Water Heater Pulling 18 Amps Continuously - Not Heating

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etbrown4

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Been doing plumbing and electrical work for nearly 40 years and here is a new one for me.

50 gal elec water heater, maybe 3 years old. Rated 4500w

It is pulling 18a on both hot wires supplying the heater so that's at 230v, measured by an Amprobe.

There is no leak and the T&P is not leaking either.

One wonders how a heater can draw it's rated current and not heat water.

Elements test ok. Resets are not tripped.

I know there can be issues with broken dip tubes and cross connections, but can't really see how either could apply here.

I also know that the situation I describe should be a physical impossibility, as current drawn is current used, and will yield an equivalent amount of heat into that water!

Tips appreciated


Water Heater Pulling 18 Amps Continuously - Not Heating
 
etbrown4 said:
Elements test ok. Resets are not tripped.
Click to expand...
Be doubly sure. If one element is not working the water may not come out as hot as expected. Also, a broken dip tube will not force cold water to the bottom and the cold water coming in can essentially go right back out, leaving the hot water in the lower part of the tank (my suspicion).
etbrown4 said:
I know there can be issues with broken dip tubes...
Click to expand...
That would be my vote at this point and until we get more info.
etbrown4 said:
... as current drawn is current used, and will yield an equivalent amount of heat into that water!
Click to expand...
Only for a pure resistance and where you have the appropriate voltage drop across that resistance.

If the current and voltage keep the same sign through both halves of the cycle, you have unity power factor and "used" equals voltage times current (i.e. energy is consumed). For non-unity, some of the current is "used" on one half of the cycle but "returned" on the other half cycle (i.e., some of the energy is temporarily stored then returned so all of the current may not be associated with consumed energy).

Things to check:

1) Do you have full voltage drop across the elements (else you can have current but no voltage which would mean no energy consumed).

2) Zero residual current (clamp around both wires). This will help check for faults.

3) Is there any heat outside the water? If there is a fault to the tank or elsewhere the object could heat up and dissipate heat into the air, earth, etc., rather than the water.

4) Is the voltage and current in phase? If you have full current and voltage that are in phase, the heat is going somewhere.

5) Check the dip tube. See if any of the water in the tank is hot and just being mostly bypassed by a broken dip tube.

6) Be sure it is plumbed correctly.
 
It becomes more complex...

230v measured across top element when powered on. Checked with 2 different meters.

Top element powers on first.

Resistance across both elements is 12.8 ohms.

18 amps still being consumed by top element....checked with 2 Amprobes.

Neither element is grounded to the frame.

The heater displays no sign of heat, top or bottom, and after an hour of consuming 18a, the hot side is cold. and yes, I know that the problem described is in theory, impossible. If it was an easy one, I would not have posted it.

Hum.............. where is that current going? It has to result in heat, or lost water ..or a bad reading somewhere, or something else.

This unit has worked properly and has been in place for 3 years.
 
etbrown4 said:
Been doing plumbing and electrical work for nearly 40 years and here is a new one for me.

50 gal elec water heater, maybe 3 years old. Rated 4500w

It is pulling 18a on both hot wires supplying the heater so that's at 230v, measured by an Amprobe.

There is no leak and the T&P is not leaking either.

One wonders how a heater can draw it's rated current and not heat water.

Elements test ok. Resets are not tripped.

I know there can be issues with broken dip tubes and cross connections, but can't really see how either could apply here.

I also know that the situation I describe should be a physical impossibility, as current drawn is current used, and will yield an equivalent amount of heat into that water!

Tips appreciated


Water Heater Pulling 18 Amps Continuously - Not Heating
Click to expand...

Are you using a solenoid tester (wiggy) or a digital meter?
 
using digital meters.

also have 2 side by side water heaters in this installation.

both using the same current.

latest idea....turning off water supply and outlet from problem heater.

thereby isolating water in the tank.

will report what happens next,
 
etbrown4 said:
using digital meters.

also have 2 side by side water heaters in this installation.

both using the same current.

latest idea....turning off water supply and outlet from problem heater.

thereby isolating water in the tank.

will report what happens next,
Click to expand...
Sounds like a good next step. If inlet tube is broken you should still get some hot water out of it, but if there is a constant flow you may be losing heat about as fast or even faster then you are gaining heat.

Is these two heaters series parallel or separate from one another with the water circuit?

Another thought is if there is any kind of circulation pump on the system and you had a broken inlet tube you very well are pumping the heat out as fast as you are gaining it, and you have kind of created a hydronic heating system out of it.
 
Last edited:
solved

solved

Old man winter caused this one.


This property has a pool equipment room and outside shower which is remote from the house.


The Pool man came yesterday and turned on water to that equipment room and left.


Our sub zero winter froze a 1/2" cpvc hot water line in that remote location, though the water supply had been off for the winter. Unbeknownst to everyone, the hot water ran all night long, making the water heater seem as if it was not heating...when it was.


Sure enough the 18amp draw was right, watts were consumed! The leak was small enough and the flow moderate enough that at the heater there was no perceptible sound of water flowing. The sound at the heater was just the normal sound of the element being on.


We chased a similar ghost 25 years ago with a sneaky T&P valve leaking. In that case it was a similar slow leak, but still enough to cool the hot water. In that case the outlet for the t&p exited two floors below outside of another condo unit, so similarly we never saw the outflow until many hours later. :cry:


Thanks for all the tips! All contributions appreciated.
 
just the cowboy said:
I have seen something similiar when the elements were covered with heavy scale.
Click to expand...

But that usually results in the elements burning out or shutting off based on an internal temperature sensor before they get to heat the water much.
If the current is going in, the heat has to come out somewhere, scale or no scale.
 
GoldDigger said:
But that usually results in the elements burning out or shutting off based on an internal temperature sensor before they get to heat the water much.
If the current is going in, the heat has to come out somewhere, scale or no scale.
Click to expand...
I agree.
A continuous drain of the heated water is one possible explanation.
A plumbing rather than an electrical problem.
 
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