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#201793 - 06/24/11 12:25 AM sealing of cables in U/G sump pump installations
bigpapa Offline
Member

Registered: 03/18/06
Posts: 75
Loc: canada
Referring to a typical water sump with pumps and floats, there is always
a danger of gasses in below ground installations. When bringing the cabtire
cables out of the sump and into a connection box above ground I have seen
some engineers specify that the cables must be sealed with a hazardous
area type seal with the poured compound.

This is horribly impractical because the failure of one pump or float would
require replacing all the equipment in the sump because all the cables
would need to be cut.

In order to prevent underground or sewer gasses from entering the junction box
and traveling into the control equipment I have often run the cables out of the
side of the sump and direct buried them. They then enter the junction box using
the normal waterproof connectors. this is not practical either because the cable can be damaged with a shovel. Another way is a short stub of PVC conduit large enough for all the cables, usually 6, to get you below ground near the sump
and then the cables are direct buried from there. The top of the conduit in the junction box can be sealed with silicone or duct seal to keep the gasses out
of the electrical system.

None of this sounds legal to me and I wonder if there is a code and end user friendly way to install sump pump wiring so that I do not have to worry about a rejection.

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#201801 - 06/24/11 02:42 PM Re: sealing of cables in U/G sump pump installations [Re: bigpapa]
Gregtaylor Offline
Member

Registered: 03/02/05
Posts: 212
Loc: Boise, Idaho, USA
I'm not Canadian but the same issue applies here. I mount a jbox above the alarm level and bring all wiring, motor leads, floats etc. to that box then seal off in a UG box just outside the vessel. That way my float and motor leads don't pass through the EY.
The biggest problem I usually have with these systems is that even though I treat them as classified, the vessel and the controllers usually aren't listed for use as classified equipment. I don't know how that gets by inspectors.

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#201803 - 06/24/11 03:26 PM Re: sealing of cables in U/G sump pump installations [Re: bigpapa]
mikesh Offline
Member

Registered: 06/07/06
Posts: 614
Loc: Victoria, BC, Canada
This is a huge maintenance issue as it is required to seal the wiring from the controls for gas migration. One of the simplest ways is to install a JB in the well above the upper water line Use cab tyre connectors from the float to the JB and install the EYS for normal wiring at the hazardous boundry to a terminal strip in the JB.
you may need to use more than 1 JB as intrinsically safe wiring cannot run in the same raceway as the pump motor leads as just 1 example.

For small sumps where the motor lead and the pill switch leads are sealed from the switch or motor and it is next to impossible for gasses to enter the cable, the sump we have accepted the raceway get cut off say 1 inch from the floor and create an air gap above the 2" limit of the hazardous location and use duct seal there to prevent gas migration up the raceway that is only providing mechanical protection or a path from the sump to the outside. Some sumps are not hazardous until there are 6 or 7 units that spill into the sump. Some sumps are for sewage and some for surface water. there has to be several occupancies attached to a sewage pump before it is considered to be hazardous but the equipment is identical regardless, so often people assume all sumps are hazardous locations. Some are and some are not even though they may both use the same equipment.

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#201807 - 06/24/11 07:47 PM Re: sealing of cables in U/G sump pump installations [Re: mikesh]
bigpapa Offline
Member

Registered: 03/18/06
Posts: 75
Loc: canada
Im reluctant to put JBs in the well because they usualy either leak or the cover screws and cable connectors are destroyed by the environment.

I am wondering if there is anything wrong with running the pump and float cables above ground in a PVC conduit but stopping it a few inches from an above ground box and then entering them into the box individually each with it's own
cable connector. the top of the conduit could be sealed around the wires.

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#201842 - 06/27/11 11:27 AM Re: sealing of cables in U/G sump pump installations [Re: bigpapa]
mikesh Offline
Member

Registered: 06/07/06
Posts: 614
Loc: Victoria, BC, Canada
If the well is a hazardous location then you have to follow section 18 so the seal between the hazardous location has to be at the boundary and only an EYS meets the code for sealing. Clearly there is the challenge of how to change the switches and the pump without having to cut the EYS out and reworking all the wires. So yes putting a JB in the well is not always such a good choice for reasons of corrosion and not many sumps transition to a dry well from the wet well. Putting a JB right at the floor and sealing the wires between the JB and the controller can allow for field changes in the float switches or pump ahead of the EYS. This might be a great place for a couple of diagrams but I am artistically challenged and posting this stuff in a forum is outside my talents.

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#201847 - 06/28/11 05:19 AM Re: sealing of cables in U/G sump pump installations [Re: bigpapa]
twh Offline
Member

Registered: 03/11/04
Posts: 892
Loc: Regina, Sask.
Which rule makes a well a hazardous location?

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#201851 - 06/28/11 10:01 AM Re: sealing of cables in U/G sump pump installations [Re: bigpapa]
bigpapa Offline
Member

Registered: 03/18/06
Posts: 75
Loc: canada
sewage sumps, parking garage sumps are two examples

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#201862 - 06/28/11 06:35 PM Re: sealing of cables in U/G sump pump installations [Re: bigpapa]
twh Offline
Member

Registered: 03/11/04
Posts: 892
Loc: Regina, Sask.
Perhaps I don't understand the problem. Teck cable doesn't need to be sealed at the boundary, and I'm not aware of other cable being treated differently. I thought the proper procedure was to take the cable out of the area to terminate it. The seal is on the device end in the pit with no seal on the safe end. When a seal is put on a cable, a union is usually installed between the seal and the device requiring the seal, to allow for easy removal. What am I missing?

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#201863 - 06/28/11 07:05 PM Re: sealing of cables in U/G sump pump installations [Re: bigpapa]
bigpapa Offline
Member

Registered: 03/18/06
Posts: 75
Loc: canada
The electrical wiring outlet on most sumps of this type is below ground. There needs to be a conduit of some kind from the sump to the controller box to draw the cables through. If the sump was in the driveway of a parkade for example you need a conduit. When the sump is classified as a hazardous area the conduit has to be sealed saying bye bye to all 7 cables if one float needs to be changed. Might as well throw out both pumps and all the other floats too because you can't splice thier cables.

In order to avoid this I am questioning whether it is legal to end the conduit before the controller and use individual cabtire connectors for each float or motor where the wires enter the controller which would be above the hazardous layer.

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#201865 - 06/28/11 08:37 PM Re: sealing of cables in U/G sump pump installations [Re: bigpapa]
twh Offline
Member

Registered: 03/11/04
Posts: 892
Loc: Regina, Sask.
Your suggestion is the way that it's done. Some inspectors might want you to use a water line just to be clear that it's mechanical protection and not a raceway. Be aware that your duct might change the classification of the area that it enters, unless it's sealed. Even if you do seal the duct, it doesn't need to be chico. Table 8 is for tubing fill for multi-conductor cables, unless the raceway is short.

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