Tankless Water Heater Repair Charlotte: Ignition Problems Solved

Charlotte homeowners love tankless water heaters for their efficiency and steady hot water. When they behave, they’re quiet, compact, and economical. When they don’t, ignition trouble tops the list of headaches. The burner fails to light, the unit throws a cryptic error, and suddenly the shower goes cold. I’ve spent years troubleshooting these systems in crawlspaces from Dilworth to Highland Creek, and the same patterns show up over and over. Ignition problems rarely come from a single cause. They’re a chain reaction of air, gas, water flow, control logic, and maintenance. Get those five right, and your tankless system runs smoothly.

This guide breaks down how ignition works, why it fails, and what a careful diagnostic looks like in Charlotte’s real conditions. You’ll see where a homeowner can safely intervene, when to call for professional tankless water heater repair, and how installation choices made on day one often decide whether ignition remains flawless or fussy for the next decade.
How tankless ignition actually works
A modern gas tankless water heater lights on demand. Cold water moves through the heat exchanger, the flow sensor spins up, and the control board runs a quick checklist. Depending on the model, the unit does a pre-purge with the fan to clear the combustion chamber, verifies the air pressure switch, opens the gas valve at a controlled rate, and triggers either a spark igniter or hot surface igniter. A flame rod confirms ignition through microamp flame rectification. If the board doesn’t see flame within a set window, it shuts gas, purges, and tries again. After a certain number of failures, it locks out and throws an error code.

Every step has a failure mode. Weak flow means the unit doesn’t even try. A dirty intake screen restricts air and confuses the pressure switch. Low gas pressure delays ignition long enough to time out. A scaled heat exchanger throttles water so much that the unit sees unstable flow and refuses to light. The flame lights but doesn’t get “seen” because the flame rod is oxidized. The control board senses a mismatch between expected and actual readings and throws a specific code. That complexity is why “I hear it click but it won’t stay lit” can trace back to anything from spiders in the vent to utility pressure dips during dinner hour.
What we see most often in Charlotte homes
Our local environment influences failure patterns. Charlotte’s municipal water is moderately hard, not the worst but enough to scale a tankless heat exchanger in two to three years without softening. Pollen and red clay dust clog outdoor intake screens in spring and after heavy storms. Many houses have flexible gas lines that were sized generously for a furnace, then a tankless unit is added later without upsizing or accounting for simultaneous loads. The result is marginal gas supply during peak use. Add in longer vent runs in townhomes and sealed crawlspaces, and you have a perfect storm for intermittent ignition failures.

On service calls, I keep finding an overlapping mix of four root causes: scale, airflow restriction, marginal gas supply, and degraded sensors or electrodes. The fix rarely requires expensive parts, yet it does require methodical testing and an understanding of how the unit “thinks.”
Reading the unit’s language: common ignition-related codes
Different brands speak different dialects, but they communicate similar ideas. You’ll see codes tied to flame failure, air supply, gas pressure, or flow. Homeowners often report “it shows a 11” or “I think it was a 12,” which helps narrow the first pass. Don’t hang the whole diagnosis on the code alone, because the board reads symptoms, not causes. For instance, a flame failure code may result from poor grounding, not fuel.

A pattern matters more than a single event. If ignition fails on the first start of the morning but works later, think condensation, cool flue conditions, or borderline gas pressure when other appliances are dormant. If the unit lights when the kitchen faucet is barely open, but not when the shower and washer run together, you are likely dealing with water heater repair charlotte https://www.washingtonpost.com/newssearch/?query=water heater repair charlotte gas supply or venting under load, not a bad igniter.
Practical checks homeowners can do safely
Two things you can do without tools: clean the inlet screens and watch the flow behavior. Most tankless units have a cold-water inlet filter. Close the service valves, relieve pressure at a hot tap, remove the filter, and rinse the sediment. If your unit has an exterior intake, make sure leaves, lint, or pest nests aren’t choking it. Glance at the condensate line, which should drip steadily during operation on high-efficiency models. A blocked condensate trap can stall the pressure switch and prevent ignition.

Pay attention to water temperature swings. If the unit starts and stops during a single shower, that stutter hints at irregular flow or a scale restriction. Ignition failures that accompany those swings often vanish after a thorough descaling and flow sensor cleaning. If you smell gas, hear persistent clicking with no light, or the unit locks out repeatedly, stop and call a pro for charlotte water heater repair. Ignition involves combustion. Caution is not optional.
The technician’s playbook: stepwise diagnosis that works
After hundreds of calls, I approach ignition faults in a predictable order, but I let the data lead.

Verify model, age, and installation history. I ask when the last descaling was done, whether there’s a water softener, and what other gas appliances run at the same time. If the unit is less than five years old with no descaling in Charlotte water, scale is already on the shortlist.

Start with venting and air. I check the intake and exhaust for obstructions, birdguards, offsets, and joint separations. A light tap on the air pressure switch tubing sometimes reveals a water droplet that migrated into the line, especially after extreme humidity. I measure the differential pressure while the fan runs. Numbers out of spec point straight to airflow or vent sizing.

