Many types of hot water heaters have electrical circuits; however, an electric hot water heater gets its name because it uses electrical power to perform the work of heating the water. Several different systems in a standard electric hot water heater work together so that the heater can perform its primary function -- to safely and efficiently heat water. These four primary systems include waterflow, temperature control, heating and safety.
Waterflow
Fresh cold water enters an electric heater at the top of the unit through the heater's inlet and into a pipe called a drip tube. The drip tube directs the water to the bottom of the heater's tank so any heated water at the top of the tank does not cool and can pass through the heater's outlet to the plumbing system when needed. When a faucet opens, it relieves the water pressure and fresh water enters the inlet, travels through the drip tube and pushes the hot water up and out of the outlet. The water then travels through pipes to the open faucet.
Temerature Control System
The control system of a standard electric water heater has two thermostat and heating element pairs extending into the tank and a control unit that provides interconnection and power. One thermostat and one heating element is located near the top of the tank and the others near its bottom. The control unit sends power through the upper thermostat and heating element and then to the lower thermostat and heating element. The interaction between water temperature and the thermostats control the water heater.
Heating Process
When first turned on, the upper thermostat takes priority and powers the upper heating element, which heats the upper tank nearest the outlet first. When finished, power transfers to the lower thermostat to heat the lower tank. When hot water is used, fresh water enters the lower tank, triggering the lower thermostat, which will attempt to heat the water as it enters the tank. As the hot water is used, the cooler water rises, triggering the upper thermostat, which will assume priority to heat the water nearest the outlet. Once that task is complete, the lower thermostat will heat the lower tank.
Safety Features
Modern electric hot water heaters have two primary safety features. The first is an over-temperature sensor that will remove all power from the unit should a thermostat malfunction. The second safety device is a pressure valve attached to the tank of the heater. If the water in the tank becomes overheated, it will cause an increase in pressure. This increase will trigger the pressure valve, which will vent the pressure out of the tank, preventing it from rupturing or exploding.
Tags: heating element, lower thermostat, thermostat heating, thermostat heating element, water enters, water heater, drip tube
