Hot Water Heater

[doc g]

what does that top (rotary)R/L switch say under the handle I see 220/110 is there a different voltage stamped under the handle like maybe 208V??? You could have iso trans wired in that way ...directly to the rotary switch, in this way you can select the incoming voltage and have the iso trans compensate with boost if need be.....Pat

[Photolomy]

what does that top (rotary)R/L switch say under the handle I see 220/110 is there a different voltage stamped under the handle like maybe 208V??? You could have iso trans wired in that way ...directly to the rotary switch, in this way you can select the incoming voltage and have the iso trans compensate with boost if need be.....Pat

STBD
SHORE

Both S1 and S2 are the same.

I'll have more time to play with it tomorrow.

I am kind of surprised that the manual doesn't go more in depth in the workings of that panel. Or maybe I am missing part of the manual.

[KPTIM]

Hi Ken,
Although your equation for calculating power is correct your description of how it applies to a simple resistive heater element is not right. Heater elements are NOT constant power devices. What I mean is a 5000 watt heater element will NOT produce 5000 watts at any applied voltage only at the rated voltage. As the applied voltage goes down the wattage the element produces goes down as well which means the current draw will go down proportionally.

You have to use the following power equation in this case:
Power = Voltage^2 divided by R (P=V^2/R)

In this equation of Power the Voltage can change but the element Resistance stays the same.

When you buy a replacement heater element for a water heater the marked wattage is specified at a specific operating voltage. Some of the better element packaging even list the wattage of the element operating at different voltages, 208, 220 and 240 volts.

Just do some simple google/internet searches of water / resistant heater current vs voltage.

If it is on the internet it has to be true.....

[tonytrakovich]

You can argue electrical theory all you want. This does not help the OP. There are some generalities we use for troubleshooting. In this case it is P=V x I. With a constant power consumption (heater element, ac unit, etc.), If the voltage goes down in a non current limited circuit, the current will go up. Big Tom Callahan: Of course, I can get a hell of a good look at a T-Bone steak by sticking my head up a bull's ass, but I'd rather take the butcher's word for it.Tommy Boy

[Photolomy]

After further testing, the shore power at this slip is 240v. Even though most of the pedestals say 3 phase 208v, and online the marina references 208v, it seems that the pedestals at the end of the docks are single phase 240v. I measured the outlets and stove and I was getting 118v and 239v. Also, the water heater is 120v. The boat does not appear to have transformers (I have searched everywhere). I will run the generator later and test the voltage when it is running, but I am thinking that it will be slightly lower than shore power, which is why the water heater was tripping on shore power and not on generator power. Either the element is marginally wrong or the breaker is marginally wrong. I say marginally because the water heater has run for a few minutes here before tripping. On the generator, it never trips. Since the element was replaced recently, my money is on the element. Tomorrow I will get a clamp on ammeter and see what the current actually is. I'll also empty the tank and replace the element with the correct wattage, and if that doesn't work, an element with slightly lower wattage.

Btw, I have watched the ammeter on the panel while turning on the hot water heater and it does seem to be pulling more than 15 amps, but not much more. I will get a better reading tomorrow. I take it that the breaker (and wiring) is your standard 15 amp limit? The breakers unfortunately do not say on them. If they are supposed to be 20 amp, then the breaker would be the issue, because it is nowhere near 20 amp.

Thanks for all of the help.

[Photolomy]

You can argue electrical theory all you want. This does not help the OP. There are some generalities we use for troubleshooting. In this case it is P=V x I. With a constant power consumption (heater element, ac unit, etc.), If the voltage goes down in a non current limited circuit, the current will go up. Big Tom Callahan: Of course, I can get a hell of a good look at a T-Bone steak by sticking my head up a bull's ass, but I'd rather take the butcher's word for it.Tommy Boy

Unfortunately, my incorrect statement that the shore power was 208v kicked off this tangent. Unlike motors, resistive elements only draw current based on the voltage across them. That is why it didn't make sense that 208v would trip the breaker and 240v would not. Now I realize that the shore power is 240v, as was probably the shore power at the other marinas, and the culprit is either a mis-sized element or a worn breaker switch. Motors under load however, will draw more current when the voltage is reduced, which is generally bad for them.

[Pascal]

Ok so your voltage is goody that’s one variable out of the way

Now what is the wattage of the element? 15 amp breaker seems too low unless you have a very small heater (1800 Watts..)

If you have a 2500 element at 120v you need a 30 amp breaker... start there.

No idea why it works on generator and not shore but if you have 118v at the outlet it should work

[Boatsb]

Is the water heater 120 or 240 volts?

Cape has never had great power. Dont measure it on the boat. Check at the pedestal.

I know of a few incidents where power issues caused significant damage.

[SEVEN]

Ok so your voltage is goody that’s one variable out of the way

Now what is the wattage of the element? 15 amp breaker seems too low unless you have a very small heater (1800 Watts..)

If you have a 2500 element at 120v you need a 30 amp breaker... start there.

No idea why it works on generator and not shore but if you have 118v at the outlet it should work

Thanks for adding your hull number Pascal. Happy Thanksgiving

[SKYCHENEY]

The OEM water heater was 240v on all of the 53's from that vintage and newer. If you have a 120v water heater, then someone replaced it and probably screwed up the wiring as well. Why people don't replace with the same as OEM is beyond me.