Municipal Water Tank GFCI

[bheller]

I have searched the NEC and have not found an answer for this question (I'll keep looking).
The situation: Municipal water storage tanks often have a mixer installed in the tank to mix the water to prevent stratification and reduce THM (Trihalomethane) formation.

The mixer is usually a 120v/1Ø 1/2 to 1 HP motor, depending on tank size. My question is, does the NEC require a GFCI for this motor? If so, can you point me to the correct code segment? I don't know that it makes a difference but municipal water tanks are usually secured from the general pubic with access limited to trained personnel.

 

[zbang]

Is the pump hard-wired or plug-in? Is it "hard-piped" or using hoses? Except in specific circumstances (such as swimming pools or fountains), hard-wired & hard-piped pumps will not need GFCI protection. If it's plug-in, the pump may not require one, but the very presence (outdoors) of a recepticle will.

Limited-access seldom, if even, removes the need for personnel protection.

 

[bheller]

It is hard-wired. The mixer comes with a control panel that contains a contactor and control logic designed for the application. The panel is usually mounted on an equipment rack at ground level. Rigid conduit is installed from the control panel to the top of the tank ending at a j-box. The mixer is installed through the manway hatch in the tank top and suspended from chains or sits on the tank bottom, depending on the height of the tank. The mixer motor is connected by rubber cord to the j-box that contains a disconnecting means.

 

[bheller]

Zbang, just for clarification...It's not a pump. It's a mixer...A submersible motor with a prop on it. Looks like a giant trolling motor.

 

[tom baker]

The limited access does not matter, even a trained person can be injured, as Zbang pointed out and also on the requirement for GFCI, not needed if hard wired.
The rubber cord concerns me. Rubber cords deteriorate over time, the insulation becomes brittle, and in the water reservoir, its very humid, the water typically has chorine in it, which is why the mixer is installed (I worked for a medium size water utility for 38 years as an electrician/instrument tech and have been inside and outside many reservoirs).
What type of cord is it, IE what information is on the jacket?
Is the mixer pump UL or NRTL listed?

 

[bheller]

Submersible motor cable is SJTOW or SJTOOW...UL, CSA & NEC underwater rated cable.
Control panel is UL/CSA listed
Submersible motor is ETL listed to UL & CSA standards.

Mr. Baker, If I understand you and Zbang correctly, it is your opinion that if the mixer is connected with RGS conduit with screw/mechanical terminals - no plug connection - then a GFCI device is not required by the NEC.
Can you point me to the correct NEC section for this?

 

[zbang]

Can't point to a section saying it isn't required because that's generally not how the NEC works- often it only says where something is required. So, yes, our opinion is that it's the mixer doesn't need a GFCI; a good analogy could be a submersible well pump.

That said, I'd schedule the cable for periodic inspection but don't have a suggestion of intervals.
Is there a means to lock-out the mixer for service? (there should be) Your procedures for entering the tank ought to include that.

 

[tom baker]

Very good on cable, motor, etc.
The requirement for GFCIs is in 210.8. Any receptacle in those locations requires GFCI protection
There are other locations in the NEC that require GFCI protection, water fountains, tire inflation equipment - these can be hard wired.
Article 680 is fountains, and swimming pools
Article 682 is artificial bodies of water
Not very applicable but these are locations where someone is going to be in the water with electrical equipment
I had a reservoir with a 1 acre in size floating cover with two cover pumps, these were hard wired, and not GFCI protected. this reservoir had a mixing pump as it was large (11 mg), that pump failed, it was the cord to the motor got kinked at the motor.
I would suggest a megger test after all installed. See what the leakage is.
Safest would be a GFCI, but it may trip due to the leakage. Send me a message with link to your products, there was talk some years ago about mixing pumps for stratification. I sent you a message you just need to reply

 

[bheller]

I sent you a link by pm that should give you all the info you need.
I was the GM for a water/wastewater utility for 12 years before I moved to my current position, so I'm familiar with reservoirs like you mentioned.
Thanks for the Articles. I had already checked those. It seems, except for some very specific equipment, GFCI's are meant primarily for receptacles. I was just hoping that water tanks would be one of those specific items mentioned. Oh well. We'll just have to argue with the manufacturer and the AHJ.

I mentioned restricted access and trained techs earlier. Reason being that they are trained to shut off any power on a tank before they climb or enter the tank.

Thanks for your input.

 

[zbang]

We'll just have to argue with the manufacturer and the AHJ.

If the manufacturer requires a GFCI in the feed, then you gotta have it- 110.3(B) "Installation and Use. Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling." Those instructions might specify breaker size, or that you must use fuses, or even not to mount something upside-down.

As for the AHJ, it's their job to cite code for violations; if they think the device must have a GFCI, they need to point directly to that section, "I like to see..." is not a code reference..... (And there will be times when it's easier to install the GFCI than argue.)

More for curiousity than anything else, would you post a link to this kind of device?

 

[winnie]

If code does not require GFCI but you think that GFCI is a good idea, then you can always add it.

If the manufacturer recommends against GFCI protection because of nuisance tripping issues, then you can add GFPE. You could even have a residual current detector connected to a recording meter and watch for trends in leakage current.

-Jon

 

[tom baker]

I would suggest reviewing 682.15 GF protection. This article is for bodies of water, does not strictly apply, but it does suggest 30 mA GF protection, and 682.14 for submersible equipment requires extra hard usage cord with W suffix.
If I a proposal was made for GFCI protection for this type of equipment in the 2026 NEC, I am confident the code panel would accept it, based on the the changes in the 2021 NEC for GFCI protection, on ranges and dryers.

 

[bheller]

Zbang, happy to post a link: https://kascomarine.com/product/certisafe-mixers/

Winnie, you have it backwards. The manufacturer recommends the GFCI. The end user does not want them due to nuisance tripping. Thanks.

Tom, I'll review 682.15 again, but you're right, it doesn't really apply. Zbang gave me the backup I was looking for. 110.3B covers this situation. if the manufacturer says the control panel should be fed with a GFCI, then a GFCI is required.

Thanks everyone for the input.

 

[tom baker]

I like the mixer, its very high quality and has the appropriate listings. Re: Nuisance tripping, the GFCI trips between 4-6 mA and if it trips what is the actual leakage current? 10, 20 mA? Potable water is not a good conductor, so could the tank and water become energized?
I had a lot of sample pumps for turbidimeters that ran on GFCIs, there were issues with tripping. When I megged the motor it had leakage that would cause the GFCI to trip. For the operators it was a defective GFCI, explaining ohms law for the current leakage was not useful. In that case, it would of been simple to put a current sensor on the pump, monitor the voltage to the pump with a relay, or an alarm GFCI.

 

[winnie]

Winnie, you have it backwards. The manufacturer recommends the GFCI. The end user does not want them due to nuisance tripping. Thanks.

I did have it backwards. What I've seen is manufacturers saying 'don't use GFCI' because they thought it was too hard to design a system that didn't have leakage current.

IMHO if a modern piece of equipment is leaking current, that equipment is broken. If the manufacturer is making good enough equipment that they are recommending GFCI, then I would use it. If the manufacturer requires GFCI, then code requires it. But if it is simply a recommendation, then GFCI becomes a design decision.

IMHO if the manufacturer is recommending GFCI, the pump is installed in a fashion that leakage current is not a life safety issue, and the customer wants to avoid what they consider nuisance tripping, then I would recommend some sort of ground fault reporting. My reasoning is that if the manufacturer is recommending GFCI, then any leaking occurring is a great warning of an incipient failure.

-Jon

 

[bheller]

Agree totally. Thanks