Explosive area question

[SparkyJunior]

I work in the water/wastewater industry and I have a situation where an existing pullbox (not explosion proof) is mounted above grade of a wetwell. the wetwell is a classified area and above the wetwell is unclassified. There are conduits running from the pullbox box through the concrete roof and the cable is then connected to the motor in the wetwell. There are "seal offs" on these conduits that make removing the cable very difficult.

I am replacing the conduit entering the wetwell because it was previously sized too small. I will also be designing a new pullbox to be installed to accomodate the larger conduit. Is it possible to use a non-explosion proof junction box without seal offs on the conduits? I have heard the use of non-hardening putty, but this, I believe, is a code violation.

Any advice or direction would be appreciated.

 

[dpc]

Raw sewage wetwells are generally classified Class 1, Division 1 in the US. For any conduit leaving the wetwell, you will need sealing fittings per NEC 501.5(A)(4).

BTW, any room or enclosed area directly adjacent to a Class 1, Div 1 area has to be classified as Class 1, Div 2, unless the exceptions noted in the NEC are met.

In years past, wetwells were not always treated as a Class 1, Div 1 area, so any retrofit electrical work in these areas can open up a real can of worms since anything you touch will have to be brought up to current codes.

NFPA 820 covers classification of hazardous areas in waste water facilties, I believe.

 

[alehman]

As dpc eluded, past practice was generally not to strictly enforce classificaiton of wetwells. I think partly because the NEC was not entirely clear. Large pump cables frequently will not fit in any standard conduit seal. Also, they must be removed periodically. In the past I've used a large non-classified and well ventilated Quazite box adjacent to the wetwell with duxseal around the cables. The idea was that any gas that gets past the duxseal would be adequately vented to the atmostphere from the pull box. Now this will apparently not be permitted.

 

[panou]

Hello to all.
I am looking for the operating temperature limits of electrical installation equipments. From the manufacturers manuals it is indicated only the maximum permissable ambient temperature. From other web sources i have seen that there is a direction reference to a term called temperature rise (DT). Can ypu please give me some links to internet for standards or manufacturer data with these references, e.g. what is the maximum operating temperature of contacts or of a coil in a contactor or a circuit breaker ? Thanks in advance for your time.

 

[alehman]

panou: please start a new thread for a new topic.

 

[LKOT591]

SparkyJunior,

This has been a problem for several technicians I have worked with. Breaking the seal every time a pump has to be pulled has typically resulted in the seal fittings not being properly installed. What we have changed over to is the following:

Route conduits from the wet well to a NEMA 4X 316 Stainless Steel junction box. The 316 stainless steel is more resistant corrosion caused by the H2S and moisture.

Inside the j-box mount corrosion resitant terminal/splice blocks(Allen Bradley 1492 Series is what I specify). Connect the submersible pump cable to these non-arcing / non-sparking terminal blocks.

Route the proper power & control field wiring and conduit from the j-box to the motor controller. In the conduit between the j-box and your motor controller install the conduit seal fitting on the field wiring which is not replaced or modified very often, if at all.

The field wiring will need to be tin-plated due to the H2S typically present in the wet well. To reduce the moisture in the j-box you can seal around the pump cable with duct seal. and be sure to install a panel breather to let the moisture out of the j-box.

I hope this helps.