Tankless Electric Water Heater – The Installation

James, our son the plumber, bought a tankless electric water heater to install in his home. He is into saving energy. It sounds like a good idea, but I’m skeptical of the efficiency of an electrical unit. The principal is sound, but can such a small unit really keep an entire house with hot water all the time?
The dimensions are 15 1/4 X 12 1/4 X 4 1/4 and it weighs 12 pounds. I am not going to say what the name of the unit is because I do not want to recommend any unit at this time.

It simply mounts to a wall, has water and electrical connections and ideally, it should be close to the most frequent use of hot water.

For example, as in this case, the bathroom. The second floor bathroom is directly above the first floor bathroom. The clothes washer is right next to the tankless water heater in the basement and the kitchen is about 20 feet away. In this position, there should be a very slight delay getting hot water.

This unit uses progressive heaters. The water passes through the first heater, then passes through a second heater and then a third. Each is sensing the flow, the temperature and energizing as necessary.

I helped James with the installation of his tankless electric water heater and this is what we did.

James mounted two short pieces of electrical Uni-strut, which are metal brackets, to the concrete wall and attached the unit. This is to provide an air gap between the wall and the unit

Next, we ran three lengths of No. 6 electrical cable to the electrical panel, which was about 10 feet away.

We then moved on to the plumbing. Due to the location of the new tankless electric water heater, the amount of copper pipe needed was less than 10 feet total for both the supply pipe and the return pipe. A few simple Ts, some elbows and the plumbing was complete.
Now that the water pipes were installed, we turned our attention back to the electrical wiring. Make sure the circuit breakers are OFF before you do anything.
This tankless electric water heater required three runs of No. 8 wire. We had plenty of No. 6, so it was used instead. When it comes to electric wiring, remember that the larger the number, the smaller the wire and by the reverse, the smaller the number, the larger the wire. So we used larger wire then we had to.

Next, three 40 amp circuit breakers were plugged in and the wires were connected. Always connect the grounds first and the power last.

Finally, we went back and rechecked that all connections were tight. I like to apply “electrical grease” to all wiring connections to eliminate any corrosion points and future problems. This is not standard grease, but a special purpose product found in the electrical department of the big box.
So far, all is good and there have been no problems with sufficient hot water for all. As the electrical bill arrives and how well the unit can handle the cold water during the winter will be interesting to see.
Here is some information that James wants you to know before purchasing a tankless electric water heater.

Each brand is a little different, but overall they are the same. Make sure you pay attention to each unit’s instructions when it comes to the install.

The major thing about the tankless electric water heater is that you have to pay attention to the gallons per minute (GPM. This unit gives at most 4 gallons GPM. Most showers use 2 to 2.5 GPM and sinks use about 1.6 GPM.

You have to factor this in if you want to use a tankless model. Large soaking tubs with large faucets can use up to 6 GPM, which means you CANNOT use this model with a large soaking tub.

If you are a couple in a small house, it may be the thing for you. If you are a couple with teenagers and a large house, this will not be right for you.

Gas tankless models can give you up to 7.1 to 11 GPM. Also, they are more efficient than electric models.


Dave Altman

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