Sewer Pump control panel install question

[elecmen]

Is explosion proof seal off fittings required between the control panel and the pump chamber per NEC? I work at several manufactured home communities. One community pumps to city sewer lines has huge 3 phase pumps and has explosion proof seal off fittings between pump panel and pump chamber. The other communities pump up to leach fields and have private septic systems. These systems do not have explosion proof fittings installed.These are smaller single phase systems. Are they required for just the city sewer system or for that matter at all. This make replacing floats and pump feeds impossible without splicing them. Please advise. Thanks

 

[darkov]

Explosion proof seal or fitting is required only in hazardous locations.
Are any hazardous materials stored around pump? If not, the answer is no.

Sent from my SGH-M919 using Tapatalk

 

[ActionDave]

There are ten sewer lift stations in my fair city. I have worked on all of them, this includes the one at the wastewater treatment plant. None of them have seal offs and I see no reason for them. Sewer gas is smelly but it's not explosive.

 

[augie47]

NEC requires explosion proof wiring including seal offs when the pump area is Classified. Whether it's classified or not is an engineering function not a NEC or electrician call.
Most of the installs in this area with pumps exceeding 1 HP are classified whereas the single family/duplex life stations are not.
On the larger systems there should be factory or local drawings available to detail the Classification.
IF explosion proof seal-offs are not needed, most manufactures recommend some type of sealing (such as duct seal) to reduce the
intrusion of corrosive fumes entering the controller.
You are dealing with a potentially dangerous situation and should verify the requirements with the factory and/or an engineer.

 

[augie47]

There are ten sewer lift stations in my fair city. I have worked on all of them, this includes the one at the wastewater treatment plant. None of them have seal offs and I see no reason for them. Sewer gas is smelly but it's not explosive.

I respectfully disagree with that statement.

 

[ActionDave]

I respectfully disagree with that statement.

Sure, if someone classifies the area then I would do everything according to code and specs. However, I have not seen a sewer gas concentrated enough that it would be explosive in any sewer lift station. Just going off my experience.

 

[augie47]

Sure, if someone classifies the area then I would do everything according to code and specs. However, I have not seen a sewer gas concentrated enough that it would be explosive in any sewer lift station. Just going off my experience.

Thanks.That makes me feel better I'm surprised you have not seen the requirement especially on treatment plants.
Maybe the still remnants make TN sewage more explosive

 

[ActionDave]

Thanks.That makes me feel better I'm surprised you have not seen the requirement especially on treatment plants.
Maybe the still remnants make TN sewage more explosive

No stills here. Lots hydroponics and grow lights. Different kind of classified area not covered in an of the 500 articles.

 

[Fulthrotl]

Is explosion proof seal off fittings required between the control panel and the pump chamber per NEC? I work at several manufactured home communities. One community pumps to city sewer lines has huge 3 phase pumps and has explosion proof seal off fittings between pump panel and pump chamber. The other communities pump up to leach fields and have private septic systems. These systems do not have explosion proof fittings installed.These are smaller single phase systems. Are they required for just the city sewer system or for that matter at all. This make replacing floats and pump feeds impossible without splicing them. Please advise. Thanks

every lift station i've ever done, has been CL I, Div I.

they have been small 3 phase 208 volt pumps, but if
you have methane gas present in the right concentrations,
it burns right nice.

and the first thing on the pipe leaving the classified area
must be the seal off. no couplings, j boxes etc. otherwise,
a listed box could be used to make changing components easier.
no such luck.

 

[augie47]

every lift station i've ever done, has been CL I, Div I.

they have been small 3 phase 208 volt pumps, but if
you have methane gas present in the right concentrations,
it burns right nice.

and the first thing on the pipe leaving the classified area
must be the seal off. no couplings, j boxes etc. otherwise,
a listed box could be used to make changing components easier.
no such luck.

Allow me to present a scenario:\
Take a look at 501.10(B)(1)(1) then back to 501.10(A)(1) Exception....
Does this not allow you to use PVC encase in a 2" concrete envelope 24" be,low grade (with the other requirements) ?
Most of our pit entries are 24" below grade so some contractors have taken advantage of this exception to use a section of PVC installed per that section to keep from field cutting and threading GRS.
Acceptable ?

 

[rbalex]

I wish folks would put questions like this in the Hazardous (Classified) Locations forum.

