hot water from inverter

IStream · Feb 4, 2015

Even assuming that your alternator could put out full rated power for an extended period of time without overheating, the extra ~40A of output will only amount to about 400W of AC power to the heater after efficiency losses.

If your water heater's already using waste heat from your engine, it may incrementally speed the time it takes to reach temp but it's basically unnecessary and will put a lot of extra wear and tear on your belts, alternator, and inverter.

Ron20324 · Feb 4, 2015

As long as you install a circuit breaker lock-out so you don't run the battery charger at the same time you use the inverter.

Don S/V ILLusion · Feb 5, 2015

This isn't the first time someone asked this question. Short answer - impractical with your elec system.
If you want details, please try searching the archives here which is full of similar detailed discussion.

kloudie1 · Feb 5, 2015

Most water heaters have a 1200-1500 watt element in 'em.. Your alternator can make (70 amperes X 14volts =) 980 watts so you'd be using battery to make up the difference until that got sucked dry. (you'd be pulling 50 plus amperes from the battery for, say, 30 minutes to get the tank hot initially.. only 25 ampere hours, but then ya have to replace that with the same alternator.. gonna fry it) To answer your question, yes it can be done with a 2000 watt rated inverter and a good installation (heavy wires and heavy terminals) .. but it is probably not a good idea .. as Istream noted, better to use waste heat from the engine to heat the water.

seadaddler · Feb 5, 2015

Water heater

I have a 2500 inverter/charger and I am guessing when boat at the factory
they made sure the water heater can't work off the inverter and also the AC
can't work off the inverter either and that is how it is wired.
If you are running the motor any way that should be making hot water any
way, I run either shore power or my Fisher Panda Gen for my hot water heater.
Nick

Maine Sail · Feb 5, 2015

Hayden Watson said:
Can an inverter be used to run the hot water heater while running the engine to charge batteries?

I have a single 210 AH Lifeline 4D for my house bank. The previous owner installed an Ample Power 109A alternator and even with the low internal resistance of the Lifeline I rarely see more than 70A of output. can I use this excess charging capacity to heat water with the 120v element with an inverter?

If this is possible, what would be a good inverter to buy?

If you have the typical Catalina 30 Seward water heater the element is usually 1500W.

1500W / 11.5V = 130A X 1.15 (inv efficiency) = 150A Load

You have 70A to work with so 150A - 70A = 80A battery load.

Lifeline Peukert 1.12 = Peukert corrected load of 103A at the battery......

Heat with the engine...

woodster · Feb 5, 2015

the other option would be to use the Honda 2000....

Stu Jackson · Feb 5, 2015

Another way to explain what the guys are telling you is that your initial question indicates that you need to address your entire ELECTRICAL SYSTEM design. It is not only the size of the inverter that is involved. If you have't yet, buy Charlie Wing's electrical book and learn about balanced electrical systems based on their intended use.

Stu Jackson · Feb 5, 2015

Hayden,

I went back an reread your earlier post.

What engine do you have? How old is the Kumma heater?

Stu

Hayden Watson said:
I have been trying for years to heat the water with the engine but on my boat it just doesn't work. I have an older tread trying to solve that problem. http://forums.catalina.sailboatowners.com/showthread.php?p=1133153&highlight=hayden

in a test last year I got a 3º rise in outlet temperature after an hour of running at cruise speed. The coolant loop from the engine drops from 140º to 134º across the exchanger in the water heater. I have a RedDot heater down stream in this loop and the coolant temp drops from 134º to 97º across it even though the fan is not running.

It is a force 10/Kuuma 6 gallon heater. I have checked for flow in the loop and it is unobstructed. There are no bubbles in the system (purged with continuous flow from an axillary pump.) I used an optical scope to inspect the inside of the tank for buildup on the heat exchanger and it is clean.

Last year I motored for 6 hours and got warm water. The Admiral is not happy.

Maine Sail · Feb 5, 2015

Hayden Watson said:
I have been trying for years to heat the water with the engine but on my boat it just doesn't work. I have an older tread trying to solve that problem. http://forums.catalina.sailboatowners.com/showthread.php?p=1133153&highlight=hayden

in a test last year I got a 3º rise in outlet temperature after an hour of running at cruise speed. The coolant loop from the engine drops from 140º to 134º across the exchanger in the water heater. I have a RedDot heater down stream in this loop and the coolant temp drops from 134º to 97º across it even though the fan is not running.

It is a force 10/Kuuma 6 gallon heater. I have checked for flow in the loop and it is unobstructed. There are no bubbles in the system (purged with continuous flow from an axillary pump.) I used an optical scope to inspect the inside of the tank for buildup on the heat exchanger and it is clean.

Last year I motored for 6 hours and got warm water. The Admiral is not happy.

With 140 degree engine temps it sounds like a raw water cooled engine? If that is the case then you will have a very tough time getting hot water...

Maine Sail · Feb 5, 2015

Hayden Watson said:
Regardless of the input heat not being at the specified 160º I should still get SOME heat from the exchanger. Input water 140º. Tank water 60º. Deferential 80º between tank and exchanger. Guestimate of exchanger 30" long by 1/2"ø = ~48 sq-in contact for water-water exchange. I only get a 3º drop across the exchanger. remember, I am seeing a 37º drop across a water / air exchanger without the fan running and it is down stream of the water heater.

I don't remember everything that I learned in thermodynamics engineering class but I do know that it would take a damn fine insulator to stop that much heat flow.

I talked tot he Kuuma engineering department and they tell me that with 140º water I should have no problems getting hot water in less than an hour. they said that after 1 - 1.5 hours the exchanger loop and the tank should be nearly the same temperature.

Even when I had a blocked coolant heat exchanger and was overheating at 200º I never got more than warm water no matter how long I motored.

Check for a bypass valve in that circuit, some Catalina's had them.......

Stu Jackson · Feb 5, 2015

Are you quite sure that the hoses from the engine to the water heater are clear?

I wasn't.

http://c34.org/bbs/index.php/topic,3769.0.html

Maine Sail · Feb 5, 2015

Hayden Watson said:
There is no bypass. I have checked the flow at several locations along the loop with a water bucket and it flows freely.

If there was a bypass the temperature at the water heater would be close to ambient rather than at the same temp as the outlet from the thermostat bypass port.

They used to use gate valves and the gate can be partially closed and cause what you are seeing...... But if you don't have a valve then maybe it is just plumbed wrong.. What engine is this?