Lochinvar Electric Water Heater Troubleshooting

The Short Answer: A Lochinvar electric that will not heat is a tripped disconnect, a popped ECO on a thermostat, a dead element, or the wrong machine in your head. ET light-duty and residential electrics are 240-volt storage tanks, not a Knight boiler and not a Squire indirect. Totally cold is the upper circuit. Short hot then cold is the lower. Lock every heater breaker off. Do not jumper an ECO.

Search Intent & The Real Problem

The badge says Lochinvar. Showers died. People paste ICON gas flash codes and Armor boiler faults onto a screw-in element tank. Lochinvar (A.O. Smith family) sells electric storage — residential dual-element and commercial ET / light-duty multi-element — plus gas water heaters, Knight/Armor boilers, and Squire indirects that have no electric elements. Read the rating plate. This page is electric storage, no heat. Sister electrics: Bradford White electric. Indirect leak/heat is HTP / SuperStor family, not this article.

What other guides get wrong

They treat every Lochinvar as a gas Knight. They skip the fused disconnect sitting next to the tank, so you “reset the ECO” on a dead 60-amp. They ohm a 4500 W element live. They mix a Squire coil that is waiting on a boiler with an ET that has its own elements. And they tell you to keep clicking the red high-limit — that is how thermostats burn up.

Step-by-Step Troubleshooting

Step 1: Identify the platform — electric tank vs everything else

• What to look for: Model and serial, volts, wattage per element, number of thermostats. A typical residential element is 4500 W at 240 V — ~18.8 A, ~12–13 Ω with power verified dead. Commercial ET elements are whatever the plate says; do not assume 12–13 Ω.
• Required tools: Flashlight, phone photo of the plate and the wiring diagram inside the cover.

If it is a Squire, stop hunting an ECO behind an element door. The boiler is the heat source.

Step 2: Power path — breaker, fuses, both legs

• What to look for: Double-pole in the panel and the local disconnect. One pole open: a lamp may glow, elements sit at 120 V and do not heat. Fused disconnects on commercial ET tanks: a single blown fuse looks like a dead heater. Instant trip is a bolted short — do not hold the handle. A breaker that will not reset stays off. Trip after a few minutes is a sheath going to ground as it expands — trips after a few minutes.
• Required tools: Panel from a dry location. Prove 0 V before the cover.

Never energize a tank you have not filled — turned on without water.

Step 3: ECO / high-limit — one reset after the cause

• What to look for: Manual-reset ECO on each thermostat (residential dual-element: upper is the one that kills all heat). Commercial ET: ECO on each thermostat/ECO combo; some electronic controls lock out and need a power cycle after the water is below the reset temperature (often ~120 °F). Click once. Repeat trip is a grounded element, a stuck thermostat, or a dry-fire. Do not tape the button. Repeated ECO: keep resetting.
• Required tools: Breakers locked. Finger on a cool tank.

Electronic residential Lochinvar/A.O. Smith controls can show codes such as an ECO / high-limit event or an upper-element circuit fault — photograph the display. Do not invent gas ICON flash counts.

Step 4: Elements and thermostats — dead, then ohms

• What to look for: Totally cold: upper element or upper thermostat. Short hot then lukewarm: lower element. With every disconnect locked and wires lifted, ohms per that wattage. 4500 W / 240 V ≈ 12–13 Ω. Any screw-to-shell continuity is a ground. Water in the electrical bucket is a gasket or a leak — leave it off; gasket leak. Lime-eaten sheaths open or ground; they do not “scale back to life” with vinegar while you live in the house.
• Required tools: Digital meter, both wires lifted, 0 V proven.

Do not replace the upper thermostat because the lower element is open. Measure.

Step 5: Lukewarm, T&P, and a tank that is actually done

• What to look for: Mixing valve or dip tube if the jacket is hot — that is not an element. T&P dribble: house static over ~80 psi or a waterlogged expansion tank; typical relief 150 psi / 210 °F. Never cap it. Wet jacket, rusty water, years of no anode: the shell is done — bottom leak map. Commercial ET tanks still fail at element gaskets first.
• Required tools: Hose-bib gauge, paper towel. No sealant on the shell.

When DIY Ends: Calling a Licensed Pro

You may confirm the disconnect, photograph the plate, and press one ECO after a confirmed full tank. Stop at live lugs, contactor panels, repeating high-limits, wet electrical compartments, and any leak from the vessel. Multi-element commercial Lochinvars are electrician-plus-plumber work. A licensed tech with the Lochinvar diagram beats a bag of “universal” elements and a second cooked thermostat.

Frequently Asked Questions

Q: Why is my Lochinvar electric water heater not heating? A: Tripped breaker or fused disconnect, open ECO, dead upper element, or a Squire waiting on a boiler. Prove 240 V dead, then hire a licensed tech if it stays cold.

Q: Where is the reset button on a Lochinvar electric water heater? A: On the thermostat ECO behind the access panel, sometimes one per element. Power off first. One press on a full tank. If it trips again, stop.

Q: Can I replace a Lochinvar electric element myself? A: Only if you can lock 240 V off, drain below the opening, and use the correct gasket and wattage. A spinning tank spud or water in the bucket is a licensed call.