(A) Submersible non-clog pumps.
(1) The pumps shall be a submersible, non-clog type made of heavy cast iron construction. The volute shall have smooth fluid passages capable of passing a three-inch minimum solid sphere. A bronze wear ring shall be pressed into the casing for guiding the impeller and to prevent corrosion. Wear rings shall be held from rotating by stainless steel set screws.
(2) The pump impeller shall be of an enclosed, two-vane, non-clog type made of cast iron and shall be properly balanced. Vane inlet tips shall be rounded to prevent stringy materials from catching on the vanes. The impeller shall be driven by a stainless steel shaft key and secured to the motor shaft by a stainless steel lock screw and washer.
(3) The motor shall be protected by two mechanical seals mounted in tandem with a seal chamber below the seals. Seal faces shall be made of carbon and ceramic. A double electrode shall be mounted in the seal chamber to detect water entering the chamber. Water in the chamber shall trigger an alarm condition as specified in the control panel.
(4) The pump motor shall be of the sealed, submersible type. Motor voltage shall be as available, and the horsepower shall be sized so as to ensure a non-overloading condition along the entire pump-impeller curve. Stator winding shall be of the open type with Class F insulation good for operating temperatures of at least 300ºF. The winding housing shall be filled with a dielectric oil which lubricates the bearings and seals.
(5) The pump motor shall have two heavy-duty ball bearings to support the pump shaft and to take radial and thrust loads. Ball bearings shall be designed for 50,000 hours B-10 life.
(6) A heat sensor thermostat shall be embedded in the winding and connected in series with the motor-starter contact coil so as to stop the motor upon high temperature. The thermostat shall reset automatically when the motor cools to a safe operating temperature.
(7) Pumps shall be supplied complete with fiberglass or aluminum guide rails and a cast iron base flange which allows for positive seating of the pump.
(B) Lift station control panel.
(1) Pump station controller. The pump manufacturer shall furnish an automatic pump station controller for the operation and control of the lift station pumps. The control panel shall provide automatic alternation of a duplex pump system and shall be complete with motor control, solid-state alternator, convenience power supply, miscellaneous controls and the like. All components shall be UL listed.
(2) Control and power wiring. The control and power wiring for the pumps and level sensors shall be arranged to extend through two separate conduits to the wet well. Conduits shall be properly sealed to protect the panel against explosive-type gases which may exist in the wet well.
(3) Panel enclosure. The enclosure shall be NEMA 4X with drip shield, 14- gauge stainless steel minimum with welded construction. The enclosure shall have an outer weather door, a hinged inner “operator’s door” and mounting hardware. All equipment, controls and the like shall be located inside of the enclosure. Selector switches, pilot lights and the like shall be located on a dead front swing-out panel, or operator’s door, located behind an outside weather door. All other equipment, exposed wiring and the like shall be located behind the swing-out panel.
(4) Controller features.
(a) The operating sequence:
1. When a pump is called for by the water level in the wet well, the control unit shall send a start signal to the appropriate pump and verify operation with the starter auxiliary contact. Appropriate verification time delays shall be included;
2. When the wet well level continues to rise, the second pump shall start;
3. When the wet well level reaches low level, the pump or pumps shall stop and pump alternation shall occur; and
4. When the pump-run verification signal is not received within the appropriate time period, the alternator shall deselect the failed pump, select the next pump, remove the failed pump from the sequence and illuminate a pump-fail light. The failed pump shall remain out-of-service and the pump-fail light shall remain illuminated until manually reset.
(b) Circuit breakers with over-current protection for each of two pumps and the convenience power transformer. Circuit breakers shall be a magnetic-hydraulic or a thermal-magnetic, ambient temperature compensated-type calibrated and factory sealed with the proper trip settings. The devices shall have a minimum interrupting rating of 10,000 RMS symmetrical;
(c) Magnetic, full- voltage starters for each of two pumps. The starter overload relays, one per phase, shall be an ambient-compensated, quick-trip type. Overload elements shall be matched to the pump motor characteristics;
(d) A convenience and control power transformer with a 120/240 volt secondary where required due to three-phase service. Said transformer shall be supplied in the panel. Circuit breakers shall be supplied for the transformer, pump controls, condensate heater and GFI receptacle. Circuit breakers shall be accessible without opening the dead front “operator’s door”;
(e) A GFI-type duplex convenience receptacle, 120V or 20A. Said convenience receptacle shall be provided at the lift station outside of the control panel as shown on the details in Appendix A of this chapter;
(f) A low-volt power supply and interface system. Said supply and system shall be suitable for operation of the float switches in an intrinsically, or explosion-proof, safe mode;
(g) An adjustable, thermostatically-controlled heater. Said heater shall provide condensate protection inside the enclosure;
(h) Two-pump automatic electronic alternator. Said alternator will alternate the pumps with each pump down-cycle;
(i) Running-time meters for each pump. The meters shall indicate the number of hours of pump operation. The meters shall be enclosed in a dustproof and moistureproof, molded-plastic case. The flush-mounted dial shall register in hours and tenths of hours up to 999.9 hours before repeating;
(j) The control panel. Said control panel shall provide status and alarm indications for each pump, namely a “pump running” light (green), a “pump failed” light (red), “seal failure” and “high wet well level”. In addition, the panel shall have a Hand-Off-Auto selector switch for each pump to control the mode of pump operation and to time modules as required for the pump-failed feature; and
(k) The local alarm system. Said system shall consist of an alarm light and shall signal any of the alarm conditions in division (B)(4)(j) above. The light shall be a weatherproof, high-intensity strobe fixture with a red lexan globe and a metal globe guard mounted on top of the enclosure.
(C) Level sensors.
(1) The level sensors shall consist of weighted floats with mercury contacts rated for low-volt operation at milliwatt levels. Each level sensor shall be furnished complete with sufficient cable length to run to the terminal box below the pump station controller and to leave slack for future level adjustments;
(2) Floats shall meet the requirements for Class 1, Division 1, Groups C and D and be intrinsically safe for installation in an explosion-hazard environment; and
(3) Furnish a stainless steel bracket mounted in the hatch opening for hanging the sensor cables.
(Ord. 2010-3, passed 10-6-2010)