Check gas supply under dynamic load. Static pressure doesn’t tell the story. I tee in a manometer at the appliance and fire the unit while a second gas appliance runs. Natural gas tankless units often want 5 to 10 inches water column at the inlet. If it sags below the manufacturer’s minimum during ignition, I trace upstream for restrictions, undersized CSST, long runs with too many fittings, or a regulator that is drifting. More than once, the fix was replacing a 3/4 inch run that necked to 1/2 inch for a few feet.

Inspect and clean the flame rod and igniter. A blue Scotch-Brite pad removes oxide gently. Strong cleaners can damage the surface. I also verify grounding, because flame rectification depends on a stable ground path. A loose bonding jumper has fooled more than one control board.

Evaluate flow and scale. I compare the unit’s displayed gallons per minute to a measured flow at a nearby fixture. If the board reports less flow than reality, the sensor may be dirty or spinning sluggishly. I open the heat exchanger circuit and pull a sample of water from the drain cocks. Brown flakes and a gritty feel scream for descaling. A thorough flush with 4 to 5 gallons of 5 percent white vinegar or a low-foaming descaler for 45 to 90 minutes usually restores performance. If the exchanger is severely scaled, you’ll see immediate improvement in ignition consistency afterward.

Validate sensors and board logic. Temperature sensors that read wildly off can cause the board to abort ignition. I cross-check with an infrared thermometer at the inlet and outlet and compare to sensor readings. If a sensor is more than a few degrees off repeatedly, it gets replaced. I reserve board replacement for last, after supply and sensor issues are resolved, because boards fail far less often than they get blamed.

That order keeps repairs efficient and reduces callbacks. When water heater replacement is suggested for an ignition issue, it’s often because these steps were skipped or rushed.
The Charlotte pattern: gas sizing and vent lengths
City neighborhoods have older gas piping. Additions and kitchen remodels layered over the years leave a spiderweb of tees and reducers. Tankless units are unforgiving if starved during ignition. I carry pipe sizing charts and treat each home as a fresh calculation. If the water heater installation was done by swapping out a tank and keeping the same 1/2 inch run, ignition trouble will follow. Upsizing that run to 3/4 or even 1 inch, depending on BTU load and length, stabilizes combustion and ends the random lockouts.

Venting deserves the same attention. Long horizontal runs, extra elbows, or shared vent spaces introduce resistance. Combustion fans compensate within limits, but at some point they cannot pull enough air to satisfy the pressure switch. I often find a blocked termination cap from insect nests in summer. Clearing the cap and adjusting the vent pitch to keep condensate from pooling has solved half-day diagnostic puzzles in ten minutes.
Scale: the silent ignition killer
You can’t discuss tankless water heater repair without talking scale. A layer of mineral inside the heat exchanger behaves like a winter coat between flame and water. The unit works harder to deliver the same outlet temperature, which alters ignition sequencing. Flow drops. The control board reads unstable conditions and errs on the side of safety by aborting ignition. Charlotte’s hardness varies by neighborhood and season, but unsoftened water will put a noticeable coat of scale inside a tankless exchanger within two years.

Descaling is not optional maintenance. If the water heater installation did not include isolation valves, plan to add them during the next service. They pay for themselves in one visit. I set up a small pump, hoses, and a bucket with a couple gallons of warm descaler, circulate it through the exchanger, and keep the inlets filtered to catch debris. After the flush, ignition is steadier, fan ramp-up sounds smoother, and outlet temperature stabilizes.

Homes with a water softener or a one-time polyphosphate feeder see fewer ignition calls. A softener also protects fixtures and extends the life of the washer and dishwasher. When homeowners weigh the cost, I show numbers: an annual descale runs about the cost of two dinners out, while a heat exchanger replacement costs many times that. Preventive care wins.
When ignition fails intermittently
The hardest calls are intermittent. The complaint is vague: sometimes it lights, sometimes it doesn’t. This is where context and patience matter. I ask about time of day, which fixtures, and weather. A pattern often emerges. Early morning lockouts can be dew and condensate pooling in the vent, especially with a long horizontal run. Evening failures correlate with neighborhood gas pressure dips when stoves, heaters, and water heaters all run. Showers that start hot then go cold, then recover, point to a flow sensor that sticks.

I bring a manometer, clamp meter for fan current, and a simple data logger for temperature. Running the unit while recording these gives a fingerprint. If the fan current spikes during pre-purge, airflow is obstructed. If gas pressure drops during the split-second the valve opens, the line is marginal. Reproducing the failure is half the job. Fixing it is often straightforward once you truly witness the variables in motion.
Electric tankless and ignition’s cousin: relay and sensor logic
Electric tankless models don’t ignite, but they can mimic ignition failure behavior. They rely on flow sensors to engage high-current relays or solid-state drives. If scale slows flow just enough, the unit never reaches the minimum threshold and clicks on and off. Loose lugs or overheated terminals create voltage drops that confuse the logic. I treat electric units the same way: verify flow, sensor readings, and power quality under load. A failing temperature sensor can abort heating in seconds and look like a gas ignition failure to the homeowner. For electric models, a licensed pro should perform any internal work due to the high amperage involved.
Installation choices that prevent ignition issues
Good water heater installation practices prevent most ignition calls. The basics look simple on paper, but execution separates a reliable system from a finicky one.

