Need some help with this one...

This is an electric on-demand hot water heater with two separate 240 V circuits feeding. The circuit on the left has to hot seven neutral, the circuit on the right has only the two hots connected. The housing to this unit is all metal and is connected to the bare wire/neutral.

There are stickers which say “this appliance must be earthed” inside the front panel(I assume this is the Chinese interpretation for “grounded”). I have a instant hot water in my home which had a similar setup where there was no dedicated ground wire but the one of my home has a plastic cover.

I have two questions: First, does this unit require a ground and is that what the stickers indicating when it says “earthed” or can the bare wire be used as both the neutral and the ground?

Second, shouldn’t the circuit on the left have its neutral/ground attached as well? I was taught by an electrician friend of mine years ago that conductors must always have voltage/amperage going both directions to prevent overheating.

Any help will be appreciated.

I don’t see anywhere that says this requires a neutral connection. If it’s two straight 240 volt circuits both bare EGC’s should be somehow connected to the ground terminal.

Do you have any type of schematic?

Both terminal blocks are labeled for Line-Line. There is no neutral on this. They eat up enough power as is on 240, it would be even worse on 120 with only 1/4 of the heating ability.

The bare wire is not a neutral. It is the equipment grounding conductor. Was there a grounding lug for them or just on the terminal strips?

The control circuits are not 240VAC.

There is a green-yellow wire(s) on one side, not the other. They go up to the controls.

The GRN/YEL is an EGC. The sticker says 220/230/240 volts and nothing about 120 volts. The output (W) goes up with the increase in voltage from 200 through 240 volts. This looks like foreign equipment.

Sorry, no schematic. This was at Friday’s inspection. I’m not familiar with a 240 volt piece of equipment without a neutral. Shouldn’t the circuit on the left still have the EGC connected since it is a separate circuit at the main panel?

The yellow/green weaves throughout and connects to the middle terminal on only the left side. It also grounds the enclosure at several places.

Yes, each separate EGC in the two branch circuits should be connected to the enclosure. They could simply be spliced together with a tail off to the EGC terminal on the left.

1) A black wire which is often known as the “hot” wire, which carries the current in to the fixture.
2) Another “hot” wire which may be blue, red or white (if it is white the code actually requires it to painted or otherwise marked one of the other colors, but often it is not) which also carries current in to the fixture.
3) A bare copper wire called the ground, the sole function of which is to enhance user safety.

Yes I know all that, but how does this not need a neutral?

Is it because there is no 120 used so the alternating current cancels itself out?

Thanks, halfway there. :slight_smile:

You didn’t click and read my link.

“If there isn’t a neutral wire then how is the circuit completed?” The answer is that when one hot wire is negative, then the other is positive, so the two hot wires complete the circuit together because they are “out of phase”.

This is why 240 volt circuits connect to double pole breakers that are essentially two single pole breakers tied together. In the main panel, every other breaker is out of phase with the adjoining breakers. So, in essence 240 volt wiring is powered by 2 - 120 volt hot wires that are 180 degrees out of phase.

Why do some 220 circuits have a neutral wire and others don’t? Because some appliances contain 110 volt internal circuits (such as timers and electronic displays) which require a neutral connection to comply with current codes. When these 4 wire appliances are connected to old 3 wire systems via a 3 wire pigtail they use the ground conductor for the neutral. Other “straight” 220 appliances such as water heaters have no need for a neutral because the current both feeds and returns by way of the two hot wires as the current polarity alternates. Ideally, in any circuit the ground wire serves only as a safety feature and never carries any current under normal circumstances.

Oh man I completely missed that link Chris. Yep that answers it. That one disconnected ground threw me for a loop. Thanks.

You would only need a neutral if the control circuit or some other portion of the unit require 120 volts. Since this is a straight 220-240 volt unit everything, including the controls should work without a 120 volt connection.

I’m guessing you have one of these:

Thanks Robert

…Reading that brochure, a home with 4 bathrooms in a cool climate requires 4 separate 60a 240v circuits. Think I’ll stick with gas.

Yeah but with the way works it only cycles all the elements on under the highest load. I’ve got an 80 electric tank, so I might move to something like this someday. It’s got to be cheaper.

If you consider a tankless WH, look at gas. You may need a second servicce if you stay with electric. That is a large cost to payback before you even break even.

I still have to do all the math(great:roll:), but I’m on propane so I think it does come out ahead.

I did notice on that particular brand the largest model requires a 300 amp service, whew!