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Old 11-11-2012, 18:38   #1
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Tankless diesel hotwater

Hello all,

The time has come for me to replace my hot water heater. Currently its a standard 120V 6 gal tank.

I'm looking for opinions on tank-less systems that integrate with hydronic heaters such as these Sure Marine Service, Inc. | Everhot Tankless On Demand Copper Water Heater

What do people like/dislike about these systems? Are there any other manufacturers that make diesel tank-less systems?

The other option would be a traditional hot water heater (~10 gal) with a heat exchanger plumbed into the hydronic system. It seems the disadvantage of this is that I would be constantly burning diesel to keep the tank of hot water hot as opposed just heating what I need. Obviously the disadvantage is not being able to capture as much hot water from running the engine or from surplus solar/wind energy. Any thoughts on this?

My situation/plans:

I'm a live aboard in Portland, OR and the long term dream currently involves higher latitude cruising. I will however be working and living aboard for the foreseeable future. I would however like to be as off the grid as possible and maybe even try living on the hook sometime soon. This would involve longer stretches without needing to turn on the engine on a daily basis, which is why I thought the on demand heat would be a good idea. Is there any subtle details of living with a tank-less on demand system I'm missing?
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Old 11-11-2012, 19:05   #2
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Re: Tankless diesel hotwater

If you already have or are planning on installing a hydronic heating system I would recommend you get a tank with 2 heat exchangers and 120 v heater element. Very simple to add to your system and fewer diesel burners to maintain.
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Old 11-11-2012, 19:45   #3
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Re: Tankless diesel hotwater

I'm watching this thread with interest as I am currently thinking about how to setup my system as well. I'm curious how people have setup hydronic systems that can be cut off so they do not distribute heat through the hoses in summer?

I'd like to be able to have heat from an engine when running, or hydronic like a webasto or maybe dickenson with a water loop. But I also dislike the idea of a lot of engine coolant running through the boat.
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Old 11-11-2012, 19:58   #4
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Re: Tankless diesel hotwater

The engine coolant should run just to the water tank and back. You can also have a loop to a heater (fixed to the oil pan) under the engine that will keep the oil warm and the engine easy to start. The coolant in a hydroponic system is similar to the coolant in the engine but is generally not mixed, at least that is my understanding.

The neat thing is you can have the heater and the A/C connected up to most of the same lines with a summer/winter switch. Check out the olympia hurricane heaters page for more info.
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Old 11-11-2012, 19:59   #5
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Re: Tankless diesel hotwater

Valves (either elect solenoid or manual) are used zone and bypass what you don't want
These systems are quite versatile allowing water coolant from the engine to heat your buss heater registers while running,for example
Nordhavn and Selene trawlers use this setup ,and often use a standard 110/220v heater c/w heat exchanger coil
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Old 11-11-2012, 20:50   #6
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Re: Tankless diesel hotwater

I installed an OL-60 from Sure with an Everhot on our boat. Awesome piece of gear, on demand hot water is not to be dismissed. Especially if, like me, you live aboard with three females. Really, just priceless.

Your screen name makes me chuckle every time. Too much time in the joint or what?!
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Old 11-11-2012, 21:28   #7
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Re: Tankless diesel hotwater

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Originally Posted by minaret View Post
Your screen name makes me chuckle every time. Too much time in the joint or what?!
That is hilarious.
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Old 26-11-2012, 22:32   #8
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Re: Tankless diesel hotwater

The OL-60 looks pretty cool. So if I'm understanding this correctly the everhot has a separate diesel burner independent of the OL-60. How do the two interact? Is the OL-60 coolant just plumbed through the everhot so it doesn't have to raise the temperature as much?

I've also been intrigued by the Hurricane Combi. Are there any opinions on this? I'm specifically curious about the 120 VAC optional heating element. Will the electric heating element create enough heat to warm the boat and provide hot domestic water? Or is it just intended to reduce the diesel fuel consumption?

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Old 26-11-2012, 23:07   #9
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Re: Tankless diesel hotwater

I am somewhat skeptical that this unit it can really make 6 gallons of hot water a minute. A little lazy to do the math at the moment, but that's a lot of heat to be produced and conveyed. My calorifier is 32 liters - something like 8 gallons - and it takes my 10kW hydronic system an hour to make it lukewarm. Bigger coils and maybe a booster pump might speed it up, but 6 gallons a minute?

I would not recommend doing without a regular calorifier. If you have hydronic heat, buy a clarifier with two coils so you get hot water any time you have either 1. Heat running, 2. Engine running, or 3. AC power. On my boat, the engine is by far the fastest way to heat water - 15 minutes or so and you can take a shower.

