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Old 05-12-2013, 21:54   #1
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Thumbs up Heat Exchanger ONLY Water Heater

First off, thanks for any help!

I'm wondering if I can save some money and increase reliability on a hot water heater that is a heat exchanger ONLY, and does NOT have any electrical functions. My boat is a 1987 Sea Ray weekender, and the only times that we need hot water is when we are anchored or moored. Obviously shorepower is not available in these situations, so an electric heating element is not desired, and I see it as just one more thing to degrade and break.....
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Old 05-12-2013, 22:16   #2
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Re: Heat exchanger ONLY water heater

I am not aware of a hot water heater commercially available without an electric element. Electric elements are not known for being unreliable. However, the heat exchanger will work without any electric power. You could get an off the shelf electric heater with heat exchanger feature and not connect the electric element to anything. It will work just fine off the engine heat.

You can find units without the engine heat exchanger as the heat exchanger does add considerable cost to manufacture. But the cost of electric elements is so small that I doubt you can find one that is cheaper without the element there being little or no demand for such a device.
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Old 06-12-2013, 01:48   #3
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Re: Heat exchanger ONLY water heater

My old hot water heater is AC and heat exchanger. I run AC when it's available, which makes it easier for the engine to maintain temp rather than heating cold water.
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Old 06-12-2013, 11:04   #4
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Re: Heat exchanger ONLY water heater

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Originally Posted by 230weekenderUSC View Post
First off, thanks for any help!

I'm wondering if I can save some money and increase reliability on a hot water heater that is a heat exchanger ONLY, and does NOT have any electrical functions. My boat is a 1987 Sea Ray weekender, and the only times that we need hot water is when we are anchored or moored. Obviously shorepower is not available in these situations, so an electric heating element is not desired, and I see it as just one more thing to degrade and break.....
If you take the electrical connections off, you will see that the heating element is threaded onto the aluminum tank. The element has a stainless threaded NPT Flange. Mine takes a 1-1/4" socket. i haven't tried to take it off yet. But i imagine it will take some torque and perhaps heat. If your'e worried about it deteriorating, you can try to take it off and plug it with the plug of same thread. I want to replace it with 12V element.
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Old 06-12-2013, 11:17   #5
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Re: Heat exchanger ONLY water heater

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... I want to replace it with 12V element.
I thought I wanted to do that. JMO.. read up on your heater carefully. Mine says specifically AC only, do NOT connect to DC. I'm not smart enough to overrule that...
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Old 06-12-2013, 11:20   #6
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Re: Heat exchanger ONLY water heater

Most of mine have been setup for heat exchange, but had the AC option.... but not connected on a couple. They seem to last pretty well. Maybe 6-8 years. Just dont hook up the AC. I like these type of units.. the water seems to stay heated overnight after a good run... and heats up quick if you run the engine. Cheap and reliable if you ask me.
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Old 06-12-2013, 11:27   #7
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Re: Heat exchanger ONLY water heater

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Originally Posted by jkindredpdx View Post
My old hot water heater is AC and heat exchanger. I run AC when it's available, which makes it easier for the engine to maintain temp rather than heating cold water.
Don't worry, your engine produces so much heat, it'll never notice the hot water heater. (assuming your thermostat is working properly).

70% of the btu's in your diesel is wasted, hence, you may as well capture a small amount in water heater.
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Old 06-12-2013, 23:45   #8
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Re: Heat exchanger ONLY water heater

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Originally Posted by 230weekenderUSC View Post
First off, thanks for any help!

I'm wondering if I can save some money and increase reliability on a hot water heater that is a heat exchanger ONLY, and does NOT have any electrical functions. My boat is a 1987 Sea Ray weekender, and the only times that we need hot water is when we are anchored or moored. Obviously shorepower is not available in these situations, so an electric heating element is not desired, and I see it as just one more thing to degrade and break.....
Here is a link to one. They are expensive but you do get water at the temp of the engine coolant. Everhot is just a heat exchanger. No heating elements.

Sure Marine Service, Inc. | Everhot Tankless On Demand Copper Water Heater

You could make one....

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Old 07-12-2013, 00:06   #9
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Don't worry, your engine produces so much heat, it'll never notice the hot water heater. (assuming your thermostat is working properly).

70% of the btu's in your diesel is wasted, hence, you may as well capture a small amount in water heater.
I have an inverter installed and when at anchor run the engine and the 800watt AC side of boiler together. Helps warm the engine that helps warm the water and dont have to run the engine so long.
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Old 07-12-2013, 10:22   #10
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Re: Heat exchanger ONLY water heater

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Originally Posted by evm1024 View Post
Here is a link to one. They are expensive but you do get water at the temp of the engine coolant. Everhot is just a heat exchanger. No heating elements.

Sure Marine Service, Inc. | Everhot Tankless On Demand Copper Water Heater

You could make one....

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But then again you could buy about 2.5 or 3 of the imported ones for that price! They seem to last 6-8 years or more....
http://www.defender.com/product.jsp?...4311&id=857175
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Old 08-12-2013, 09:38   #11
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Re: Heat Exchanger ONLY Water Heater

The reason you would not want to conne t DC is 1 amp AC = 10 Dc. So if
the AC is 10 AMP that is 100 amps DC which will drain the batteries.

We have a EverHot connected to our Webasto diesel heating sysyem so our hot watet is free. We also have a marine hot water heater connected to the main 671 engine and AC that we use when the Webasto is not running. The marine hot water has lasted 10+years. Used 24/7 in the warmer months.

Anyway best to buy with both so you have hot water when at the dock and away.
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Old 08-12-2013, 10:36   #12
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Re: Heat Exchanger ONLY Water Heater

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Originally Posted by rw58ph View Post
The reason you would not want to conne t DC is 1 amp AC = 10 Dc. So if
the AC is 10 AMP that is 100 amps DC which will drain the batteries.
Assuming a 120vac element connected to 12vdc it would actually draw only approximately 1/10th of the current and very little heating would occur.
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Old 08-12-2013, 11:04   #13
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Re: Heat Exchanger ONLY Water Heater

I just replaced our Seaward 6 gallon heater. Some judicious internet shopping found one for all of $236. Gee, why not just install it and don't connect if you want. It'd cost more to find one without an electric element.
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Old 08-12-2013, 12:46   #14
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Re: Heat Exchanger ONLY Water Heater

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Originally Posted by Stu Jackson View Post
I just replaced our Seaward 6 gallon heater. Some judicious internet shopping found one for all of $236. Gee, why not just install it and don't connect if you want. It'd cost more to find one without an electric element.
Or connect it and only use it when you want. I had my (~20 yr old) water heater turned off at the breaker panel. Then figured out power company was charging me an $8/mo minimum. Turned on the AC to my water heater and I have hot water from the tap. Use less propane and my bill is still around $8 a month.
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Old 08-12-2013, 13:04   #15
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Re: Heat Exchanger ONLY Water Heater

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Or connect it and only use it when you want.
Good idea, Jim. Based on recent input on our C34 Forum, these heaters last anywhere from 10-15 years. Mine went 16. That's less than $25 a year!

Also, FWIW, two other things:

1 Don't leave the power on all the time. Just use it for anywhere from 15-30 minutes to heat the water, then turn it off. While there is a thermostat in most units, why "overheat" the water unnecessarily?

2 Get in the habit of using the HOT water faucet even if you don't have hot water - it keeps the water moving through the coils in the heater and avoid the rotten egg syndrome.
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