Electrical Connection Methods in Wet Well Design
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Electrical Connection Methods in Wet Well Design
In pump station system design, it is common for some aspects of the electrical design to be given less than adequate attention. This article focuses on electrical connection methods. Specifically, the designer must consider the connection of electrical equipment inside the underground wet well to the above-ground electrical control system. In wastewater pump stations, the wet well is classified as a hazardous area, due to the potential build-up of explosive gas. Egress of electrical cables from the wet well can be tricky business, since there are a variety of ways to run the cables and make electrical connections. Romtec Utilities has devised three methods for electrical connection; direct connection, above-ground junction box and below-ground junction box.
Direct Connection
A direct connection is defined as conduits that run from the inside of the wet well directly to the electrical control panel. The advantage of the direct connection method is simplicity. Just before entering the panel, seal-offs are installed to prevent migration of hazardous gas from the wet well (when classified as hazardous area). The seal-offs would be omitted in unclassified systems.
When choosing the direct connection method the mounting location of the control panel is restricted by the maximum length of the cables on the pumps and floats. Standard cable lengths are 50 feet. Longer lengths up to 100’ can be special ordered. Remember to consider the wet well depth when determining the distance between the wet well and control panel.
Below-ground Junction Box
The below-ground junction box from Romtec Utilities contains components to meet hazardous area requirements and at the same time provides ease of maintenance without having to defeat seal-offs. See photo of the interior of a typical Romtec Utilities below-ground junction box. Consider this method when:
• The wet-well is classified as a hazardous area.
• The control panel is mounted over 25 to 30 feet from the wet well.
• The wet well is located in a high traffic area.
• Removing pumps or float without defeating seal-offs is required.
Above -ground Junction Box
The above-ground junction box from Romtec Utilities combined with the cable tray provides the most user friendly method of pump and level sensor connection. In addition to meeting most hazardous area requirements, the above ground junction box is impervious to ground flooding or corrosion. See photo of the Romtec Utilities above-ground junction box. Consider this method when any of the following statements are true:
• The wet-well is classified hazardous area.
• The control panel is mounted over 25 to 30 feet from the wet well.
• Removing pumps or float without defeating seal-offs is required.
• Ground water or flooding is expected.
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