Tankless water heater.

[Rico]

I have installed my tankless water heater. It required two 50AMP breakers. One for each heating element (separately wired)in the unit. The only problem is that the water that the heater produces is luke warm, not hot! The manual that came with it suggests that the problem could be either that the water flow rate is too high, or that the voltage is two low. The flow rate has been tested on low, no improvement. Therefore I must conclude that it is a case of low voltage. The manual stated that the voltage required was 220-240 Volts. The meter/supply box on the outside of my house is labelled "120/240V". How can I test or establish the actual voltage being supplied to my house? The 50amp breakers are attached to a subpanel in my shed, and not the main panel in my house. The unit is wired to the breakers with the manufacturers suggested 8AWG wire. I also heard that 240v and 120v might be used interchangeably to denote the same amount of suplied voltage. Is there truth to this? Can anyone clarify?

[kactuskid]

How far of a run is it from your shed to the heater, if it's under 100 feet then the wire size should be 6 gauge for a 50 amp breaker. AND are these 50 amp breakers double pole breakers, meaning they take up 2 complete breaker slots each?

Also, my experiance with tankless heaters is that they only really get hot when no other water is being drawn from other sources and the flow is set low on the shower valve.

[LazyPup]

Although we commonly speak of 120 or 240v in fact it may vary from one locality to another, and in some instances it may vary daily as in the case of brown outs during peak demand times. Residential current commonly varies from 110 to 125 volts from one locality to another.

If you look at the wires from the utility company to your house you will see three wires. One wire is the common wire and the other two wires are hot (energized) wires.

Each of the hot (energized) wires carries 120volts, however they are constantly at opposite polarity. Alternating current constantly changes polarity 60 times per second and while one wire is 120volt positive voltage, the opposite wire is 120volts negative voltage. (you may have noticed that the electric meter and all your appliances are rated for 60hz current.

If you look on the back of your computer, stereo or TV set you may notice a switch to change it from 50 to 60 hz power. (In europe they use 50 hz.)

Now imagine the common wire as being a zero reference point. If the power from one of the energized wires is measured to the common wire a meter will show 120volts however, Voltage is a measurement of the total difference of potential between any two points in a circuit. If you were to measure from one hot wire to the other the meter would show 240volts (120volts positive plus 120volts negative.)

In the home you normal outlets are connected to single pole breakers in the service panel. The power from either energized wire passes through the breaker to the outlet and back to the common buss, thus the outlets supply 120volts.

Heavier appliances such as electric ranges, water heaters, HVAC, laundry driers and such are connected by means of two-pole breakers which draw power equally from both energized wires at the same time. The advantages of using a higher voltage is that it requires less amperage to supply the same total energy or watts to the appliance. By using the higher voltage the system can be installed with lighter guage wire and it also insures a more balanced load on the service panel.

To measure the actual voltage in your home you can get a simple inexpensive multimeter for about $10 to $15. Set the meter on the AC volt scale and insert the test probes into the slots in a wall outlet. Be very careful to hold the test probes by the insulated handles and do not touch the metal tips while testing or a serious electrical shock will occur.

The meter would then show the voltage from one of the main hot wires to common, which will normally be between 110 and 125 volts. The higher voltage in your home will be 2 times the output for a wall outlet, therefore if you measure 120volts at the outlet you would have 240volts on the larger appliances.

If your water heater can be converted from 220 to 110 volts it must have dual heating elements in each section. When the elements are connected in series it would work on 240 volts, but if the elements were connected in parallel it would operate on 120 volts.

Converting a 220 motor or appliance should only be done by a trained electrician because if the voltage cut in half, the amperage would double and it would require installing heavier wire to supply the load.

If your water heater is being supplied from a sub-panel, that panel may only be connected to a single pole breaker and would then only be able to supply 120 volts.

[kactuskid]

Lazypup, just so not to confuse the poster, every instance in your post where you mentioned ground, it is not ground you are referring to, it is the neutral wire. The 3 cables comming from the pole to a home has 2 power wires and a neutral wire. Ground is a very different and separte thing even though they are connected together in a main electrical panel.

Rico, as Lazypup says, if you have 3 cables going to the mast on the outside of your house then you have 240 volts. If you have an electric range or dryer or HaD an electric water heater then you have 240 volts supplied to your house.

[Rewired]

Lazypup:
Not to confuse things again but where you mentioned "dual elements" and being able to change voltage, it should be SERIES for 240 volts and PARALELL for 120 volts.. Each element would be a 120V rated element.. Sorry, just thought I'd clarify a bit!

A.D

[LazyPup]

KACTUSKID,,you are certainly correct, while the third wire in the service entrance is at ground potential it is properly identified as the circuit common and should not be confused with the house grounding system.

REWIRED-Thank you for catching my mistake on series and parallel. I was thinking right but it appears I explained it backwards.

Please note that I have edited the post to correct the mistakes.

[Hube]

Maybe i,m missing something here, but Lazy Pups very fine explanatory post never mentioned the "GROUND" word even once, nor did the original poster mention the "GROUND" word.

[LazyPup]

Hube..you dont see the word ground because, thanks to my esteemed colleauges it was pointed out that my post had errors which i then edited.

[Rico]

Thanks guys, especially Lazypup for his great thorough explanation. I figured out the problem.

Never having wired a 240V appliance, I was stumbling in the dark, or learning on the go as I prefer to think of it. Although I had correctly installed the two 50Amp breakers, I had only attached one hot wire to each, using the second hot wire as the return wire (neutral). So instead of connecting the second hot wire to the other free space on the 50AMP breaker, I connected it to the Neutral Tie Block. I did this with both breakers (both heating elements).
Consequently it should be no surprise that my water was luke warm and not hot as I was only delivering half power to both heating elements in the heater.

Lazypup's description of how a 240 V appliance uses both hot wires supplying the house (or both sides of the main breaker) to create 240 V was quite useful to me. (each side is 120V. 120 x 2 = 240V)Previously I had imagined that if somthing bridged both sides of the panel without first tapping in to a neutral, that there would be a large explosion with great arcs of electricity. Now, I know that this is not so, and that this is exactly how 240 Volt appliances work via the use of a Double Pole Breaker (in my case, two double pole 50AMP breakers).

Before I was willing to risk applying my new understanding of the theory to actual practice, I thought that it would be prudent to first test the theory out with my multimeter, instead of the expensive tankless waterheater. I therefore summoned the courage to take my tiny little spindly cheapo multimeter and touch one test probe on to a free space on the left side of my breaker panel, and the other one to a free space on the right side. Sure enough, just as Lazypup suggested, I got a reading of roughly 240V !! And just as importantly, the fingers holding the probes (mine) had not turned into cajun fried chicken fingers in a flash of lighting and a puff of smoke. This gave me the confidence to procede with putting the theory in to practice.

So I simply removed each second hot wire from the Neutral Tie Block, and attached them to the second free space on each 50AMP double pole breaker. Voila. I now have PIPING HOT water that will never run out!
I took a long hot victory shower to celebrate. After two weeks of cold showers, this felt damn good!

Consequently, I would really recommend Tankless Hot Water Heaters. The water is plenty hot, and the temperature is easily adjustably by a dial on the outside of the box. When no hot water is running (95% of the time) no electricity is being used, which is a savings to you and better for the environment. In addition, it will never explode like a malfunctioning missle silo in your basement, as the Tank-Type hot water heaters have been known to do on occasion. Most importantly, you never run out of hot water! This is very useful at 7:00 a.m. after your wife has had a long shower and you are next in line!

Thanks for all the assistance guys.

Rico