Water heater implosion

[GoTanklessToday]

Does the wat3er heater take 120 per element? Is this how you get to 240? I wired this heater in with 10-2 romex coming out of a 30amp breaker.

Molo

There are 120 volt electric heaters, but most commonly they are 240 volt. each element needs 240 to heat. They both always have 120 volts, with the stats determining which element is going to get the other leg required to heat. If the stat is satisfied, the stat contact stays open.

Just for the record, in a 240 volt circuit (water heater, dryer, range, etc), both colored wires are "hot", and of course the bare is a ground. In a normal 120 volt circuit (like for the lights, etc) only one wire is "hot", with the other colored wire going to the neutral bus and the bare to ground.

 

[Molo]

This heater is a 240 heater. Is it a problem that it's wired with 10-2?

 

[Sponsor]

 

[GoTanklessToday]

This heater is a 240 heater. Is it a problem that it's wired with 10-2?

10-2 is the required size of wire from the breaker to the water heater.

 

[Molo]

I do not understand the difference between 120 and 240. I always thought that 240 required a big heavy wire and a special plug like an electric range and an electric dryer. Apparantly I am able to provide 240 through a 10-2 wire though. Could someone please clarify this for me.

TIA,
Molo

 

[Cass]

Most main panels have 2 legs each carrying 120V.

Think of each leg being a separate water service coming into a house.

A common 120V outlet on a wall has 1 black wire that carries 120V from 1 of the legs, 1 white wire that goes to the neutral, and 1 bare copper wire for ground that also goes to the neutral bar. If you take the white neutral wire and remove it from the neutral bar and connect it to the other leg that the black wire is not connected to it would also be 120V. 120V (from 1 leg) +120V (from the other leg) = 240V.


If you were to connect it to the same leg as the black wire you would still only have 120V.

Although the 2 legs each have 120v they don't match each other electrically so when they meet, as in the 2 wires touching, you get an explosion. This is what allows it to work right when they meet in a electrically controlled environment like a stove or clothes dryer.

Breaker / fuse size is what determines the amperage and wire size not if it is 120V or 240V.

All wire connections to the legs in a panel must be through a breaker or fuse never directly to the bus bar.

It is more complicated than this, but this is a simple explanation so you can grasp the idea of how it works.

 

[Molo]

Ok, When I wired the 10-2 into the box. I used a 30amp breaker. I wired the black into the breaker. The white to the neutral bus bar, and the ground to the ground bus bar. Is this wrong?

TIA,
Molo

 

[Rancher]

I wired the black into the breaker. The white to the neutral bus bar, and the ground to the ground bus bar. Is this wrong?

Molo, do you own a voltmeter? Yes this is wrong, you are wiring a 240 volt water heater with only 120 volts, the white need to wired to a ganged 240 volt breaker, i.e. twice as wide as your current breaker, it takes up two stabs on the breaker panel. You need to mark that white wire on both ends with black electrical tape, indicating that it is a hot wire.

Rancher

 

[Molo]

The 30 amp breaker that is in the box has two spots for wires, does this make it ganged? Do I simply have to put the white into the other spot that is empty to make this a 240 volt connection?

Molo

 

[Jadnashua]

Yes, and if you move the white wire to the other connection on the breaker, you'll have 240vac to the device. To be safe and correct, you should mark the white (normally neutral) with black tape or marker to indicate that it is hot. A 240vac device in a normal home supply doesn't use a neutral, but today's code for things like a dryer or stove use it, normally for 120vac parts (light the lamp on a stove or the motor on a dryer).

 

[Molo]

Does it matter if the breaker is a 120/240 breaker or do I need a 240 only breaker?

TIA,
Molo

 

[Rancher]

Does it matter if the breaker is a 120/240 breaker or do I need a 240 only breaker?

Breakers are rated in Amprage, if the breaker you are hooking up to looks to be twice as wide as the other breakers in the box, then it is breaking both sides of the 120 volt circuit, therefore it is a 240 volt breaker.

Rancher

 

[Molo]

Thanks to the help of everyone who posted here I have Finally gotten this water heater straightened out.

THANK YOU !

