Electric Golf Cart Facility

[scott_walowsky]

- Is this a Class I Division 2 location? I'm struggling with how to design this facility.
- The batteries in the golf carts give off hydrogen when charging, mostly after they're fully charged. According to my calculations (with numbers from the battery manufacturer) the hydrogen concentration in my building will reach explosive concentration (4%) within 11.3 hours if there's no ventilation. There is definitely ventilation under normal operation. So, this sounds exactly like what is described in NEC 500.5(B)(2)(2).
- If it is indeed CID2, then why are the chargers manufactured with common "household" plugs on the 120VAC cord? NEC 501.145 requires something much more sophisticated. I seriously doubt that the chargers themselves are listed for use in a classified location. The plug at the end of the DC cord, which plugs into the golf cart, is also suspect.
- If it is CID2... The lighting fixtures, switches, fan motors, blah, blah, blah, will all have to be listed for use in classified locations. Typical power tools won't be allowed for maintenance on the golf carts.
- I'm not a golfer, so I haven't seen this type of facility before. I've obviously got some phone calls to make and maybe some site visits, too. If anybody has some experience and/or advise on this topic I'd love to hear it.

 

[rbalex]

It is not Class I, Division 2. In fact, unless there is something in addition to batteries involved, it is fundamentally prohibited from being classified. See Section 480.9(A).

 

[Rampage_Rick]

I've got a copy of the Club Car storage facility design manual. I looked on their website but can't seem to find the original. From the manual:

Recommended Storage Facility Electrical Requirements
120/240 Single Phase and/or 120/240 Two or Three Phase
Number of cars ? 10 amps ? 2
Example: (72 cars) 72 ? 10 ? 2 = 360 amp service required

120/208 Three Phase
Number of cars ? 10 amps ? 3
Example: (72 cars) 72 ? 10 ? 3 = 240 amp service required

Recommended Storage Facility Ventilation Requirements
Club Car recommends a minimum of five air exchanges per hour in a golf car storage facility. This value has been the historical industry standard apparently based on experiences. The charge facility ventilation system needs to provide enough fresh air to insure that the hydrogen gas concentration will never exceed 2% by volume.
To estimate battery gassing by calculation, we used a published value of .418 liters hydrogen/amp-hr for each battery cell. For our 48-volt system we have the following characteristics:

Charge finish rate: 4 amps
Number of cells on 48 V system: 24
Gassing Flow Rate = .418 liters/amp-hr-cell ? 4 amps ? 24 cells = 40.13 liters/hour

The gassing only occurs at this rate during the final portion of the charge cycle. Depending on the depth of discharge, this time period will vary. The deeper the discharge, the longer the gassing event.

If you assume a 30 minute finish = 20 liters/car total volume
If you assume a 1 hour finish = 40 liters/car total volume

The total volume is not as important as the gas flow rate. The flow rate is what will determine the gas concentration level at any given time. Note that this flow rate is only valid for the PowerDrive™ 48-volt charging system that has a constant current finish and will not change as the batteries age.

**edit** I found the PDF on my computer. Here you go

 

[dereckbc]

There are no classified requirements. I have yet seen a golf cart garage sealed up. The biggest thing you have to worry about is a very large service and dedicated circuits for the chargers because they all get charged at the same time when they close and pull the carts into the shed and hook them up at the same time.

Golf cart batteries are sealed batteries (VRLA) and do not emmit hydrogen gas under normal conditions.

 

[Rampage_Rick]

Uhhh, we have a fleet of ~85 electric Club Car Precedents and I can tell you that they do emit hydrogen. Ours have four 12V 120Ah Trojan T1275 deep-cycle batteries.

In addition to the electrics we have another ~35 gas Precedents. Basically it comes down to economics. A round of golf in an electric costs $0.60 whereas the same trip in a gas cart costs $6.00. The electrics can only make one round a day, two if the charging cycles are carefully planned (8-hour turnaround) The gas carts are good to go, as the turnaround time is nothing more than a wash and a fill-up if necessary.

