GFCI on Lab Equipment.

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I have a hot water bath in a lab that incubates bacteria samples. It is pretty important that the bath stays on and maintains a certain temperature.

The equipment has metal housing, a stainless steel water tub, and the lab has hard counter tops and impervious floors and people stick their hands in the water to pull out samples. Everything is pointing to GFCI requirement. When the circuit is powered from a GFCI, the equipment trips in a few hours. I checked the circuit and everything is fine. I called the equipment manufacturer and they said that their equipment should not be plugged into GFCI protected outlets.

Does anyone have any ideas?
 

GoldDigger

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Staff member
Location
Placerville, CA, USA
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The equipment has high leakage. Their UL listing (they are listed?) does not allow that but they don't care.
If GFCI is not mandatory but just a design feature you could install GFP at the 30ma level instead.
Or you could power the heaters from the ungrounded secondary of an isolation transformer and provide a ground detector.
I think that you can stretch one of the exceptions to mandatory grounding to justify this.
 

kwired

Electron manager
Location
NE Nebraska
Is it supplied via a 15/20 amp 120 volt receptacle? If not I don't see GFCI protection being required, if so other conditions need consideration before it absolutely must be GFCI protected.

It may still be a good idea to GFCI protect it though for the safety of users.

Meg the heating elements, maybe one of them is failing to ground.
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
IMHO if the equipment is tripping a GFCI, then the equipment is broken. Manufacturers don't want to believe this, but with modern insulation materials you can design for low leakage on just about any small appliance.

With that said, I think you first need to determine if a GFCI is mandatory. IMHO if you have a situation where you've determined that a GFCI is not mandated by code, but is instead a really good design decision, then you can start looking at alternative methods for providing equivalent protection.

-Jon
 

growler

Senior Member
Location
Atlanta,GA
I called the equipment manufacturer and they said that their equipment should not be plugged into GFCI protected outlets.

IMHO if the equipment is tripping a GFCI, then the equipment is broken. Manufacturers don't want to believe this, but with modern insulation materials you can design for low leakage on just about any small appliance.

These manufacturers know their equipment will not work with a GFCI protected receptacle. The customer shouldn't buy this type of cheap crap but it happens all the time.

We have no choice on where GFCI protected receptacles are required, either they are required or they are not. If you are in an area where GFCI protected receptacles are required then you must install them.

If people wish to operate a piece of equipment (cord & plug) that trips a GFCI in an area where GFCI protection is required they can use an extension cord to an area where GFCI protection is not required and all they have to worry about is OSHA, the Fire Marshal and maybe death. It a free country.
 

growler

Senior Member
Location
Atlanta,GA
Everything is pointing to GFCI requirement. When the circuit is powered from a GFCI, the equipment trips in a few hours. I checked the circuit and everything is fine. I called the equipment manufacturer and they said that their equipment should not be plugged into GFCI protected outlets.


The equipment is cord and plug connected. Does this area require GFCI protection for some reason? If GFCI protection is not required then install a regular receptacle and don't worry about it.

I install receptacles (building wiring ) and what people choose to plug into those receptacles is not my concern or under my control.
 
The equipment is cord and plug connected. Does this area require GFCI protection for some reason? If GFCI protection is not required then install a regular receptacle and don't worry about it.

I install receptacles (building wiring ) and what people choose to plug into those receptacles is not my concern or under my control.


Normally I would agree with you. In this case, I am the plant electrician and I eat lunch with the lab ladies everyday. I feel it is my responsibility to provide them with electrically safe working conditions.
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
Normally I would agree with you. In this case, I am the plant electrician and I eat lunch with the lab ladies everyday. I feel it is my responsibility to provide them with electrically safe working conditions.

The best you can do is to get a unit that won't trip a GFCI. The manufacturer has told you they won't work on a GFCI, and it's obvious they were correct.

I see no reason a hot water bath unit can't be manufactured that won't, by design, trip GFCI's.
 

mpoulton

Senior Member
Location
Phoenix, AZ, USA
5mA+ leakage to ground is not normal or acceptable, I don't think. If the GFCI trips due to the equipment, the equipment presents a shock hazard and should not be used until the problem is fixed. I'd throw this back on the manufacturer. If that's just not possible and this equipment must be used anyway, a 30mA GFPE device would provide some protection.
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Thinking outside of the box here, and possibly not something that could practicably be implemented in a legal fashion: Arrange safeguarding so that the GFCI protection is enabled only when people are actually interacting with the machine.

For example, you could have the machine in a fume hood, and only have GFCI protection when the hood sashes are up. That way, if the GFCI trips there will be a person there to fix the issue, and if a person is there they have GFCI protection.

One issue that crops up is equipment with a reliable ground that has significant leakage to ground. It _isn't_ a shock hazard because the current is following a path protected from human interaction. The problem is that the GFCI has no way of telling the difference between current flowing on a solid metallic path to the EGC, or through a person.

-Jon
 

iwire

Moderator
Staff member
Location
Massachusetts
One issue that crops up is equipment with a reliable ground that has significant leakage to ground. It _isn't_ a shock hazard because the current is following a path protected from human interaction.

Unless the EGC becomes compromised then the shock hazard is high. EGC pins on plugs seem to self destruct quickly.
 

growler

Senior Member
Location
Atlanta,GA
I see no reason a hot water bath unit can't be manufactured that won't, by design, trip GFCI's.

They do make equipment like this that will not trip a GFCI protected circuit. It's the type of heater they use. I worked on some equipment and the first version worked fine on a GFCI protected circuit and then they made the smart decision to change out the heaters ( they leak and trip a GFCI ).

I would would question the UL listing of this equipment if it's listed. Do they have it labeled as not working with GFCI protection. Was it made in America or farther east?
 
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