[tangler]

I am trying to install a tankless 220v hot water heater in my kitchen. There is a 220v outlet on the backsplash of the counter that was there when I moved in and have never used. I plan to use this as a 220v source. When I put the meter to the bare copper ground and 1 wire on the outlet I read 120v. I am guessing that both sides add up to 220V? Y/N? I am trying to establish that there is truly 220 here. Also, am I wrong to use this as a junction box for the heater? I intend on putting a blank plate over it so it won't be used for anything else later...

[Credendovidis]

I am trying to install a tankless 220v hot water heater in my kitchen. there is a 220v outlet on the backsplash of the counter that was there when I moved in and have never used. I plan to use this as a 220v source. when I put the meter to the bare copper ground and 1 wire on the outlet I read 120v. I am guessing that both sides add up to 220V? Y/N? I am trying to establish that there is truly 220 here. Also, am I wrong to use this as a junction box for the heater? I intend on putting a blank plate over it so it wont be used for anything else later...

The US grid provides two phase power. Phase - neutral - phase, with between each phase and neutral 110 Volt.
We here in Europe use three phase power with 220 Volt between any of the three phases and neutral 220 Volt (between the phases you get 380 Volt - which can be used for heavy duty tools and appliancies).
For you to get 220 Volt you need wiring to both phases in your distribution box.

Don't use a 2 phase wiring installation for anything else than the 220 Volt installation connected to it.
The neutral is not required (though earth is always compulsory). If you use electrical piping, do not use that particular pipe for anything else.
.
If you have a multimeter : measure first between neutral and one phase --> 110 Volt AC. Than between neutral and the other phase --> again 110 Volt AC.
Finally measure between both phases --> 220 Volt AC.
As stated : in the US no neutral is required when you need 220 Volt.
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Contact me if you encounter problems (bookmark my handle)
In Europe I am a qualified electrical engineer.
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Success!
;)

[Ben8n]

Just use the ground leg and add the other two legs together together they should equal around 220 if there is a slight flux nothing really worth worrying about

[stanfortyman]

The US grid provides two phase power. Phase - neutral - phase, with between each phase and neutral 110 Volt.

This is just a correction so as not to confuse folks.
IN the US we use SINGLE phase for residential. Commercial can be either single ohase or three-phase.

Two hots off a single transformer is still single phase. There is basically NO such thing as "two-phase" anymore anywhere in the US.


Tangler, what is the draw of this unit?
"220", or more accurately 240v, is only half the equation. Just saying you need "220" tells us the voltage. What is the amperage, or wattage, of this unit??

[donf]

Tangler,

You are correct, if you measure between the Black and Red terminals, you should see a 240 VAC difference between the poles. Measuring between Neutral and each phase you should see 120 VAC. Are you in the US or a different country.

However you still have a lot of work to do before you start yanking wires

First you have to file for a electrical Permit to make a change to your main panel. Just to do that, you have to describe exactly what you are doing, what breakers will be replaced because of the difference in amperage, you need to find the circuit breaker for this outlet and determine what it was used for. It's not normal that you find a 240 VAC outlet on a back splash.

[tangler]

thanks for the responses Guys! My first try here and I am impressed. I am in vancouver british columbia. The unit is a bosch ae9.5 240v 40 amp rated current. So... thanks to you I have established there is 240v there. NEXT MYSTERY -the former owner installed this outlet for a european bread maker. He pointed out the breaker to me before he left -a double 30 -I just checked and fpond out this was NOT the breaker -found 2x15 amp single breakers turned off this 220v outlet -mystery -there are also 2 110v outlets on the same circuit along that counter on the same 2x15 amp breaker. How can that be?

[tangler]

And... what do I have to do to install this unit now?

[stanfortyman]

and...what do I have to do to install this unit now?

FORGET that existing receptacle and call an electrician to run you a new 50 amp, 240v circuit.
That unit DRAWS 40 amps, so you will need a 50 amp circuit.

