Hot Water Heater

[Boatsb]

Lower voltage raises amps. That's how it can trip the breaker.

[northshoreone]

I would check the Hot water breaker. I had it happen to me this spring! Worked great last fall when I went to start it up in the spring it would be fine for a min or so and then trip. It was a bad breaker causing it to trip. Replaced the breaker and all is fine!

[KPTIM]

How does lower voltage raise amps?

Basic Ohms law,
Current(I) = Voltage(V) / Resistance(R)

Ohm's law states that the electrical current (I) flowing in a circuit is proportional to the voltage (V) and inversely proportional to the resistance (R). Therefore, if the voltage is decreased, the current will decrease provided the resistance of the circuit does not change.

[Boatsb]

What is an amp?

Remember the basics.

[KPTIM]

An AMP is the current flowing through the circuit (basic).
Water heater elements are purely resistive.

Amps are calculated by dividing the (Applied voltage) by the (heater element resistance)
Amps = Volts / Resistance
Note: The element resistance does not change with applied voltage.

Assuming a 5000 watt water heater element DESIGNED to work on 220 VAC.
The element resistance is about 9.68 ohms.

When operating at the designed 220 volts the current will be about 22.72 Amps.
22.72 Amps = 220 Volts / 9.68 Ohms
In this case the heater element is generating about 5000 watts.

When operating at the lower 208 volts the current will be about 21.48 Amps.
21.48 Amps = 208 Volts / 9.68 Ohms
In this case the heater element is generating about 4469 watts.

When operating at the higher 240 volts the current will be about 24.79 Amps.
24.79 Amps = 240 Volts / 9.68 Ohms
In this case the heater element is generating about 5950 watts.

This only applies to resistive loads. None inductive loads like AC compressors, motors, transformers and refrigerators behave a lot different. That is a entirely different discussion.

[Boatsb]

Without tearing into it too deep.

What's the elements rating?

Many are replaced over the years. If it's a 208 volt element it will draw higher amperage.

What else is on the panel drawing the voltage down and increasing amp draw?

Tigers lots of variables.

[SKYCHENEY]

A 1978 53MY will have two isolation transformers in the generator room, aft on each side.

This will produced 240v to the water heater and is not selectable. All shore power runs through them. You should see a selector on your main panel next to the volt meter. You can select input shore voltage or trans out voltage to display.

The water heater issue sounds like maybe the wrong element. Check that element and wiring. OEM was a 4500 watt element which draws quite a bit but makes for a quick recovery.

[Photolomy]

Thanks Sky. However, I didn't see transformers in the gen room. Also, the AC panel is reading a solid 240, even with the A/C units on. So, either there are transformers somewhere on this boat, or a 100+ pedestals that say 208v are wrong. But, I think the issue is as suggested. The element is wrong (or the breaker switch is marginal) and the issue isn't low voltage on shore, but slightly higher voltage on shore. I will report back after more trouble shooting. Oh, I also see no indication of transformer on the breaker panel.

The picture attached was taken a month ago at a different marina. The generator monitor is not functional because the new generator remote control was mounted elsewhere on the helm.

IMG_4423-2.jpg

[Photolomy]

Here is a better image...

https://lightroom.adobe.com/shares/b...10138f903ad176

[t109a60]

How does lower voltage raise amps?

Basic Ohms law,
Current(I) = Voltage(V) / Resistance(R)

Ohm's law states that the electrical current (I) flowing in a circuit is proportional to the voltage (V) and inversely proportional to the resistance (R). Therefore, if the voltage is decreased, the current will decrease provided the resistance of the circuit does not change.

Tim,

In this case it's not a matter of Ohm's law. Rather, the power equation POWER=VOLTAGE x CURRENT.
Your heater element is rated at a certain power (wattage). As supply voltage goes down, the current draw
will increase to match the same power consumption. Ergo, lower voltage results in higher current
draw (tripped breakers). The reverse is also true.

Hope this helps........