Special-Purpose Outlets—Water Pump, Water Heater Chapter Nineteen Special-Purpose Outlets—Water Pump, Water Heater

Objectives After studying this chapter, you should be able to: Understand the operation of jet pumps, submersible pumps, and their components Understand the operation of electric water heaters and their components

Objectives (cont’d.) Be familiar with the NEC® requirements for designing the branch circuit, including conductors, cables, raceway, motor branch-circuit short-circuit ground-fault and overload protection, disconnecting means, and grounding for water pumps and electric water heaters

Objectives (cont’d.) Figure out various electrical connections for “Time-of-Use” metering Calculate the effect of voltage variation on heating elements and motors Understand the hazards of possible scalding Discuss heat pump water heaters

Water Pump Circuit In rural areas where there is no public water supply, dwellings need their own water supply For the most part, submersible pumps dominate the residential market

Jet Pumps A jet pump creates downward pressure that forces water up a discharge pipe into a water tank The jet pump continues until tank pressure reaches 40 psi When the tank pressure falls below 20 psi, the pump restarts

FIGURE 19-1 Components of a jet pump. © Cengage Learning 2015 7 4

Submersible Pumps Consists of a centrifugal pump driven by an electric motor The pump and motor are contained in one housing The pump is located at the bottom of a deep well pipe below the water line The pump is controlled by a disconnect switch, pressure switch, and limit switches located near the water tank

FIGURE 19-3 Submersible pump. © Cengage Learning 2015 6

Motor Circuit Design NEC® Table 430.52 lists different types of protection for motors If values in Table 430.52 are not at standard size, it is acceptable to select the next higher rating

Motor Circuit Design (cont’d.) Motor Overload Protection Overload protection keeps the motor from dangerously overheating Common installations require motor overload protection not to exceed 125 percent of FLA

Motor Circuit Design (cont’d.) Disconnecting means The NEC® requires all motors to have a means of disconnect from electrical supply Common installations require motor overload protection not to exceed 125 percent of FLA Disconnect must be in sight 50 ft (15m) of controller and motor

Grounding Proper grounding of the well casing and submersible pump motor will minimize or eliminate stray voltage problems PVC water piping is often used today Sometimes a grounding electrode conductor is required between the neutral bar of the main service disconnecting means and the well casing

Water Heater Circuit Typical wattage ratings range from 1500 watts to 5500 watts Electric water heaters use a resistance heating element to raise water temperature

FIGURE 19-5 Typical electric water heater showing location of heating elements and thermostats and electrical connection. © Cengage Learning 2015 15 7

Water Heater Circuit (cont’d.) Combination controls regulate the temperature of the water Scalding water is avoided by an upper temperature limit of 120°F Water heaters need a 240-volt circuit

Electric Water Heater Branch Circuits NEC® classifies the water heater to be a continuous load (422.13) Branch-circuit rating must not be less than 125 percent of the nameplate rating NEC® 422.11(E) states how to size the overcurrent device

Effect of Voltage Variation on Resistive Heating Elements Heating elements in the water heater in this residence are rated 240 volts A resistive heating element will only produce rated wattage at rated voltage Always use rated voltage to calculate the resistance, current draw, and wattage of a resistive heating element

Effect of Voltage Variation on Motors Formulas for inductive circuits such as an electric motor are complex NEMA rated electric motors are designed to operate at ±10 percent of their nameplate voltage

Heat Pump Water Heaters Residential heat pump water heaters can save 50 to 60 percent over resistance-type electric water heaters The heat energy transferred to the water is three to four times greater than the electrical energy used Work in conjunction with resistance-type electric water heaters