Water Heater Options

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crowleykirk

Veteran Member
Joined
Jun 19, 2020
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43
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Hello all.
I'm researching options for a new boat build but looking at finding a water heater solution that does not require shore power.

There are the obvious "camping" solutions but I'd rather have an integrated system that is easy to use in the head.

The new vessel we are looking at now over the diesel vessel we were looking at is twin 300 Yamaha's. I will install a solar system but as of now can't find a water heater that would work with an invertor unless you have tons of solar power.

I suppose some kind of RV propane system could be used, we love the one in our camper but on a gas boat that just adds to the volatility.

Just thought I'd post and see if anyone has crossed this bridge. Not looking for a long shower, just a quick soak, turn off, and rinse. And when I say solar I'm not talking about sun showers.

Take care,
Kirk
 
I have onboard, plumbed in series Two, 2.5 Gallon point of use electric water heaters. Each one has a 1500W 120 V ac element that will raise the water temperature by 90º F. in about 22 Minutes, consuming about 550Wh or about 50 Ah @12 V. each.

I normally run one, then once it is hot, the other.

Provided you have a reasonable solar array for recovery and about 300 Ah of storage I don't see a reason why this would not work.

5 Gal. of 140º F. hot water makes a nice shower.
 
On a youtube video of a home built outboard powered mini-trawler, the owner/builder tapped into the cooling system of the outboard and routed it to standard marine water heater with an integrated heat exchanger. Seemed like a bold move but it worked for him.

He didn't show the plumbing for it, just described it and that it worked well for him. He discussed it at the 9 minute mark and his is a mercury outboard. I'm a big fan having hot domestic water at my disposal underway on my own boat without running the generator.

 
Hello, thanks for your reply. Can you be specific about the heaters you are using? So this is a 100% solar-powered system?
Thank you,
Kirk
 
What are your plans for heating? If you go hydronic you can use the boiler to heat water as well as waste engine heat.
 
I'll check this out. Maybe even though I mentioned no camping solutions a Yakima solar heater could be an alternative. I'm with you, I'm not wanting a generator or more complicated systems. My wife and I have a truck camper and it has a small water heater we don't use much. Sponge baths work pretty well between stops in RV parks where we take a longer shower. I look at the boat in the same way. We don't need something expensive and complicated for a quick rinse. Heck, a bug sprayer and some boiled water might even be a solution.
 
My heaters are a Bradford White RE1-2U6, which are 2 Gal. (not 2.5 Gal, Ooops!) residential water heaters, about 12" high and 10" in diameter. They are not Marine rated heaters, but why do they need to be? For other reasons they are also plumbed in series to my 17 Gal. water heater.

My old Xantrex 3kW Modified Sine Wave inverter powers them from my 1300 Ah 12V lead acid battery bank. A 300 Ah bank of LiFePo would likely work just fine as the draw is about 130 A for 20 Min. each.

I have no solar onboard, but it does not matter how the power is generated (solar, grid, wind, genset) as long as you have enough of it to replenish you battery bank.
 
6 gallon electric water heater and a Honda 2K portable genny. Water Heater, Stove, Oven, AC on a battery backed invertor is going to require a huge bank and a way a to recharge it.
 
Lets face it, heating hot water uses a lot of power. You are going to need a system to replace that power in a reasonable amount of time or use a genset.

Yes, my 3000W inverter with 800 amp hour bank can heat up the water. Now to put that power back into the batteries. So thats about 130 amps at 12v for 20 minutes. Never mind anything else that is on, lights, pumps...

Now if I am right, your panels would need to put out about 40A for one hour to put back that power.

As always, the math must be done to battery bank size to load and what can be put back into the battery bank. What about rainy days? Solar out put would be low.

I started to go down this road and threw my hands up. For 45 minuets a day, 20 in the morning and 20 at night at just use the genset. At the same time as heating the water I am recharging the house bank. For me, its just not worth it.
 
crowleykirk said:
We don't need something expensive and complicated for a quick rinse. Heck, a bug sprayer and some boiled water might even be a solution.
Click to expand...

If you are serious about this, check the various solar bags. These sufficed for me for many years in small (22-31') sailboats. If you are willing to take your morning shower at 4PM, they work remarkably well. (In the last couple decades, I've demanded better, but I'm just sayin')
 
For a new build, hydronic would be a great choice, as mentioned. Get heat and hot water together (maybe not so great in the Summer). Assuming they can install it.

But probably the best option all around might be to spec a generator. It solves the hot water problem and much more.
 
It is simple to plumb a summer loop that by passes the air handlers. Or turn the thermostats down. I had a summer loop but seldom used it. Turning the thermostats down was usually all i needed to do.
sjisailor said:
For a new build, hydronic would be a great choice, as mentioned. Get heat and hot water together (maybe not so great in the Summer). Assuming they can install it.

But probably the best option all around might be to spec a generator. It solves the hot water problem and much more.
Click to expand...
 
