They also come in propane flavor. One fuel source, you could cook, heat water and heat the cabin.
pigslo

 

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.

 

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.

 

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.

 

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..

 

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.

 

Have a peek I though this was an interesting site and you could check to see if they make a CNG version http://www.tanklesswaterheatersdirect.com/shop/tanklesswaterheaters/aquastar/aquastarindex.htm#1600h

 

Tankless

I had tankless electric water heaters in my home years ago but had lots of problems with leaking. The company replaced them 3 times before going bankrupt. Apparently the problem was with the expansion from rapid heating. The gas models were not affected. From what I have read the new models don't have this problem. The drain on a 12 volt system would be very high but you could directly wire the unit to be used only when connected to shore power. This would be the most practical. If you dont need instant hot water when you dock you could use a 110 volt tank water heater (about 5-7 gallons) hooked up the same way. If you installed extra insulation around it you would have hot water for a few hours after casting off whereas the tankless has no hot water after bering disconnected. Just remember that if you live in a cold area you need to be able to winterize the unit.

 

Tankless heater

During a 8 year span when I had horses instead of boats ( I know, poor choice) I needed hot water for a wash rack for the horses. I bought a unit from Lowes and if I remember right it was about $150.00. Just plugged in and hooked to a garden hose. Did not get super hot but plenty warm for bathing. We put a "Y" connector in so we could mix cold water back in after the heater to regulate temp.
If you want something to use in the slip this would work.

Horses and that wife are gone. Boats are back in my life again.

 

If you choose to go to the on-demand type, esp propane, check first with your insurance company... many models are not approved and installation could jeopardize a future claim/coverage.

We looked at a boat once that had had such a heater, and the PO had ripped it all out for that reason (but didn't do a nice job of it so there were holes left over all over the place)

Also, they are generally not all that small and need to be installed where they can easily be vented, (ie, not under a quarterberth) so I'm not sure there's much of a space saving over a conventional marine HW tank.

 

Hey all, original poster here. I guess I wasn't as clear as I could have been in the original post.

The question was about which tankless water heaters people had experience with, and which they liked.

I should have clarified by saying that I'm refering to 110v/AC powered units only. I realize this limits my hot water to dockside power sources only. That's OK. If I want hot water in a pinch I can always use my galley stove.

Any suggestions?

 

You probably won't find a marine unit that is 110AC only. Best bet is to go with one from Lowe's or Home Depot.