120 volt AC Tankless Electric Water Heater

[Dockhead]

Originally Posted by john61ct

. . . I agree adding propane infrastructure just for a HWS may be overkill. . . .

Not only that, but propane instant water heating is almost impossible to install safely in a boat. Such a device should not be installed inside the main hull volume.

You can get enough heat out of your main engine cooling circuit for tankless heat. Just need a correctly sized heat exchanger. But then you'd only be able to shower while motoring.

I think there is a pretty good reason why 99% of cruising boats use a normal calorifier with some ability to store high temperature water. The standard marine calorifier is a really useful and versatile device which can take heat from electrical elements (including dump heat from solar or wind), engine waste heat, and/or hydronic furnace. So you can have domestic hot water -- key for elementary comfort in colder latitudes -- from a variety of different energy sources.

[Maka]

I have used Paloma tank less water heaters in off grid houses. No reason they would not work on a boat.

Uses propane to heat water.

Run it only when you want hot water. It is an on demand system.

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[transmitterdan]

Originally Posted by Paul L

So how much diesel do you think you need to burn for a 10 min shower? It is miniscule with our ITR.

This heater isn't like the "instant on" heaters we have been discussing. It is relatively low power and can raise one gallon of water 60 degrees F (15C) per minute at 0.28 gallons of fuel per hour. So a sort of hot shower with much lower flow rate than many would consider acceptable. I am sure it meets your needs but it isn't the same as instant on heaters most people think about.

Can you say how much this unit cost new?

[Paul L]

Originally Posted by transmitterdan

This heater isn't like the "instant on" heaters we have been discussing. It is relatively low power and can raise one gallon of water 60 degrees F (15C) per minute at 0.28 gallons of fuel per hour. So a sort of hot shower with much lower flow rate than many would consider acceptable. I am sure it meets your needs but it isn't the same as instant on heaters most people think about.

Can you say how much this unit cost new?

It really is on-demand full flow hot water. It is also a full boat heater, so you are paying for both. It fits in the space of a normal hot water tank. It is 33,000btu/hr

[Bleemus]

Originally Posted by Maka

I have used Paloma tank less water heaters in off grid houses. No reason they would not work on a boat.

Uses propane to heat water.

Run it only when you want hot water. It is an on demand system.

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Don't let your insurance company see it. They will make you remove it.

[transmitterdan]

Originally Posted by Bleemus

Don't let your insurance company see it. They will make you remove it.

If you hide something from your insurance company then you basically don’t have insurance so your money is wasted. If you make a claim they will find whatever you tried to hide and can deny the claim. So it’s not a good idea to hide stuff from the insurer. Better to not install things the insurance does not cover.

[john61ct]

And presumably decline to pay if the boat explodes.

So, it seems no instant HWS is practical and safe for a boat.

Insulated tank, heat exchange with the engine, 12V and 120V elements.

For maximum flexibility or high-volume use cases, add a diesel Webasto-style water heater, in which case for cold climates this can become the hydronic system for space heating the whole boat, maybe even an engine block pre-heater.

[Bleemus]

Originally Posted by transmitterdan

If you hide something from your insurance company then you basically don’t have insurance so your money is wasted. If you make a claim they will find whatever you tried to hide and can deny the claim. So it’s not a good idea to hide stuff from the insurer. Better to not install things the insurance does not cover.

That was the point I was trying to make.

[RobinScurr]

Consider this:

Duoetto MK2 Dual Voltage 10L Water Heater (12v / 240v)
https://www.amazon.com/dp/B0747M4CSS...v_ov_lig_dp_it

As I recall, it will heat water 15 degrees F in 20 minutes on 12 volt DC, 25 amps. I found a performance chart but can't put my hands on it right now. This is the only 12 volt heater I could find. Re-fitting a typical 6 gallon heater with a 12 volt element would work, but would take forever if you really wanted the water hot.

[RobinScurr]

I now see that Duoetto MK2 Digital Water Heater (10L 12v/240v) has several 12v hot water heater options, including a 5L/1.3 gal 12v/15A unit.

AQUEOUS WATER HEATER (5L 12V)
Aqueous Water Heater (5L 12v)

They are all out of Australia, but may for for a "warm" shower with moderate power use?