 List of Key Controls & Parts for Electric Hot Water Heaters - Inspection, Diagnosis, & Repair
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Electric water heater controls, switches, & valves: This article describes the location, function, and troubleshooting of key controls and parts in electric hot water heater operation. Additional hidden controls on an electric hot water heater include its thermostat, high temperature cutout. We address these under-the-covers water heater controls beginning at Electric Water Heater Repair Guide. 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.
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But watch out: sometimes an electric water heater is installed as an additional or backup hot water source, so you'll also want to see if you have other hot water heating equipment installed, such as a Tankless Coil for Hot Water.
List of Electric Water Heater Controls & Operation
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Page top sketch is courtesy Carson Dunlop Associates. Reproduction of this web page electronically at other websites is prohibited. Also see TIMERS for ELECTRIC WATER HEATERS. If you cannot find information you need here or if you have comments, questions, suggestions for inspecting and diagnosing water heaters Contact Us
Carson Dunlop's sketch describes the sequence of operation that turns on the electric water heater's heating elements. If one of these heating elements has failed, the quantity or the temperature of hot water provided will be substantially reduced.
- A pressure/temperature relief valve - See RELIEF VALVES - TP VALVES
- Cold water in and hot water out supply piping
- A cold water inlet shutoff valve
- A water tank drain valve
- A thermostat to set water temperature, located at one (or both) of the electric heating elements - Refer to our diagnosis of a failed electric water heater element at Temperature of Hot Water is Too Low.
- An electrical switch to turn power off to the water heater;
- An energy-saving timer is installed on some electric water heaters - see TIMERS for ELECTRIC WATER HEATERS
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Check the Sacrificial Anode & Dip Tube of Your Water Heater Tank
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The dip tube on many water heaters functions as a sacrificial anode, as we show here. By constructing the dip tube of a metal which is more readily corroded than the steel of a steel hot water tank, the anode protects the hot water tank from early failure due to corrosion. Here Carson Dunlop's sketch shows the location of the sacrificial anode on an electric water heater.
If your water supply happens to be highly conductive or corrosive (see WATER TESTING GUIDE) then the dip tub/sacrificial anode in the water tank may indeed corrode away until it leaks (dropping the hot water temperature) or disappears entirely.
If your hot water smells like rotten eggs, you should definitely check the condition of the sacrificial anode on the hot water heater, no matter what kind of water tank you've got installed.
For details of how to inspect or replace the sacrificial anode or dip-tube on a water heater, please see Water Heater Anodes & Dip Tubes |
Check the Hot Water Tank Temperature and Pressure Safety Relief Valve
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Our photo (left) shows an unsafe extension tube on a water heater tank - the diameter of the extension(1/2") is less than the valve opening diameter (3/4").
This restriction could prevent proper valve operation should unsafe over pressure or over-temperature conditions occur at the water heater.
For details about water heater relief valves, please see Testing the Water Heater Temperature Pressure Relief Valve |
Electric Water Heater Controls Behind the Removable Cover Panels on the Heater
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Additional "hidden" controls on an electric hot water heater include its thermostat, high temperature cutout.
We address these under-the-covers water heater controls, including the water heater temperature thermostat next, beginning at Electric Water Heater Repair Guide. |
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Frequently Asked Questions (FAQs) about the controls & switches found on electric water heaters
Question: hot water tank connected to my central heating system is used as an immersion heater
I have a hot water tank which is connected into my central heating system. In the summer
I use it as an immersion heater using electricity. The problem is that the water is too
hot when I use the immersion heater. How can I adjust the water temperature. - John Newing 6/16/11
Reply:
For a water heater that is used for both domestic hot water and heating, I'd suggest adding an automatic mixing valve right at the water heater hot water outlet line. The valve can be set to the desired domestic water temperature for washing and bathing; the valve works by mixing cold in with the outgoing hot.
You can also permanently lower the electric water heater temperature setting by opening the access cover to the control and setting the temperature dial to a lower number.
Also take a look at ANTI SCALD VALVES
Question: water heater output is scalding even with our thermostats set to their lowest settings
With both thermastats set at the lowest setting the water is scalding hot. What is causing this? - Anon 8/12/11
Reply:
Sounds like a bad thermostat control, or two of them. See
Question: lose pressure when turning on hot water
I have pressure inthe bath tub when the cold water is running, but lose some pressure when turning on the hot water - Aaron 3/12/12
Reply:
Aaron,
Depending on several variables, particularly water piping layout and routing, in some buildings, turning on hot water will, by taking water off of a common cold supply line, cause a drop in cold pressure. Bosch warns of this problem in their installation instructions for their low pressure tankless water heaters, products sold currently mostly out of the U. S. but also sold in that country until about 2004.
Question: our water won't get hot
Water will not get hot when turn on hot water in house - Claude 11/29/12
Reply:
Claude
See ELECTRIC WATER HEATER ELEMENT TESTS - you may need to replace your water heater elements.
Question: can I re-wire my water heater controls to convert from sequential to simultaneous operation?
I understand residential HW heaters are usually sequentially wired.
I want to set up my ordinary 240vac, two-heater, water heater for maximum economy. I will use a 240ac DPST NO relay as a latching relay. One pole to hold the relay in until a thermostat opnes, the other to control the HW heater power. Press a button, the relay latches and stays latched until the HW heater thermostat shuts off the controlling element.
I would like to change the HWH from sequential to simultaneous operation. What are the advantages/disadvantages to this change and are there any dangers in this change.
Thanks,
Norm
Bandership@earthlink.net
Reply:
Norm,
I agree in concept that one could perhaps change all of the electrical components on a given water heater: elements, controls, safety devices, thermostats &c. to convert from one type of water heater operation (sequential) to another (simultaneous) heater element operation, connecting the heater also to a properly wired and sized electrical circuit.
But frankly I would not take a chance on re-wiring a water heater to operate in any manner other than that specified by the manufacturer for that particular heater and model. Doing so could be unsafe. If you're admant about proceeding, start by giving the manufacturer of your heater a call, ask to speak with a technical engineer, and let us know what is her response.
Daniel
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
- Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
- John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: johncranor@verizon.net
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides:
- Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
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- The Home Reference Book, a reference & inspection report product for building owners & inspectors.
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Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
 The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
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