Shrew said:
6 gallon electric water heater and a Honda 2K portable genny. Water Heater, Stove, Oven, AC on a battery backed invertor is going to require a huge bank and a way a to recharge it.
Click to expand...

I've been seeing TV ads for a solar-powered portable "generator" -- maybe worth a look...

-Chris
 
It's a small battery and a small solar panel in a box. I don't need to look at the specs to know it's not worth a lot in a boat's DC energy budget.
ranger58sb said:
I've been seeing TV ads for a solar-powered portable "generator" -- maybe worth a look...

-Chris
Click to expand...

Shrew said:
It's a solar panel, a battery and an invertor in a box.
Click to expand...
 
Yeah, coming to that conclusion. It's not a huge deal just wondering what others have figured out. At some point how much do you spend and build for a 5-minute shower? And all this for my wife really. And she has "roughed" it for many. many years in our adventures. A genes would certainly solve most everything.
 
Yeah, the boat is a 36-footer and will be new so no reason to cheap out I just like simple systems. Even mounting Yakama shower tanks would be a great option as a main source or a backup.
 
Yes, I've looked at this as well. Very simple. And effective. Would be fine on the hook and then the wife can grab a marina shower as needed.
 
We use a Jackery solar generator and LOVE it. It's all the 110v we need in our camper. We will for sure be using it on the boat as well. Obviously would not heat a full-blown hot water heater system. But does almost everything else we need, it will even run a microwave. I have solar on my camper. I even run an oxygen machine at night as needed. Then just plug the charging cord into a 12v outlet and while we are out and about we get a full charge easily. We also have a fold-out portable solar system that is super efficient but have found out it's just not needed unless it's a cloudy day then I might bust it out.
 
We used to use a solar bag shower for years before we got our camper.
They work great if it's warm enough outside and you grab that late afternoon shower, nothing better:)
 
Just ran across this today. I get a Camper Adventure newsletter and this was in there. This would be easy to convert any engine into your generator. Obviously, the engine must be running but there you go.

Simple. You have an engine and fuel already on board. I just opened this up, haven't even read the details but looks interesting for those of us who like to tinker and figure out possible simpler solutions.

https://www.cargenerator.com
 
Heat Exchangers option

Easy to do this on a new build

choosing a marine water heater, it's important to consider safety features such as overheat protection, pressure relief valves, and ignition protection.


Whale Seaward 11 Gallon Hot Water Heater with Front Heat Exchanger
4.8(9)
Amazon.com, + more
$601.64
This water heater can operate on 120-volt AC power, on engine coolant heat exchange, or both. It has an 11-gallon capacity, a double-walled front heat exchanger, a 100 psi rating, and an integrated temperature and pressure relief valve.
 
:socool:
Huntclub1 said:
Easy to do this on a new build

choosing a marine water heater, it's important to consider safety features such as overheat protection, pressure relief valves, and ignition protection.


Whale Seaward 11 Gallon Hot Water Heater with Front Heat Exchanger
4.8(9)
Amazon.com, + more
$601.64
This water heater can operate on 120-volt AC power, on engine coolant heat exchange, or both. It has an 11-gallon capacity, a double-walled front heat exchanger, a 100 psi rating, and an integrated temperature and pressure relief valve.
Click to expand...

I'll have a look, thnak you.
 
We are a Raritan boat, if we need something and Raritan makes it, that is who we purchase from. Why, their support is fantastic. Look here (Introducing our Product of the Month: 1700 Series Marine Water Heater - Raritan Engineering Blog).
We have a Raritan 1700 water heater, 20gal model. We also have the heat exchanger model. In case you aren't aware, the heat exchanger uses the engine to heat the water in the water heater.
With the water heated this way, the hot water will last about a full day & then some, it takes some of the strain off the water heater element. We carry 300g of fresh water.
We have an inverter with 6, 6V L16 AGM batts and a solar setup with 3, 220W Xantrex Max Flex solar panels. The longest we have anchored in 1 spot was 4 days on the Kentucky River and our system seemed to work well to supply hot water for dishes and shower.
Now, all that said you might not have space for a 20g water heater. You may not have the solar or batt capacity for a system like what we have.
I think if you consider the heat exchanger you will heat most of your needs that way without adding other systems, propane, to your boat.
BTW we have 2 135HP Lehman's. They run at 180 degrees which is certainly hot enough for any water you might need. We usually, for several hours, need to run the cold side wide open to mix with the hot to be usable.
Any specific questions, PM me.
 
Isotemp water heaters advertise 750 watt hearing element. While the total number of watts (power) would be required, the low power draw would be much less likely to overload an inverter, the OPs concern.

defender.com

Isotemp Slim 20L Marine Water Heater

Isotemp Water Heaters General Features: All Isotemp water heaters use two thermostats: a temperature thermostat and a safety thermostat designed to trip in the event the tank is run dry All Isotemp water heaters come standard with a mixing valve
defender.com defender.com

Peter
 
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