Just to update this thread. I ordered a new manual for my boat, along with the electrical drawings. The original manual seems to have gotten wet. I'll post another thread on the manual you get when you order it (it is pretty nice). But the real help was the electrical drawings because they identify the circuit breakers and amp ratings. The hot water heater breaker is 15 amps, which is probably marginal. So, as mentioned earlier in this thread, I think by Scott, I may have to get a slightly lower wattage (higher resistance) element to keep the water heater from tripping the circuit. Or maybe the element that they installed is wrong. I know the water heater was 1500 watts, which at 110v is only 13.6 amps, and at 118v (what I was seeing on the voltmeter) it is only 12.7 amps. In any event, it seems to be tripping right at that value, so, either the element in there is not 1500 watts, or the breaker is bad.
Welcome to the Hatteras Owners Forum & Gallery. Sign Up or Login
+ Reply to Thread
Results 41 to 50 of 60
Thread: Hot Water Heater
-
12-06-2018 07:03 PM #41Senior Member
- Join Date
- Jun 2018
- Posts
- 1,069
Re: Hot Water Heater
Prometheus
1978 53' MY Hull #529
Viera, FL
-
12-24-2018 09:46 AM #42Senior Member
- Join Date
- Jun 2018
- Posts
- 1,069
Re: Hot Water Heater
I finally got around to replacing the heating element in the water heater. The water heater is designed for a 1500 watt element, but the mechanic up north had put in a 2000 watt element. That would have been fine, better even, but the breaker is rated at 15 amps, and the 2000 watt element was drawing 16.5 amps. Technically, a breaker is only designed to run continuously at 80% of its rated capacity, which is 12 amps for a 15 amp breaker. I replaced the element with a 1500 watt element and all is fine.
Prometheus
1978 53' MY Hull #529
Viera, FL
-
Re: Hot Water Heater
Great catch and cheap fix.
SEVEN
1979 53' MY Hull #563
Antioch, California
-
12-24-2018 01:03 PM #44
Re: Hot Water Heater
So go back to post #6 in the thread.
Scott
41C117 "Hattatude"
Port Canaveral Florida.
Marine Electronics and Electrical Products Distributor.
-
12-24-2018 02:51 PM #45
-
-
12-24-2018 07:40 PM #47Senior Member
- Join Date
- Jun 2018
- Posts
- 1,069
Re: Hot Water Heater
The generator is probably lower voltage. Higher would result in even more amps.
The element I took out had a resistance of 7.3 ohms, and the shore voltage was 118v, which results in a current of 16.2 amps (I = 118 / 7.3) and a power of 1911 watts (P = 118 * 16.2). The element I replaced it with had a resistance of 10.3 ohms, which results in a current of 11.5 amps (I = 118 / 10.3) and a power of 1357 watts (P = 118 * 11.5).
I haven't had a chance to measure the generator voltage yet, but I will soon.
For others that might pass this thread, the troubleshooting should go something like this.
When you open the access panel on the side of the water heater (with the power off of course!), you can get to the heating element. You can disconnect (and reconnect) the wires easily. Disconnect it and measure its resistance. If it is very low (< 3 ohms) or very high (> 30 ohms) then it is probably fried. A very low resistance would indicate that the element's coating ruptured and it is shorting via the water in the tank. A very high resistance would indicate that the element broke.
You can do all of this without emptying the tank and removing the element.
If it isn't fried, then divide the voltage by the resistance to determine the amperage, and then multiply that by the voltage to determine the power. Now that you know the power and amperage, you can compare it to the specs of the water heater and to the breaker rating to see if it all jives. In my case, as soon as I measured the resistance of the existing element, I realized it was a 2000 watt element, not a 1500 watt element. At 120 volts, a 1500 watt element should have had a resistance of 9.6 ohms. But it had a resistance of 7.3 ohms. The elements are not manufactured to a very tight tolerance, so the resistance will vary, but within some bounds. Also, once I decided to drain the tank and remove the element, it said 2000 watt on it.
Note: larger water heaters will have two elements, top and bottom.
Usually, the problem will not be the wrong element, unless you know that someone replaced the element. Usually, it will be a fried element, no resistance or infinite resistance. That is especially the case I think with boats, if you are not careful to bleed the tank of air before turning it on.
Which brings another question...
I always turn off the shore water when I leave the boat. Likewise, I turn off the water heater as well, just to make sure that the tank doesn't empty somehow and fry the element. Is this generally what others do? I suppose if I am not gone too long (a day or less) then the tank will retain a lot of its heat.Prometheus
1978 53' MY Hull #529
Viera, FL
-
Re: Hot Water Heater
Mine has a 4500 watt element at 230v. Can you say Fast recovery? Yes, never had a problem with all three showers running at once.
Sky Cheney
1985 53EDMY, Hull #CN759, "Rebecca"
ELYC on White Lake--Montague, MI
-
-
12-25-2018 08:46 AM #50
Re: Hot Water Heater
I’m curious about this. Higher voltage would obviously generate more watts, but I’m not sure it would change the amps. Then again your first post said the shore power was 108 volts, so your generator is likely higher voltage.
According to online sources, applying 240 volts to a 120 volt element quadruples the watts. If I understand this, higher voltage would also increase the amperage.1977 Hatteras 58' MY, Hull No. 304, 4-stateroom galley up model with 8V71TIs in Knoxville, Tennessee