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

2. 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

3. 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

4. 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

5. 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

6. 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

7. FIGURE 19-1 Components of a jet pump. © Cengage Learning 20157 4

8. 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

9. FIGURE 19-3 Submersible pump. © Cengage Learning 20156

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

11. 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

12. 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

13. 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

14. 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

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

16. 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

17. 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® (E) states how to size the overcurrent device

18. 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

19. 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

20. 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