particular a larger reduced impedance EGC will reduce clearance times for 'solid' faults. But in the case of a fault with impedance (say a fault in the middle of a resistive load, or a fault making poor contact), the impedance of the EGC makes little difference in fault clearing time. This is because overcurrent protection cannot distinguish between normal operating current and fault current at normal levels.

Residual current detection (including GFCI devices) will distinguish between normal operating current and fault current, even with low levels of fault current.

-Jon

Fault impedance will limit frame touch voltage.

UL studies on arcing faults, at least at the 120 volt level indicate 0.03 ohms of impedance.

The brunt is driven by the resistivive divider principle and source "sag" for larger circuits.

 

[curious101]

Can you provide more information about the food warming equipment? For example, is it 120V or 240V? Does it heat with resistive elements or with microwaves, and if the latter does it use an internal transformer (which is typically quite heavy) or a switching supply aka inverter? Does it have a motor, possibly variable speed? I'm asking because sometimes an appliance can produce electrical noise or interference that can make a GFCI susceptible to tripping. I'm not saying this is the problem, just that more details like this are needed as winnie mentioned in his post #35 above.

This is a great set of questions to investigate (I will keep these questions and will propose to investigate). It looks like the preference is to replace the GFCI with a regular breaker, because the investigation seems too elaborate.... The equipment in question is both a drink dispenser (208V/1ph or 240V/1ph, depending on site; this is a commercial chain) and a hot dog roller (120V). Thank you!

 

[curious101]

What sort of food heating equipment is it? Is it something that has a surge loading when it comes on? Did anyone test the load amperage? Your response in post #18 seems to be at odds with comment in post #34 that this equipment is having issues in multiple sites. Does this mean similar equipment at different buildings? Or, that one piece moved about?

Ps does the equipment trip immediately or after some time running?

This is a great set of questions to investigate (I will keep these questions and will propose to investigate). It looks like the preference is to replace the GFCI with a regular breaker, because the investigation seems too elaborate.... The equipment in question is both a drink dispenser (208V/1ph or 240V/1ph, depending on site; this is a commercial chain, so there are projects at many sites) and a hot dog roller (120V). Thank you!