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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #1  
Old 01-18-2008
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Tankless Water Heaters

My Force 10's hot-engine-water cicuit rotted at the connection points after 3 years of use. I was giving serious consideration to just bypassing the curcuit and continuing to use it, but thought I might regret that, not knowing how bad off the guts of the unit may be.

Because I was contemplating the possibility of running without the ability of making hot water from the engine - I don't need it much for my cruising today, mostly day trips and short stints where I'm in a slip more than half the time, I'm now considering saving some space by using a tankless water heater. There are a number on the market and they range in price from $150 to 1,000. I think I'm limited to a 110V set up.

Any recommendations? Any advice on whether or not this is a good or bad idea? Any real-life experiences out there with this relatively new concept?

And for those who are watching...there are a few threads out there from me, they're all legit. It all started with gunk in my diesel tank, which required remove, predicated upon the removal of the water heater, which has now given me access to the quadrant, so I'm also looking at an auto-pilot install.

Thanks all.
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Old 01-18-2008
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They also come in propane flavor. One fuel source, you could cook, heat water and heat the cabin.
pigslo
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Old 01-19-2008
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Thanks, but already set up w/CNG for the galley. And really do want the space, may need to expand battery bank due to a recent fridge add.
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Old 01-19-2008
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I think it is a bad idea to go with a 110 VAC setup. You'd be much better off with a propane or diesel on-demand tankless water heater. If you go with a 110 VAC setup, the drain on your electrical system will be enormous... Have you even looked at the specs for these in terms of the power they consume??? If the 110 VAC setup has a 1500 W heater element, you'd be drawing about 140 amps at 12 Volts. A ten minute shower and doing the dishes would cost you 30-40 amp-hours of electricity alone... not counting inverter and re-charging losses.

You'd end up running the engine to replace all the electricity you pull out of your battery banks if you're anchored out for a weekend. Your boat is diesel powered more likely than not, so by going with a diesel one, you wouldn't even need to add any additional fuel or tanks.
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Old 01-19-2008
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A tankless..

A marine indirect/electric type hot water heater is in a sense a giant thermos that has a "coil" or "element", if you will, of tubing running through it which engine coolant flows in and out of. This coil is submersed inside the "thermos" and transfers heat from the engine to the domestic H20 much like a radiator does to air.

If I read your statement correctly you want to "by-pass" this unit. If you do be sure you don't disturb the engines cooling flow.

The easiest way to do this, not necessarily the best way, is to disconnect both the supply and returns from the engine cooling system at the hot water heater. Then simply put a male/male barbed coupling in between these two hoses and bleed any air out of your engines cooling system.

By-passing the domestic side is the same (male/male hose barb) and is what I do in the winter when I winterize my system so I don't have to fill my entire water heater with antifreeze just the domestic water pipes/tubing.
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Last edited by Maine Sail; 01-19-2008 at 02:41 PM.
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Old 01-19-2008
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Halekai-

A tankless water heater generally has a heat exchanger grid of some sort and a combustion chamber built around it, so that the water can enter it and leave the other end "heated". In a house, it'd be called an on-demand water heater, since it doesn't leave hot water sitting around in a tank and only comes on when the hot water demand is triggered. AFAIK, most tankless water heaters have no way of using the engine coolant to heat the water, since there is no tank for the engine coolant coil to be submerged in. They're usually either propane or diesel. They can be electric too, but most marine units aren't due to the relatively high AC requirements.
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Old 01-19-2008
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Depends on what you want to do and where you want to use it. A "tankless" or "flash" hot water heater can be a small unit, like you bolt under a sink to make a couple of cups of scalding water. They use a 110V coil to heat a small "thermos" bottle and keep a couple of cups of hot water at hand.

Or there are larger units with no thermos, that rely on making lots of heat and running it across a grid of small pipes carrying cold water, superheating it real fast and putting it out as hot water in real time. Available in ranges like 2-8 gallons per mminute, designed to run your kitchen and bathroom at home. If you only want to use the hot water while docked--that's probably the cheapest. If you want to use the hot water underway...that's a lot of power and you are back to gas fired, CNG or propane, unless you've got a lot of boat and a lot of AC power available.
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Old 01-19-2008
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Have a peek I though this was an interesting site and you could check to see if they make a CNG version http://www.tanklesswaterheatersdirec...ndex.htm#1600h
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Old 01-19-2008
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Quote:
Originally Posted by sailingdog View Post
Halekai-

A tankless water heater generally has a heat exchanger grid of some sort and a combustion chamber built around it, so that the water can enter it and leave the other end "heated". In a house, it'd be called an on-demand water heater, since it doesn't leave hot water sitting around in a tank and only comes on when the hot water demand is triggered. AFAIK, most tankless water heaters have no way of using the engine coolant to heat the water, since there is no tank for the engine coolant coil to be submerged in. They're usually either propane or diesel. They can be electric too, but most marine units aren't due to the relatively high AC requirements.
Thanks for catching that! I guess I had not had my coffee yet and was thinking "indirect water heater" becaue that's what the OP wants to bypass but typing tankless water heater because he wants to replace it with one. From what I read he has one of these Force Ten Water Heater..


I was merely trying to describe how to quickly and easily by pass his indirect/electric Force Ten that he currently has..
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Last edited by Maine Sail; 01-19-2008 at 02:44 PM.
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Old 01-19-2008
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Been there, done that... got the t-shirt. Believe the OP has a fairly traditional tank-based hot water heater, and now that the tank is shot, wants to get something that is less space intensive, so that he can increase his battery bank size... or that's the impression I've gotten from what he wrote. Apparently, he's added a refrigerator and wants to add an autopilot... both of which suck DC quite well.

Quote:
Originally Posted by halekai36 View Post
Thanks for catching that! I guess I had not had my coffee yet and was thinking "indirect water heater" but typing tankless water heater. I thought he had one of these Force Ten Water Heater..


I can't say I've ever seen a Force Ten "tankless" water heater but have seen the Force Ten "indirect" style liekt eh one above..
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
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—Cpt. Mal Reynolds, Serenity (edited)

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