 

[petersonra]

- Is this a Class I Division 2 location? I'm struggling with how to design this facility.
- The batteries in the golf carts give off hydrogen when charging, mostly after they're fully charged. According to my calculations (with numbers from the battery manufacturer) the hydrogen concentration in my building will reach explosive concentration (4%) within 11.3 hours if there's no ventilation. There is definitely ventilation under normal operation. So, this sounds exactly like what is described in NEC 500.5(B)(2)(2).
- If it is indeed CID2, then why are the chargers manufactured with common "household" plugs on the 120VAC cord? NEC 501.145 requires something much more sophisticated. I seriously doubt that the chargers themselves are listed for use in a classified location. The plug at the end of the DC cord, which plugs into the golf cart, is also suspect.
- If it is CID2... The lighting fixtures, switches, fan motors, blah, blah, blah, will all have to be listed for use in classified locations. Typical power tools won't be allowed for maintenance on the golf carts.
- I'm not a golfer, so I haven't seen this type of facility before. I've obviously got some phone calls to make and maybe some site visits, too. If anybody has some experience and/or advise on this topic I'd love to hear it.

It is very hard to contain hydrogen. My guess is that your golf cart facility does not actually rely on the fan forced ventilation to prevent explosive concentrations of hydrogen so 500.5(B)(2) would not be an issue.

 

[scott_walowsky]

Conclusion!

Conclusion!

- To me, it's still a bit of a gray area. However, I've come to an agreement with the AHJ; rather easily, in fact. Here is the argument I presented to the AHJ. In the end, there doesn't seem to be any NEC article that 100% fits this situation. One could even argue that 511 doesn't apply because the golf carts are not gaseous-fuel vehicles; this is more than likely intended to mean gasoline, propane, etc., but I wasn't able to come up with anything better.

- I knew all along that golf cart facilities are not built using explosion proof devices. Besides, the golf carts, the chargers, any common electric hand tools, etc. would not be allowed inside of a Class I Division 2 location because they are not listed for use in such a location. So, I knew the answer all along, I just needed to find something to back it up before I could sign my name to it.

- Anyway, for those of you on the edge of your seat waiting to hear what had happened with this delima, this is the information I sent to the AHJ. He was very happy to allow the facility to be unclassified.



1. Article 480 doesn't apply to our golf cart facility. It is intended for stationary storage batteries; our batteries are not stationary. But, 480.9(A) requires that provisions be made for sufficient ventilation of the gases from the battery to prevent the accumulation of an explosive mixture. We have sufficient ventilation.

2. 500.5(B)(2)(2) defines a Class I Division 2 location as a location in which ignitable concentrations of gases are normally prevented by ventilation but might become hazardous through failure of the ventilating equipment. This describes our golf cart facility.

3. 511.3(A)(7) says that where lighter-than-air gaseous fuels vehicles are stored, the area within 18 inches of the ceiling shall be considered unclassified where ventilation of at lease 1cfm/sqft of ceiling area is provided. More than this minimum ventilation is provided. And this removes the requirements of a Class I Division 2 location eluded to above in 500.5(B)(2)(2).

4. Article 625 doesn't apply to our golf cart facility. It is intended for electric vehicles, but specifically excludes golf carts. Even though, 625.29(D)(1) requires ventilation as listed in Table 625.29(D)(2). That table requires 49cfm of ventilation for each electric vehicle. More than this minimum ventilation is provided.

The ventilation in our golf cart facility works like this:
- There are 3 exhaust fans that pull fresh air into the building from the west side of the building and exhaust out to the east side. Each fan is 1HP and 3180cfm. One fan is always running. The 2nd and 3rd fans are controlled by hydrogen sensors that are mounted in the ceiling. If any one of the sensors reads 1% hydrogen concentration the 2nd fan starts, at 2% the 3rd fan starts. Hydrogen can become flammable at 4%. We're keeping the concentration at a maximum of half the flammable concentration.
- So, even though some of these NEC articles aren't obviously applicable to our project, we've met the ventilation requirements of all of them.

 

[rbalex]

...
The ventilation in our golf cart facility works like this:
- There are 3 exhaust fans that pull fresh air into the building from the west side of the building and exhaust out to the east side. Each fan is 1HP and 3180cfm. One fan is always running. The 2nd and 3rd fans are controlled by hydrogen sensors that are mounted in the ceiling. If any one of the sensors reads 1% hydrogen concentration the 2nd fan starts, at 2% the 3rd fan starts. Hydrogen can become flammable at 4%. We're keeping the concentration at a maximum of half the flammable concentration.
- So, even though some of these NEC articles aren't obviously applicable to our project, we've met the ventilation requirements of all of them.

Which protection technique listed in Section 500.7 applies? If you insist 500.5(B)(2)(2) applies, it is still a Class I, Division 2 location. The ventilation only prevents it from being Division 1.