I have also thought about tankless instant heaters, and there are electric ones that definitely work. Electric tankless heaters don't have the problem of conveying the heat. If you have a genset then it would be pretty simple to take showers with the genset running.
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Old 26-11-2012, 23:32   #10
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Re: Tankless diesel hotwater

For full time liveaboard use I do not recommend the Hurricane
Two friends boats that were used as liveaboards (a 42 foot Canoe cove and a small 40 ft Nordhaven) had these installed and they both had reliability issues with them within the first two years of instalation
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Old 27-11-2012, 00:21   #11
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Re: Tankless diesel hotwater

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Originally Posted by assfortress View Post
The OL-60 looks pretty cool. So if I'm understanding this correctly the everhot has a separate diesel burner independent of the OL-60. How do the two interact? Is the OL-60 coolant just plumbed through the everhot so it doesn't have to raise the temperature as much?

I've also been intrigued by the Hurricane Combi. Are there any opinions on this? I'm specifically curious about the 120 VAC optional heating element. Will the electric heating element create enough heat to warm the boat and provide hot domestic water? Or is it just intended to reduce the diesel fuel consumption?



They are totally separate systems. Just happened to install and plumb them at the same time.


Rockin' tunes btw!
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Old 27-11-2012, 00:32   #12
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Re: Tankless diesel hotwater

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Originally Posted by Dockhead View Post
I am somewhat skeptical that this unit it can really make 6 gallons of hot water a minute. A little lazy to do the math at the moment, but that's a lot of heat to be produced and conveyed. My calorifier is 32 liters - something like 8 gallons - and it takes my 10kW hydronic system an hour to make it lukewarm. Bigger coils and maybe a booster pump might speed it up, but 6 gallons a minute?

I wouldn't be surprised if that number is correct or at least close to correct. The Everhot has a great deal of copper coil inside the burner, I bet the water has to go through 20-30 feet of copper pipe in the burner. It enters cold and comes out piping hot, and I use 1" hose and a high pressure PAR pump. So it is heating the water as fast as I can put it out. The pump keeps up pressure in the accumulator just fine with both showers on, and the water stays plenty hot throughout. Never measured how much water per minute is put out by both showers running at once, I doubt it's 6 gallons a minute and obviously only part of that is hot. But it's more than capable enough of runnning two endless hot showers at once, which is good enough for me.


I would not recommend doing without a regular calorifier. If you have hydronic heat, buy a clarifier with two coils so you get hot water any time you have either 1. Heat running, 2. Engine running, or 3. AC power. On my boat, the engine is by far the fastest way to heat water - 15 minutes or so and you can take a shower.

I agree with that. I kept my original water heater which has a heat exchanger with the engine and is AC. It's actually a great unit, and while the Everhot makes hot water much quicker, if you are already under way it seems silly not to make use of those BTU's. After running for awhile the hot water becomes dangerously hot with the exchanger, you could be scalded in the shower potentially if you weren't careful.



I have also thought about tankless instant heaters, and there are electric ones that definitely work. Electric tankless heaters don't have the problem of conveying the heat. If you have a genset then it would be pretty simple to take showers with the genset running.


What's the difference in conveying heat between electric and diesel?
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Old 27-11-2012, 01:55   #13
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Re: Tankless diesel hotwater

We had a Dickerson diesel heater with the water heating coils inside the burner. And a 50 gal insulated water tank mounted higer then the heater. it then fed bus heaters in both the forward state room and the aft state room also the pilot house !! worked well in alaska in Ancorage in the winter !! Just saying threres some good things in old style stuff !!
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Old 27-11-2012, 02:08   #14
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Re: Tankless diesel hotwater

Chartered a Seawind 1000 some time ago with a gas system.

Worked very well.
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Old 27-11-2012, 03:32   #15
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Re: Tankless diesel hotwater

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Originally Posted by minaret View Post
What's the difference in conveying heat between electric and diesel?
An electric heater puts 100% of the heat directly into the water -- the heating element is directly in the water.

Heat from diesel has to be transported which limits the amount which can be put into the water.

However, your real life experience trumps my armchair skepticism -- if it works, it works -- very cool. I might try something like that myself. I can't believe you can get two endless showers out of it -- unbelievable. Love to have that on my boat.

My problem is that my boat was built with a 50 liter calorifier which died last spring, and I could only replace it with a 32 liter calorifier due to the shape of the space it goes into under the raised salon sole. It's not enough for a boat with 7 bunks not counting the salon. Hot showers were kind of a problem this summer when the boat was full of people.

People who sail in the tropics don't really understand what a problem this is for those of us in colder climates

That device might really be a good addition if it really works as you say, and if -- IF -- I can find a space for it. I could plumb it into the hydronic system ahead of all the fan coils so it "steals" all the heat when it's being used. What are the dimensions of it?
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