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AGE of WATER HEATERS
AIRBOUND HEAT SYSTEM REPAIR by WATER FEED VALVE
ALTERNATIVE HOT WATER SOURCES
ANODES & DIP TUBES on WATER HEATERS
ANTIFREEZE for BOILERS
ANTI SCALD VALVES
APPLIANCE DIAGNOSIS & REPAIR
APPLIANCE EFFICIENCY RATINGS
AQUASTAT CONTROL Functions
BACKDRAFTING HEATING EQUIPMENT
BACKFLOW PREVENTER, HEATER WATER FEEDER
CARBON MONOXIDE - CO
CHECK VALVES, WATER SUPPLY
CHEMICAL CONTAMINANTS in WATER
CHIMNEY INSPECTION DIAGNOSIS REPAIR
CLOGGED SUPPLY PIPING
DEBRIS in WATER SUPPLY, Water Heater
DRAIN a WATER HEATER TANK
ELECTRIC WATER HEATERS
FLOODED HEATING EQUIPMENT REPAIR
FLOODED WATER HEATER REPAIR
GALVANIC SCALE & METAL CORROSION
GAS BURNER Flame & Noise Defects
GAS FIRED WATER HEATERS
GAS PIPING, VALVES, CONTROLS
HOT WATER SUPPLY
INDIRECT FIRED WATER HEATERS
MANUALS & PARTS GUIDES - HVAC
MIXING / ANTI-SCALD VALVES
NO HEAT - NO HOT WATER: HEATER DIAGNOSIS
NOISE / SOUND DIAGNOSIS & CURE
NOISE CONTROL for HEATING SYSTEMS
NOISE, PLUMBING CHECKLIST
NOISE, WATER HEATER
ODORS GASES SMELLS, DIAGNOSIS & CURE
ODORS IN WATER
PIPING IN buildings, Clogs Leaks Types
PLASTIC Plexvent / Ultravent RECALL
PLUMBING FIXTURES, KITCHEN, BATH
RELIEF VALVE LEAKS
RELIEF VALVES - Water Heaters
SCALE REMOVAL, WATER HEATERS
SEWER GAS ODORS
SOLAR HOT WATER HEATERS
SOOT on OIL FIRED HEATING EQUIPMENT
SPILL SWITCHES - Flue Gas Detection
TANKLESS WATER HEATERS
Temperature Pressure Relief Valves - Water Heaters
THERMOSTATS, WATER HEATER
TIMERS for ELECTRIC WATER HEATERS
WATER CONSERVATION MEASURES
WATER CONTAMINANT LEVELS
WATER HAMMER NOISE DIAGNOSE & CURE
WATER ODORS, CAUSE CURE
WATER PIPES, Clogs Leaks Types
WATER PRESSURE & FLOW MEASUREMENT
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER QUANTITY IMPROVEMENT
WATER SOFTENERS & CONDITIONERS
WINTERIZE A BUILDING
Fix the electric water heater reset switch: This article describes how and why to test the high temperature cutoff switch and how to use the hidden reset switch on electric water heaters.
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This series of articles describes how to inspect, operate, diagnose, and repair electric hot water heaters. The articles at this website will answer most questions about electrical water heaters as well as many other building plumbing system inspection or defect topics. Reproduction of this web page electronically at other websites is prohibited.
Before testing the electric water heater elements we should check out the high temperature cutoff switch since a problem there will simply turn off power to both heating elements.
On an electric water heater the upper heating element may have two, three, or four electrical terminals, and above the upper thermostat is a high temperature cutoff switch with four terminals. You should be able to identify these parts by looking at the water heater's wiring diagram found on the tank or inside the panel cover.
The electric water heater high-temperature cutoff switch will turn off the entire water heater if temperatures are too high. If this cutoff is not working the water heater will simply not heat at all. You can use this switch to test to confirm that the incoming electrical power circuit is indeed bringing power to the water heater.
Turn off electrical power to the heater at the electrical panel: WARNING: possible fatal electrical shock. See DMMs VOMs SAFE USE OF and see VOLTS / AMPS MEASUREMENT EQUIP. General electrical inspection safety advice is at SAFETY for ELECTRICAL INSPECTORS.
Set the multi tester or VOM to its 250 VAC scale, and attach the tester probes or alligator clips to the two uppermost terminals on the control (L1 and L3 on the top left and top right in our photo below). These are normally the incoming electrical wires from the power circuit to the heater. "L" refers to "Line voltage" on most controls.
Test for line voltage: Now you can turn on electrical power to the heater. Your VOM should show voltage close to the voltage on the water heater's identification tag: typically this will be 208V or 240V for a 240V water heater, or it might be just 115V or 120V for a 120V water heater. If you do not see voltage close to the rated voltage you need to call an electrician to diagnose and repair the problem.
Test the High Temperature Cutoff Switch itself: set the VOM to its Ohm or resistance scale using the most sensitive setting (R x 1).
If you cannot reset the control then this device is not working and it needs to be replaced.
FYI we do not usually find a problem with this electric water heater high limit cutoff switch.
The most common problem on an electric water heater that is not heating is a burned-up water heating element - tests that we describe next at How to Test Electric Water Heating Elements.
Question: my electric water heater is not working
We suddenly find we have no hot water. I have an electric hot water heater. - Paul 11/1/12
Check that the water heater has electrical power, then try pressing the reset switch described above.
Electric water heaters are among the easiest to troubleshoot;
See ELECTRIC WATER HEATER REPAIR GUIDE for our complete & detailed electric water heater troubleshooting procedures.
Watch out: removing access covers on an electric water heater exposes live voltage-wires: touching them can cause injury, shock, or death.
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