Okay, let's break down the electrical and plumbing concerns you have regarding this tankless electric water heater.

GFCI Protection



You are likely required to have GFCI protection, regardless of hardwiring. The National Electrical Code (NEC) requirements for GFCI protection have expanded significantly over the years. While hardwiring used to be a possible exception in some cases, the current NEC almost universally requires GFCI protection for outlets serving appliances in wet locations like kitchens and bathrooms. The "hardwiring doesn't matter anymore" is likely correct. This is because the focus has shifted from how the appliance is connected to where the appliance is located. The location dictates the need for GFCI protection, not the wiring method. Install GFCI breakers. Using GFCI breakers is the most straightforward way to comply with the code in this situation. It protects the entire circuit and provides the required safety.

Why Plumbers Might Not Service It



Electrical vs. Plumbing

Plumbers are generally experts in water supply and drainage systems. While they can connect the water lines to the tankless water heater, they are usually not qualified or licensed to work on the electrical components inside the unit. The heating elements, control boards, and other electrical parts require an electrician's expertise and licensing.

Concerns About the Unit Itself



Online Purchase/Unknown Brand

Purchasing electrical appliances online from unfamiliar brands can be risky. Quality control, parts availability, and service support are often questionable.

Heating Element Failure

This is a legitimate concern. Electric tankless water heaters rely heavily on their heating elements. If the elements are poorly made or the unit isn't properly installed and maintained (e.g., hard water issues), they can fail prematurely.

Parts and Service

If the homeowner insists on this unit, you need to research the availability of replacement parts before installation. See if you can find online suppliers or local distributors who carry the specific heating elements for that model. Also, determine if there are any electricians or appliance repair technicians in your area who are willing to work on that brand.

Homeowner Communication

It's important to have a frank conversation with the homeowner about these potential issues. Make sure they understand the risks associated with an unknown brand and the potential difficulty in getting it repaired.

Electrical Load and Cost



112 Amps is a HUGE Load

This is a significant electrical load for a residential service panel. You need to verify that the home's existing electrical service (the size of the main breaker and the service entrance cable) is adequate to handle this additional load.

Electrical Service Upgrade

It is highly probable that you will need to upgrade the home's electrical service to a larger capacity (e.g., from 100 amps to 200 amps) to accommodate this tankless water heater. This is a substantial cost.

Cost Analysis



Initial Costs

Tankless units are expensive to purchase and install (especially with the electrical upgrade).

Operating Costs

While tankless heaters are more efficient, they typically cost more per year than a standard electric tank. Electric rates vary considerably, but with a high-draw tankless like this, it's safe to assume the monthly bill will be much higher than a traditional tank heater.

Usage Patterns

You mentioned one dishwasher, a kit sink, bath sink, and washing machine. That is a very small load for a 112-amp unit.

Is it Worth It?

For this level of load, an electric tankless may not be practical. A gas tankless could be a better solution, or even a heat pump water heater.

Recommendations


GFCI Breakers

Install GFCI breakers on the circuits feeding the tankless water heater.2.

Verify Electrical Service

Before* starting any work, have an electrician perform a load calculation on the home's electrical service to determine if it can handle the additional 112 amps. Be prepared for the likelihood of an electrical service upgrade.3.

Parts Availability

Research the availability of replacement heating elements for the specific model of tankless water heater.4.

Service Support

Check with local electricians and appliance repair technicians to see if they are willing to work on this brand of tankless water heater.5.

Alternatives

Discuss alternative water heating solutions with the homeowner, such as a high-quality traditional electric tank water heater, a gas tankless water heater (if gas is available), or a heat pump water heater.6.

Homeowner Communication

Explain the potential risks, costs, and limitations of the tankless water heater. Document this conversation in writing to protect yourself from future liability.

In summary, the code likely requires GFCI protection, and you need to be very cautious about the electrical load, parts availability, and serviceability of this specific tankless water heater. Thoroughly investigate these issues and advise the homeowner accordingly. Flag for review