Electric water heater getting 120V to ground on each feed but 0V between them. Bad breaker?

[m_p_v_13]

Water heater was not providing hot water. I replaced elements after testing showed resistance was out of spec (6 ohms instead of 10-15). Still no hot water. Check voltage coming into heater with Simpson Analog meter. Reading is 0 volts between the two wires, but about 115V from each wire to ground (the tank).

This seems like I must be getting the same (in phase) 120 V power to each lead instead of the separate (180 degree out of phase) power signal.

The wiring has not changed!

I do notice that the circuit breaker for the water heater is "soft". It does not have the snap and spring tension of other similar breakers in the box.

Is it possible for a breaker to fail in this way?

Thanks for any help.

[Leroy]

Sounds like one leg is open, either in the wiring or in the breaker. If you feel competent enough, pull the panel cover and measure the two hot lines at the breaker. This should help you diagnose it. Do NOT do this if you're not familar with the procedure and are the least bit wary doing it.

Yes, a breaker can fail in this fashion, and if it has, the panel cover will have to be removed to replace the breaker.

Leroy

[m_p_v_13]

Thanks Leroy.

If one leg were open, wouldn't I get a reading of 0V for that wire versus ground?

[Leroy]

No. The open line would 'float' to the voltage of the working hot wire.

[Leroy]

Think of it as a voltage divider circuit. you've got 115 volts going into a 15 ohm resistor going to a 20 Kohm analog meter to ground. voltage would barely drop aacross the hw heater element.

[Leroy]

BTW, did you check the thermostat(s)? go here:

[trader4]

That of course is assuming he's measuring it with the feed wires connected to the heater, which seems reasonable, as it accounts for the readings. Also, if he's measuring the resistance of the elements without disconnecting, then he's probably reading both elements in parallel which is why he's getting about half what he's expecting.

[m_p_v_13]

I did not have the feed wires disconnected when checking voltage on them. Duh. I see how an open leg could cause my reading since (assuming the thermostat was working) there would be a circuit (including the element) between the feed leads.

I did however test the element resistance with one wire disconnected.

So I was getting the same phase 120, because it was from the same lead by way of the circuit through the element (and not from the breaker). I'm embarrassed that I missed this.

Thanks Leroy and trad.