 

[scott_walowsky]

- My interpretation is that 500.7 does not apply at all and neither does 500.5(B)(2)(2). The reason is that my interpretation of 511.3(A)(7) says that the area "...shall be considered unclassified..." So, not only does this take it out of the realm of Division 1, but this takes it out of the realm of all Divisions and all Classes. But, this is merely my interpretation.

- Besides my interpretation, the AHJ for this one specific project has deemed this area to be unclassified. Since the AHJ has agreed that the area will be considered unclassified, then my design is not required to include any hazardous location treatments.

 

[bobgorno]

I would make sure your ventilation is adequate based on calcs and safeguarded against failure. Relying on hydrogen sensors is only as good as your maintnenance and calibration program.

Maybe you can find guidance in the IBC or IFC. API RP500 has a seciton on batteries that can help guide from a "common sense" aspect.

Bob G.

 

[rbalex]

I have no objection to the location being unclassified. I said it was unclassified in my original post.

I would remind you it was your previous post that said:

…
2. 500.5(B)(2)(2) defines a Class I Division 2 location as a location in which ignitable concentrations of gases are normally prevented by ventilation but might become hazardous through failure of the ventilating equipment. This describes our golf cart facility.
…

[rba note: underline added]

I simply pointed out, if it describes your facility, then it is Division 2. Fortunately, it doesn’t describe your facility.

The installation is within the scope of Article 480 (Section 480.1). The batteries are storage batteries by definition (Section 480.2) and they are not being charged while they are in motion as they would be in an automobile; i.e., they are stationary.

The installation is not within the scope of Article 511 at all, so Section 511.3(A)(7) does not apply. More to the point, any hydrogen present is a byproduct of the process – it isn’t a “fuel.”

You are correct about Article 625.

If you want to get highly technical, do a "Fugitive Emissions" calculation (NFPA 30, Annex F) and you will find you won’t generate enough hydrogen to worry about. In other words, the hydrogen sensors are a waste of money and they don’t meet the requirements of Section 500.7(K) anyway.

Edited spelling and grammer (hopefully) and added the underline note above.

 

[scott_walowsky]

480:
- I'm still not convinced that this project is within the scope.
- 480.1 Scope: The provisions of this article to all stationary installations of storage batteries.
- I don't agree that a golf cart parked inside a building qualifies as a stationary installation. If I drive a golf cart into a building, have I installed it? Is it now stationary? I don't know.
- Regardless, I think we've met the requirements of 480.9(A).

511:
- I still think 500.5(B)(2)(2) does describe this project.
- "In which ignitable concentrations of gases or vapors are normally prevented by positive mechanical ventilation and which might become hazardous through failure or abnormal operation of the ventilating equipment..."
- But my argument to the AHJ is that 511.3(A)(7) subtracts the classification that is added by 500.5(B)(2)(2).
- I have also noted that I'm not completely convinced that 511 is truly applicable (the fuel thing). But, the battery is the power source (sorta like a fuel) and it is this battery that emits the hydrogen.

But, I still don't know.
- 511 and 480 are certainly the most appropriate things I've found in the NEC. Both of them have similar requirements. I guess the best reasoning I can come up with for 511 over 480 is that 480.9(A) calls for "sufficient diffusion and ventilation," while 511.3(A)(7) calls for "at least 1cfm/sq ft." I have a number I can fall back on from 511, but not from 480.
- I've talked this over with a few different people. I still haven't seen anything specific in the NEC that is without a doubt the rule for this situation. Everybody seems to agree that the building is designed as it should be.
- The important things are that I'm confident that the building will operate safely and so is the AHJ and the AHJ has approved the design.

 

[rbalex]

Basically, you are grossly overdesigning and wasting money with your hydrogen sensor design; however, since you never needed to classify the installation in the first place for any reason, you are not creating a safety hazard and you have your AHJ?s blessing ? so I have nothing to say beyond what you have already refused to listen to.

Electrical area classification is neither rocket science nor trivial; but done properly, it takes a fair amount of experienced judgment.

 

[weressl]

I've got a copy of the Club Car storage facility design manual. I looked on their website but can't seem to find the original. From the manual:



**edit** I found the PDF on my computer. Here you go

Note that the manufacturer's instructions do not over-ride 480. Take into consideration that not all batteries are charged at the same time and the rate of gassing varies. I would consider these stationary batteries as the are not moving:grin: while being charged.

Roof vents at the high points of the structure are sufficent to allow even the remotest possibility of gas accumulation and most of the cart charging facilities I have seen are constructed so.

I think Bob had summed it up nicely and conscisely as always.