| Metric | Specification |
|---|---|
| Difficulty Level | Advanced / Technical |
| Estimated Time | 60 to 120 Minutes |
| Tools Needed | Digital Multimeter, Phillips #2 Screwdriver, Needle-nose Pliers, Flashlight |
| Estimated Cost | $0 (Loose wire) — $600+ (Heat Exchanger/PC Board) |
**Rinnai Error Code 19** indicates a detected **electrical grounding fault** or an internal short circuit within the unit’s circuitry. This safety mechanism triggers when the PC board detects that current is leaking to the ground, potentially due to moisture ingress, component failure, or a compromised heat exchanger.
If you are seeing this code, you are likely experiencing a total loss of hot water as the system enters a hard lockout state to prevent electrical hazards or further hardware damage. You might hear the fan attempt to spin followed by an immediate shut-off and a rhythmic beeping from the controller. While this sounds daunting, as a senior engineer, I can assure you that with a systematic diagnostic approach, we can identify the specific failure point—whether it’s a simple loose wire or a component that requires replacement—and get your system back online.
How to Fix Rinnai Error 19 (Step-by-Step)
- Safety First: Disconnect Power and Gas
Before attempting any internal diagnostics, you must prioritize safety. Turn off the electrical power to the unit by unplugging it or flipping the dedicated breaker. Close the gas shut-off valve leading to the unit. Since Error 19 involves electrical grounding, there is a legitimate risk of electric shock if the chassis is energized. Use your multimeter to verify there is zero voltage present at the terminal block before touching any internal components.
🛑 Safety First: Read Before Repairing
For your safety and to avoid voiding the warranty, please check the official docs.
- Remove the Front Cover and Inspect for Moisture
Unscrew the four Phillips head screws located at the corners of the front panel and lift the cover off. Use a high-lumen flashlight to meticulously inspect the interior. Look for “white tracking” (dried mineral deposits) or active water droplets on the wiring harnesses, the bottom of the cabinet, and the PC board casing. If you find moisture, the source of the leak must be repaired (often the heat exchanger or a loose O-ring) before the electrical fault can be cleared.
- Check the Wiring Harness Integrity
Examine the bundle of wires connecting the various sensors to the PC board. Look for pinched wires, melted insulation, or signs of rodent damage. A single wire with exposed copper touching the metal cabinet will trigger Error 19. Ensure all molex connectors are seated firmly into the PC board; vibrations from the fan can occasionally wiggle these loose over several years of operation.
- Perform a Continuity Test to Ground
Set your digital multimeter to the Ohms (Ω) or Continuity setting. Place one probe on a clean, unpainted metal part of the water heater’s chassis (ground). Place the other probe on the various terminals of the power input and the leads going to the fan motor and igniter. You should not have continuity between the “hot” electrical paths and the ground. If your meter beeps or shows low resistance when touching a component lead and the frame, you have found your short circuit.
- Inspect and Clean the Flame Rod and Igniter
The flame rod and igniter sit inside the combustion chamber and are prone to carbon buildup. If carbon bridges the gap between the electrode and the burner plate, it can create a path to ground. Carefully remove these components, clean them with a fine-grit sandpaper or a wire brush until the metal is bright, and reinstall them. Ensure the ceramic insulators on these parts are not cracked.
- Dry the PC Board and Reset
If you suspect humidity or minor splashing caused the fault, you can use a can of compressed air or a hair dryer (on a cool setting) to thoroughly dry the PC board and all electrical connections. Once dry, reassemble the unit, restore gas and power, and perform a hard reset by cycling the power button on the controller. If the code persists after thorough drying and wire inspection, the PC board itself likely has internal damage and requires replacement.
What Triggers this Code?
In the world of appliance engineering, a grounding fault is rarely a random occurrence; it is typically the result of an environmental factor or component degradation. Here are the primary catalysts for Error 19:
- Moisture Ingress and Condensation: This is the most common culprit. If the venting system is not sloped correctly or if there is a leak in the heat exchanger, water can drip onto the electrical connectors or the PC board itself. Water acts as a bridge, allowing voltage to “leak” from the intended circuit to the metal chassis of the unit, triggering the ground fault interrupt.
- Heat Exchanger Breach: Over time, thermal stress and acidic condensate can cause pinhole leaks in the copper heat exchanger. When these leaks occur, pressurized water sprays into the combustion chamber or onto the wiring harness. This creates a direct path to ground, which the PC board detects as a catastrophic electrical failure.
- Component Insulation Breakdown: Components like the igniter electrodes, flame rods, or the fan motor have internal insulation. High heat environments over many years can cause this insulation to become brittle and crack. Once the internal copper wiring makes contact with the outer casing, a short to ground occurs.
- Voltage Spikes or PC Board Failure: A significant power surge can damage the sensitive capacitors and traces on the Printed Circuit Board (PCB). If the internal logic that monitors the ground state is damaged, it may “hallucinate” an Error 19 even if the external wiring is perfectly intact.
Symptoms of Rinnai Error 19
The most obvious symptom is the flashing “19” numerical code on your digital wall controller or the internal PC board LED display. However, the physical manifestations of this fault often include the unit failing to ignite entirely. You may hear the internal combustion fan kick on for a few seconds as the system performs its pre-purge safety check, only to have it abruptly cut power before the igniter sparks.
In cases of an intermittent grounding fault, you might experience “lukewarm” water or “sandwiching” (bursts of hot and cold water) because the unit is rapidly cycling on and off as it detects and clears the fault. Furthermore, if the grounding issue is caused by a water leak, you may notice moisture pooling at the bottom of the cabinet or a distinct “hissing” sound of water hitting the hot burner block just before the error code displays.
How to Prevent Error 19
Preventing grounding faults is largely about moisture management and electrical stability. First, ensure your tankless unit is flushed annually with a descaling solution. Scale buildup in the heat exchanger causes “hot spots” which lead to metal fatigue and eventual leaks—the primary cause of water-induced electrical shorts.
Second, install a dedicated surge protector specifically designed for tankless water heaters. These units are essentially computers that heat water; their PC boards are highly sensitive to “dirty” power and voltage spikes which can blow the internal grounding circuits. Lastly, ensure that your venting is installed with a slight pitch toward the exterior (for non-condensing units) or that your condensate trap is clear (for condensing units) to prevent acidic water from backing up into the cabinet and frying the electronics.
Frequently Asked Questions
Q: Can I bypass Error 19 just to get a quick shower?
A: Absolutely not. Error 19 is a fundamental safety lockout. Bypassing a grounding fault could result in the metal chassis of the heater—and by extension, your copper water pipes—becoming electrically energized. This poses a severe risk of electrocution to anyone using water in the house.
Q: Is Error 19 covered under the Rinnai warranty?
A: It depends on the root cause. If the error is caused by a manufacturing defect in the heat exchanger or a failed PC board within the warranty period (typically 5-12 years for the exchanger, 5 years for parts), it should be covered. However, if the fault is due to “scale” buildup from hard water or a power surge, Rinnai may deny the claim.
Q: Does Error 19 mean I need a whole new water heater?
A: Not necessarily. Most Error 19 issues are resolved by replacing either the wiring harness ($), the PC board ($$), or the heat exchanger ($$$). While a heat exchanger replacement is expensive, it is still significantly cheaper than the $3,000+ cost of a full new unit installation. Always diagnose the specific component before assuming the unit is “totaled.”