One more question.. Is turning the thermostates down something I can do with the power on to the unit? Is it as simple as loosening the screw and sliding the "pointer" over?

TIA,
Molo

 

[GoTanklessToday]

Thanks to the help of everyone who posted here I have Finally gotten this water heater straightened out.

THANK YOU !

One more question.. Is turning the thermostates down something I can do with the power on to the unit? Is it as simple as loosening the screw and sliding the "pointer" over?

TIA,
Molo

There is no loosening, simply put a flat blade screwdriver into the slot and turn the stat to the desired temp. Make both stats the same temp. As for power on... its perfectly fine to do that, but I always instruct customers to turn it off just as a safety measure. Someone comfortable with electricity can certainly do it safely with power on.

 

[Cass]

I have always set the upper stat 5 degrees lower than the setting on the lower stat.

 

[Molo]

No problem with pushing the reset like you mentioned. Pushing it just manually pops the bi-metal discs back into the closed position (or does nothing if it was already closed). Checking for a grounded element requires an ohm meter (i use analog for simplicity, but hard to find now). The heater must be full of water. Turn off the power, remove the wires from both elements. With the ohm meter in the continuity mode, put one lead to one post on the element, and the other lead to the metal of the tank. Scratch the metal a few times with the second lead to ensure a good contact. If you see the needle move, (or otherwise see "continuity") the element is grounded. Repeat the drill on both studs of both elements.

What does "grounded" mean? The outer sheath of the element has cracked and water is now getting inside the element to the filiment. It will work like this for some time. The problem with the grounded element (aside from a potential shocking problem) is that the element is now able to heat the water with 120 volts (normally takes 240). This is the second most common reason for a tripped high limit. A bad lower stat is #1. Others have suggested replacing the stats in pairs when there is a problem. I agree 100% with this theory. If in doubt, replace them both and be done with it.

And I always laugh when someone says they can use a meter to check the stats. It's impossible to check the stats with 100% certanty. Even the "heat it up" trick isn't reliable, because the act of removing the stats from their holders will oftentimes break the contact loose that had stuck closed. I like to prove the things I can prove ( elements are not grounded, and are drawing amps under voltage), and then proceed to the obvious conclusion.

I have a $2 continuity tester that has a red light. Can I use this to check to see if the water heater is grounded properly? Also should I place some insulation over and around the thermostats on this electric water heater/

Thanks,
Molo

 

[GoTanklessToday]

Does the wat3er heater take 120 per element? Is this how you get to 240? I wired this heater in with 10-2 romex coming out of a 30amp breaker.

Molo

No, each element takes 240 to heat. 120 is always at each element, with the stats deciding which will get the other 120. The proper size breaker and wire is dependant on the wattage of the elements. (or the other way around..)

 

[Molo]

Thanks tankless, but I was hoping to get an answer to thread number 35.

TIA,
Molo

 

[GoTanklessToday]

I have a $2 continuity tester that has a red light. Can I use this to check to see if the water heater is grounded properly? Also should I place some insulation over and around the thermostats on this electric water heater/

Thanks,
Molo

No, you cant use that type of tester. It needs to be a meter type, something that is powered by battery, or other means to get the needle or reading to register.

As for the insulation, you should have a plastic cover plate for the stat that you installed. If you have a hard time finding one, go to a lowes and find their "dead appliance" area and rob one off a dead tank waiting for pickup. The plastic cover plate protects the connections from touching anything, namely wet insulation when the heater starts leaking (and it will). If wet insulation is touching the contacts, you will get a nice "surprise" if you touch it with the power on. After the plastic plate is in place, then yes, its a good idea to cover that whole thing with insulation before putting the main cover back on.

 

[Jadnashua]

If you went from the ground on the heater to some otherground and th elight came on, you'd have a big problem. Checking grounds in this manner isn't reliable unless it is really bad. You really need a meter. They're inexpensive (or at least can be) - less than $20, and often $10 on sale at Radio Shack, HD, or Sears, etc. You can spend a lot more, and you'll get more accuracy, and other bells and whistles, but if you are only trying to measure voltage - the inexpensive ones are pretty good.