What has been correctly stated so far is that sealing will depend on how the location is classified; however, neither Article 500 nor any other Article in the NEC will directly tell you how to classify in this situation.

Section 500.4(B) IN No. 2 refers to NFPA 820, Standard for Fire Protection in Wastewater Treatment and Collection Facilities. It covers the full range of wastewater treatment and collection facilities. It may or may not be locally adopted, but failure to comply with it will usually leave the facility's owner open to liability because it is still a nationally recognized safety standard. The most common would be an insurance carrier's refusal to cover damages.

One of the most commonly misunderstood concepts for Division 1 is that it is not always, or necessarily even often, hazardous. Hazardous conditions only have to be possible during the normal operation of the facility.

Hazardous conditions range in parts per hundred, "smelly" conditions range in parts per thousand or even millions, so smelling it may not be hazardous but it could be. In fact, it may become most hazardous when you can no longer smell it.

 

[JFletcher]

I wish folks would put questions like this in the Hazardous (Classified) Locations forum.

What has been correctly stated so far is that sealing will depend on how the location is classified; however, neither Article 500 nor any other Article in the NEC will directly tell you how to classify in this situation.

Section 500.4(B) IN No. 2 refers to NFPA 820, Standard for Fire Protection in Wastewater Treatment and Collection Facilities. It covers the full range of wastewater treatment and collection facilities. It may or may not be locally adopted, but failure to comply with it will usually leave the facility's owner open to liability because it is still a nationally recognized safety standard. The most common would be an insurance carrier's refusal to cover damages.

One of the most commonly misunderstood concepts for Division 1 is that it is not always, or necessarily even often, hazardous. Hazardous conditions only have to be possible during the normal operation of the facility.

Hazardous conditions range in parts per hundred, "smelly" conditions range in parts per thousand or even millions, so smelling it may not be hazardous but it could be. In fact, it may become most hazardous when you can no longer smell it.

H2S is detectable by nose at like 0.5ppb. And you are correct, if you can't smell it, it's likely because the concentration has risen to the point where it deadens the nose, and you can no longer smell it. This is when people die.

I have read and heard of dozens of stories of people dying in confined spaces from gas build up, and more dying trying to rescue them but I've seen only one sewer explosion, and iirc, it was because of a natural gas leak into the system, which could happen anywhere. Digester explosions, otoh.... ever see what happens when a 90' 30 ton concrete lid blows off a tank? :blink:

The LEL of H2S and CH4 are 4 and 5%, respectively, or 4000ppm and 5000ppm. I agree with ActionDave; I've never seen a wetwell or lift station come close to those numbers, and even if they did, and there was ignition, it would be a flash, not a sustained fire.

eta: Mr Alexander, can you or one of the other mods move this topic to the Hazardous forum?

 

[rbalex]

H2S is detectable by nose at like 0.5ppb. And you are correct, if you can't smell it, it's likely because the concentration has risen to the point where it deadens the nose, and you can no longer smell it. This is when people die.

I have read and heard of dozens of stories of people dying in confined spaces from gas build up, and more dying trying to rescue them but I've seen only one sewer explosion, and iirc, it was because of a natural gas leak into the system, which could happen anywhere. Digester explosions, otoh.... ever see what happens when a 90' 30 ton concrete lid blows off a tank? :blink:

The LEL of H2S and CH4 are 4 and 5%, respectively, or 4000ppm and 5000ppm. I agree with ActionDave; I've never seen a wetwell or lift station come close to those numbers, and even if they did, and there was ignition, it would be a flash, not a sustained fire.

eta: Mr Alexander, can you or one of the other mods move this topic to the Hazardous forum?

I have no quarrel with either your or ActionDave's experience. However, NFPA 820 is based on the combined experience of many people in the wastewater industry. That's why it is a nationally recognized safety standard. It has a very comprehensive table of classified locations.

 

[kwired]

I suspect many municipal applications they over classify "just in case".

I have been in many livestock applications that are probably not much different in levels of methane present or maybe even worse in some instances, but ventilation is a must for animal health reasons and likely keeps the explosion potential of such gases at a minimal risk.

 

[tom baker]

We sleeve the pump cable from the submersible up to a j box on the outside of the WWLS. On the wall the cable is exposed, and protected by a SS guard. the connections are easily made in the j box. Its a simple but effective system, complies with the NEC, and makes replacing equipment easy. I will see if I can post a picture.
Never put a splice or j box in a wetwell, it will not last.