Kitchen food warmers, GFCI issues

Status
Not open for further replies.

dpcarls1598

Master Electrician
Location
Minnesota, USA
Occupation
Master Electrician
I have multiple food warmers (the kind that have water immersed heating elements with a service tray above them) in our school kitchens on GFCI outlets, mostly 208v, 50a single phase that are a complete pain.
The new schools and recently remodeled kitchens of course meet the new code with GFCI protection for the outlets but these units, even the brand new ones trip especially after sitting for the summer or over COVID.
The kitchen service company comes out, removes the ground wire from the plug and runs the unit for an hour or so to eliminate the moisture in the insulation around the coils then reconnects and it works until the next extended school break.
I‘m not removing the GFCI protection or doing anything against code. It’s a school and everything I do there is beyond code just because it’s kids and if anyone can get into mischief, it’s kids!!!
Anyone else seeing this and what are your thoughts?
 

Jon456

Senior Member
Location
Colorado
The kitchen service company comes out, removes the ground wire from the plug and runs the unit for an hour or so to eliminate the moisture in the insulation around the coils then reconnects and it works until the next extended school break.
Are they disconnecting the ground wire then reconnecting it? Or are they eliminating the ground entirely?
 

Jon456

Senior Member
Location
Colorado
What are your thoughts?

When in service, these are operating at virtually 100% humidity. So I don't see how they are getting more moisture while in storage than while in service. Unless the staff are leaving them filled with water during the extended periods of disuse.

Nevertheless, it seems that these should be designed/built so there is zero leakage current regardless of the humidity or if water is left in them for extended periods of time. Perhaps the school needs to find better quality food warmers.

I can say that I've found some restaurant equipment suppliers to be unscrupulous (even downright criminal). So maybe the warmers the school got were "refurbished" then re-sold as new. Or maybe they were low-quality overseas knockoffs.
 

dpcarls1598

Master Electrician
Location
Minnesota, USA
Occupation
Master Electrician
When in service, these are operating at virtually 100% humidity. So I don't see how they are getting more moisture while in storage than while in service. Unless the staff are leaving them filled with water during the extended periods of disuse.

Nevertheless, it seems that these should be designed/built so there is zero leakage current regardless of the humidity or if water is left in them for extended periods of time. Perhaps the school needs to find better quality food warmers.

I can say that I've found some restaurant equipment suppliers to be unscrupulous (even downright criminal). So maybe the warmers the school got were "refurbished" then re-sold as new. Or maybe they were low-quality overseas knockoffs.
They are a common unit, about $2,500 each made in USA 👍. Good idea about checking what condition they are left in when stored. From the repair company, this sounds like in pain in their rump too.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
When in service, these are operating at virtually 100% humidity. So I don't see how they are getting more moisture while in storage than while in service. Unless the staff are leaving them filled with water during the extended periods of disuse.
Even though they may be at a lower humidity environment during storage, they are still not getting a daily heating above boiling point at the center of the element. So they may build up a higher total moisture or have the moisture present inside the almost completely sealed element move closer to the center (hot) portion of the ceramic-insulated element.
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
IMHO these systems are defective from the manufacturer. But fighting that particular fight might not be worth the effort. It is probably worth complaining to the company so that they fix the problem in the future, but I doubt they would change your equipment to solve the problem.

There is _always_ some leakage. It is impossible to remove. Even if you have _perfect_ insulation you have capacitive coupling. But in this case you clearly have imperfect insulation; once the insulation gets dried out there is less leakage and the unit works just fine.

Rather than running this system temporarily without and EGC, I'd look into some way to operate it at reduced voltage in order to 'bake out' the insulation. Maybe you can talk the manufacturer into building such a 'bake out box'.

-Jon
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
This has been an issue with imported equipment and using standard breaker to run the elements on high for a period of time dries the equipment out enough that the will then work on a GFCI device. This is the first I have heard of this issue on domestic equipment.

When I attended the Eastern Section IAEI meeting a NEMA rep was telling about a 400 unit apartment project where they were having to connect all of the electric ranges to a standard breaker and run the elements on high to dry them out and then install the code required GFCI breaker.
 

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
... Rather than running this system temporarily without and EGC, I'd look into some way to operate it at reduced voltage in order to 'bake out' the insulation. Maybe you can talk the manufacturer into building such a 'bake out box'.

I think a reduced voltage "bake out" might work in the OP's equipment if the heating elements are not immersed in water as they are during usage, because considerably less power (and therefore applied voltage that produces leakage currents) would be needed to reach an element temperature comparable to that when operating in water.

But because the power dissipated goes as V2 (ignoring the temp coefficient of resistance), with appliances for air heating it's possible you might not be able to reduce the voltage and therefore current leakage enough to prevent GFCI tripping, while still obtaining a sufficent temperature for driving out the moisture. Just a thought ...
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
....

There is _always_ some leakage. It is impossible to remove. Even if you have _perfect_ insulation you have capacitive coupling. But in this case you clearly have imperfect insulation; once the insulation gets dried out there is less leakage and the unit works just fine.

....

-Jon
FWIW, domestic equipment designed for 240V can be expected to benefit from balanced leakage when fed from 120-0-120, allowing for looser leakage specs. When supplied from three phase 208Y/120 that effect is gone.
 

micabay

Appliance Tech
Location
Kitsap, WA
Occupation
Appliance Tech
Same issue with gas ovens that use a hot surface ignitor. The ignitor absorbs moisture in shipping and trips the GFCI until it drys out.
Hey Tom, This is the first I've heard of oven ignitors and moisture absorption. Ive yet to experience this or hear about it from other appliance techs. Whom let you know about this? Though I have noticed range install/ LP conversions have dropped off since Nielson's closed and Albert Lee moved into their building.
-One of the Appliance guys.
 
Last edited:
Status
Not open for further replies.
Top