Rinnai Tankless Error Code 19: What an Electrical Grounding Fault Means for East Cooper Homes
If your Rinnai tankless is flashing Code 19 in Charleston, Daniel Island, Mount Pleasant, or anywhere else in East Cooper, the heater is telling you it found an electrical grounding problem. In plain terms, something inside the unit is shorting out, and the heater won't fire until that's sorted.
I'm Christian with Avery & Sons Plumbing + Tankless. Here's a straight walkthrough of what Code 19 means, what you can safely check, and when it's time to call.
What Code 19 actually means
Rinnai lists Code 19 as an electrical grounding fault. It covers both their SENSEI and non-SENSEI models.
Here's how it usually shows up: you turn on a hot tap, water starts flowing, and Code 19 pops up right away. You won't see a flame in the burner box. According to Rinnai's troubleshooting guide, that pattern means there's an electrical short in one of the heater's components.
The heater runs a low-voltage DC circuit to a bunch of parts, and Rinnai points to a few likely spots for the short:
A wiring harness. These are the bundles of wire running between the circuit board and the parts it controls.
The water flow control valve. It's the part that manages how much water moves through the heater.
The bypass valve. It mixes some cold water in to help hold your temperature steady.
Any other part on that DC circuit. The short can really be anywhere on that circuit.
So Code 19 isn't one specific broken part. It's the heater saying "something on my circuit is grounding out where it shouldn't," and the job is tracking down which piece.
How a pro finds the short
Rinnai's method is simple, but it has to be done carefully. With the heater opened up, a tech unplugs one part at a time and tries to fire the heater after each. If the heater cycles normally three times with a certain part unplugged, that's the part with the short. Then it gets repaired or replaced.
That means working inside a live gas appliance with the cover off, so it isn't a homeowner job.
Safe checks you can do yourself
Keep this list short. If you ever smell gas, leave the house and call your gas utility. Don't troubleshoot.
Write down what you see. Note the code, whether it appears the instant you turn on hot water, and whether it comes back every time.
Think about anything recent. Did you have a storm, a power outage, a leak near the heater, or any recent work on the unit? Tell your tech. It helps narrow things down.
Look without touching. If the heater is mounted outside, check whether water is pooling on or around it, or whether the cover is damaged. Don't open the cover.
Try one reset. Turn it off at the controller, kill the breaker for 30 seconds, and power it back on. If Code 19 comes right back when you run hot water, stop there and leave it off.
Please don't unplug parts inside the heater yourself. That diagnostic step is for someone trained to work on gas appliances.
When to call a pro
Call if Code 19 keeps coming back after a reset, if you notice water around or inside the heater, or if you just don't have hot water and aren't sure why. A proper service visit should inspect the wiring harnesses, work through the parts on the DC circuit one at a time to isolate the short, and repair or replace whatever's causing it.
A local note
We live in a humid, salty, stormy corner of the world. From Daniel Island to Mount Pleasant to downtown Charleston, a lot of tankless heaters are mounted outside or in garages where they see plenty of weather. When we're out on any Rinnai call, we like to give the whole unit a once-over: the wiring, the venting, and how long it's been since a descaling flush. Our hard water around East Cooper is behind a lot of the other codes we see.
Soft next step
If your Rinnai is showing Code 19, try one reset, and if it sticks, leave it off and get it looked at. Avery & Sons Plumbing + Tankless can help. Call (843) 305-5555 or visit averysplumbing.com. We're local, we work on these heaters every week, and we'll tell you straight what it needs.
A short circuit is the heater being honest with you. Let's find it and get your hot water back.
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