IMO this is NOT for anyone but the most seasoned DIYer or a pro.

[Stratmando]

Sounds like he had 2 120 volt circuits and stole off each to get 240 volts for a special item.
We can't do that here, and not likely there.
Would run new 40 or 50 Amp as required

[KISS]

Let me try to explain something. The high voltage distribution voltage, in the killovolt range is single phase with respect to ground. Somebody decided to take a secondary of 240 V and center tap it. Thus, you get 120-0-120. The center tap is at ground and the two 120 volts are 180 deg out of phase.

Thus you can have a 240 V outlet and 120 Volt outlets on the same breaker. Legal - probably not. It happens within a piece of equipment all the time. The 240 V breaker is two 120 V breakers mechanically coupled together, so if one side draws too much current, they both cut off.

[stanfortyman]

If a two pole breaker is used then what is there is likely legal, IF on a 15A breaker. Single pole breakers can ONLY supply 120v circuits.

Again, all moot points for the OP's situation.

[Fr_Chuck]

Yes and esp in many parts of the US, you will find 208vt not 240 vt.
On many motors this can be seroius, as many motors will not run on 208.
Some are rated 208/220 but some are not. We have had many power units not working properly because people ordered 220vt because that is what they think they have without checking first.

[stanfortyman]

In a residence it is safe to say you will pretty much never see 208v.

If it's not a residence it's NOT DIY.

[Fr_Chuck]

Can't say about residence, ( except for my rental homes) I work with almost 100 percent commercial equipment.

But I would wonder, why would or how could a house sitting next to the industrial building have 240, if the building next door had 208?

[KISS]

There are some places in the country that have three phase residential power. There was a discussion on another board concerning this. It became a surprise for a lot of people.

3 phase systems cost more money. You need a 3 phase panel and a single phase panel. Even though it would be 208 single phase and 120 single phase. If you wanted 240, you could certainly have it just my adding a transformer. Y is typically 208, while delta 3-pahse systems are 240 and they can be transformed with a transfomer.

So, you have a 3 phase high voltage distribution right next to a residential house. So, pick one of the lines, call it single phase, connect it to a transformer that supplies 240 center tapped and your done. The residential cost is less.

Now, what happens if the residential guy wants to put 3 phase in the attached garage for his mill and lathe for his hobby buildng widgets?

Is 3 phase allowed? Might be if it's zoned commercial.

Does he have to bring in a single 3 phase feed and then must give up the single phase feed?

-or- What happens if the area is zoned residential but a 3 phase power line is available in front of his house getting to a commercial business like a school? Can he connect?

Must he then use a phase converter?

[stanfortyman]

This ALL depends on the POCO. MOST will NOT spend the $$$ to bring three phase into a residence. Why? Because it is simply NOT worth it, at least to them.
WHAT in a residence could possible need three phase? HVAC units? Possibly, if the house is HUGE. Machines and tools? Possibly. Then again, if someone has that many three-phase tools that is less of a home and more of a commercial shop and should be treated as such.

Are there residences with three-phase services. Yes, they do exist. Are they common? NO. This is the rarest of rarities.

[Trault]

What's wrong if I have 120V on each leg to ground of a 240V circuit, but 6v between each leg?

Thanks,
Mike

[hkstroud]

You don't have a 240V. You have two 120 V lines sharing a neutral. Each leg is in the same half of the cycle.

What are you trying to do?

[KISS]

It depends a lot on where and how it's measured.

With the heater on and one fuse blown, you would indeed measure 120 from each side, but it's an artifact of the measurement. In one case it's 120 to ground and in the other it just includes a low value resistor.

If you assume breakers, then the scenero is less likely, but if you have a fuse pull out, this can be what's happening.

If this is a new install, then other possibilities exist such as Harold's.

[stanfortyman]

You don't have a 240V. You have two 120 V lines sharing a neutral. Each leg is in the same half of the cycle.

A 240V circuit would not have a neutral.