Start with gas supply. Size lines for the full BTU load and the actual distance, not an ideal chart. Account for other appliances that may run simultaneously. Use smooth sweeps and minimize unnecessary fittings. Confirm dynamic pressure at the unit during commissioning.

Venting matters. Keep runs as short as the layout allows, maintain proper pitch, and use approved materials with tight joints. Terminate where wind and debris are least likely to interfere. Outdoor units still need clear intake paths. Keep at least the manufacturer’s minimum clearance around terminations, and avoid venting into high-traffic mulch beds where landscaping debris accumulates.

Provide service valves and cleanouts. Plan a straight shot to connect a descaling pump. Label shutoff valves. Add a condensate neutralizer and trap where needed to prevent premature corrosion and pH damage downstream. A clean electrical ground is not optional. Without it, flame sensing becomes guesswork.

Finally, educate the homeowner. A five-minute walk-through on cleaning inlet screens, recognizing early signs of scale, and what to do if an error appears prevents emergency calls. If a homeowner understands why short hot water taps can confuse a tankless unit, they’ll avoid triggering nuisance lockouts.
Repair or replace: making the call
Not every ignition problem warrants water heater replacement. I advise clients to weigh the unit’s age, maintenance history, condition of the heat exchanger, and the cost of parts. A ten-year-old unit with heavy corrosion, repeated board failures, and no isolation valves might be a candidate for replacement. A five-year-old unit that only needs descaling, a flame rod, and a gas line correction should be repaired. Replacement also makes sense when a remodel adds hot water demand beyond the unit’s capacity, which stresses ignition cycles and shortens component life.

When we do water heater installation Charlotte homeowners appreciate clear upfront numbers. I present options: repair with parts and reconfigure gas or venting, or install a new, properly sized system with service valves, water treatment, and documented commissioning. The right answer depends on the home, not a one-size-fits-all formula.
Seasonal behavior: why ignition issues spike
Spring and fall produce a spike in calls. In spring, pollen clogs intakes, and sudden temperature swings make vent condensation unpredictable. In fall, gas furnaces come online, changing the pressure dynamics across the system. The first cold snap exposes marginal gas sizing. I schedule preventive visits at the change of seasons to check airflow, test dynamic gas pressure, and descale if due. Clients who keep that cadence rarely see ignition lockouts.

Storms matter, too. After a heavy rain, condensate lines can back up if the trap is marginal or pitched poorly. A half inch of water stuck in the vent loop can stall the pressure switch and water heater replacement https://www.linkedin.com/company/rocket-plumbing/about/ kill ignition. Clearing the line and correcting the slope fixes it. After sanding and pressure washing decks, fine dust migrates into outdoor unit intakes. A quick rinse of the intake screen is a surprisingly effective cure.
What a thorough service visit includes
When we come out for tankless water heater repair on an ignition complaint, expect a structured visit. We start with error history and visual inspection. We test airflow, gas under load, and sensor readings. We descale if the exchanger shows signs of restriction or it’s overdue by time. We clean electrodes, verify grounding, and confirm condensate handling. We reassemble and run the unit through multiple cycles, including low-flow and high-demand tests. If parts are needed, we stock common items: flame rods, igniters, sensors, pressure switches, and gaskets for popular brands. The goal is to leave the unit not just lit, but stable across operating conditions.
The small habits that extend life
Tankless systems reward attention with long service. A few habits reduce ignition trouble to almost zero:

Install and maintain water treatment appropriate to your hardness. Even a small cartridge conditioner can buy time between descales.

Clean the cold inlet filter twice a year, more often if you have well water or sediment-prone lines.

Those two steps keep flow and heat transfer in the sweet spot where ignition is easy. If you add a softener after installation, retune the unit’s inlet temperature rise and flow settings if your model allows. Softer water heats faster, and the control logic can be optimized to reduce short cycling.
When to call for professional help
If you see repeated lockouts, smell gas, or notice soot or discoloration around the exhaust, stop using the unit and call for charlotte water heater repair. Intermittent ignition can be annoying, but safety flags are non-negotiable. A pro will bring calibrated gauges, the right cleaning materials, and brand-specific know-how to interpret codes correctly. If you are weighing water heater installation or a proactive water heater replacement because of persistent ignition issues, getting a proper load calculation and a venting assessment up front saves money and frustration.
Final thoughts from the field
Ignition problems are solvable. In Charlotte, the fix usually comes down to three corrections: restore clean airflow and condensate handling, ensure adequate gas pressure during real-world demand, and remove scale that robs flow and heat transfer. Put those right, and the control board stops fighting physics. Your showers stay hot, the unit runs quietly, and you stop thinking about it entirely. That’s the goal of any good tankless water heater repair: not just a lighted flame today, but a system that lights easily every day that follows.

Rocket Plumbing
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Address: 1515 Mockingbird Ln suite 400-C1, Charlotte, NC 28209
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Phone: (704) 600-8679
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