The required laundry circuit is permitted to serve multiple receptacle outlets in the laundry. Would a gas tankless water heater mounted in the laundry area and plugged into the laundry circuit for ignition be considered a violation?

Read the directions of the tankless. Most ask for a dedicated branch circuit.

Igniters use virtually no energy to speak of.

Such an appliance would not trigger any electrical issues -- in a direct sense.

The issue is what are the consequences if the breaker trips because of another receptacle load on the same circuit?

Is the device going to be venting unlit gas into a confined space?

Its issues should trigger concern beyond 'Division 16.'

From the Installation Instructions "Electrical Connection:
The water heater requires a standard 3 prong 120 VAC, 60 Hz properly grounded wall outlet. Plug the 6ft long
power cord into the wall outlet"

The draw is under 2 amps

Anything could cause a power outage to the unit regardless of where it is plugged in and it will not create a hazard, if there is no power for ignition the gas valve will not open.

A dedicated circuit is not required per the instructions.

My question is, what prohibits the unit from plugging into the laundry circuit? I don't think anything does, but I wanted confirmation.

210.11(C)(2) says


It does not specify what, in that laundry area, can or can't be plugged into one of those receptacle outlets.

The intent is that you have enough available power to accommodate the normal loads you have in the laundry, a washing machine and an iron, mostly. I do not see small cord and plug auxiliary loads from gas fired appliances being a problem. If they plugged in a 110v electric water heater we would have to talk. That does infringe on the 50% rule for fixed in place appliances in 210.23(A)(2). Bear in mind 210.11(C)(2) does say "receptacle outlets" and "no other outlets", so you can't have any hard wired equipment on that circuit.

I would see this as a minor infraction of rules and I don't think anyone would red flag for it. However there are some AHJ's out there who might.

BigB, you've seen the elephant in the room.

It's rare for a 'laundry room' to be just a laundry room. Most often, the same room will contain something else: a toilet, a furnace, the water heater, is an entryway, or is in the corner of a large open area (such as a basement or garage).

It's a situation where it's easy to create 'de minimus' violations.
When there's a gas furnace, what's the harm in the igniter sharing the laundry circuit? Even though you're violating TWO 'specified circuit' code rules.
In an open area, where does the 'laundry' area end? It's so easy to create a violation simply by running an extension cord to a workbench. How's the inspector going to prevent that?

I'll revert to my 'default' setting: IMO, the code has trespassed into a design issue, where it ought not be.

Unless the heater required a dedicated circuit, via plans, or mfg, I would not have an issue with the ignitor being on the laundry circuit. Provided it was within the laundry area.

That "laundry area" is not really well defined tho. If the builder put in a nice counter for folding clothes (and a receptacle for the iron), the owner might decide he needs a workbench more and the missus can fold the clothes in the bedroom.

As a matter of convenience and serviceability, I always give "critical" devices like water heaters and boilers their own dedicated circuit. I would rather not complicate things by having "variables" like receptacles and light fixtures on the same circuit as such devices.

Why chance things?